question

What is the average rate at which temperature increases with depth in the Earth's crust?

answer

30°C/km

question

Metamorphism:

answer

change affected by pressure, heat, and water that results in a more compact and more highly crystalline condition

question

Metamorphic rock:

answer

rock that has undergone changes in texture, mineralogical, or/and chemical composition in the solid state

question

Main factors driving metamorphism:

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-internal heat of the Earth -Earth's pressure -Earth's fluids

question

metamorphic rocks, even those exposed at earths surface, are mainly the products of processes acting on rocks at deaths ranging from the ____ to the ____ ____

answer

upper to the lower crust

question

most metamorphic rocks are formed at depth of __to__ km

answer

10 to 30 km, in the middle to lower half of the crust but they can also occur at the earths surface

question

How Do Rocks Metamorphose?

answer

-Through partial or complete recrystallization of minerals in the rocks over long periods of time -Rocks remain in solid state during metamorphism

question

Role of Pressure in Metamorphism

answer

-Greater pressure (burial, collision, etc.) - confining pressure tends to decrease the space available for mineral growth; density -Stress causes preferred orientation of minerals - differential stress (directed pressure)

question

confining pressure

answer

a general force applied equally in all directions. just as a swimmer feels greater confining pressure when diving to greater depths, a rock descending to greater depths in earth's interior is subjected to progressively increasing confining pressure

question

directed pressure

answer

is force exerted in a particular direction, as when you squeeze a ball of clay between your thumb and forefinger. Directed pressure, also called differential stress, is usually concentrated within particular zones or along discrete planes.

question

ex of directed pressure

answer

the compressive force exerted where lithospheric plates converge, and it results in deformation of the rocks near the plate boundary. heat reduces the strength of a rock, so directed pressure is likely to cause severe folding and other forms of ductile deformation, as well as metamorphism in mountain belts where temperatures are high.

question

rocks subjected to differential stress may be ...

answer

severely distorted, becoming flattened in the direction the force is applied and elongated in the direction perpendicular to the force.

question

metamorphic recrystallization may align minerals in a particular direction depending on the type of ___ applied to the rock

answer

stress

question

Role of Temperature in Metamorphism

answer

Heat: greatly affects a rock's mineralogy and texture; increases mobility of elements Geothermal gradient: measure of variation of temperature with depth (average 30°C/km)

question

geothermal gradient

answer

is the increase in temperature with increasing depth in earth's interior

question

geothermometer

answer

because different minerals crystallize and remain stable at different temperatures, we can use a rock's mineral composition as a kind of geothermometer to gauge the temperature at which it formed

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Role of Fluids in Metamorphism

answer

Fluids (H2O): act as a catalyst during metamorphism - aids the exchange of ions between growing crystals

question

metasomatism

answer

hydrothermal fluids carry dissolved carbon dioxide as well as chemical substances that are soluble in hot water under pressure. As hydrothermal solutions percolate up to the shallower parts of the crust, they react with the rocks they penetrate, changing their chemical and mineral compositions and sometimes completely replacing one mineral with another without changing the rock's texture. this kind of change in a rock's composition by fluid transport of chemical substances into or out of the rock is called metasomatism

question

where do these chemically reactive fluids originate?

answer

-most rocks contain water in minute pores (the space between the grains) -this water comes from chemically bound water in clays. -water forms part of the crustal structures of metamorphic minerals such as micas and amphiboles. -the carbon dioxide dissolved in these high-tempeature fluids is derived largely from sedimentary carbonated: limestones and dolostones

question

Metamorphic Grade - the intensity of metamorphism

answer

reflects the temperatures and pressures it was subjected to during metamorphism -High grade: High temperature and high pressure at deeper zones of the crust -Low grade: Low temperature and low pressure at shallower crustal regions

question

plate tectonic processes such as ____ and _____, are the mechanisms that form most metamorphic rocks

answer

subduction and continent-continent collision (which transports rocks and sediments into the hot depths of the crust)

question

limited metamorphism may occur where rocks are subjected to elevated temperatures near _____ _____

answer

igneous intrusions. The heat is locally intense but does not penetrate deeply; thus the intrusions can metamorphose the surrounding country rock, but the effect is localized

question

Types of Metamorphism

answer

Regional Contact Seafloor Burial Shock (impact) Ultra-high Pressure

question

contact metamorphism

answer

occurs locally, adjacent to igneous intrusions, and along fractures that are in contact with hot fluids -high temperatures -low stress environment -little change in bulk composition of the rock -limited to very thin zones because lavas cool quickly at the surface and their heat has little time to penetrate deep into the surrounding rocks and cause metamorphic changes

question

regional metamorphism

answer

occurs where both high temperatures and high pressures are imposed over very large areas, such as deep within the cores or rising mountain ranges, and it is accompanied by folding of rock layers -the different stresses result from the type of tectonic forces at convergent boundaries - it occurs in volcanic mountain belts, such as the Andes, where subducted plates sink deep into the mantle. and it occurs in the cores of mountain chains produced by continent continent collisions, such as the Himalayas

question

burial metamorphism

answer

the most common type of metamorphism and occurs on a regional scale as rocks form and get buried -caused by confining pressure -caused by increase in temperatures and pressures as sediments are gradually buried deeper in the crust -low grade metamorphism

question

rocks produced by high pressure and ultra high pressure metamorphism are ____ because they form at ____ depths

answer

rare; great most high pressure metamorphic rocks form in subduction zones as sediments scraped from subducting oceanic plates are plunged to depth over 30 km

question

unusual metamorphic rocks once located at the base of Earth's crust can sometimes be found at Earth's surface. These rocks are called

answer

eclogites; indicating depths over 80 km. in some cases these rocks contain microscopic diamonds, indicative of depths greater than 120 km

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The Amount of Change During Metamorphism Depends on:

answer

The grade of metamorphism The duration of metamorphism The composition of the rock

question

shock metamorphism

answer

occurs when a meteorite collides with earth. upon impact, the energy represented by the meteorites mass and velocity is transformed into heat and shock waves that pass through the impacted country rock. -the country rock can be shattered and partially melted to produce tektites -rare on earth

question

Metamorphic Textures from low grade to high grade:

answer

-increasing intensity of metamorphism -increasing grain or crystal size -increasing coarseness of foliation

question

Changes in Texture are Due to ______

answer

Recrystallization -Grain size -Shape of grains -Directed stress will orient minerals in two ways: --Lineation --Foliation (a set of flat or wavy parallel planes produced by deformation)

question

Foliated Rocks Classification is based on:

answer

texture mainly, metamorphic grade, grain (crystal) size, type of foliation, banding

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Foliated

answer

exhibits foliation, which are parallel (or nearly parallel) layers of flat minerals (or cleavage planes) that have been realigned as a result of pressure and re-crystallizatoin

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foliation

answer

a set of flat or wavy parallel cleavage planes produced by deformation under direct pressure. -foliation places may cut through the bedding of the original sedimentary rock at any angle or be parallel to the bedding

question

a major cause of foliation?

answer

the formation of minerals with a platy crystal habit, chiefly the micas and chlorite, under directed pressure.

question

Texture types of foliated rocks:

answer

-slaty cleavage -phyllitic texture -schistosity -gneissic texture

question

slaty cleavage

answer

nearly perfect, planar parallel foliation of very fine grained minerals. - Common metamorphic rock is slate, a product of low-grade metamorphism

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phyllitic texture

answer

wavy foliation of fine-grained material, exhibiting a shiny or glossy luster. -common rock is phyllite, a product of low-grade metamorphism

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schistosity

answer

a parallel to sub-parallel foliation of medium to coarse-grained minerals. -common rock is schist, product of intermediate to high-grade metamorphism

question

gneissic texture

answer

a parallel to subparallel foliation of medium to coarse grained minerals. It is usually distinctly banded, alternating bands of ferromagnesian and quartz, feldspars, or carbonate minerals. -common rock is gneiss, a product of high-grade metamorphism

question

slate are the ____ grade of foliated rocks

answer

lowest. commonly produced by the metamorphism of shales or, less frequently, volcanic ash deposits.

question

phyllites are rocks of a slightly ___ grade than the slates but are similar in character and origin

answer

higher. they tend to have a more glossy sheen resulting from crystals of mica and chlorite that have grown a little larger than those of slates. they tend to split into think sheets, but split less perfectly than slates

question

schists, which are ______ grade rocks, are among the most abundant metamorphic rock types.

answer

intermediate. they contain more than 50 percent platy material, ,saintly the micas muscovite and biotite. they may contain thin layers of quartz, feldspar, or both, depending on the quartz content of the parent shell

question

Gneiss are _____ grade, ____ grained rocks in which the ratio of granular to platy minerals is ____ than it is in slate of schist. the result is ____ foliation and thus ____ tendency to split

answer

high grade, coarse grained, poor foliation, little tendency. gneiss, is a coarser foliation of light colored rocks with coarse bands of light and dark minerals throughout the rock. Under high pressures and temperatures, the mineral assemblages of the lower-grade rocks containing micas and chlorite are transformed into new assemblages dominated by quartz and feldspars, with lesser amounts of micas and amphiboles.

question

temperatures ____ than those necessary to produce gneiss may begin to ____ the country rock. The result is a mixture of igneous and metamorphic rock called ____?

answer

higher, melt, migmatite.

question

Metamorphic rocks result from the recrystallization of existing rocks while they are still in a solid state.

answer

True

question

Non-foliated

answer

metamorphic rocks that do not have obvious layering of platy minerals. They are usually characterized by granular texture of cataclastic texture (fracturing and crushing). -Examples of granular rocks are marble, quartzite, and anthracite coal

question

granoblastic rocks are _______ metamorphic rocks composed mainly of crystals that grow in equant (equidimensional) shapes, such as cubes and spheres, rather than in _____ or _____ shapes

answer

nonfoliated, platy or elongate shapes. -these rocks result from metamorphic processes, such as contact metamorphism, in which directed pressure is absent, so foliation does not silicate minerals.

question

hornfels

answer

-granular texture over all even though it commonly contains pyroxene, which makes elongate crystals and some micas -not foliated, and its platy of elongate crystals are organized randomly

question

quartzites

answer

-are hard, white rocks derived from quartz-rich sandstones. - some are homogenous, unbroken by preserved bedding or foliation. -others contain thin bands of slate or schist, relics of former interceded layers of clay or shale

question

marble

answer

-are the metamorphic products of heat and pressure acting on limestones and dolomites -some show a smooth, even texture of interlocked calcite crystals of uniform size -others show irregular banding or mottling form silicate and other mineral impurities in the original limestone

question

greenstones

answer

metamorphosed mafic volcanic rocks. -many of these low-grade metamorphic rocks form when mafic lavas and ash deposits react with percolating seawater of other solutions. -large areas of seafloor are covered with basalts that have been slightly or extensively altered in this way at mid-ocean ridges -chlorite gives these rocks their greenish cast

question

granulite

answer

-high grade metamorphic rock that is also referred to as granofels, has a homogenous granular texture -it is medium-to-coarse-grained rock in which the crystals are equant and show only faint foliation. -formed by the metamorphism of shale, impure sandstone, and many kinds of igneous rocks

question

type of texture classification: porphyroblasts

answer

-newly formed metamorphic minerals that may grow into large crystals surrounded by a much finer grained matrix of other minerals -found in rocks formed by contact and regional metamorphism -vary in size, ranging from a few millimeters to several centimeters in diameter -garnet and staurolite are two common minerals that for porphyroblasts

question

descriptors of non-foliated textures

answer

-crystalline -micro-crystalline -sandy texture -glassy texture

question

crystalline

answer

composed of medium to coarse grade textures, visible crystals

question

micro-crystalline

answer

composed of medium to coarse grade textures, crystals are fine grained or barely visible

question

sandy texture

answer

a medium to coarse grained aggregate of fused sand-sized grains that resembles sandstone

question

glassy texture

answer

a homogenous texture with no visible grains, resembling glass

question

Stability of Minerals

answer

Most minerals are stable over a relatively narrow range of pressure and temperature (e.g., ice unstable above 0°C) The stability range of different minerals sometimes overlap and provide insights into the metamorphic history of rocks

question

Metamorphic Facies

answer

- grouping of rocks of various mineral compositions formed under different grades of metamorphism from different parent rocks. Each facies has certain minerals that are indicative of pressure and temperature. The minerals in a rock can therefore be clues to the (pressure and temperature) history of the rock

question

two essential points that characterize the concept of metamorphic facies

answer

1. given the same metamorphic grade, different kinds of metamorphic rocks form from the parent rocks of different composition 2. given parents rocks of the same composition, different kinds of metamorphic rocks form at different metamorphic grades

question

As a parent rock is metamorphosed, it changes from a low-grade rock to high-grade rock. example:

answer

parent rock: shale low grade: slate low-intermediate grade: phyllite intermediate grade: schist intermediate-high grade: gneiss high grade: migmatite

question

in the regional metamorphism of basalt, for example:

answer

parent rock: basalt diagnesis: zeolites low grade: greenschists intermediate grade: amphibolites high grade: granulates

question

The pyroxene-bearing granulites are the products of high-grade metamorphism in which the temperature is high and the pressure is moderate. The opposition condition, in which pressure is high, and temperature is moderate, produces rock of the ___grade

answer

blueschist grade -comes from parent rocks or various starting compositions, from mafic volcanic rocks to shaley sedimentary rocks

question

another metamorphic rock formed at extremely high pressures and moderate to high temperatures is

answer

eclogite, which is rich in garnet and pyroxene

question

isograd

answer

show where one mineral zone containing rocks of one metamorphic grade, changes to another

question

Exhumation -

answer

-transported back to earth;s surface -Subducted light metamorphic rocks are driven upward by buoyancy

question

each metamorphic rock has a distinctive history of changing conditions of temperature and pressure that is reflected in its texture and mineral composition. This history is called a metamorphic ________

answer

P-T path. -this path can be a sensitive recorder of many important factors that influence metamorphism--such as sources of heat, which change temperatures, and rates of tectonic transport (burial and exhumation), which change pressure. Thus, P-t Paths are characteristic of particular plate tectonic settings

question

by increasing erosion rates, climate may help drive the flow of metamorphic rocks from _____ in the Earth's crust to earth's _____

answer

deep, surface

question

Which of the following rocks represents the highest metamorphic grade?

answer

Gneiss

question

The parent rock of a quartzite is __________.

answer

sandstone

question

"protolith"/parent rock

answer

the rock type or source before it was metamorphosed to its present state

question

Which mineral is commonly used to determine a metamorphic P-T path?

answer

garnet

question

Geochronology

answer

- the study of time in relation to the Earth.

question

Historical Geology

answer

- branch of Geosciences that deals with the Earth's past.

question

Two Ways to Date Geologic Events

answer

relative and absolute dating

question

Relative dating (fossils, structure, cross-cutting relationships):

answer

how old a rock is compared to surrounding rocks

question

Absolute dating (isotopic, tree rings, etc.):

answer

actual number of years since the rock was formed

question

Steno's Laws Nicholas Steno (1669):

answer

-Principle of Superposition -Principle of Original Horizontality

question

Principle of Superposition:

answer

In a sequence of undisturbed layered rocks, the oldest rocks are on the bottom and the youngest layers at the top

question

Principle of Original Horizontality:

answer

layered strata are deposited horizontally or nearly horizontally (parallel to the Earth's surface) under the influence of gravity

question

stratigraphic succession

answer

a chronologically ordered set of star

question

Fossils

answer

- comes from the Latin, fossilus, meaning "something dug up." -Consist of the remains of ancient organisms, or other evidence of their existence. -Found primarily in sedimentary rocks.

question

Smith's principle of faunal succession

answer

states that the sedimentary strata in an outcrop contain fossils in a definite sequence. The same sequence can be found in outcrops at other locations, so strata in one location can be matched to strata in another location

question

Smith book, "General Map of Strata in England and Wales"

answer

the first geologic map of an entire country

question

Paleontology

answer

The study of life in the past based on the fossil remains of plants and animals -most common fossils they founds were the shells of invertebrate animals -Fossils that are preserved in sedimentary rocks are used to determine: 1) relative age 2) the environment of deposition

question

Charles Darwin studied paleontology as a young scientist, and he collected many unusual fossils on his famous voyage aboard the ____

answer

Beagle (1831-1836) -Darwin proposed his theory of evolution by natural selection which provided framework for paleontology: if organisms evolve progressively over time, then the fossils in each sedimentary bed must represent the organisms living when that bed was deposited.

question

Correlation

answer

-No single area records a complete record of Earth history. -Record must be correlated from one area to another. -Fossils play a key role. -Correlation across the Atlantic Ocean played a pivotal role in the advent of plate tectonics.

question

geologic time scale

answer

divides earth's history into intervals marked by distinctive sets f fossils, and it places the boundaries of those intervals at times when those sets of fossils changed abruptly

question

to represent the rich history of the Precambrian, a division of the geologic time scale longer than the era, called the ____, was introduced.

answer

eon

question

____ eons, based on the isotopic ages of terrestrial rocks and meteorites, are now recognized. They are called....

answer

4 eons: -Hadean Eon -Archean Eon -Proterozoic Eon -Phanerozoic Eon

question

____ eon is the earliest eon, who's named comes from ____, began with the formation of Earth 4.56 billion years and ended about 3.9 billion years ago. During its first 660 million years, Earths was bombarded by chunks of materials from the early solar system. Although very few rock formations survived this violent period, individual ___ grains 4.4 billion years old have been found, indicating that earth had a ____ crust within 160 million years of its formations

answer

Hadean, Hades (greek word for hell), zircon grains, felsic crust

question

the second earliest eon, the _____ eon, its name comes from _____. Rocks of the ____ age range from 3.9 to 2.5 billion years old. The_____ and the _____ were established during this eon, and ____crust accumulated to form the first stable continental masses. The process of plate tectonics were probably operating. Life, in the form of primitive _____-_____ ______, became established.

answer

Archean, archaios (greek word for ancient), Archean age, geodynamo and the climate system, felsic, single-celled microorganisms

question

the last part of the Precambrian is the _____ eon (from the Greek words ___ and ___, meaning "earlier life", which spans the time interval from 2.5 billion to 542 million years ago. By the beginning of this eon, the plate tectonics and climate systems were operating like they do today. Organisms that produced ____ as a waste product (as ____do today) increased the amount of ____ in the atmosphere. Although life remained soft-bodied, some organisms evolved into sophisticated creatures with____ _____ _____. The increase in atmospheric _____ to nearly present day concentrations toward the end of tis eon may have encouraged single-celled organisms to evolve into _____ ____ and _____, which are preserved in the late _____ fossil record

answer

Proterozoic Eon, Greek words proteros and zoi, organisms that produced oxygen as a waste product, like plants do today, cells containing nuclei, increase in oxygen, encouraged the growth multicellular algae and animals, which are preserved in the Proterozoic fossil record

question

the start of the _____ eon is marked by the first appearance of _____ fossils at the beginning of the _____ period, now dated at 542 million years ago. The name of this eon-- from the Greek ____ and ____-- certainly fits, because it comprises all three eras recognized in the fossil record: The ____ (542 million to 251 million years ago), ______(251 million to 65 million years ago), and the _____(65 million years ago to present)

answer

Phanerozoic Eon, shelly fossils, Cambrian period, phaneros and zoi (visible life), Paleozoic, Mesozoic, Cenozoic

question

basic intervals of geologic time scale are the ___

answer

eras; -the Precambrian -the Paleozoic -the Mesozoic -the Cenozoic

question

the eras are subdivided into ____

answer

periods; usually named for the geographic locality in which the formations representing them were first or best described, or for some distinguishing characteristic of the formations.

question

some periods are further subdivided into ___

answer

epochs

question

many of the major boundaries in the geologic time scale represent mass extinctions-

answer

short intervals during which a large proportion of the species living at the time simply disappeared from the fossil record, followed by the blossoming of many new species.

question

ex of mass extinction: at the end of the _______, which killed off 75 percent of the living species, including all ______, was almost certainly the result of a large meteorite impact that darkened and poisoned the atmosphere and plunged Earth's climate into many years of bitter cold. This disaster marks the ends of the ____ era and the beginning of the ____ era

answer

Cretaceous, dinosaurs, end of Mesozoic, beginning of the Cenozoic

question

ex of mass extinction: the largest mass extinction, at the end of the _____ period, which defines the _____-_____ boundary, eliminated nearly 95& of all living species.

answer

Permian Period, Paleozoic-Mesozoic boundary

question

ex of mass extinction: the mass extinction at the ____-____ boundary (55 million years ago) was not one of the largest of such event but it is significant in the evolution of life because it paved the way for ____, including the ____, to radiate into an important group. It was the result of abrupt ____ ____. The end of the ____ epoch occurred when suddenly the ocean belched an enormous amount of ____ into the atmosphere that caused temperatures to rise dramatically.

answer

Paleocene-Eocene boundary, mammals, primates, global warming, Paleocene epoch, methane

question

the _____ and ____ periods of the _____ era, have together accounted for almost 60% of the worlds petroleum production.

answer

Jurassic and Cretaceous periods ( the age of the dinosaurs) of the Mesozoic era -abundant in marine life that helped provide a lot of the organic matter that was buried in the sediments. This carbon-rich material has been cooked up and transported into the oil reservoirs

question

earliest period of geologic history recorded by faunal successions was the _____, when animal life, in the form of shelly fossils, suddenly appeared in the geologic record

answer

Cambrian

question

many rock formations were clearly older than the ____ period because they occurred below the ____ rocks in the stratigraphic successions. But these formations contained no recognizable fossils, so there was no way to determine their relative ages, and all such rocks were lumped into the general category _____

answer

Cambrian, Cambrian, Precambrian

question

John Drayton

answer

-South Carolina geologist John Drayton was one of the first to correlate sedimentary beds regionally using fossils. -Drayton was Governor of South Carolina when he founded the University of South Carolina in 1801. USC Department of Geology (now Earth & Ocean Sciences) is the second oldest in the United States.

question

SARA L. SAMSON

answer

1981 - SARA L. SAMSON, a graduate student in geology at the USC, on a field trip near Batesburg, S.C., found a trilobite - from an ancient sea 400 million years ago, was thrust up onto this continent and stayed behind when the sea opened again to form the modern Atlantic Ocean. -CONTINENTAL DRIFT: LATEST FOSSIL FINDS LINK ANCIENT AFRICA TO THE CAROLINAS

question

Unconformities

answer

Surface between two beds that were laid down with a time gap between them--the boundary along which the two existing formations meet-- is called an unconformity. -surfaces where erosion has removed rock layers. "Missing time"

question

sedimentary sequence

answer

a series of beds bounded above and below unconformities.

question

unconformities are classified according to the relationships between the layers above and below them. types of unconformities:

answer

disconformity, nonconformity, and angular unconformity

question

disconformity

answer

an unconformity in which the upper sedimentary sequence overlies an erosional surface developed on an underformed, still horizontal lower sedimentary sequence. -Sea levels drop and broad tectonic uplifts often create disconformities

question

nonconformity

answer

the upper sedimentary beds overlie metamorphic or igneous rocks

question

angular unconformity

answer

is one in which the upper beds overlie lower beds that have been folded by tectonic processes and then eroded to more or less even planes. -the two sequences have bedding planes that are not parallel

question

Cross-cutting Relationships

answer

The geometry of rock bodies, and their relationship with adjacent bodies, allows geologists to place rock units in relative chronological order Used for relative dating of igneous intrusions, faults, and sedimentary strata -because the deformation or intrusion events must have taken places after the affected sedimentary beds were deposited, those structures must be younger than the rocks they cut. -if the intrusions or fault displacements are eroded and planed off at an unconformity and then overlaid by younger sedimentary beds we know those structures are older than the younger strata

question

Which of the following is the best statement of the principle of original horizontality?

answer

Sediments are deposited as horizontal layers

question

Sequence Stratigraphy

answer

Stratigraphic analysis in which the major geologic units are bound by unconformities Used widely with seismic data, especially in petroleum exploration

question

Divisions in the worldwide stratigraphic column based on variations in preserved fossils Examples?

answer

Cambrian - Cambria, England Devonian - Devon, England Jurassic - Jura Mountains, Switzerland

question

Absolute Geochronology

answer

-Add numbers to the stratigraphic column which was originally based on fossils and correlation -Based on the regular radioactive decay of some chemical elements

question

Isotopes

answer

Are atoms of the same element with different numbers of neutrons. -most are stable but the nucleus of a radioactive isotope can spontaneously disintegrate, or decay, emitting particles and transporting the atom into an atom of a different element --Example: the carbon atom (C) typically has 6 neutrons and 6 protons (called C12), but there are also small amounts of C13 and C14

question

the original atom is called

answer

the parent

question

the product of decay is its

answer

daughter

question

Ions

answer

When an atom loses or gains an electron to or from another atom it is called an ion -Positively charged ions (loss of electron) - cations -Negatively charged ions (gain of electron) - anions

question

Isotopic Dating

answer

-the use of naturally occurring radioactive elements to determine the ages of rocks -Radioactive elements (parents) decay to stable, non-radioactive elements (daughters) The rate at which this decay occurs is constant and known If we know the rate of decay and the amount present of parent and daughter we can calculate how long this reaction has been occurring

question

crystal minerals more than _______ years old have been dated using uranium isotopes

answer

4 billion years

question

major radioactive elements used in isotopic dating

answer

Parent: Daughter: Uranium-238 Lead-206 Uranium-235 Lead-207 Potassium-40 Argon-40 Rubidium-87 Strontium-87 Carbon-14 Nitrogen-14

question

Types of Radioactive Decay

answer

alpha decay beta decay electron capture

question

alpha decay:

answer

loss of a 4He (2n, 2p) e.g., 147Sm decays to 143Nd

question

beta decay:

answer

neutron to proton e.g., 87Rb decays to 87Sr

question

electron capture:

answer

proton to neutron e.g., 40K decays to 40Ar

question

Half-life

answer

-The half-life of a radioactive isotope is defined as the time required for half of it to decay to the daughter product -The half-life is CONSTANT and does not vary with time, temperature, pressure, etc.

question

Direct Measurement of the Rates of Geologic Processes

answer

-Absolute ages give real numbers to Earth's history -Dating precision decreases with increasing geologic time -Global Positioning System (GPS) allows measurements of processes, such as plate motion, ± 1 mm/year

question

deep sea drilling vessels such as the ____ _____ have taken cores from sedimentary beds around the worlds oceans. Geologists can use the carbon-14 method to estimate when the shells recovered from these sediments were formed, and they can measure the stable isotopes of oxygen to estimate temperature of the seawater in which the shell-producing organisms lived.

answer

JOIDES RESOLUTION

question

the record from deep sea drilling shows a cooling trend beginning about 3.5 million years ago and the subsequent development of rapid climate cycles that became especially large during the _____ epoch. The low temperatures during these cycles, which were as much as 8 degrees Celsius below the present-day temperature of Earth's surface correspond to this epochs "____ ___" when ____ covered large areas of North America, Europe, and Asia

answer

Pleistocene epoch, "Ice Ages", glaciers

question

Evidence from astronomy tells us that the universe began with the Big Bang:

answer

a cosmic explosion of matter and energy that expanded from a single densely packed point

question

nebular hypothesis

answer

the origin of the solar system could be traced to a rotating cloud of gas and fine dust.

question

the two gases that form nebulae clouds are

answer

hydrogen and helium, the two elements that make up all but a small fraction of our sun.

question

formation of the sun:

answer

under the pull of gravity, matter began to drift toward the center of the nebulae cloud accumulating into a pro-star, the precursor of our present Sun. Compressed under its own weight, the material in the proto-Sun became dense and hot. The internal temperature rose to millions of degreases, at which point nuclear fusion began.

question

Planets form

answer

although most of the matter in the original nebula was concentrated in the proto-Sun, a disk of gas and dust, called the solar nebula, remained to envelop it. The temperature of the solar nebula rose as it flattened into a disk. It became hotter in the inter region. Once formed, the disk began to cool, and many of the gases condensed. Gravitational attraction caused the dust and condensing material to clump together (accrete) into small chunks, or planetesimals. In turn, the planetesimals collided and stuck together, forming larger, moon-sized bodies. In a final stage of cataclysmic impacts, a few of the larger bodies, swept up the others to form the planets in their present orbits. This happened rapidly.

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the four inner planets in order of closeness to the Sun are

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1. Mercury 2. Venus 3.Earth 4. Mars

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the four inner planets are known as _____ planets. In contrast to the outer planets, they are ____ and made up of rocks and metals. They formed closed to the Sun, where conditions were so hot that most of the ___ materials (materials that most easily become gases) boiled away. Radiation and matter streaming from the Sun--the solar wind--blew away most of the hydrogen, helium, water and other light gases and liquids on these planets. Thus, the inner planets were formed mostly from the _____ matter that was left behind, which included the rock-forming _____ as well as metals such as ____ and ____.

answer

terrestrial planets, small, volatile materials, dense matter, silicates, iron and nickel

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the four outer plants in order of closeness to the sun are

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1. Jupiter 2. Saturn 3. Uranus 4. Neptune

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most of the volatile materials swept from the region of the terrestrial planets were carried to the ____ outer reaches of the Solar system to form the _____ outer planets and their satellites. These planets were ___ enough and their gravitational attraction ____ enough to enable them to hold onto the ____ nebular material. Thus, although they have ___ and ____ cores, they are composed mostly of ___ and _____ and the other ___ materials of the original nebula

answer

cold, Giant, big enough, strong enough, lighter nebular material, rocky and metal-rich cores, hydrogen and helium and the other light materials

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not all the material from the solar nebula ended up in planets. some planetesimals collected between the orbits of ____ and ____ to form the _____ ______. This region now contains more than 10,000 _____ with diameters larger than 10 km.

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Mars and Jupiter, form the asteroid belt, asteroids

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the biggest asteroid is ____, which has a diameter of 930 km.

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Ceres

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must meteorites, ______(def)____, are tiny pieces of asteroids ejected from the asteroid belt during collisions with one another

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chunks of material from outer space that strike earth

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comets

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aggregations of dust and ice that condensed in the cooler outer reaches of the solar nebula. Most comets orbit the Sun far beyond the outer planets, forming concentric "halos" around the solar system

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gravitational differentiation:

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the transformation of random chunks of primordial matter into a body whose interior is divided into concentric layers that differ from one another both physically and chemically. this occurred in early earths history, when the planet got hot enough to melt

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collision with a Mars-sized body ejected debris that formed the ____ and ____ the outer part of the Earth

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Moon, melted

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As a result of the tremendous impact energy absorbed during Earth's formation, its entire interior was heated to a "soft" state in which its components could move around. ____ materials sank to the core, releasing gravitational energy and causing ____ _____, and _____ materials floated to the surface and formed ______. The rising ____ matter brought interior heat to the surface, where it could radiate into space. In this way, Earth differentiated into a _____ planet with _____ main layers. A _____, a _____, and an ____ ____

answer

heavier materials, more melting, and lighter materials, formed the crust, rising lighter matter, zoned planet, with 3 main layers, a central core, a mantle, and an outer curst

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Earths core

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-iron accounted for 1/3 of the primitive planet's materials -the iron and nickel, sank to form a central core, which begins at a depth of about 2890 km. -molten on the outside -but solid in a region called the inner core, which extends from a depth of about 5150 km to Earth's center at about 6370 km. The inner core is solid because the pressures at the center are too high for iron to melt

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Earth's crust

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molten materials that were less dense than iron and nickel floated toward the surface of the magma ocean. There they cooled to form Earth's solid crust -ranges in thickness from about 7 km in oceans to 40 km on continents. -continental crust began to accumulate early in earth's history from silicates of relatively low density with a felsic composition and low melting temperatures -oceanic crust is constantly being recycled and generated because it is more dense than the continental crust which drives it into subduction zones and not continental crust.

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earths mantle

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-between the core and the crust lies the mantle, the layer that forms the bulk of the solid Earth - it is made up of the material left in the middle zone after most of the denser material sank and the less denser material rose toward the surface - it is about 2900 km thick and consists of ultramafic silicate rocks containing more magnesium and iron the crustal silicates do. -convection in the mantle removes heat from earth's interior -because the mantle was hotter early in Earth's history, it was probably convecting more vigorously than it does today. Some tectonic activity may have been operating by the "plates" were much smaller and thinner, and the tectonic features were probably very different from the linear mountain belts and long mid-oceann ridges we now see on Earth's surface.

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Earth's ocean and atmosphere form

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-the planetesimals that aggregated into our planted contained ice, water, and other volatiles such as nitrogen and carbon. -originally, these volatiles were locked up in minerals carried by the aggregating planetesimals. -as Earth differentiated, water vapor and other gases were freed from these minerals, and released through volcanic activity. -almost all the hydrogen escaped to outer space, while the heavier gases enveloped the planet. -some of the air and water may have come from volatile-rich bodies, such as comets, that struck the planet after it had formed. -the comets, for example, are composed largely of frozen water plus frozen carbon dioxide and other gases. -countless comets may have bombarded Earth early in its history, contributing water and gases to the early oceans and atmosphere.

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the moons materials are _____ than Earths, probably because the _____ matter of the giant impacting body _____ _____ in Earth. The lunar core is therefore ____, compromising only about ___ percent of the lunar mass

answer

materials are lighter, heavier matter, remained embedded, lunar core is therefore small, compromising only about 20 percent of the lunar mass

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two types of terrain on moon

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-rough areas that appear light-colored with lots of big craters - and smooth, dark areas, usually circular in shape, where craters are small or nearly absent. light-colored regions are the mountainous LUNAR HIGHLANDS, which cover about 80% of the surface the dark regions are low-lying plains called LUNAR MARIA, because they looked like seas to early Earth-bound observers

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the heavily cratered lunar surface we see today is that of a very old, geologically dead body, dating back to a period early in the history of the solar system known as

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the Heavy Bombardment, when crater-forming impacts were very frequent.

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relative time scale for the formation of lunar surfaces principles:

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-craters are absent on new geologic surface, older surfaces have more craters than younger surface -impacts by small bodies are more frequent than impacts by large bodies; thus, older surfaces have larger craters -more recent impact craters cross-cut or cover older craters

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by applying these principles and by mapping the number and sizes of craters--- a procedure known as ____ ____--geologists show that the ___ ____ are older than the ____ ____

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crater counting, Lunar Highlands are older than the Lunar Maria

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The Late Heavy Bombardment explains why so few rocks on Earth have ages ______ than _____ billion years. It is this event that marks the end of the _____ eon and the beginning of the ____ eon

answer

greater than 3.9 billion years, Hadean eon and the beginning of the Archean eon

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Mariner 10 was the first and only spacecraft to visit _____ when it flew by the planet in March 1974. It mapped less than half the planet, and we have little idea of what is on the other side. It confirmed that this planet has a geologically dormant, _____ crated surface. It is the _____ surface of all the terrestrial planets. It shows very few features that are due to ___ ____ having reshaped its surface.

answer

Mercury, heavily crated, oldest surface, tectonic forces

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____ is a geologically active planet with a ______ mantle like Earths. Its surface shows evidence of tectonic activity, especially _____. The _____ was the spacecraft that used radar to show high-resolution pictures of this planets surface. It is also called the _______ Planet.

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Venus, convecting mantle, volcanoes, Magellan, Volcano Planet.

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On August 3, 2004 the first new mission to Mercury in 30 years was launched successfully. After 7 years in Space, _____ arrived on March 18, 2011, and entered a mapping orbit.

answer

Messenger

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____ surface is most similar to Earths. It has features suggesting that liquid water once flowed across its surface, and liquid water may still exist in its deep subsurface. Parts of the surface consists of ______ _____ terrain, but other parts are covered with ____ and ____. ______ ____, at 25 km high, is a giant, recently active volcano--- the tallest mouton in the solar system. The ___ ____ canyon, 4000 km long and averaging 8 km deep, is five times deeper than the Grand Canyon and stretches the distance from New York to LA

answer

Mars, ancient cratered terrain, lavas and sediments, Olympus Mons, The Vallis Marineris Canyon

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The Mars Exploration Rovers, named ___ and ____ went to mars in June 2003, accompanied by the ____ ____, an orbiter equipped with geologic remote sensing tools. Another new orbiter, ____ _____ ____, which started in 2006, has collected a vast set of observations that show evidence of aqueous processes over broad regions of the planet. The ____ lander conducted operations in the polar region of Mars and confirmed the presence of water ice just a few centimeters below the dusty surface. The largest rover ever built, named _____, will search for environments that might have been habitable for microorganisms

answer

Spirt, Opportunity, Mars Express, Mars Reconnaissance Orbiter, The Phoenix, Curiosity

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The oldest parts of North America's crust, built during the most ancient episodes of deformation, tend to be found in the northern interior of the continent. This huge region was named the ____ _____ because the crystalline rocks that form the upper crust emerge from the surrounding sediments like a _____ partially buried in the dirt of a ____.

answer

Canadian Shield, shield, battlefield

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The Canadian Shield, which includes most of ____ and the closely connected landmass of ____, is _____ _____. In other words, it has remained largely undisturbed by rifting, continental drift, or continent-continent collision throughout the ________, but it has been eroded nearly flat. It consists primarily of _______ granitic and metamorphic rocks, such as ____, together with highly deformed and metamorphosed sedimentary and volcanic rocks, and it contains major deposits of ____, ___, ____, _____, and ____. Large portions of the shield were formed during the _____ eon, representing one of the oldest records of Earth's history.

answer

Canda, Greenland, is tectonically stable, Phanerozoic, Precambrian, gneisses, iron, gold, copper, diamond, and nickel, during the Archean eon.

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One important type of mineral deposit occurs in distinctive geologic units called "_____ ____", where _____-age island arcs were stitched together to form vast volcanic terrains composited dominantly of ____ _____ rocks. The ____ are composed of minerals with a ___ hue, such as chlorite, actinolite, and other ___ amphiboles.

answer

greenstone belts, Archean-age, metamorphosed mafic rocks, greenstones, green, green

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Within the interior platform are broad sedimentary basins, roughly circular or oval depressions where the sediments are _____ than in the surrounding areas. Most of these features are____ _____ ___, that is, regions that subsided when heated portions of the lithosphere cooled and contorted.

answer

thicker, thermal subsidence basins,

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Extensive flat-laying (platform) sediments have been deposited on stable continental crust around the periphery of the Canadian Shield and also near its center, beneath ____ ___. The vast, low-lying, sediment-covered region south and west of the Canadian Shield, which includes the ____ ___ of Canada and the United States, is called the ____ _____. The _____ basement rocks of the _____ ____ are a continuation of the Canadian shield, although here they lie under nearly flat layers of _____ sedimentary rocks, typically less than 2 km thick.

answer

Hudson Bay, Great Plains, Interior Platform, Precambrian basement rocks, Interior Platform, Paleozoic sedimentary rocks.

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On the edges of these ____ tectonic provinces are ____ metamorphic belts where most of the present-day ____ ____ are formed. These ___ ____ formed elongated topographic features near the margins of the continent.

answer

older, younger, mountain chains, mountain chains

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An example of of an interior platform is the _____ ____, a circular area of about 200,000 km^2 that covers most of the _____ ____ of _____. This basin subsided throughout much of the _____ era and received sediments more than 5 km thick in its central, deepest parts. The sandstones and other sedimentary rocks of these basins, laid down under tectonically quiet conditions, have remained unmetamorphosed to this day. The interior platform basins contain important deposits of ____, ___, ____, and ___ ___

answer

Michigan Basin, Lower Peninsula of Michigan, Paleozoic era, uranium, coal, oil, and natural gas.

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The two main examples are the ____, which runs down the ____ edge of North America and includes the ___ Mountains, and the ____ ___ ___, which runs ____ to _____ on the continents ___ margin from ____ to ____

answer

Cordillera, western, Rocky Mountains, Appalachian fold belt, southwest to northeast, eastern margin, from Alabama to Newfoundland

question

The rock assemblages and structures of the old, eroded Appalachian Mountains resulted from the ______-_____ collisions that formed the supercontinent ____ 470 million years ago. The ____ side of the Appalachians is bounded by the ____ ____, a region of slightly uplifted, middy deformed sediments that is rich in coal and oil.

answer

continent-continent collision, Pangaea, western, Allegheny Plateau

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The ____ greenstone belt, one of the worlds largest, contains an enormous volcanic caldera complex about 2.7 billion years old.

answer

Abitibi Greenstone Belt

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Moving _____, we encounter regions of increasing deformation. The folded and faulted _____ sedimentary rocks of the ____ ___ ____ ____. The eroded mountains of the ___ ___ ___, composed of highly metamorphosed ____ and ____ rocks, which were thrust as sheets over the sedimentary rocks of the ___ and _____ _____. The hilly ____, containing ____ and _____ metamorphosed sedimentary and volcanic rocks, intruded by granite and thrust over ___ ___ rocks. The modern ___ ___, made up of relatively undisturbed sediments of ____ age and _____, underlain by rocks similar to those of the _____

answer

eastward, Paleozoic rocks, Valley and Ridge Province, Blue Ridge province, Precambrian and Cambrian rocks, Valley and Ridge Province, Piedmont, Precambrian and Paleozoic, Blue Ridge rocks, coastal plain, Jurassic age, and younger, Piedmont

question

The stable interior platform of North America is bounded on the ___ by a younger complex of mountain ranges and deformation belts. This region is part of the ___ ___ ____, a mountain belt that extends the length of North America from ____ to _____. Across its middle section, between San Francisco and Denver, the Cordilleran system is about 1600 km wide and includes several different tectonic provinces: the ____ ____ along the Pacific Ocean; the lofty ____ ____; the ___ and ____ province; the high tableland of the _____ ____; and the rugged ____ _____, which end abruptly at the edge of the ___ ____ on the stable interior platform

answer

west, North American Cordillera, Alaska to Guatemala, Coast Ranges along the Pacific Ocean, the lofty Sierra Nevada, the Basin and Range province; the high tableland of the Colorado Plateau, and the rugged Rocky Mountains, which end abruptly at the of the Great Plains on the stable interior platform.

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The North American Cordillera was formed during the ______ of the _____ Plate beneath the ____ ____ continent.

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subduction, Farallon Plate, North American continent

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The ____ ___ ___ and continental shelf were areas of ____ during the breakup of Pangaea and have since _____

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Atlantic Coastal Plain, rifting, subsided

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The study of the layers in sedimentary rock is known as _________.

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Stratigraphy

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The principle of superposition states that _______________.

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undisturbed sedimentary layers get progressively younger from bottom to top

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outcrop

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the solid rock that underlies the ground surface--the bedrock--is exposed

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geologic cross sections

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diagrams showing the features that would be visible if vertical slices were made through part of the crust

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deformation=

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strain

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deform

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change volume or shape of rock by Stress

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stress

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-force applied to rock

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The types of faults and folds we see depend on the main tectonic focus in the upper crust, which are produced mostly by horizontal movements of plates. The tectonic forces that act at plate boundaries are thus predominantly horizontally directed. Horizontal plate movements exert three types of tectonic forces:

answer

Compressional -squeezed Tensional - pull apart rock, Shear - sideways slip on parallel planes.

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Tensional

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-stretch and pull rock formations apart, dominate at divergent boundaries where plates move away from each other

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Compressional

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squeeze and shorten rock formations, dominate at convergent boundaries, where plates move toward each other

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Shear

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which push two sides of a rock formation in opposite directions, dominate at transform-fault boundaries, where plates slide past each other

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tectonic stress leads to _____

answer

strain

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strain

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Any change in original shape or size of an object in response to stress acting on the object

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tensional tectonics

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extension of continental crust produces normal faults with high dip angles in the upper crust that flatten with depth, forming curved fault surfaces. -produces a rift valley bounded by normal faults

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compressive tectonics

answer

compression of continental crust occurs on low-angled thrust faults -in subduction zones, oceanic lithosphere slips beneath an overriding plate along a huge thrust fault, or megathrust. -words largest earthquakes are caused by sudden slips on megathrusts -thrust faulting is the most common type of faulting within continents undergoing compressive compression. -sheets of crust may glide over one another for tens of kilometers along nearly horizontal thrusts faults, creating overthrust structures -when two continents collide, the crust can be compressed across a wide zone, resulting in mountain building; during such collisions, the brittle basement rocks ride over one another by thrust faulting while the more ductile overlying sedimentary rocks compress into a series of great folds, forming a fold and thrust belt -large earthquakes are common in fold and thrust belts

question

shearing tectonics

answer

sharing of continental crust occurs on a nearly vertical strike-slip fault. -a transform-fault is a strike-slip fault that forms a plate boundary. -transform faults such as the San Andreas can offset geologic formations by long distances, but as long as they stay aligned with the direction of relative plate motion, the blocks on either side can slide past each other without much internal deformation. - Long transform faults are rarely straight, however, so deformation patterns along these faults can be much more complicated

question

Many rocks occur naturally in ____

answer

layers; Sedimentary rocks Lava flows Metamorphic rocks (foliated)

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Many features within rock bodies are either ____ or _____

answer

planar or linear; Minerals Foliation

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Dip

answer

angle of steepest descent of the bed from the horizontal; max. angle between inclined plane & horizontal.

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Strike

answer

at right angles to the dip direction; direction of line formed by intersection of a horizontal plane & an inclined plane.

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Types of Deformation

answer

Elastic Ductile (plastic) Brittle (rupture)

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Elastic stress:

answer

return to original shape. -temporary change in shape or size of a body that is recovered when the stress is removed

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Ductile (plastic) stress:

answer

Ductile flow, keep deformed shape. lower crust and mantle rocks. -permanent change in shape or size of a body that is not recovered when the stress is removed ---marble behaves as a ductile material at the high confining pressures found deep in the crust

question

Brittle (rupture) stress:

answer

fracture, break, upper crust rocks, earthquakes -the body undergoes little change under the stress, until it breaks suddenly (earthquakes) ---marble behaves as a brittle material at low confining pressures --more likely with lower temperatures and pressures, harder rock types, more rapid deformation, and tensional rather than compressive forces

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Strength

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-Ability of an object to resist deformation -Compressive or tensile

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Folding of Rocks is influenced by?

answer

the type of rock and the compressive forces

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Ductile deformation causes ____?

answer

folding

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Folds -

answer

-common form of deformation observed in layered rocks. -occurs when an originally planar structure, such as a sedimentary berm is bent into a curved structure. the bending can be produced by either horizontally or vertically directed forces in the crust. -come in all sizes -the bending can be gentle or severe, depending on the magnitude of the applied forces, the length of time they were applied, and the resistance of the rocks to deformation -caused by compression - permanent, plastic deformation.

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the two sides of a fold are called its

answer

limbs

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axial plane

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is an imaginary surfaces that divides a fold as symmetrically as possible, with one limb on either side of the plane.

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Symmetrical folds -

answer

vertical axial planes with limbs dipping symmetrically away from the axis, and a horizontal fold axis

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five types of folds:

answer

anticline and syncline and plunging folds and monocline and overturned folds

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fold axis

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the line made by the lengthwise intersection of the axial plane with the rock layers

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Asymmetrical folds -

answer

-folds don't remain symmetrical always. -if they have one limb that dips more steeply than the other it is asymmetrical. -these have inclined axial planes -occurs when the direction of the deformation forces is oblique to the layering of the beds. -these are common

question

Plunging folds

answer

folds rarely stay horizontal, so if the fold dies out or appears to plunge into the ground. if a folds axis is not horizontal it is called a plunging fold with a dipping axis.

question

Overturned Folds

answer

when the deformation is so intense that one limb has been tilted beyond the vertical it is called an overturned fault -both limbs dip the same direction, but the older layers in the bottom limb is precisely the reverse of their original sequence, aka-- older rocks are on top of younger rocks

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anticline

answer

up-arched fold (oldest strata in middle).

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syncline

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down-arched fold into troughs (youngest strata in middle).

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Monocline -

answer

a bend in flat or uniformly dipping layers.

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ex of monoclines:

answer

-San Rafael Mountain, Utah monocline -Roxborough State Park

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Domes -

answer

circular anticlines

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Basins -

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circular synclines

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Most of world's petroleum and natural gas production comes from ____?

answer

anticlinal traps.

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Joints

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a type of fracture -a crack along which there has been no appreciable movement -found in almost every outcrop, and they create surfaces that are more vulnerable to weathering.

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Brittle Deformation causes ___?

answer

faults

question

faults

answer

fractures with movement along fracture (fault plane).

question

measure the orientation of a fault how?

answer

by its strike and dip

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the movement of the block of rock on one side of the fault with respect to that on the other side can be described by a ____ _____ and by the _____ ______, or _____

answer

slip direction and by the total displacement, or offset

question

faults are classified by their

answer

slip direction

question

dip-slip fault

answer

-is one on which there has been relative movement of blocks of rock up or down the dip of the fault plane -caused by compressive or tensional forces

question

oblique-slip fault

answer

when blocks of rock move along the strike and simultaneously up or down the dip -caused by shearing in combination with either compression or tension

question

Strike-slip faults-

answer

shear, slide sideways. -a fault on which the movement has been horizontal, parallel to the strike of the plane -caused by shearing forces

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oblique-sip, strike-slip, and dip-slip require further classification because

answer

the movement can be up or down or right of left. To describe these movement, geologists call the block of rock above a dipping fault plane the handing wall and the block of rock below it the foot wall

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hanging wall

answer

the block of rock above a dipping fault plane

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foot wall

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the block of rock below a dipping fault plane

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a dip-slip fault is called a _____ if the rock's hanging wall moves downward relative to the foot wall, extending the structure horizontally

answer

normal fault

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a dip-slip fault is called a ______ if the hanging wall moves upward relative to the foot wall, causing a shortening of the structure

answer

reverse fault

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a _____ is a low-angled reverse fault, that is, one with a dip of less than 45 degrees, so the movement is more horizontal than vertical

answer

thrust fault

question

when subjected to horizontal compression, brittle rocks of the continental crust usually break along thrust faults with dips of about ____ degrees or less, rather than along more _____ dipping reverse fault

answer

30 degrees; steeply dipping

question

fault types

answer

normal, reverse, strike-slip, thrust

question

Normal faults

answer

- extension, hanging wall down.

question

Reverse faults

answer

compression, hanging wall up

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ex of reverse fault

answer

Lewis thrust fault in Glacier National Park

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two types of strike-slip faults

answer

Left-lateral - opposite block moves left. Right-lateral - opposite block moves right (San Andreas fault).

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scarp

answer

a fault may form this, it is a cliff that marks the position where the fault surface intersects the ground surface.

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a fault must be _____ than the youngest rock its cuts and ____ than the oldest disrupted formation that covers it

answer

1.younger 2. older

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An up-arched fold with the oldest strata in the middle is:

answer

anticline

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The dip of a layer in a geologic formation can vary between ___________.

answer

0-90 degrees

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Continents are made and deformed by

answer

plate tectonic processes

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Continental rocks are generally older ____

answer

than oceanic rocks

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Lithosphere floats on a viscous layer below the continents, known as the ____, within the Earth's mantle

answer

asthenosphere

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Continental shields and platforms make up the most ____ parts of the continental lithosphere, called ___, and contain the eroded remnants of ancient deformed rocks.

answer

stable, cratons

question

Around these cartons are ______ ____ ___ that were formed by later episodes of ______ deformation. The youngest orogenic, such as the ___ ____ ____, are found along the ____ margins of continents, where tectonic activity caused by relative plate movement continues to deform the continental curst.

answer

elongated mountain belts, compressive deformation, North American Cordillera, active margins

question

the ____ margins of continents--- those that are attached to oceanic crust as part of the same plate and thus not near plate boundaries-- are zones of ___ crust, ___ during the rifting the broke older continents apart and initiated ____ ____. This rifting often occurred along older mountain belts such as the _____ ____ ___

answer

passive, extended, stretching, seafloor spreading, Appalachian fold belt

question

ex of craton

answer

the North American crayon, comprises the Canadian Shield and the interior platform

question

continental components:

answer

Stable cratons: - Shields - Platforms • Folded mountain belts (orogens)

question

Formation of cratons

answer

-formed in the Archean by the accretion of smaller rafts of lithosphere -the first continental crust with long-term stability began to form around 3.3 to 3.0 billion years ago. -In North America, the oldest surviving example is the central Slave province in northwestern Canada where the Acasta gneiss is founds. - granite-greenstone terrains - high-grade metamorphic terrains

question

microbes

answer

single-celled microorganism were flourishing 3.5 billion years ago. They must have been composed of carbon-rich compounds, and they must have contained genes- molecules with instructions for growth and reproduction.

question

stromatolites

answer

rocks with distinctive thin layers formed by microbial communities as matted sheets and domes in lakes and tidal flats. -some of the best evidence for life in the early Archean comes from stromatolites -common in Precambrian continental cratons and have been identified in sedimentary rocks of early Archean age.

question

all major groups of animals on earth today originated in the beginning of the ____ eon, the _____ era, and the early _____ period during a rapid evolutionary radiation called the _____ _____

answer

Phanerozoic eon, Paleozoic era, Cambrian period, Cambrian explosion

question

Continental Shields

answer

Central, oldest rocks in continents (up to 3.96 byo) • Low elevation and relatively flat • "Crystalline basement" metamorphic and igneous rocks • once tectonically active

question

Canadian Shield

answer

- oldest rocks of N. America

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Stable Platforms

answer

• Shields covered with horizontal sedimentary rocks • Sandstones, limestones, and shales deposited in ancient shallow seas

question

How Continents Grow

answer

Magmatic differentiation Continental accretion Accretion of island arcs Accretion of continental fragments Accretion along transform faults Accretion by continental collision/rifting

question

Magmatic differentiation (addition):

answer

-the process of magmatic differentiation of low-density, silica rich magma in Earth's mantle and vertical transport of this buoyant, felsic material from the mantle to the crust is called magmatic addition. -most new continental crust is born in subduction zones from magmas formed by fluid-induced melting of the subducting lithospheric slab and the mantle wedge above the slab. These magmas, which are of basaltic to andesitic composition, migrate toward the surface, pooling in magma chambers near the ace of the crust.

question

accretion

answer

the integration of crustal material previously differentiated from mantle material into continual massed by horizontal transport during plate movement. examples: on the active margins of North America.

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Continental accretion:

answer

buoyant fragments of crust attached to continents as the result of plate motions - amalgamation or accretion of terranes - exotic terranes (seem out-of-place)

question

The volume of the continents has increased by about ____

answer

2 km3/year for the past 4 Ga

question

Accretion of island arcs

answer

time 1: a plate carrying a continent subducts beneath an oceanic island arc time 2: the continental crust is more buoyant than the subducting lithosphere and is not subducted with it time 3: the island arc crust becomes welded to the island continent

question

Accretion of continental fragments

answer

time 1: a buoyant oceanic or continental fragment is carried into a plate collision zone time 2: the fragment is more buoyant than the subducting lithosphere time 3: the fragment becomes welded to the overriding plate

question

Accretion along transform faults

answer

time 1: two plates slide past each other along a transform fault time 2: a terrane fragment on plate B is carried along the margin of plate A time 3: when the fault becomes inactive, the fragment becomes welded to plate A in a position distant from its original position

question

Accretion by continental collision/rifting

answer

time 1: a plate carrying a continent sub ducts beneath another continental plate time 2: the continent is not subducted, so two continents are welded together along a set of trust faults time 3: later, rifting and seafloor spreading carry the continental plates apart, leaving a fragment of one continent welded to the other

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Orogeny

answer

-A general term for mountain-building processes • Folding and thrusting of rock layers • Often accompanied by magmatic activity and metamorphism -most periods of mountain building resulted from plate convergence

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the ____-____ ___. the breakup of Pangaea sent Africa, Arabia, and India northward, causing the ___ Ocean to close as its lithosphere was subducted beneath _____. The ____, are the most spectacular result of ____-____ collision. They were firmed from overthrust slices of the old northern portion of ____ stacked one atop the other. The horizontal compression and formation of fold and thrust belts also thickened the crust north of ___, causing the uplift of the huge ___ ___, which now has a crustal thickness of 60 to 70 km. Further compression has pushed China and Mongolia ___, out of ___ way. Most of this sideways movement has taken place along the major ___-___ faults. The mountains, plateaus, faults, and great earthquakes of ____, extending thousands of kilometers from the ___-____ suture, are all results of the ___-___ orogeny

answer

Alpine-Himalayan Belt, Tethys Ocean, Eurasia, Himalayas, continent-continent collision, India, India, Tibetan Plateau, eastward, India's ways, strike-slip faults, Asia, Indian-Eurasian suture, Alpine-Himalayan Orogeny

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MOUNTAINS are located at ____ and _____

answer

hot spots and plate boundaries

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Hot Spots

answer

- Mid plate - Hawaii - Plate boundary - Iceland

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Divergent boundaries

answer

--Oceanic spreading centers - world's longest mountain ranges. - Continental rifts - E. African Rift, Basin & Range - US -the narrow belts of shallow earthquakes that run through ocean basins coincide with mid ocean ride crests and their offsets on transform faults. ****Tensional forces at divergent boundaries cause normal faulting

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transform fault boundaries

answer

earthquake activity is even greater along the transform-fault boundaries that offset mid-ocean ridge segments -these earthquakes have strike-slip fault mechanisms, just as one would elect where plates slide past each other in opposite directions. -for earthquakes along these transform faults, the slip direction indicated by the fault mechanisms is left-lateral where the ridge crest steps right and right-lateral where it steps left. These directions are the opposite of what would be needed to create the offsets of the ridge crest but are consistent with the direction of slip predicted by seafloor spreading

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Convergent boundaries

answer

--Ocean - ocean boundaries - Island arcs - Japan, Philippines, Carolina slate belt. --Ocean - continent boundaries. Volcanic arc - Andes. --Continent - continent collision - Himalayan Mountains & Tibet plateau. Appalachian Mountains. ***worlds largest earthquakes, such as the Tohuko -fault mechanisms were caused by horizontal compression along megathrusts, the huge thrust faults that form the boundaries where one plate is subducted beneath another. Generates deadly tsunamis -ruptures of descending plates in subduction zones causes Earth's deepest earthquakes

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intraplate earthquakes

answer

a small percentage of global seismic activity originates within plate interiors. the foci of there are relatively shallow, and most occur on continents. ex: New Madrid Missouri, The Charleston, SC, and the Cape Ann, near Boston, Massachusetts. -many occur on old faults that were once part of ancient plate boundaries. these faults no longer form plate boundaries but remain zones of crustal weakness that concentrate and release intraplate stresses. ex: one of the deadliest intraplate earthquakes occurred near Bhuj in the state of Gujarat, in western India

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a fault system

answer

the zone of deformation between two moving plates is usually made up of a network of interacting faults -fault system in So Cal is an example

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TORRES DEL PAINE (Patagonia), 4000ft,1300.

answer

The door to the ANDES

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OJOS DEL SALADO (CHILE):

answer

At 6885 m, this is the world's highest active volcano, although the edifice itself is not large -- its basement is at about 4500 m

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HUASCARAN (Peru): (22,204 feet, 6,768 m),

answer

The highest point in the Cordillera Blanca. In 1962 a hanging glacier broke from the mountain's northern flank, killing 6,000 people in the village of Ranrahirca

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CHIMBORAZO (ECU): 20,700', 6310 m.

answer

The summit of Chimborazo constitutes the furthest point from the center of the Earth because of the high elevation, the location of the mountain at the equator and the oblateness of the Earth

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The Wilson Cycle

answer

1. rifting during the breakup of a supercontinent 2. passive margin cooling and sediment accumulation during seafloor spreading and ocean opening 3. active margin volcanism and terrain accretion during subduction and ocean closure 4. orogen during the continent-continent collision that forms the next supercontinent

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What mountain chain runs along the eastern margin of North America?

answer

B) the Appalachians

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SOUTHERN APPALACHIANS AND THE GROWTH OF THE CONTINENTS

answer

• Wilson Cycle • Continental accretion • Arc - continent collision • Continental collision • Continental rifting • Failed rifts • CAMP volcanics

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Appalachians extend from ____ to ______

answer

Alabama to Newfoundland.

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The Carolina Piedmont is made of

answer

Island arc rocks accreted to North America

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continents are made up of:

answer

A. Ancient granitic cratons B. Island arcs accreted to the edges of the cratons C. Exotic terranes (microplates) D. All of the above Answer: D, all of the above

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Earthquakes

answer

are vibrations of the Earth caused by the sudden release of energy as rocks move along fractures or faults.

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Earthquakes occur when

answer

brittle rocks being stressed suddenly break along faults

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most large earthquakes are caused by ruptures of ____ faults, where past earthquakes have already weakened the rocks on the fault surface. The two blocks of rock on either side of the fault slip sudden, releasing energy in the form of ____ ___, which we feel as the ground shaking. When the fault slips, the stress is ____, dropping to a value ____ the rock strength. After the earthquake, the stress begins to ___ again, eventually leading to another large earthquake. The faults involved in this repeated cycle are called _____ faults, and they are concentrated in the zones that form ___ ____, where most of the stress and strain caused by plate movement is concentrated

answer

preexisting faults, seismic waves, reduced, below, increase, active, plate boundaries

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Elastic Rebound:

answer

Explains Why Earthquakes Occur on active faults in Earth's crusts -stressed rocks are strained elastically (by elastically, we mean that the blocks would spring back and return to their undeformed, stress-free shape if the fault were suddenly to unlock), so that when a fault breaks, the rocks on either side of the fault returnn to their uniformed, stress-free shape

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what is Elastic rebound?

answer

return of rocks to original shape after an earthquake

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ELASTIC REBOUND THEORY

answer

-Energy is stored in rocks as they bend. -When rock strength is exceeded, they break and snap back or "rebound" = earthquake. -some of this elastic energy is radiated as seismic waves, which can cause violent shaking many kilometers away -implies that there should be a periodic buildup and release of elastic energy at faults. --however, most active faults, including the San Andreas, rarely exhibit this simple behavior. For instance, all of the strain accumulated since the last earthquake may not be released in the next, that is, the rebound may be incomplete, or the stress on one fault may change because of earthquakes on nearby faults. this irregularity is one reason why earthquakes are so difficult to predict

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Seismic waves 3 types:

answer

Body waves: -Primary-Pressure Waves (P-Waves) -Secondary-Shear Waves (S-Waves) Surface Waves: -Rayleigh waves -Love waves

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focus

answer

the point at which fault slipping begins

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epicenter

answer

is the geographic point on Earth's surface directly above the focus

question

the focal depth of most earthquakes occurring in continental crust range from about __ to __ km

answer

2 to 20 km

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continental earthquakes below __ km are rare, because under the ___ temperatures and pressures found at those ____ depths, continental crust behaves as ____ rather than a ____ material.

answer

20 km, high, greater, ductile, brittle material

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in subduction zones, where ___ oceanic lithosphere plunges into the mantle, earthquakes can originate at depths greater than ___ km.

answer

cold, 600 km

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the longer the fault ____, the greater the fault ___

answer

rupture, slip

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Fault Slip -

answer

the amount of ground displacement in an earthquake

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aftershocks

answer

almost all large earthquakes trigger smaller earthquakes called aftershocks. they follow the mainshock, and their foci are distributed in and around the rupture plane of the mainshock. -aftershock sequences can't be described by the simple elastic rebound theory -although fault slipping during mainshock decreases the stress along most of the rupture surface it can increase the stress on parts of the fault surface that did not slip or where the slip was incomplete, as well as in the surrounding regions. -they occur where that stress exceeds the rock strength

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foreshock

answer

is a small earthquake that occurs near but before a mainshock. -One or more foreshocks have proceeded many large earthquakes.

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P-waves (Primary waves)

answer

- fastest, compressional, like sound waves, can travel through solid, liquid, or gaseous materials. -"push pull waves"- they push or pull particles of matter in the direction of their path of travel

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S-waves (Secondary waves)

answer

- shear waves, can not travel through liquids or gases, only solid materials, half the speed velocity of P waves. -shear waves that displace material at right angles to their path of travel.

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Surface waves

answer

-last waves to come, slow -travel around Earth's surface -damage structures Rayleigh waves - like water waves Love waves - shear waves

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fault mechanism

answer

the pattern of ground shaking also depends on the orientation of the fault rupture and the direction of slipping, which together specify the fault mechanism of an earthquake. -the fault mechanism tells us whether the rupture was on a strike-slip fault, normal, or reverse fault. it also tells us whether the motion was right-lateral or left-lateral.

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SEISMOLOGY

answer

the study of earthquakes

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Seismograph

answer

-instrument that records and measures earthquake vibrations.

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A seismogram

answer

shows the varying amplitude of ground oscillations beneath the seismograph Determine time, location, and magnitude

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Locating Earthquakes

answer

-Seismic waves from an earthquake move out concentrically from the focus and arrive at distant seismographic stations at different times. -At least 3 recording stations are necessary to determine the location of an epicenter

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How to locate earthquakes:

answer

-Use P & S wave arrival times to calculate distance -With 3 seismograph stations, locate epicenter (place on earth's surface above the focus or hypocenter).

question

Which set(s) of waves is/are most likely surface waves?

answer

set C

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Intensity

answer

is a measure of the damage done by an earthquake.

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Mercalli Scale:

answer

I X (Not felt) (Damage total) Small Large earthquake Far Near Deep Shallow Well-built Poorly built structures Bed rock Alluvium or mud

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Magnitude

answer

the amount of energy released by an earthquake. -earthquakes magnitude is the main factor that determines the intensity of the seismic waves it produces and thus the earthquake's potential destructiveness

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Richter Magnitude Scale

answer

-two earthquakes at the same distance from a seismograph differ by one magnitude if the size of their ground motions differ by a factor of 10 -the ground movement of an earthquake of magnitude 6, therefore, is 10 times that of an earthquake of magnitude 5 -a magnitude 7 earthquake produces ground motions that are 100 times greater than those of a magnitude 5 earthquake. -the energy released as seismic waves increases even more strongly with earthquake magnitude, by a factor of about 32 for each Richter unit. -A magnitude 7 earthquake released 32 x 32, or about 1000, times the energy of a magnitude 5 earthquake. Logarithmic scale: -Amplitude of magnitude 6 wave is 10 X larger than a magnitude 5. -Energy released by a magnitude 6 is 30 X larger than by magnitude 5. -So seismic waves of magnitude 6 are 100 X larger than magnitude 4 waves and 900 X more powerful.

question

moment magnitude

answer

the seismic moment of an earthquake is defined as a number proportional to the product of the area of faulting and the average fault slip. the corresponding moment magnitude increases by about one unit for every 10-fold increase in the area of faulting.

question

____ earthquakes occur less often than ____ ones. The number of quakes per year decreases by a factor of ___ with each magnitude unit.

answer

large, smaller, 10

question

intensity scales

answer

used for estimating the intensity of shaking directly from an earthquake's destructive effects. Scale most used today is called the modified Mercalli intensity scale

question

Largest earthquake measured was a magnitude of?

answer

9.5- Chile

question

Most earthquakes occur at

answer

plate boundaries

question

the largest earthquakes occur at

answer

convergent boundaries

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Earthquakes outline ?

answer

tectonic plates

question

San Francisco, 1906

answer

-18 April 1906, Magnitude 8.3 ->700 fatalities, San Andreas Fault

question

Tohoku (Japan), 2011

answer

-11 March 2011 -Magnitude 9.0 -$309 billion in damage -15,700 fatalities, 4,670 missing -Subduction zone

question

Two of the largest "intraplate" (away from plate boundaries) earthquakes:

answer

-New Madrid, Missouri, 1811-1812 -Charleston, South Carolina, August 31, 1886 - largest reported earthquake in the eastern U.S.

question

Charleston, South Carolina, August 31, 1886 Charleston intraplate earthquake produced

answer

-Damage all over the eastern US. "sand blows" volcanoes and fissures. Can be used to identify paleo-earthquakes.

question

Destructive effects of earthquakes

answer

Ground shaking: -Structures built on solid bedrock suffer less damage. -Structures on soft wet mud or sand suffer most. Ground may behave like liquid = liquifaction. -Adobe and mud-walled structures - weakest. -Steel and wood frame structures flexible and strong. Fire: -Earthquakes break electric, gas, and water lines. Tsunami: -Seismic sea waves - "Tidal Waves" -Travel at several hundred km/hr in open ocean. -Wave height ~ 1 meter -Wave length - several hundred kilometers -Slow down and pile up at shorelines Ground Failure: -Landslides and liquifaction

question

seismic hazard

answer

describes the frequency and intensity of earthquake shaking and ground disruption that can be expected over the ling term at some specified location.

question

seismic risk

answer

describes the damage that can be expected over the long term in a specified region, such as a country or state, usually measured in terms of casualties and dollar losses per year

question

Earthquake Prediction

answer

-Seismic risk maps - based on distribution and intensity of past earthquakes. -Long-range prediction - regulate zoning and building codes - saves lives and money-- emergency response (plan ahead and have emergency supplies, rescue teams, evacuation procedures) -Short-term prediction --Precursor earthquakes --Land deformation --Water level in wells --Magnetic field --Electrical resistance of ground --Animal behavior --Radon gas --Low frequency radio waves **Very few successful short-term predictions have been made.

question

recurrence interval

answer

the time required to accumulate the strain that will be released by fault slipping in a future earthquake-- can be calculated from the rate of relative plate movement and the expected fault slip, as estimated from the displacements observed in past earthquakes

question

The size of a magnitude 8 earthquake is how much larger than that of a magnitude 6 earthquake?

answer

C) 100x

question

Earthquakes that originate at depths greater than 100 km are associated with ______ plate boundaries.

answer

convergent

question

Structures built on what suffer the most damage in an earthquake?

answer

Wet mud or sand

question

The center of the Earth is about ___ km below us ... the deepest well is

answer

6,400; < 15 km.

question

Heat inside the Earth drives the _______ and ______

answer

the core's geodynamo and the mantle convection.

question

Earth's interior is explored by using information from _____ and their passage through the body of the Earth

answer

seismic waves

question

the travel times and paths of P and S waves an be used to contrast models of Earth's ____ ____

answer

internal layers

question

P- wave shadow zone

answer

between 105 degrees and 142 degrees

question

S-wave shadow zone

answer

extends from 105 degrees to 180 degrees

question

the absence of ____ waves on seismograms recorded at large distances from earthquake foci revealed the ___ state of Earth's core

answer

shear, liquid

question

seismologists have used seismic waves reflected by sharp boundaries between Earth's layers to estimate the ___ of the boundaries

answer

depths

question

seismic waves can also be used to probe the ___ parts of Earth's crust. this technique, called ___ ___, has a number of practical applications. Seismic waves generated by artificial sources, such as dynamite explosions, are reflected by _____ ____ at ____ depths in the crust. Recording these reflections has proved to be the most successful method for finding deeply buried ____ and ___ ____. Reflected seismic waves are also used to measure the depth of water tables and the thickness of ____. As sea, ___ waves can be generated, and oceanographic sips routinely use the underwater sound they produce the measure the depth of the ocean and the thickness of sediments on the seafloor

answer

shallow, seismic profiling, geologic structures, shallow depths, oil and gas reservoirs, compressional waves

question

Seismic velocity depends on

answer

the type of material (composition), temperature, and pressure

question

When waves move from one type of material to another, they change ___ and ____

answer

speed and direction

question

The Fish Bowl Experiment

answer

a way to show how seismic waves move to help explain Earth's interior

question

How do we know about the interior of earth?

answer

-Deep Drilling -Seismic Waves --Waves move out in a sphere from the source. --Seismic waves are refracted (bent) like light from air to water. --Waves are reflected. Useful for exploration.

question

How do waves move in the Interior of the Earth?

answer

-Waves move out in a sphere from the source. -Seismic waves are refracted (bent) like light from air to water. -Waves are reflected. Useful for exploration. -Primary wave (P-wave) = pressure -Secondary wave (S-wave) = shear. Can not travel in liquids.

question

Earth's Core causes shadow zones for?

answer

1. P-waves between 2. S-waves because outer core is liquid.

question

Inner Core is

answer

solid

question

Density of core

answer

10-13 g/cm3

question

Core is made up mostly of

answer

Core is mostly iron - (based on density and meteorites) with some nickel (inner core) & sulfur (outer core).

question

Temperature Increases with Depth:

answer

The Geotherm Curve

question

Average geothermal gradient:

answer

20 - 30°C/km

question

Seismic Tomography Uses Travel Times to Create 3-D Images of Earth's Interior

answer

reveals hot and cold rocks because seismic waves slow down in hot rocks

question

upper continental crust

answer

felsic rocks (granite): 6 km/s = rough values for P-wave velocities in igneous rocks

question

upper mantle

answer

ultramafic rocks (peridotite): 8 km/s

question

oceanic crust or the lower continental crust

answer

mafic rocks (gabbro): 7 km/s

question

Seismic date show that Earth's crust is thin (about __ km) under ____, thicker (about __ km) under the ____, ___ ____ ____, and thickest (as must as ___km) under ___ ___

answer

-7 km, under oceans -33 km, under the stable, flat-lying continents 70 km, under high mountains

question

CRUST/MANTLE BOUNDARY =

answer

"MOHO" (Mohorovicic) -composed primarily peridotite, composed of olivine and pyroxene -the layering of the upper mantle is caused by the effects of increasing pressure and temperature on peridotite

question

2 types of Crust (6.75 km/s) how many kilometers deep and what are they made up of?

answer

-Continent (35 km, granodiorite) -Ocean (7 km, basalt/gabbro)

question

Mantle how many kilometers deep and what is it made up of?

answer

(8 km/s)(peridotite)

question

ASTHENOSPHERE

answer

part of mantle -because partial melting allows peridotite to flow more easily, geologists identified the LVZ with the top part of the asthenosphere Discovered by Low Velocity Zone (LVZ) Weak, partially molten 75-250 km deep.

question

LITHOSPHERE

answer

-Rigid plates -Includes crust & upper mantle 75 - 150 km thick -mantle, just below the MOHO, is cold. It is part of the lithosphere like the crust. -lithosphere on average is about 100 km, highly variable though, ranging from about no thickness near spreading centers, to over 200 km beneath the cold, stable continent cratons

question

transition zone

answer

-about 400 km below the surface, S-wave velocity increased by about 10 percent within a narrow zone less than 20 km thick. -This jump in S-wave velocity can be explained by a phase change in olivine, the major mineral constituent of the upper mantle, whose ordinary crystal structure is transformed into a denser, more closely packed structure at high pressures. -in the region from 410 to 660 km below the surface, mantle properties change slowly as depth increases. -near 660 km, the S-wave velocity abruptly increases again, indicating a second major phase change in olivine to an even more closely packed crystalline structure. -because it contains two major phase changes, the layer between 400 and 700 km is called the transition zone.

question

lower mantle

answer

--Below the transition zone, the seismic wave velocities increase gradually and do not show any more unusual features until close to the core-mantle boundary. This relatively homogenous region, more than 2000 km thick, is called the lower mantle

question

core/mantle boundary

answer

-about 2890 km below the surface, we encounter the most extreme change in properties. -here the material changes abruptly from a solid silicate rock to a liquid iron alloy. -because of the loss of rigidity, the S-wave velocity drops from about 7.5 km/s to 0 and the P-wave velocity drops from more than 13 km/s to about 8 km/s, causing the core shadow zones -density, increases by about 4.5 g/cm^3 -this large density difference, keeps the core-mantle boundary very flat and prevents any large-scale mixing of the mantle and core -heat conducted out of the core increases the temperatures at the base of the mantle as much as 1000 degrees C -some geologists believe this hot region to be the source of mantle plumes that rise all the way to Earth's surface, creating hot spots

question

KIMBERLITE PIPES

answer

Peridotite - inclusions from mantle Coesite - high pressure quartz - less than 300 km depth. Diamonds - high pressure carbon - more than 100 km depth. Diamonds - high pressure carbon - more than 100 km depth.

question

HEAT FLOW

answer

Most of Earth's heat is generated by radioactive decay. The Earth is cooling off.

question

GRAVITY

answer

Newton: Force of gravitational attraction (F) between 2 masses (m1 and m2) is proportional to the products of their mass and inversely proportional to the square of the distance (D) between their centers of mass: F = G (m1 x m2) / D2 where G = gravity constant

question

Isostasy

answer

Deflection of plumb line in India survey less than expected Because Himalayas have a "low density root" - The mountains float like icebergs = isostasy.

question

Low Density Root

answer

In fact, continental crust under the Himalayas, Tibet, and the Altiplano can be up to 70 km thick

question

FLEXURE

answer

But lithosphere has elastic strength (like ice on a frozen lake) so it bends (flexure) under the weight of the mountains. Isostasy is regional.

question

ISOSTATIC REBOUND:

answer

Continents rebound after the ice sheets melt. Up to 300 m in 10,000 years.

question

Gravity used for mineral and Gas Exploration

answer

Mining - valuable minerals associated with high density igneous rocks Oil Exploration - oil found with low density salt domes

question

Earth's Magnetic Field

answer

is like the field that would be produced by a giant bar magnet placed at the Earth's center -Earth has a dipole (N&S poles) magnetic field. -Field produced by convective electrical currents in the outer core at core/mantle boundary. --Inclination = deviation from horizontal. --Declination = angle between geographic N & magnetic N.

question

Northern Lights are produced by

answer

the interaction of solar radiation and the Earth's magnetic field

question

Magnetization

answer

-When hot magma cools below Curie temperature, magnetic minerals (magnetite) are frozen in the direction of the earth's field. -Magnetic minerals in sediments line up with the earth's field.

question

When magnetic field weakens ....?

answer

it may reverse

question

Magnetometers

answer

can be used to detect magnetic ore bodies.

question

What does NOT hold up mountain belts?

answer

high density "roots"

question

Which layer in the Earth does not transmit S waves?

answer

outer core

question

Where is the Earth's magnetic field produced?

answer

the liquid outer core

question

Seismic tomography can detect relatively warm regions of the mantle because seismic waves?

answer

Travel more slowly through these regions

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