Chapter 7 Plate Tectonics
Terms in this set (40)
Wegener's supercontinent - the most recent one in Earth's history
the hypothesis that suggested all continents are in constant motion on the surface of the Earth
Who proposed the hypothesis of continental drift?
He couldn't prove HOW plates could move (and his degree was in astronomy).
Why didn't other scientists believe Wegener's hypothesis?
He found glacial grooves in warm continents like Africa.
What climate evidence did Wegener find for his hypothesis?
Glossopteris was found in Antarctica, but it only grows in swampy conditions.
What fossil evidence did Wegener find for his hypothesis?
Mountain ranges on different continents were the same age and composition.
What rock evidence did Wegener find for his hypothesis?
underwater mountain range where seafloor spreading happens
process by which new oceanic crust forms along a mid-ocean ridge and older oceanic crust moves away from the ridge
it's less dense than the surrounding rock (convection currents)
Why does magma rise from a mid-ocean ridge?
flat, smooth oceanic crust covered by sediment far from a mid-ocean ridge
near the abyssal plain
Where is oceanic crust older - close to the mid-ocean ridge or near the abyssal plain?
near the mid-ocean ridge
Where is oceanic crust hotter and less dense - near the mid-ocean ridge or the abyssal plain?
a state in which magnetized objects will orient themselves to point north
a state in which magnetized objects will orient themselves to point south
What does basalt have in it that allows the rock to record the Earth's current magnetic field when it forms?
composition, age & magnetic character
If you take a sample of the ocean floor 100 miles east of a mid-ocean ridge and 100 miles west of the same ridge, what 3 things will those samples have in common?
the theory that Earth's surface is made of rigid slabs of rock that move with respect to each other
cold, rigid, outermost layer of Earth
plastic-like layer of Earth (like silly putty) that the plates sit on allowing them to move
divergent plate boundary
type of boundary where two plates separate
landform created when two oceanic plates diverge
landform created when two continental plates diverge
transform plate boundary
type of boundary where two plates slide past each other
convergent plate boundary
type of boundary where two plates collide
deep ocean trench and island arc
two landforms that result from two oceanic plates converging
landform created when two continental plates converge
deep ocean trench and volcanoes
landforms that result from and oceanic plate and a continental plate converging
process where denser plate sinks below a more buoyant plate
oceanic - it's more dense
When a continental plate and oceanic plate converge, which one subducts? Why?
older, colder, denser oceanic plate
When two oceanic plates converge, which one subducts?
What do we use to monitor plate movement now?
earthquakes and volcanoes
What two natural disasters occur at plate boundaries?
the circulation of material caused by differences in temperature and density
radioactivity in Earth's core
Where does the heat come from to drive the convection currents in the asthenosphere and move the plates?
happens when convection moves the lithosphere at the top of the current
occurs when gravity forces the mid-ocean ridge rock to move oceanic crust away from the ridge
force that brings the rest of the plate with it as it is subducted into the mantle at a deep ocean trench
deep ocean trench
The landform where subduction occurs in seafloor spreading.
slab pull, basal drag, ridge push
Along with convection currents, what 3 forces work together to move Earth's crust?