%Plate Tectonics Flashcards
What is subsidence?
The downward vertical motion of Earth’s surface is called subsidence.
What is isostasy?
Isostasy is the equilibrium between continental crust and the denser mantle below it.
What is uplift?
The upward vertical motion of Earth’s surface is called uplift.
What are the three types of stress?
Compression- Squeezing stress
Shear- Parallel forces acting in opposite directions
Tension- Stress that pulls something apart
What is strain?
A change in the shape of rock caused by stress is called strain.
What are the two types of strain?
Elastic strain- does not permanently change, or deform, rocks
Plastic strain- creates a permanent change in shape(occurs when rocks are weak or hot)
When rocks fail, which is when strain breaks rocks rather than just changing their shape, what forms?
Faults form.
Where are the largest landmarks produced?
The largest landforms on Earth are produced by compression at convergent plate boundaries.
What landforms can be created by compression?
Mountain ranges, ocean trenches, and volcanic arcs
What are ocean trenches?
Ocean trenches are deep, underwater troughs created by one plate subducting under another plate at a convergent plate boundary.
What are volcanic arcs?
A curved line of volcanoes that forms parallel to a plate boundary is called a volcanic arc.
What are the two ways volcanic arcs(or island arcs) can form?
- In the ocean- when plates converge and one plate subducts under another plate it creates volcanoes on the ocean, which form islands.
- On land- when an oceanic plate subducts under a continental plate. The volcanoes then sit on top of the continent.
What are the two landforms formed by tension?
Mid-ocean ridges
Continental rifts
How do mid ocean ridges form?
As tension stresses cause oceanic crust to spread apart, hot rock from the mantle rises. Because hot rock is less dense than cold rock, the hot mantle pushes the seafloor upward. In this way, long, high ridges are created in Earth’s oceans.
How do continental rifts form?
When divergent boundaries occur within a continent, they can form continental rifts, or enormous splits in Earth’s crust. Tension stresses in the cold upper part of the crust create faults. At these faults, large blocks of crust move downward, creating valleys between two ridges.
