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109 Cards in this Set

  • Front
  • Back
How old is the oldest oceanic crust?
200 million years
What occurs when two plates collide and one sinks below the other?
Oceanic-continental convergence
Plate boundary in which lithospheric plates slide past each other:
Transform plate boundary (EX: San Andreas Fault in California, where the Pacific Plate slides past the North American Plate.)
What name did Alfred Wegener give to his theory of horizontal crustal movements?
Continental drift
Where are black smokers and deep-sea vent communities found?
Mid-ocean ridges
Where do accretionary wedges form?
Above subduction zones
Continental mountain ranges are usually associated with:
Convergent boundaries
Areas where the lithosphere sinks into the asthenosphere:
Subduction zones
The age of the oceanic crust created at mid-oceanic ridges _________________ with increasing distance away from the mid-oceanic ridge.
Layer of the Earth that is made of minerals rich in the elements iron, magnesium, silicon, and oxygen:
In the 1950s, a seismologist showed that the global system of mid-ocean ridges was:
An active seismic belt - or zone of earthquakes
Where are the deepest places in the ocean?
What causes movement of Earth's tectonic plates?
Convection currents below the lithosphere
What type(s) of evidence did Wegener use to support his theory?
-Distribution of fossils (Mesosauris, Glossopteris)
-Distribution of climatic belts
-Matching geologic units
-Geographic fit of the continents
Why was Wegener's theory rejected by geophysicists of the 1920's?
Lack of a mechanism for continents to plow through oceanic crust
Which layer of the Earth is made up of tectonic plates?
The line of volcanoes that circles most of the Pacific Ocean:
“Ring of Fire”
Where were magnetic stripes found to be symmetrical?
At the Mid-Atlantic oceanic ridge
The ____ is made of solid rock that flows very slowly.
Who proposed sea-floor spreading?
Harry Hess
The type of tectonic plate boundary involving a collision between two tectonic plates:
Convergent boundary
What proved continental drift?
The border between two adjacent lithosphere plates:
Plate boundary
What theory did magnetic anomalies on the seafloor give rise to?
Seafloor spreading
Fossil found on the continents of South America, Africa, India, and Australia:
Glossopteris, a fern
A rock formed from hardened ancient glacial deposits:
What type of magnetic anomaly was produced by lava that erupted in the geologic past, when the north magnetic pole was in the northern hemisphere?
Preserved a positive magnetic anomaly.
What is the San Andreas Fault in southern California an example of?
Transform plate boundary
What layer is associated w/ plastic behavior?
What plate is subducting beneath southwestern Canada and the northwestern Unites States?
The Juan de Fuca plate
What produces the ocean floor and the rock beneath it?
Magma from deep within the Earth rises and eventually erupts along the crest of the ridges to create new oceanic crust.
Layer of Earth that is composed of mostly iron and nickel:
Seafloor spreading was supported as an idea after which discovery was made during WWII?
Mid-ocean ridge system, middle of the Atlantic Ocean
Why do the volcanic rocks that make up the sea floor have magnetization?
Because as they cool, magnetic minerals within the rock align to the Earth's magnetic field.
Explain the 3 layers of rock sequences that Wegener found on the continents?
-The top (youngest) layer is lava flows.
-The middle layer is composed of sandstone, shale, and coal beds.
-The bottom (oldest) layer is called tillite and is thought to be a glacial deposit.
A centralized area characterized by high heat flow and volcanic activity at the surface:
Hot spot
Describe the 3 sublayers of the mantle:
HighestUPPERMOST MANTLE – solid rock
MiddleASTHENOSPHERE – not solid or liquid; soft/squishy layer
LowestLOWER MANTLE – solid rock
When did the supercontinent Pangaea begin to break apart?
About 200 million years ago
Plate boundary in which lithospheric plates move toward each other:
Convergent plate boundary (EX: The west margin of the South American continent, where the oceanic Nazca Plate is pushed toward and beneath the continental portion of the South American Plate)
The most common rock on Earth:
The average rate of movement of the North American Plate has been estimated at 2.5 centimeters per year. How much wider is the Atlantic Ocean than when Christopher Columbus crossed it in 1492? Remember, 1 meter = 100 centimeters.
About 13 meters
Magnetic anomalies that are weaker than expected:
Negative magnetic anomalies – induced when the rock cools and solidifies w/ the Earth's north magnetic pole in the SOUTHERN geographic hemisphere. The resultant magnetic field is less than expected b/c the Earth's magnetic field is reduced by the magnetic field of the rock.
Areas where fluids beneath the Earth's crust rise, flow laterally, and then fall:
Convection currents
Which modern continents were derived from Gondwana?
South America, Africa, Antarctica, Australia, India
What has been the most useful method for determining the structure of the earth's interior?
Seismology-studying seismic waves
What serves as the "plates" of the plate tectonic theory?
The creation of new oceanic crust at mid-ocean ridges and movement of the crust away from the mid-ocean ridges:
Seafloor spreading
Describe oceanic crust:
Thin; heavy; basalt
What is the approximate thickness of the earth's crust?
30 km
The apparent movement of Earth's magnetic poles over time:
Polar wandering
Differences in the magnetic field from place to place:
Magnetic anomalies
Plate boundary in which lithospheric plates move away from each other:
Divergent plate boundary (EX: Mid-Atlantic ridge)
What is the lithosphere composed of?
The crust and uppermost mantle
A steep-walled valley on the sea floor adjacent to a continental margin:
Plate tectonics is a combination of what 2 ideas?
Continental drift and sea-floor spreading
What boundary (discontinuity) separates the crust and the mantle?
Rocks that make up the ____ crust are older than rocks that make up the ____ crust.
Continental, oceanic
Who DID, and who DID NOT accept Wegener's continental drift hypothesis?
a) Wegener’s work WAS UNACCEPTED in the northern hemisphere.
b) In the southern hemisphere, where geologists were familiar with the rocks that Wegener used to support his hypothesis, continental drift WAS ACCEPTED.
Describe continental crust:
Thick; lightweight; granite
Magma is generated at:
Subduction zones
What type of magnetic anomaly would lava erupting at the present time preserve?
A positive magnetic anomaly b/c the Earth's magnetic pole is in the northern hemisphere.
Which layer of the earth's interior is liquid?
Outer core
A scientist who specializes in the study of earthquakes:
What did Wegener use to determine the distribution of climate zones in the geologic past?
The distribution of specific rock types - For example, glacial till and striations (scratches on the rock), sand dunes, and coral reefs, indicate polar, desert, and tropical climates.
The region along a convergent boundary where one plate sinks beneath another:
Subduction zone
What was the final, indisputable evidence (discovered in the 1960s) for seafloor spreading and consequently plate tectonics?
Parallel magnetic “stripes” recorded in ocean floor
An opening in the oceanic crust where molten materials can escape:
In which layers of rock were Glossopteris fossils found?
The bottom and middle layers.
Which layer produces the earth's magnetic field?
Outer core
The Vine-Matthews hypothesis explains the origin of:
Seafloor magnetic anomalies
The Himalaya Mountains are believed to be the current location of a(an):
Continent-continent convergent plate boundary
The moho separates the ____ from the ____.
Crust, mantle
Places where the magnetic field is stronger than expected:
Positive magnetic anomalies – induced when the rock cools and solidifies with the Earth's north magnetic pole in the NORTHERN geographic hemisphere. The Earth's magnetic field is enhanced by the magnetic field of the rock.
The movement of continents over the Earth's surface and in their change in position relative to each other:
Continental drift
Who believed that heat trapped in the Earth caused convection currents?
Arthur Holmes
A mass of highly deformed rock that is scraped off the subducted plate and plastered to the edge of the ocean floor:
Accretionary wedge
How do geologists observe Earth’s interior?
By recording and studying seismic waves
What does Pangaea mean?
"All land"
What occurs when two plates collide and crumple up, forming tall mountains?
Continental-continental convergence
The process by which the ocean floor sinks beneath a deep-ocean trench and back into the mantle:
A rift valley forms where two plates ____.
Why are apparent polar-wander paths different for different continents?
Because continents move w/ respect to each other, while the Earth’s magnetic poles remain fixed.
What was Alfred Wegener's explanation for 300-350 million year old (Paleozoic) glacial deposits (or till) in areas near the equator?
The continents were once located near the earth's poles.
____ form from where two plates collide.
A boundary between the layers of the Earth:
A deep oceanic trench is found at:
Subduction zones
The oceanic lithosphere is thinnest near the ____ and thickest near the ____.
Mid-oceanic ridge, oceanic trench
Who proposed the theory of continental drift?
Alfred Wegener
Geologists believe that areas of intense geologic activity, indicated by earthquakes, volcanoes, and/or mountain building, mark the boundaries between what?
Lithospheric plates
The distribution of earthquakes, volcanoes, and mountain ranges define ____ plates and ____ plates.
7 large, 20 smaller
Occurs over areas of sea floor where basalt has normal polarity:
Positive anomalies
Volcanic activity in the Cascade Mountains of America's Pacific Northwest is associated with a(an):
Ocean-continent convergent plate boundary
Which continents made up Laurasia?
North America, Asia, Greenland, Europe
Who presented an explanation for the global rift system?
Harry Hess
The oceanic lithosphere is created at ____ and consumed at ____.
Mid-ocean ridges, subduction zones
____ is (are) distributed in narrow, linear belts that circle the Earth.
During times when continents move w/ respect to one another, they develop _____; but when continents are stuck together, they develop _____.
Different apparent polar-wander paths, the same apparent polar-wander path
Curving chains of active volcanoes:
Volcanic arcs
Times when the Earth’s field flips from normal to reversed polarity, or vise versa:
Magnetic reversals
The lithosphere ____ when a load is placed on it, whereas the asthenosphere ____.
Bends, flows
Earthquakes serve as the most definitive indicator of a(n):
Plate boundary
What type of magnetic pattern do the rocks record if the magnetic pole is in the southern hemisphere?
A reverse (negative) magnetic pattern
Where are black smokers found?
Along the mid-ocean ridge
What occurs when two plates collide and the older, denser plate bends and sinks into the mantle?
Oceanic-oceanic convergence
Earthquakes beneath the Pacific Ocean occurred at ____ ____, but earthquackes beneath Siberia and China occurred at ____ ____.
Shallow depths, deep depths
What did geologists discover by measuring paleomagnetism in successively older rocks?
They found that the apparent position of the Earth’s magnetic pole relative to the rocks changes through time.
What happens when oceanic crust collides with continental crust?
The heavier oceanic crust is subducted into the earth's mantle.
The outer core is ____, and the inner core is ____.
Liquid, solid
Who proposed that lava erupted at different times along the rift at the crest of the mid-ocean ridges preserved different magnetic anomalies?
Vine and Matthews