Chapter 25 Flashcards
a system of mountain ranges on the seafloor separated by valleys
mid-ocean ridge
long narrow depression that forms between peaks along the mid-ocean ridge
rift valley
the boundary where two plates collide
convergent plate boundary
when a thick and buoyant continental plate meets a thin and dense oceanic plate, the denser plate dives beneath the continent in a process called what?
subduction
the boundary between two plates that are moving apart
divergent plate boundary
this type of boundary where plates slide horizontally past each other in opposite directions
transform plate boundary
a sudden movement or vibration of the ground that occurs when rocks slip and slide along enormous cracks in Earth’s crust called faults
earthquakes
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 match up like puzzle pieces
- they found large animal fossils
- mountain ranges match up; rocks are made of same composition and age
what was the name of the super continent?
Pangaea
who came up with the seafloor spreading hypothesis?
Harry Hess
what did he use to map the bottom of the seafloor?
he used sonar
who discovered the mid-ocean ridge?
Harry Hess
where on the bottom of the seafloor is the youngest rock going to be found?
nearest to the MOR (mid-ocean ridge)
what are the types of plate boundaries?
divergent, convergent, and transform boundaries
how do convergent plate boundaries move?
they come together (converge)
subduction zones only occur with which type of plate boundary?
convergent plate boundaries
what two types of crust are involved in plate movement?
oceanic crust and continental crust
what are the types of land forms that can be created when oceanic and continental crust converge?
deep-sea trenches and volcanoes
what land forms are created when two oceanic crusts converge?
deep-sea trenches and hot spots (creates islands)
what land forms are created when two continental crusts converge?
mountains
how do divergent plate boundaries move?
they diverge
what are two specific examples of divergent plate boundaries?
MOR (only on oceanic crust) and East African Rift (only continental crust)
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 does a convection current work?
- magma heats up, becomes less dense, and rises
2. magma cools down, becomes more dense, and lowers
what are other forces that help plate movement?
slab pull, ridge push, and friction
what types of plate boundaries have shallow earthquakes?
divergent and transform plate boundaries
which boundaries have deep earthquakes?
convergent plate boundaries
what are the four types of stress that can be applied to rocks?
compression, tension, shear (two things rubbing together), and torsion (twisting) stress
what are the types of deformation?
elastic and plastic deformation
what happens to a rock if elastic deformation occurs?
as soon as the stress is released, it returns to its original shape
what happens to a rock if plastic deformation occurs?
as soon as the stress is released, it will remain in its new shape
what types of seismic waves are there?
primary waves, secondary waves, and surface waves
which type of seismic waves moves the fastest?
primary wave (p-wave)
what type of wave is a p-wave?
a compression wave (back and forth)
what types of waves are s-waves?
transverse waves (up and down)
what types of material can p-waves move through?
solids and liquids
what types of material can s-waves move through?
only solids
which waves are the most dangerous and complex?
surface waves
what are the two scales that help us measure earthquakes?
the Richter scale and the Mercalli scale
what does the Richter scale measure?
the amount of energy released
what does the Mercalli scale measure?
the amount of damage caused
