CH 25 Flashcards
a system of mountain ranges on the seafloor separated by valleys
mid-ocean ridge
a long, narrow depression that forms in between peaks along the mid-ocean ridge
rift valley
the boundary where two plates collide
convergent plate boundary
the process of which when a thick and buoyant continental plate meets a thin and dense oceanic plate, the denser plate dives beneath the continent
subduction
the boundary between two plates that are moving apart
divergent plate boundary
boundary where plates slide horizontally past each other in opposite directions
transform plate boundary
the sudden movement or vibration of the ground that occurs when rocks slip and slide along enormous cracks in Earth’s crust called faults
earthquake
a crack in Earth’s crust along which rock has moved
fault
a sudden release of strain energy as rock moves along a fault
elastic rebound
the point of origin for an earthquake
focus
the point on Earth’s surface directly above the focus
epicenter
Who came up with the continental drift hypothesis?
Alfred Wegener
What were some pieces of evidence that supported Wegener’s hypothesis?
- coastlines linked up nearly perfectly
- large land animal fossils
- mountain ranges and rocks types link up
What was the name of this super-continent?
Pangaea
Who came up with the Seafloor Spreading Hypothesis?
Harry Hess
How did Harry Hess map the bottom of the seafloor?
sonar
Who discovered the mid-ocean ridge (MOR) system?
Harry Hess
Where is the youngest seafloor rock located?
near the MOR
What are the types of plate boundaries?
divergent, convergent, transform
How do convergent plate boundaries move?
they collide
Subduction zones only occur during which type of plate boundary?
convergent plate boundary
What two types of crust are involved in plate movement?
oceanic crust & continental crust
What are the types of land forms that can be created when oceanic crust and continental crust converge?
deep-sea trenches & volcanoes
What types of land forms can be created when two oceanic crusts converge?
deep-sea trenches & hot spots (creates islands)
What type of land forms can be created when two continental crusts converge?
mountains
How do divergent plate boundaries move?
apart
What are two specific examples of divergent plate boundaries?
MOR (oceanic crust only) & the East African Rift
How do transform plate boundaries move?
they slide past each other
What is a specific example of a transform plate boundary?
the San Andreas Fault (two continental crusts)
How do convergent plate boundaries move?
together
How does a convection current work?
- magma heats, becomes less dense, rises
2. rock cools, becomes more dense, sinks
What are other forces that help plate movement?
slab pull, ridge push, friction
What types of plate boundaries have shallow earthquakes?
divergent & transform
Which type of plate boundary has deep earthquakes?
convergent
What are the four types of stress that can be applied to rocks?
- compression
- tension
- shear
- torsion
What are the types of deformation?
elastic & plastic
What happens to a rock during elastic deformation?
Soon as the stress is released, it returns to it’s original shape.
What happens to a rock during plastic deformation?
After the stress is released, it stays in the new shape.
What types of seismic waves are there?
primary waves, secondary waves, & surface waves
Which type of seismic wave moves the fastest?
primary wave (p-wave)
How do primary waves move?
compression waves
How do secondary waves move?
transversal waves
What types of materials can p-waves move through?
solids & liquids
What types of materials can s-waves move through?
solids
Which waves are the most complex/dangerous?
surface waves
What two scales are used to help measure earthquakes?
the Ritcher Scale and the Mercalli Scale
What does the Ritcher Scale measure?
the amount of energy released?
What does the Mercalli Scale measure?
the amount of damage caused
