Chapter 7 Plate Tectonics

lithospheric plates
lithospheric plates
Large pieces of Earth’s lithosphere moves over athenosphere

continental plates
continental plates
Thick lithosphere plates made of andesite & granite form continents. Less dense than oceanic plates

oceanic plates
oceanic plates
Thin lithosphere plates made of basalt from ocean floor
Denser than continental plates

topographic map
topographic map
a map that shows the surface features of an area

contour line
contour line
A line on a topographic map that connects points of equal elevation

contour interval
contour interval
the difference in elevation from one contour line to the next

plate tectonics
plate tectonics
Theory how piece’s of Earth’s surface moves

tectonic plate
tectonic plate
a piece of the lithosphere that moves around on top of the asthenosphere due to mantle convection currents

plate boundary
plate boundary
Where two tectonic (lithospheric) plates meet

mantle convection currents
mantle convection currents
the transfer of thermal energy by the circulation or movement in Earth Mantle. Believed to be the driving force of plate tectonics.

Continental Drift
Continental Drift
Idea that continents move around on Earth’s surface

Pangaea
Pangaea
ancient huge landmass composed of all the continents joined together. Supercontinent

convergent boundary
convergent boundary
Lithospheric plate boundary where 2 plates come together

subduction
subduction
Process that a lithospheric plate sinks into the mantle

volcano
volcano
a in the Earth’s crust (lithosphere) where magma has come to the surface. Caused by convergent plate boundaries or Hot Spots.

magma
magma
molten (melted) rock beneath the earth’s surface

lava
lava
magma that reaches the earth’s surface

Ocean Trench
Ocean Trench
a long steep-sided depression in the ocean floor caused by one plate sinking below another.

Pacific Ring of Fire
Pacific Ring of Fire
region around the Pacific Ocean where most of the volcanoes and earthquakes on Earth occur regularly

divergent boundary
divergent boundary
A lithospheric plate boundary where 2 plates move apart

sea-floor spreading
sea-floor spreading
new sea floor is created at mid-ocean ridges and continents are pushed apart from each other

Mid-Ocean Ridge
Mid-Ocean Ridge
A long chain of undersea mountains

Rift Valley
Rift Valley
a deep valley that forms where two plates move apart. Caused by a divergent boundary

earthquake
the shaking of earth surface produced by the rapid release of energy in earths crust. Caused plates shifting. Found along all plate boundaries.

seismic waves
seismic waves
wave generated by an earthquake.Primary (first,push/pull), Secondary (side to side), Surface (slowest, destructive)

epicenter
epicenter
The point at which seismic waves first reach the surface.

fault line
fault line
a break or crack in Earth’s surface. Caused by shifting and moving plates.

Alfred Wegener
Alfred Wegener
A German scientist who proposed the theroy of continental drift

Harry Hess
Harry Hess
theory of sea-floor spreading & plate tectonics

tsunami
tsunami
seismic sea wave that begins over an earthquake focus and can be highly destructive when it crashes on shore

convection currents
convection currents
circular movement of a substance due to changes in temperature and density

conduction
conduction
the direct transfer of heat from one substance to another substance that it is touching

hotspot
hotspot
A weak spot in the middle of a tectonic plate where magma surfaces; forms a volcano (ex: Hawaii & Yellowstone)

Mantle Plume
Mantle Plume
Heated lower mantle rock that rise toward lithosphere because it is less dense than surrounding mantle rock

Plate tectonics
Plate tectonics
The theory that explains how large pieces of the lithosphere, called plates, move and change shape.

Tectonic plate
Tectonic plate
(Large movableplates under the Earth’s surface.) part of of the lithosphere (15 plates) that moves around on top of the asthenosphere due to mantle convection currents

Plate boundary
Plate boundary
Where two tectonic (lithospheric) plates meet

Mantle convection currents
Mantle convection currents
The transfer of thermal energy by the circulation or movement in Earth Mantle. Believed to be the driving force of plate tectonics. Hot material (less dense) rises, and cool material (more dense) sinks causing the plates to move above the mantel.

Theory of Continental Drift
Theory of Continental Drift
Wegner thought that millions of years ago Earth’s continents were joined together like a completed jigsaw puzzle. Then, as time passed, some force pulled the puzzle pieces apart. The continents slowly moved to the positions they are in today. Wegner’s idea became know as the Theory of Continental Drift

Pangaea
Pangaea
According to geologists, the earth originally had only one “supercontinent” that drifted apart, subsequently into the 7 continents. Name the “supercontinent

Subduction zone
Subduction zone
A destructive plate margin where oceanic crust is being pushed down into the mantle beneath a second plate

Magma
Magma
molten (melted) rock beneath the earth’s surface, A molten mixture of rock-forming substances, gases, and water from the mantle

Ocean Trench
Ocean Trench
a long steep-sided depression in the ocean floor caused by one plate sinking below another from subduction.

Sea-floor spreading
Sea-floor spreading
When two oceanic plates pull apart, magma rises and new crust is formed on the ocean floor.

Mid-Ocean Ridge
Mid-Ocean Ridge
an underwater mountain chain where new ocean floor is formed. Caused by Divergent Boundary

Rift Valley
Rift Valley
a deep valley that forms where two plates move apart. Caused by a divergent boundary

Divergent boundary
Divergent boundary
A boundary along which two tectonic plates move apart, characterized by either a mid-ocean ridge or a continental rift valley.

List 3 pieces of evidence that support the Theory of Continental Drift
1. similarity of fossils found on continental coasts
2. the close fit of the continental coastlines
3. the matching of glacial grooves on different continents
4. the rocks match

What forms when an oceanic plate is subducted under a continental plate?
An ocean trench and volcanic mountains

What causes the movements of tectonic plates?
Convection currents in Mantle

What happens to the tectonic plates at a divergent plate boundary?
When 2 tectonic plates move away from one another

What happens to tectonic plates at a convergent boundary?
A collision between 2 plates

Earthquake
violent shaking of the earth’s interior, from faults in the earth.

Volcano
the opening in the Earth’s crust that allows magma to reach the earths surface.

Trench
very deep, elongated cavity bordering a continent or an island arc; it forms when one tectonic plate slides beneath another.

Volcanic Island Arc
Island arcs are volcanic islands that form parallel to ocean trenches in subduction zones. The Pacific Ring of Fire is home to many of these groups of islands. Volcanoes that form above hot spots like the Hawaiian islands are not volcanic arcs.

Ring of Fire
a ring of volcanoes around the Pacific Ocean that result from subduction of oceanic plates beneath lighter continental plates.

What do geologists study?
Materials the earth is made of, the processes that shape the earth and its inside.

What is Basalt?
Dense thick rock, that mainly makes up the floors of the oceans.

What is Granite?
Rock that is not as dense as Basalt, and mainly makes up continental crust ?

What is Continental Crust?
part of the earth’s crust that forms the continents mostly granite.

What is Oceanic Crust?
part of the earth’s crust that is under the oceans.

Mantle
The area between the Crust and the Core. The top of the mantle is hot rock, underneath that is an area of soft flowing material, followed by sold mantle material. Its about 3000 km thick.

lithosphere
The crust + the top part of the mantle that is solid hot rock.

asthenosphere
The soft portion of the mantle that is soft and can flow. It is just below the lithosphere.

Core
Center portion of the earth made of nickle and Iron. Has an outer liquid portion and a solid inner portion.

Outer Core
The liquid part of the core.

Inner Core
The inner part of the core that is solid. Intense pressure keeps the nickle and iron solid.

What creates the earth’s magnetic field
The spinning of the earth’s solid inner core

What make’s the inner core spin?
Currents in the outer core.

What is the Core made of?
Iron and Nickle

What is the Mantle made of?
Silicon, Oxygen, Iron and Magnesium

heat transfer
movement of energy from a hot substance to a cold substance.

name the three types of heat transfer
radiation, conduction, convection.

radiation
the transfer of energy through empty space. There is no direct contact between the cold and the hot.

Examples of radiation
Sunlight warming the earth, heat from a fire

conduction
the direct transfer of heat from one substance touching another.

example of conduction
touching a hot spoon

convection
heat transfer from the movement of fluid or gases. Heated fluid flows transferring heat form one part of the liquid to another part of it.

example of convection
A whole pot of water on a stove getting hot, not just the bottom of it

convection current
a flow or current that transfers heat in a liquid

describe sea floor spreading?
At mid ocean ridges, molten rock rises through the crack in the crust, pushing it apart and hardening. This happened over and over adding new sea floor like a conveyor belt.

Where does sea floor spreading happen?
at mid ocean ridges.

What is the evidence for sea floor spreading?
Younger rock is in mid ocean ridges, and rock gets older as you move away from the ridges.

Describe subduction
at a deep ocean trench, the ocean floor sinks down underneath the continental plate. its pushed back down into the mantle where it becomes liquid again. its what happens on the other side form sea floor spreading

Describe plate tectonics
The lithosphere is not unbroken. Its split into plates. The convection currents of the asthenosphere move the plates around where the collide and spread apart and shape the face of the earth

Name the types of plate boundaries
Transform, convergent and divergent

transform boundary
a plate boundary where two plates slide past each other in opposite directions. Crust is neither created or destroyed.

what creates an earthquake
plates slipping against one anther at a transform boundary

divergent boundary
a boundary where two plates move apart. A mid ocean ridge is a divergent boundary, so is a rift valley.

convergent boundary
where two plates come together and converge.

Denser: Oceanic or Continental Crust ?
Oceanic

Why is oceanic crust denser than continental?
Oceanic is Basalt, Continental is Granite. Basalt is denser than granite

Denser: Basalt or Granite?
Basalt

What happens when two plates of oceanic crust collide at a ocean trench?
The denser plate plate dives under the other

What happens two plates of continental crust collide ?
They are too light for subduction to happen. They get squeezed together to make mountain ranges.

What happens when a plate carrying ocean crust and a plate carrying continental crust collide?
Since the ocean crust is heavier, it sinks beneath the continental crust plate.

What is Pangea
the name given to the huge supercontinent that formed when all the continents were connected

What is a constructive force to a geologist?
One that creates land masses.

What is a destructive force to a geologist?
One that destroys land masses

What is a fault ?
a break in the earth’s surface where plates slip past one another.

What is a rift valley?
A divergent boundary on land, where plates spread apart and create a valley that slowly sinks lower and lower. It can eventually fill with water to become a sea or ocean.

The layer of mantle that can flow is called
asthenosphere

where does subduction of the ocean floor take place?
in ocean trenches

What powers plate tectonics (the movement of the plates)?
convection currents in the asthenosphere

Alfred Wegener
the Continental Drift Theory was proposed by-

Theory of Continental Drift
Theory that continents move due to centrifical force

Theory of Plate Tectonics
Theory that plates that move due to convection currents

Alfred Wegener
credited with the theory of Continental Drift

Harry Hess
credited with the theory of Plate Tectonics

sea floor spreading
when two oceanic plates pull apart, magma rises and new crust is formed

convection currents
circular movement of a substance due to changes in temperature and density

plates
large pieces of earths crust that move due to convection currents

oceanic crust
earths crust located under the ocean

continental crust
earths crust made of land

pangea
large supercontinent that existed 250 million years ago

divergent boundary
when two plates pull apart

convergent boundary
when two plates come together

transform boundary
when two plates grind past each other

rift valley
formed when two plates pull apart and land falls downard

island arc
a chain of volcanic islands formed at an ocean-ocean convergent boundary

volcanic arc
a chain of volcanic mountains formed at an ocean-continental convergent boundary

mountain range
formed at a continental-continental convergent boundary

subduction zone
the more dense plate us pulled into the mantle under the less dense plate

Mid Atlantic Ridge
divergent boundary in the middle of the Atlantic Ocean

trench
depression formed at a subduction zone

lithosphere
another name for the crust

aesthenosphere
another name for them mantle

crust
outer layer of the Earth, the thinnest layer

mantle
thickest layer of the Earth, part liquid part solid where convection currents are found

mountain range
form at continental-continental convergent boundaries

temperature inside Earth
increases with depth

pressure inside Earth
increases with depth

fault
a break in the earths crust that moves

igneous rock
formed from cooling lava

hot spot
area where magma from the mantle continually breaks through the crust

hot spot example
Hawaiian islands

age of ocean rocks
younger near sea floor spreading zone

high risk cities
cities where earthquakes and volcanoes are likely to happen

low risk cities
cities where earthquakes and volcanoes are not likely to happen

plate tectonics evidence
rocks, fossils, climate, puzzle fit, glaciers, sea floor spreading

rate of plate movement
5 cm/year

rock crystals
form when rocks cool slowly

crust density
ocean crust is more dense

Wegener’s evidence
fossils, rocks, climate

Wegener’s flaws
how continents moved

Pangaea
The supercontinent formed near the end of the Paleozoic era when plate movements brought all the landmasses of Earth together.

mid-ocean ridge
the undersea mountain chain where new ocean floor is produced.

sea floor spreading
The process that creates new sea floor as plates move away from each other at the mid-ocean ridges

crust
The thin and solid outermost layer of the Earth above the Mantle.

mantle
The layer of hot solid rock between the Earth’s crust and core.

lithosphere
a rigid layer made up of the uppermost part of the mantle and the crust

outer core
a layer of molten iron and nickel that surrounds the inner core of Earth

inner core
a dense sphere of solid iron and nickel at the center of Earth

continental drift
the hypothesis that the continents slowly move across Earth’s surface

Alfred Wegener
A German scientist who proposed the theory of continental drift

tectonic plates
individual sections of the lithosphere of the earth. They fit together in a way similar to a jigsaw puzzle, but are always moving very slowly, on top of the mantel

transform boundary
A plate boundary where two plates slip past each other, moving in opposite directions (San Andreas Fault)

convergent boundary
A plate boundary where two plates come together, or collide (Himalayas, Andes mountains)

subduction
the process by which dense oceanic crust material is overridden by lighter continental crust and sinks down into the mantle

divergent boundary
A plate boundary where two plates move away from each other. (Mid-atlantic Ridge)

plate boundary
the region where two tectonic plates are in contact

crust
the thin and solid outermost layer of the Earth above the mantle

mantle
the layer of rock between the earth’s crust and core

core
the central part of the Earth below the mantle

lithosphere
the solid, outer layer of the earth that consists of the crust and the rigid upper part of the mantle

asthenosphere
the soft layer of the mantle on which the lithosphere floats

mesosphere
The strong, lower part of the mantle between the asthenosphere and the outer core

tectonic plate
a block of lithosphere that consists of the crust and the rigid, outermost part of the mantle

continental drift
the hypothesis that states that the continents once formed a single landmass, broke up, and drifted to their present locations

sea-floor spreading
the process by which new oceanic lithosphere forms as magma rises toward the surface and solidifies

plate tectonics
the theory that explains how large pieces of the Earth’s outermost layer, called tectonic plates, move and change shape

convergent boundary
the boundary formed by the collision of two lithospheric plates

divergent boundary
the boundary between two tectonic plates that are moving away from each other

transform boundary
the boundary between tectonic plates that are sliding past each other horizontally

compression
stress that occurs when forces act to squeeze an object

tension
Stress that occurs when forces act to stretch an object

folding
the bending of rock layers due to stress

fault
a break in a body of rock along which one block slides relative to another

normal fault
a fault in which the hanging wall moves down relative to the footwall

reverse fault
A fault in which the hanging wall moves up relative to the foot wall

strike-slip fault
opposing forces cause rock to break and move horizontally

folded mountains
When rock layers are squeezed together and pushed upward.

fault-block mountains
Form when tension causes large blocks of rock to drop down in relation to other rocks. Tilting of rock layers can occur as tension pulls the rock layers apart.

volcanic mountains
Mountains that form when magma erupts onto Earth’s surface.

What are two types of evidence that geologists have used to learn about Earth’s interior?
direct evidence from rock samples and indirect evidence from seismic waves

Rocks from inside Earth give clues about ( )?
Earth’s structure

What can geologists do from rock samples brought up by drills?
inferences about conditions inside Earth where these rocks formed

What do geologists do when earthquakes produce seismic waves?
record the seismic waves and study how they travel through Earth

What reveals the structure of the planet?
the speed of seismic waves and their paths

Using data from ( ), geologists have learned that Earth’s interior is made up of several layers?
seismic waves

What are the three main layers of Earth?
crust, mantle, and core

What do Earth’s layers vary in?
size, composition, temp, and pressure

( ) increase as you travel further down into Earth’s layers?
temp and pressure

What inside Earth releases energy and further heats the interior?
radioactive substances

What are the high temps inside Earth a result of?
heat left over from the formation of the planet

Why does pressure increase as you travel further into the interior?
the weight of the rock above

What is the crust? What does it include?
a layer of solid rock that includes both dry land and the ocean floor

Where is the crust thickest? Thinnest?
under mountains, beneath the ocean

How thick is the crust?
5-70 km

What does oceanic crust consist of?
rocks such as basalt

What does continental crust consist of?
rocks such a granite

Earth’s mantle is made of rock that is very ( ), yet ( )?
hot, solid

How thick is the mantle?
3,000 km

How thick is the lithosphere?
100 km

The layer of the mantle beneath the lithosphere is less ( ) than the rock above? Why?
rigid, under increasing pressure and hotter

The asthenosphere is ( ) than the rest of the mantle, yet ( )?
softer, solid

What is the layer of the mantle beneath the asthenopshere that is solid and extends all the way to the core?
the lower mantle

What is the core made mostly of?
iron and nickel

What two parts does the core consist of?
a liquid outer core and a solid inner core

How thick is the core?
about 3,500 km

Despite enormous pressure, the outer core is ( )?
liquid

What does extreme pressure do in the inner core?
squeezes the atoms of iron and nickel so that they can

What creates Earth’s magnetic field?
convection currents in the outer core

When you use a compass, the compass needle aligns with what?
the lines of force in Earth’s magnetic field

What are the three types of heat transfer?
radiation, conduction, and convection

What is the absence of heat?
cold

Heat tranfer by radiation takes place with no what?
direct contact between a heat source and an object

How does a spoon in a pot of soup heat up by conduction?
heat moves from the soup and pot to the particles of the spoon, the particles near the bottom of the spoon vibrate faster as they are heated, they bump other particles and heat them too, and the entire spoon heats up

What is responsible for some of the heat transfer inside Earth?
conduction

What happens during convection?
heated particles of fluid begin to flow, this flow transfers heat from one part of the fluid to another

What causes the heat transfer by convection?
differences of temp and density in a fluid

What happens to particles when a liquid or gas is heated?
they move faster and spread apart, take up more space, and the fluid’s density decreases

What happens when a fluid cools?
its particles move more slowly and settle together more closely

What causes convection currents in the mantle?
heat from core and mantle

What are the convection currents like in the mantle?
mantle rock rises slowly from the bottom to the top, the rock cools and sinks back down

What are convection currents like in a pot of soup?
soup at bottom becames less dense, warmer and floats over the cooler, denser soup at top, the warmer soup cools and is pulled down by gravity and is heated again

What sets convection currents in motion?
heating and cooling of the fluid, changes in the fluid’s density, and gravity

Convection currents continue as long as ( ) is added?
heat

What was Wegener’s hypothesis?
all the continents were once joined together in a single landmass and have since drifted apart

What did Wegener gather evidence from to support his theory about continental drift?
land features, fossils, and climate change

What was Wegener’s evidence from land features?
mountain ranges on Africa and South America line up, coal fields on Europe line up w/ones on North America

What was Wegener’s evidence from fossils?
fossils of plants and animals have been found on many seperated continents, the animals couldn’t have crossed large bodies of water, the continents carried the fossils with them when they seperated

What was Wegener’s evidence from climate?
fossils of tropical plants have been found on an island in the Arctic Ocean, when the plants lived, the island must of had a warmer climate closer to the equator

What is Wegener’s evidence from climate in South Africa?
rocks show scratches from glaciers, indicating that it was once located closer to the South Pole

Why did other geologists reject Wegener’s idea?
he couldn’t provide the force that pushes or pulls the continents

What did many geologists think was the cause of mountains?
cooling and shrinking of Earth

What did Wegener say caused mountains?
continents collide and their edges crumple and fold

continental shelf
granite base; shallow part of continental margin; varies greatly in width; biologically rich

oceanic crust made out of
basalt

continental crust made out of
granite

continental crust is ____ than oceanic crust, but _____ dense
thicker, less

oceanic crust is ____ than continental crust, but____ dense
thinner, more

oceanic crust is geologically ____ than continental crust
younger

continental crust is geologically ____ than oceanic crust
older

___ of earth is covered by ocean
71%

Bacon
noted that continents fit together like puzzle pieces

Wegener
named Pangaea, created theory of continental drift

continental drift
continents moving apart, once were all together with Pangaea

plate tectonics
current theory where continents are stuck on plates, and entire plates are moving

continental slope
edge of continent; steep slope leading to sea floor; drop off

submarine canyons
cut into shelf at right angles; caused by landslides, earthquakes, turbidity currents

continental rise
build up of sediments at base of continental slope

abyssal plain
flat seafloor; “without bottom”

seamount
undersea volcano; doesnt come out of water

guyot
flat-topped seamount; eroded and sunken down over time

mid ocean ridge
system of submarine volcanoes that circle the globe like seams of a baseball; includes some of the tallest mountains in the world; where new crust is being produced; hydrothermal vents

trench
deep depression in sea floor; happen when one plate is subducting another; island arc; no hydrothermal vents

island arc
volcanic chains of islands usually found by trenches

a lot of seafloor features are found at
plate boundaries

lithosphere
crust and upper mantle; floating on top of asthenosphere

crust
brittle cracked outer portion of earth

core
very dense high-pressure area of flowing magma

oceanic crust is ___ km thick on average
5

continental crust is ___ km thick on average
20-50

divergent boundaries
where plates are moving apart as magma emerges and cools to form new oceanic crust

convergent boundaries
where plates come together and subduction occurs

mid ocean ridges drive
plate movement

asthenosphere
all mantle below lithosphere

divergent boundary features
MOR, hydrothermal vents, abyssal plain, ocean basin

O-C features
volcanic mountain chains, trenches; Andes Mountains

O-O features
volcanic islands, trenches; Aleutian Islands

C-C features
mountain belts; Himalayans

evidence of plate tectonics
hot spots, paleomagnetism, sediment, age

why plates move theories
slab pull, thermal convection

transform boundary
plates slide past each other, friction, earthquakes

all ocean basins are a result of ____
seafloor spreading

features found parallel to trenches
volcanoes, island arcs, MOR, continental margin

features at plate boundaries
trenches, MOR, volcanic islands, volcanic mountains

Which key discovery of the 1950 helped end the debate over continental drift?
Paleomagnetism

Why does Igneous rocks interact with magma?
Magma polarizes as it cools.

A horizontal magnet would be found measuring the Earth’s magnetic field at the
Equator.

How long after Wegener’s death was continental drift still heavily contested?
20 years.

The angle a free-swinging magnet forms is the
magnetic inclination.

Which of the following latitudes would have the greatest angel for a a free-swinging magnet?
90°

What important information can be gleaned from a rock’s paleomagnetic inclination?
The former latitudes of the rock

the study of paleomagnetism initially led to the conclusion of
apparent pole wondering.

what piece of evidence caused scientists reluctantly to accept the movement of of continents?
paths for pole movement varied from continent to continent.

If Europe and North America were joined together at one point,
Their polar wandering paths would coincide with each other.

What discovery made in the 1960s advanced the continental drift theory?
Symmetric bands of rock w/ reversing polarities.

At mid-ocean ridges
the seafloor is spreading.

Which model explained how continental drift occurs?
plate tectonics

The lithosphere consists of
crust and upper mantle.

Directly below the lithosphere is the
asthenosphere

What phenomenon causes the Earth’s crust to split into plates?
heat from the mantle

How many large plates currently exist?
6

The authors of “Plate Tectonics” compare isostasy to
blocks of wood floating on water.

The origin of the word tectonics is
Greek.

How do lithospheric plates move as? Where do they mainly interact?
they move as individual units; mainly on their edges.

What are the three type of plate margins?
Divergent, Convergent and Transform.

Divergent margins in continental crust results in a
rift valley

What sea formed at a rifting center
Red Sea

The Andes are an example of a(n)
ocean-continent subduction zone

an ocean-ocean subduction zone can be found in near
Indonesia

When two continental plates collide , the result is
crumbling into a mountain range

In what direction is the Pacific Plate moving at the San Andreas fault?
north-northwest

The annual rise of tectonic movement is typically between
1 and 10 cm (0.4 to 4 in)

by studying earthquakes, geologists have
determined the shapes of tectonic plates

during a earthquake, tectonic motion provides
directional pressure

Why do rocks sliding along one another move slowly?
the friction between the rocks requires energy to overcome it.

the boundary between rocks where earthquakes can occur is called a
fault

the focus is the
location beneath the Earth’s surface where the earthquake begins

the mapped-location of an earthquake corresponds to its
epicenter

why are earthquakes at diverging margins weak?
the magma presents at these regions cannot break and cause friction

deep focus earthquakes occur MOST often at
collision zones

which margin typically has the widest range of earthquakes depths?
subduction zones

Benioff zones are associated with
subduction zones

one of the dominant questions still remaining about plate tectonics is
what causes subduction

what source of energy in the mantle contributes to the movement of the tectonic plates?
thermal

the temperature of the Earth’s core is approximately
5000° C (9000° F)

the earths core maintains its temperature through
radioactive decay

conduction involves
passing heat between adjoining atoms

the authors of “Plate Tectonics” provide boiling points as a metaphor for
a convection cell

a major advantage of convection over conduction is
the speed of heat transfer

when rock in the mantle heats, it
moves up towards the surface

heated rock in the asthenosphere
moves laterally

current theories suggest that the Earth cools itself through
convection cells

cool rock
denser than hot rock

mantle plumes differ from ordinary convection cells in their
shape of rising rock

which islands formed over a mantle plume?
Hawaii

seafloor spreading directly involves
igneous rocks

What does convection and the lateral movement of plates create?
Distinctive geologic and topographic features.

when the old lithosphere joins with magma, the process involved is
subduction

How long did the poles wandered around the Earth?
Several hundred million years

When did the first mechanism finally appear to aid the geophysicists?
Early 1960s

How can geologists determine where the youngest rocks are found at the bottom of the seafloor?
Youngest ones along the centerline ridge.

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