Geologic Time – Chapter 18 – Flashcards
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_________; placing rocks and events in their proper sequence of formation
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Relative age dates
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Relative age dates -Before the discovery of __________, geologist in the late 1700s through the early 1900s were able to construct the geologic time scale by rock characteristics.
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Radioactive
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_________: specifying the actual number of years that have passed since an event occurred
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Absolute age dates
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Absolute age dates -After the discovery of __________, geologists were able to assign numeric ages to the geologic time scale
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Radioactivity
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______________: in a sequence of sedimentary rock layers, the OLDEST ROCKS ARE ON THE BOTTOM, and they get progressively YOUNGER AS YOU GO TOWARDS THE TOP.
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Law of superposition
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_____________: fossil organisms that are preserved int he rocks SUCCEED ONE ANOTHER IN A DEFINITE AND DETERMINABLE ORDER, so that any time period can be recognized by its fossil content.
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Principle of Fossil Succession
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What are the five layers of rock from oldest to youngest
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Supai Group - Hermit Shale - Coconino Sandstone - Toroweap Formation - Kaibab Limestone
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What are some examples of principles of relative dating? (4)
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-Principle of original horizontality -Principle of cross-cutting relationships - Inclusions -Unconformity
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Principles of Relative Dating -____________ - Layers of sediment are generally deposited in a horizontal position. Rock layers that are flat have not been disturbed
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principle of original horizontality
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Principles of Relative Dating - ____________ - Younger features cut across older feature. These include features such as igneous intrusions (large or small) and faults
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Principle of cross-cutting relationships
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Principles of Relative Dating -__________ - is a piece of rock that is enclosed within another rock. Rock containing this is younger
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Inclusions
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Principles of Relative Dating -__________ - Is a break in the rock record produced by exposure and erosion and/or non deposition of rock units
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Unconformity
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What are the three types of Unconformities?
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-Disconformity -Nonconformity -Angular Unconformity
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Type of Unconformities ___________: An erosional surface separating TWO UNITS OF LAYERED SEDIMENTARY ROCKS
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Disconformity
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Type of Unconformities _____________: an erosional surface separating IGNEOUS OR METAMORPHIC ROCKS BELOW and SEDIMENTARY ROCKS ABOVE
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Nonconformity
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Type of Unconformities ___________: An erosional surface separating TILTED OR FOLDED SEDIMENTARY ROCKS BELOW and FLAT-LYING SEDIMENTARY ROCKS ABOVE
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Angular Unconformity
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____________ defines the inner gorge boundary of the Grand Canyon. Schists below the ____________ are metamorphic rocks, while those above are sedimentary rocks.
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Nonconformity
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There is ____________ in the Black Canyon of the Gunnison National Park with igneous and metamorphic rocks above, and substantially younger sedimentary rocks above
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Nonconformity
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Ma=_________ Years (Mega-anna) Ga=_________ years (Giga-anna)
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-Million Years -Billion Years
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There is _________ __________ at Siccar Point, Scotland with VERY steeply tilted rocks below and relatively flat-lying sedimentary rocks above
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Angular Unconformity
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There is ____________ in Zion National Park, Utah. Between each dune set there is an erosional surface, signifying a gap in time between depositions
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Disconformities
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Rocks are deposited horizontally. This is example of?
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Formation of an Angular Unconformity
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Rocks are folded or tilted. This is example of?
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Formation of an Angular Unconformity
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Folded rocks are eroded. This is example of?
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Formation of an Angular Unconformity
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New rocks are deposited horizontally on top of folded rocks. This is example of?
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Formation of an Angular Unconformity
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-_______-the remains or traces of prehistoric life
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Fossil
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The remains of relatively recent organisms (teeth, bones, shells, etc.) This is an example of?
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Types of fossils
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Entire animal, flesh included may be preserved, but are very rare - Frozen mammoths in Alaska and Siberia - Even human fossils (otzi) This is an example of?
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Types of fossils
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Types of fossils: -Given enough time, remains may be _________ (literally "turned into stone") - Original bone, wheel teeth, even wood gets replaced with minerals from the surrounding rock (usual silica)
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Petrified
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What are some TYPES OF FOSSILS?
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-Molds & Casts -Carbonization -Tracks & trails -Burrows & resting placing -Coprolites -Gastroliths
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Types of Fossils: __________: the shape of the organism is preserved in the rock
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Molds & Casts
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Types of Fossils: __________: thin residue of carbon is left
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Carbonization
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Types of Fossils: ______: animal footprints preserved in soft sediments
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Tracks & trails
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Types of Fossils: _______: traces of animal activity in soft sediments
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Burrows & resting placing
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Types of Fossils -________ (fossil poo): - Gives us information about the food habits of organisms
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Coprolites
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Types of Fossils -_______ ("stomack stones") - Dinosaurs INGESTED rocks to help digest food - The dinosaurs' stomachs essentially acted as rock TUMBLERS, rounding and polishing the rocks - The __________ were either passed out of the animal's system, or were left behind after the animal died and decayed
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Gastroliths
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What are two conditions favoring FOSSIL PRESERVATION
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-Rapid burial -possession of hard parts
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Conditions favoring FOSSIL PRESERVATION: -___________: -Scavengers and decomposers cannot destroy the remains -_________: - Shells, bones and teeth are more likely to be preserved than fleshy material
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-Rapid burial -Possession of hard parts
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What are three SPECIAL and UNCOMMON cases for fossil preservation? -_________ (fossilized tree resin) - insects, spiders, and even lizards -_________ - Mammoths, sloths, saber-toothed cats, dire-wolfs -_________-Wooly mammoths, mastodons, Otzi
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-Amber -Tar pits -Ice
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Fossil Correlation - Recall the ________ of ____ ______: -Fossil organisms succeed each other in a DEFINITE and DETERMINABLE order -Any time period can be RECOGNIZED by its fossil content
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Principle of Fossil Succession
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Fossil Correlation -Certain ______ are much better indicators than others - Some fossils span large TIME PERIODS, while others span very short time periods - Some fossils are LOCALIZED in small geographic areas while others are found worldwide - Some fossils span large TIME PERIODS, while other span very SHORT TIME. These are called _________
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-Fossils -index fossil
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What are three examples of INDEX FOSSILS?
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-Inoceramus -Mucrospirifer -Paradozides
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Examples of INDEX FOSSILS -__________: bivalve (clam) genus found world-wide that flourished in the cretaceous (modern bivalves still exist)
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Inoceramus
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Examples of INDEX FOSSILS -___________: brachiopod genus that flourished world-wide in the devonian (modern brachiopods still exist, though rare)
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Mucrospirifer
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Examples of INDEX FOSSILS -__________: trilobite genus found world wide, and flourished in the middle Cambrian (extinct)
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Paradoxides
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-____________: -Index fossils can be used to match rocks of similar ages across different geographic regions. - This process has been used to correlate rock units across continents, supporting the THEORY OF PLATE TECTONICS
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Correlation of rock layers
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-__________ - Establishing NUMERICAL AGES for the geologic past - Dates are obtained using RADIOACTIVE ISOTOPES - ATOMIC STRUCTURE
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Absolute Age Dating
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Atomic structure -_________: positively charged particles with mass -_________: neutral particles with mass -_________: negatively charged particles that orbit the nucleus
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-Protons -Neutrons -Electrons
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What are four examples of of ATOMIC STRUCTURE?
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-Atomic Number -Mass Number -Isotope -Radioactivity
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Atomic Structure -__________: - An element's identifying number - Equal to the huber of protons in the atom's nucleus
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Atomic Number
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Atomic Structure -___________: - Sum of the number of protons and neutrons in an atom's nucleus
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Mass number
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Atomic Structure -________: - Variant of an atom - Differs in the number of neutrons - Results in a different mass number that the parent atom
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Isotope
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Atomic Structure -Isotope - ______ _______ - an unstable RADIOACTIVE ISOTOPE - _______ ______ - this isotopes resulting from the decay of a parent
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-Parent isotope -Daughter product
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Atomic Structure -________: - Spontaneous changes (decay) in the structure of unstable atomic nuclei
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Radioactivity
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What are the three types of radioactive decay?
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-Alpha emission - Beta emission -Electron capture
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Types of radioactive decay: -____________ - Emission of 2 protons and 2 neutrons - Mass number is reduced by 4 and the atomic number is lowered by 2 - Common example: U 238 - Th 234
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Alpha emission
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Types of radioactive decay: -_________ - An electron is EJECTED FORM THE NUCLEUS creating a proton - Mass number remains unchanged and the atomic umber increases by 1 - Common example: Pb 214 - Bi 214
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Beta emission
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Types of radioactive decay -_________ - An electron is CAPTURED BY THE NUCLEUS - The electron combines with a proton to form a neutron - Mass number remains unchanged and the atomic number decrease by 1 - Example: K 40
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Electron capture
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________: the time required for one half of the radioactive nuclei in a sample to decay
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Half-life
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Principle of ________ ________ - The percentage of radioactive atoms that decay during one half time is always the ams (50%) -However, the actuarial number of parent atoms that decay continually decreases -Comparing the ratio of parent to daughter isotopes to the number of half lives yields the age of the sample
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Radiometric dating
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Very shot half-life (5730 years) which can be used to date very recent events -70,000 years maximum This is an example of?
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Dating with C14 (radiocarbon dating)
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________ is produced in the upper atmosphere by cosmic ray bombardment
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Carbon -14 (Dating with C14) (radiocarbon dating)
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The C get incorporated in CO2 which is then absorbed by living organisms
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Dating with C14 (radiocarbon dating)
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C14 dating has become an important tool for _______, _______, and ________ who study very recent Earth history
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anthropologist, archeologists, geologist
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-The mineral containing the RADIOACTIVE ISOTOPE must be in a closed system for the entire duration -To avoid potential problems, ONLY FRESH, UNWEATHERED rock samples should be used This is an example of?
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Sources of error
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The _____________- a "calendar" of Earth history
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Geologic time scale
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Subdivides 4.6 billion years of earth's history into units. This is an example of?
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Geologic time scale
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Originally created using relative dates. This is an example of?
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Geologic time scale
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Radiometric dating has allowed us to assign numerical ages to the sequence. This is and example of?
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Geologic time scale
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What are the four names of eons?
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-Phanerozoic -Proterozoic -Archean -Hadean
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Eon- -_________: ("visible life") - the most recent eon, began about 542 million years ago -_________: oxygenation of the atmosphere, first multicellular -_________: oldest know cyanobacteria fossils, photosynthesis begins, first evidence of plate tectonics -_________: the oldest eon, very primitive atmosphere and oceans. Likely highly acidic environmental conditions. Oldest known rock on earth: Acosta Gneiss
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-Phanerozoic -Proterozoic -Archean -Hadean
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_____ - subdivision of an eon
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Era
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What are the three ears of the Phanerozoic eon?
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-Cenozoic -Mesozoic -Paleozoic
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Eras -______: "recent life" Age of mammals, the Era in which we live. -_______: "middle life" Age of the Dinosaurs, end at the cretaceous Paleocene extinction, ends at the Cretaceous-Paleogene extinction (formerly K-T boundary) -_______: "ancient life" Marked by the sudden emergence of a wide variety of life in the fossil record "Cambrian explosion", ends at the Permian Extinction.
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-Cenozoic -Mesozoic -Paleozoic
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Eras are subdivided into __________.
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Periods
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What are the three periods?
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-Cenozoic periods -Mesozoic periods -Paleozoic periods
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Periods -________: - Paleogene and Neogene (formerly Tertiary), and Quaternary
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-Cenozoic periods
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Periods are subdivided into ________
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Epoch
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Paleozoic Era -_________- First tree sized land, plants, first amphibians fishes flourish
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-Devonian
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What are the six Paleozoic Era?
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-Devonian -Silurian -Ordovician -Cambrian -Permian -Pennsylvanian -Mississippian
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Paleozoic Era - 251 Ma: ________-__________ boundary Mass Extinction - 90% of all marine organisms, 70% of terrestrial organisms - Cause is still highly speculative: Meteorite? Volcanoes? Global warming? Combination?
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-Permian-Triassic
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Paleozoic Era -_______: First mammal like reptiles (synapsids) -_______: Extensive swamps, produced massive coal deposits amphibians coal -_______: Gymnosperms (conifers, ginkos, palms, etc.) flourish, amphibians flourish, First reptile
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-Permian -Pennsylvanian -Mississippian
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Mesozoic Era - 65.5 Ma - __________-_________ boundary (formerly K-T) Mass Extinction - 75% (marine?) species - Causes favored include Chicxulub impact and/or massive volcanic climate change (probably cooling)
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Cretaceous-Paleogene
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What are the three characteristics of Mesozoic Era?
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-Cretaceous -Jurassic -Triassic
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Mesozoic Era -__________: First birds, first flowering plants (angiosperms)
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-Cretaceous
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Allosaurus, Brachiosaurus, Archaeopteryx (bird), Stegosaurus, Pterodactyl (no a dinosaur). These are all examples of?
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Jurassic species (Mesozoic Era)
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Ankylosaurus, Triceratops, Utahraptor, Tyrannosaurus rex. These are all examples of?
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Cretaceous Species ( Mesozoic Era)
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What are the three characteristics of the Cenozoic Era?
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-Quaternary -Neogene -Paleogene
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Cenozoic Era -___________: First genus: HOMO in early Pleistocene. Pleistocene glaciations and megafauna (think "Ice Age"). First home sapiens appear about 200,000 yrs ago
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Quaternary
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Cenozoic Era -__________: Mammals continue to flourish, first hominids (family: hominid) appear in the Miocene, some extraordinarily large species - "megafauna"
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Neogene
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Cenozoic Era -__________: Mammals, birds, insects, and flowering plants flourish; reptiles dwindle. First horses, first primates, first whales.
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Paleogene
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Periods -________ starting with the oldest: - Triassic, Jurassic, Cretaceous
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Mesozoic Periods
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Periods -_________ starting with the oldest: - Cambrian, Ordovician, Silurian, Devonian, Mississippian, Pennsylvanian, Permian
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Paleozoic Periods
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Paleoozoic Periods -_________-First land plants, first insects fishes flourish
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Silurian
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-_________-First fishes appear, invertebrates still prevalent
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Ordovician
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__________: First organisms with shells (invertebrates) dominate the oceans trilobites, cephalopods, brachiopods
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Cambrian
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Paleozoic Era -542 Ma: __________ _________ boundary - Marks the beginning of visible life
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Precambrian-Cambrian
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Mesozoic Era -__________: dinosaurs flourish, first birds
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Jurassic (Mesozoic)
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Mesozoic Era -___________: First dinosaurs, first mammals
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Triassic
