Plate Tectonics Flashcards
(149 cards)
1
Q
Mid-Atlantic Ridge
A
basaltic mountain range that spans the length of the Atlantic ocean w/rock chemistry and dimensions unlike mountain ranges found on continents
2
Q
Plate Tectonics
A
The theory that the outer layer of the earth (lithosphere) is broken in several plates, and these plates move relative to one another causing the major topographic features of the earth and most earthquakes and volcanoes.
3
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Oceanic Crust
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Thin, outer layer of the earth which makes up the rocky bottom of the ocean basins. It is made of rocks similar to basalt. And as it cools becomes even more dense than the upper mantle below.
4
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Transform definition
A
Place where 2 plates slide past each other, creating strike slip faults
-Most transform boundaries are found on ocean floor, around mid-ocean ridges.
5
Q
Chemical Layers of the Earth
A
Crust
Mantle
Core
6
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Crust
A
the outermost chemical layer of the earth. As defined by its low density and higher concentrations of lighter elements. 2 types oceanic and continental
7
Q
Moho
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Short for mohorovicic. The seismically recognized layer within the earth in which the crust ends and the mantle begins.
8
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Mantle
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Largest chemical layer by volume.
Middle chemical layer. Made of mainly iron and magnesium silicates. It is generally denser than the crust (except older oceanic crust) and less dense than the core.
9
Q
Core
A
- Looking at seismic date first discovered in 1906
- The innermost chemical layer of the Earth. made chiefly of iron and nickel. Both liquid and solid components.
10
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Physical Layers of the Earth
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5 Distinct Physical Layers base on how each layer responds to stress.
- Lithosphere
- Asthenosphere
- Mesosphere
- Outer Core
- Inner Core
11
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Lithosphere
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The outermost physical layer of the earth. Made of the entire crust and upper mantle. It is brittle and broken into a series of plates. These plates move in various ways
12
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Asthenosphere
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A ductile physical layer of the earth. Below the lithosphere. Movement within is the main driver of plate motion, as the overriding lithosphere is pushed by this.
- Mechanically weak
- Moves due to convection currents
- Relatively unbroken
13
Q
Mesosphere
A
- Also called lower mantle.
- A solid, more brittle physical layer of the earth.
- Below Asthenosphere
14
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Outer core
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The outer physical layer of the core.
- Liquid
- responsible for magnetic field and flips of it
- If it were to stop moving or become solid it would result in loss of magnetic field and would result in Earth getting stripped of life-supporting gases and water. This is what happened to Mars
15
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Inner Core
A
The innermost physical layer of the earth. It is solid
-Hottest part of the earth is solid. The minerals making it up should be liquified or vaporized at this temp but the immense pressure keeps them solid.
16
Q
Passive Margin
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A boundary between continental and oceanic plates that has no relative movement. Making it a place where an oceanic plate is connected to a continental plate. BUT it is not a plate boundary
17
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The 3 Types of Tectonic Plate Boundaries
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- Divergent
- Convergent
- Transform
18
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Convergent Definition
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Place where two plates come together. Causing subduction or collision.
AKA Destruction boundaries
19
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Divergent Definition
A
Place where two plates are moving apart. Creating either rift (continental lithosphere) or a mid-ocean ridge
20
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Transform Definition
A
Place where two plates slide past each other. Creating strike slip faults.
- Most transform boundaries are found on the ocean floor, around mid-ocean ridges.
- Significant seismic activity. Very little mountain building or volcanism
21
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Subduction definition
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Oceanic plate descends below a less dense plate. Causing the removal of the plate from the surface.
- Causes the largest earthquakes possible
- Volcanoes
22
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Trench
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Deepest part of the ocean where a subducting plate dives below an overriding plate.
23
Q
Accretionary Wedge
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Mix of sediments that form as a subducting plate descends and the overriding plate scrapes material and material is added.
24
Q
Terrane
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A geological province which is added (accreted) to a continental mass via subduction and collision
25
Slab
A name given to the subducting plate. Where volatiles are driven out at depth. causing volcanism
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Mantle Wedge
The area of the mantle where volatiles rise from the slab. Causing flux melting and volcanism
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Flux Melting
The process in which volatiles enter the mantle wedge and the volatiles lower the melting temperature causing volcanism.
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Volatiles
Components of the magma which are dissolved until it reaches the surface, where they expand
29
Volcanic Arc
Place with a chain of mountain volcanism on a continent. From Oceanic-Continental subduction
30
Forearc Basin
Any depression formed between the arc and the trench. Commonly between the arc and accretionary wedge.
All subductuib zones have a forearc basin. Between thr volcanic arc and oceanic trench.
-experiences a lot of faulting and deformation activity
31
Back-Arc basin
A lot of faulting and deformation activity
Extension- subduction— volcanic arc gets stretched until it cracks and collapses to form a back arc.
**back arc basin can develop into continental rifting zone.
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Thrust Faults
AKA Compressional back arc faults
A lower-angle reverse fault. Common in mountain building
Thin-Skinned - Faulting that is not dep into the crust. Typically only involves sedimentary cover. Not basement rocks
Thick-skinned- Faulting that is dep into the crust. And typically involves crystalline basement rocks
33
Orogeny
The process of uplifting mountain within mountain belts. Primarily via tectonic movement. Mountain belts are the result from movement.
34
Collision
When two continents crash with no subduction (Thus little to no volcanoes) since each continent is too buoyant. Many of the largest mountain ranges and broadest zones of seismic activity come from collisions.
35
Obduction
Process which allows a continental plate to bring up an oceanic plate. Frequently occurring in collision zones.
36
Rift
Area of extended continental lithosphere. Forming a depression. Rifts can be narrow (focused in one place) or broad (spread out over a large area with many faults)
Graben, half-graben, horst
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Graben
A valley formed by normal faulting
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Half-Graben
A valley formed by normal faulting on just one side.
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Horst
Uplifted mountain block caused by normal faulting
40
Decompression
melting that occurs as material is moved upward and pressure is released. Typical found at divergent boundaries or hot spots
41
As a rift forms on a continent, what feature can form next?
Ocean basin
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How is magma generated at divergent boundaries?
Decreased pressure
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Dextral
Movement in a transform setting which it moves toward the right across the fault. As viewed across the fault. Objects will move to the right
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Sinistral
Transform motion in which the relative motion is to the left. As viewed across the fault, objects will move to the left.
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Transpression
A segment along a transform which has a compressional component, sometimes creating related thrust faulting and mountains
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Transtension
A place along a transform with an extensional component, sometimes including normal faulting, basin formation, and volcanism.
47
Piercing Point
An object that is cut by a fault which allows the amount of movement to be determined. This is useful for all faults but more commonly used in strike-slip faults.
48
What famous transform fault is known for being the boundary between the pacific plate and the North American plate?
San Andreas Fault
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What are the two ways transform faults move?
Left (sinistral) and right (dextral)
50
Why are piercing points important with transform boundaries?
They track the movement
51
What makes transform boundaries different from other boundaries?
Transform has less volcanoes
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Wilson Cycle
J. Tuzo Wilson
the cycle of opening ocean basins with rifting and seafloor spreading then closing the basin via subduction and collision, creating a supercontinent.
-Operating at least 3 billion years
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Hot Spots
Rising stationary magma, forming a succession of volcanism. this is reflected as islands on oceanic plates, and volcanic mountains or craters on land
- Only type of volcanism not associated with subduction or rifting zones.
- Seems totally disconnected from any plate tectonics processes.
- We do not know what causes them
- Active volcanoes over hot spot with extinct extending in a line that shows the movement of the plate
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Tomography
A process of using 3D seismic arrays to get subsurface images
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According to the Wilson Cycle, what feature or process is most likely to occur after collision and formation of a supercontinent?
Rifting
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What features or processes are common in hot spots?
volcanism
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What makes the Hawaiian hot spot different than the Yellowstone hot spot?
Different types of tectonic plates
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Which tectonic setting places the asthenosphere farthest from the surface?
Continental collisions
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A line of shallow earthquakes with little or no volcanism is likely evidence of what type of plate boundary?
Transform
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What happens to the crust as you move towards the mid-ocean ridge?
The crust gets younger
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Why are there not as many earthquakes or volcanoes on the east coast of North America as the west coast of North America?
It is not close to a plate boundary (passive margin)
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Which boundary is least likely to be dangerous to humans?
Mid-ocean ridge
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Which plate boundary has the largest and deepest earthquakes?
Subduction
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Why did Alfred Wegner never get the support of the scientific community for his hypothesis of continental drift during his lifetime?
He could not provide a mechanism for how continents moved
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Divergent Earthquakes
Mostly shallow and in a narrow zone along the boundary.
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Ocean-Continent Convergent Earthquakes/Volcanoes
- Ocean plate subducts
- Quakes shallow to deep in a wide zone on one side of the boundary
- Volcanoes on the continent side
- The addition of water to the mantle lowers melting point of the rock ---> causes rocks to melt
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Ocean-Ocean Convergent Quakes/volcanoes
- Quakes shallow at trench to deeper under overriding plate and mostly on one side.
- Volcanoes in a chain on the overriding plate
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Continental-Continental Convergent Quakes/volcaones
- No subduction
- No significant volcanoes
- Huge Mountain ranges
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Transform Oceanic Quakes/Volcanoes
Quakes in narrow belt along boundary
| -No significant volcanoes
70
The Earth's core is made of what material?
Iron
71
The Moho is a boundary between which two layers?
Mantle and crust
72
The Earth's magnetic field is generated in what part of the Earth?
The Core
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The lithosphere is...
1. Thin & liquid
2. Thick & softened
3. Thin & softened
4. Thin & Brittle
4. Thin & Brittle
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The lithosphere is distinguished by its...
1. Composition
2. Mechanical properties
2. Mechanical properties
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How does the asthenosphere differ from the lithosphere mantle?
1. The asthenosphere is hotter and softer
2. The asthenosphere has a different composition
3. The asthenosphere is hotter and harder
4. They are the same thing
1. The asthenosphere is hotter and softer
76
What is a seamount?
an undersea volcano
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A Fathometer measures....
The depth of the ocean
78
Which of the following is the best statement of seafloor spreading hypothesis?
A. The seafloor grows from the hotspots as magma spreads over the seafloor\
B. New oceanic lithosphere is formed at the mid ocean ridge by volcanic eruptions. This new seafloor is then moved sideways away from the ridge thus enlarging the ocean basin. In other places the seafloor is destroyed by sinking back inside the earth at deep ocean trenches.
C. The seafloor grows at the mid ocean ridges and thus the Earth is swelling.
D. The continents plow through the ocean basins, spreading over the seafloor.
B. New oceanic lithosphere is formed at the mid ocean ridge by volcanic eruptions. This new seafloor is then moved sideways away from the ridge thus enlarging the ocean basin. In other places the seafloor is destroyed by sinking back inside the earth at deep ocean trenches.
79
Why did the US scientific community install seismometers around the world after WW2?
To monitor nuclear activities of the Soviet Union
80
Which locations have what is called a "Wadati-Benioff" zone?
Deep trenches
81
How old was the oceanic crust closest to the Mid-ocean ridges?
less than 10 million years old
82
What kind of rock is formed along mid-ocean ridges?
basalt
83
How many years ago did the earth's magnetic field last reverse?
700,000 years
84
What kind of pattern is formed by the magnetic fields of the seafloor?
stripes
85
Why is the mid ocean ridge higher than the surrounding ocean basin?
It is supported by hot, lower density mantle rock
86
What force pushes ocean plates away from the ridge?
The gravitational force of the mass on the slope of the ridge pushing away from the ridge
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What is the source of the slab pull force?
Stronger gravitational pull on the cooler denser rocks of the subducting slab
88
What is the temperature above which earthquakes are unlikely to occur in the subducting slab?
600 degree C
89
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Which force is usually the greater force in moving the plates?
A. Magnetism
B. They are all equal
C. Slab Pull
D. Ridge Push
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C. Slab Pull
90
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Which of the following ideas are examples of Pseudoscience?
A. Astronomy
B. Evolution
C. The existence of Ghosts
D. Climate Change
E. Astrology
```
C. The Existence of Ghost
| E. Astrology
91
Put the following parts of the scientific method in order.
____ Accept your explanation as a scientific theory.
____ Share your ideas with other scientists so they can replicate your results or critically examine your ideas.
____ Test and revise hypotheses until a hypothesis passes all tests.
____ Propose hypotheses to answer question or solve to problem.
____ Make observations and ask a question or state a problem.
1. Make observations and ask a question or state a problem.
2. Propose hypotheses to answer question or solve to problem
3. Test and revise hypotheses until a hypothesis passes all tests.
4. Share your ideas with other scientists so they can replicate your results or critically examine your ideas.
5. Accept your explanation as a scientific theory.
92
According to the textbook chapter, who is considered to be the first modern scientist?
Galileo
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All scientific claims are falsifiable which means...
Question options:
A) if there is no evidence that they are false, they are assumed to be true.
B) The idea may be tested and in principle could be found to be false if it fails the tests.
C) The ideas are proven wrong.
D) They are more true than false
B) The idea may be tested and in principle could be found to be false if it fails the tests.
94
In science, if the facts do not support your hypothesis it is acceptable to ignore them and invent alternative facts. True or False?
False
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In science, if a hypothesis is not supported by the facts it is acceptable to discard it and invent an alternative hypothesis that is supported by the facts. True or False?
True
96
What causes the volcanism to occur along this plate boundary? (South American and Nazca)
Melting of mantle rocks above the subducting plate
97
What is the name of the plate that is subducting under the South American Plate?
Nazca Plate
98
Why are there no volcanoes in most of Peru and southern Chile?
Due to flat slab subduction
99
Earthquakes in South America can be generated by several mechanisms. Which of these is NOT one of those mechanisms?
A. Tsunami-generating megathrust earthquakes like the 1960 Quake
B. Actually these are all correct
C. Intraplate earthquakes in the subducting plate like the magnitude 7.9 Chimbote quake of 1970
D. Continental intra-plate earthquakes like the one in San Juan, Argentina in 1944.
B. Actually these are all correct
100
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Which of the following plates are colliding with Eurasia?
A. Arabian Plate
B. North American Plate
C. Indian Plate
D. African Plate
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A. Arabian Plate
C. Indian Plate
D. African Plate
101
How long ago did the Indian plate begin to collide with Eurasia?
50 Million years
102
Where do the largest earthquakes occur along the Himalayan plate boundary?
on the shallow portion of the Megathrust Boundary
103
By how many centimeters per year is the crust shortened in Nepal and Tibet?
2 cm/y
104
When the Gorkha Earthquake struck and moved Kathmandu towards the south, how did people react to the ground movement? Question options:
a) They staggered and some fell.
b) They did not react at all. They did not feel it.
c) They all dropped to the ground
d) They all ran in different directions
a) They staggered and some fell.
105
Which of the following earthquake hazards were mentioned as occurring during the Gorkha Earthquake? (More than 1)
```
A. Building Collapse
B. Tsunami
C. Landslides
D. Fire
E. Ground shaking
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A. Building Collapse
C. Landslides
E. Ground shaking
106
How do the areas of greatest earthquake risk relate to the locations of major population centers. (Himalayas)
Major population centers are at great risk from earthquakes due to population increase and poor building practices
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Other then mid-ocean basins, where on Earth is the best example of current (active) rifting?
East Africa
108
Objective
An observation that is completely free of bias.
| Anyone and everyone would make the same observation
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Subjective
An observation which is influenced by the observer's personal bias
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Quantitative
An observation which is based on numerical data. These observations are preferred because they can be used in calculations.
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Qualitative
An observation which is based on non-numerical data. While these types of observation are not preferred, they can be useful.
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Falsifiable
The idea that any claim in science can be proved wrong with proper evidence.
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Hypothesis
A proposed explanation for an observation that can be tested.
114
Theory
An accepted scientific idea that explains a process using the best available info
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Pseudoscience
A method of investigation that claims to be scientific, but does not hold up to full scientific scrutiny.
Examples- Astrology, paranormal studies, young earth creationism, and cryptozoology
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Scientific Method
The idea in science that phenomena and ideas need to be scrutinized using hypothesizing, experimentation, and analysis. This can eventually result in consensus or scientific theory
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Scientific Method Steps
1. Observation, problem, or research question.
2. Hypothesis
3. Experiment and hypothesis revision
4. Peer Review, publication, and replication
5. Theory Development
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Deductive Reasoning
Taking known truths in order to develop new ideas.
| Example - A=B, B=C, then A=C
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Inductive Reasoning
Establishing evidence (Including new observations) to infer a possible truth.
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Mid-Ocean Ridge
A divergent boundary within an oceanic plate, where new lithosphere and crust is created. As the two plates spread apart
121
Epicenter
The location at the surface directly above the focus of an earthquake. Typically associated with strong damage.
122
Divergent Definition
Place where 2 plates are moving apart, creating either a rift (continental) or mid-oceanic ridge (oceanic).
123
Subduction Volcanoes/Quakes
Largest possible earthquakes possible as the subducting can lock as it goes down.
Volcanism is also caused as the plate releases volatiles into the mantle, causing melting
124
Slab
Name given to the subducting plate, where volatiles are driven out at depth causing volcanism
125
Oceanic-Continental Subduction
Where an oceanic plate subducts beneath a continental plate, causing volcanic arc to form.
Cascade Mountain in Pacific NW
Andes in South America
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Oceanic-Oceanic Subduction
Where a dense ocean plate subducts beneath a less dense oceanic plate, causing an island arc to form.
Aleutian Islands
Lesser Antilles
127
Hawaiian Hotspot
- One of the most active hot spots
- At least 80 million years old
- Kilauea volcano is the main vent for this hotspot and has been actively erupting since 1983
- Much of the volcanic island chain is underwater. Stretches for almost 6,000 km
128
According to the Wilson Cycle, what feature or process is most likely to occur after collision and formation of a supercontinent?
Rifting
129
What is the biggest difference between hotspot volcanism in and island chain and plate tectonic volcanism in an island chain?
Hotspots have age trends
130
A line of shallow earthquakes with little or no volcanism is likely evidence of what type of plate boundary?
Transform
131
Back-Arc Fault
Young buoyant oceanic plates are converging and subducting at a relatively high velocity, they may force the overlying continental plate to buckle and crack. This is back-arc faulting.
Extensional- pull rocks and chunks of plates apart
Compressional (AKA Thrust Faults) push them together.
132
Rift Valley
Large faults drop into deep depressions known as rift valleys, which often contain keystone-shaped blocks of down-dropped crust known as GRABENS. The shoulders of grabens are called HORSTS. If only 1 side of a section drops is called a HALF-GRABEN
133
What is the name of the transform fault east of the subduction zone? (Alaska)
Queen Charlotte Fault
134
Which part of the Aleutian Trench has steeper subduction angles?
Western part
135
Where are deeper earthquakes located along this subduction zone? (Alaska)
Further north of the trench
136
Yakutat terrane
- It began to collide about 25 million years ago
- It is uplifting the Chugach and St. Elias mountains
- it is bounded by the Queen Charlotte-Fairweather fault and the Chugach-St. Elias fault
- It is an interface of high friction
137
Which of the following hazards generated by the 2002 M7.9 Denali fault was mentioned in the video?
Rock avalanche
138
How fast is the Caribbean Plate moving relative to the North and South American plates?
2 cm/year
139
Along this boundary, which plate subducts under which plate? (Antilles)
The "Atlantic" plate subducts under the Caribbean Plate
140
How to the depth of earthquakes change across the boundary? (Antilles)
The deeper quakes are further west of the boundary
141
Volcanoes are located above where the subducting slab reaches what depth? (Antilles)
100 to 150 km depth
142
Why is the accretionary prism of sediments thicker in the southern part of the plate boundary than in the northern part of the plate boundary? (Antilles)
Due to sediment input from the Orinoco River onto the Atlantic plate.
143
What type of event was the Guadaloupe earthquake of 1843?
It is not clear
144
Which of the following is NOT a reason for low friction along this subduction zone? (Antilles)
Question options:
Release of water from hydrated minerals in the subducting slab.
The subducting slab is old, cold, and dense.
Lava from volcanoes is seeping into the boundary
Lava from volcanoes is seeping into the boundary
145
Could a tsunami affect the islands of the Lesser Antilles?
Yes, this is possible and has happened in the past.
146
What is the name of the volcano that killed 30,000 people on the island of Martinique?
Mt. Pelee
147
How does the video characterize the threat of earthquakes in the Gulf of California?
more of a nuisance than a threat
148
Why is the risk of earthquakes stronger in the area north of the gulf, such as the Imperial Valley (California)
Because soft sediments can amplify the seismic waves.
149
What is the name of the seismic gap where a large earthquake may still be building up?
Iquique seismic gap
