Plate Tectonics (College Board AP® Environmental Science): Flashcards
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Define tectonic plates.
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Define tectonic plates.
Tectonic plates are the large pieces that Earth's crust is broken into, which have moved throughout geological time.
What is the place where two tectonic plates meet called?
The place where two tectonic plates meet is called a plate boundary (or plate margin).
Define convergent plate boundary.
A convergent plate boundary is where two tectonic plates collide.
Which plate subducts when an oceanic plate meets a continental plate?
The oceanic plate subducts beneath the continental plate because it is denser.
True or False?
When two continental plates collide, the denser plate subducts.
False.
Two continental plates have similar density, so neither subducts; the crust is forced upward to form mountains, such as the Himalayas.
When an oceanic plate subducts beneath another oceanic plate, a curved chain of volcanic islands called an forms.
When an oceanic plate subducts beneath another oceanic plate, a curved chain of volcanic islands called an island arc forms.
Why do volcanoes form where an oceanic plate subducts beneath a continental plate?
Subduction causes magma to rise, forming volcanic mountain ranges such as the Andes.
Define divergent plate boundary.
A divergent plate boundary is where two tectonic plates move apart, creating new crust.
Why are earthquakes frequent and powerful at convergent boundaries?
Earthquakes are frequent and powerful at convergent boundaries because of the intense pressure where the plates collide.
As plates pull apart at a divergent boundary, magma rises and solidifies to form new oceanic crust in a process called .
As plates pull apart at a divergent boundary, magma rises and solidifies to form new oceanic crust in a process called seafloor spreading.
What landform develops when two continental plates diverge?
When continental plates diverge, the crust thins and forms a rift valley, such as the East African Rift.
True or False?
Volcanoes only form at convergent plate boundaries.
False.
Rising magma at divergent boundaries also creates moderate volcanic activity along mid-ocean ridges and rift zones, as in Iceland.
Define transform plate boundary.
A transform plate boundary is where two tectonic plates slide past each other horizontally, in opposite directions or in the same direction at different speeds.
What is the main hazard at transform plate boundaries?
Transform boundaries mainly produce earthquakes, as friction between the sliding plates builds stress; the San Andreas Fault in California is an example.
Define hot spot.
A hot spot is a place where magma rises through the crust independently of plate boundaries, such as Hawaii.
About % of earthquakes occur close to or at a plate boundary.
About 95% of earthquakes occur close to or at a plate boundary.
Define fault.
A fault is a fracture in Earth's crust where two blocks of rock move relative to each other due to tectonic forces.
What is the Pacific Ring of Fire?
The Ring of Fire is a tectonically active region surrounding the Pacific Ocean, known for earthquakes and volcanoes. About 75% of active volcanoes occur around it.
Why are plate boundary maps useful?
Plate boundary maps are useful because they help predict geological activity, such as volcanoes, island arcs, and earthquakes.
Define locked fault.
A locked fault is a section of a fault that is stuck due to friction, preventing movement between tectonic plates.
How does a locked fault cause an earthquake?
Stress builds until it overcomes friction, so the fault suddenly slips and releases stored energy as seismic waves.
True or False?
The longer a fault stays locked, the weaker the eventual earthquake.
False.
The longer a fault stays locked, the more stress accumulates, so the earthquake is more powerful when the fault finally moves.
Which secondary hazards can a locked-fault earthquake trigger?
A locked-fault earthquake can trigger aftershocks as stress redistributes along the fault and, near oceanic regions, tsunamis.
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