Drifting Continents
pgs. 76-79
pgs. 76-79
Wegener's theory that all continents were once connected and have slowly drifted apart:
Continental Drift
What technology allowed scientists to map the ocean floor?
sonar
Deep underwater canyons where the ocean floor sinks down into the mantle.
Deep-ocean trench
Pieces of Earth's crust, separated by cracks are called _________.
Plates
At this boundary, plates come together/collide:
convergent
The single landmass, or supercontinent from about 300 million years ago:
Pangaea
What is the name of the longest mountain chain where new crust is being added on the ocean floor?
Mid-ocean ridge
PROCESS when the ocean floor sinks back into the crust/mantle:
subduction
The Theory of Plate Tectonics states that the plates are in constant ________.
Motion
At this boundary, plates move apart (divide):
Divergent Boundary
Give an example of the landmass evidence Wegener used to support his theory of Continental Drift:
Mountain Ranges line up- South America and Africa
- North America (Appalachian) and Africa (Little Atlas)
Coal Fields line in- North America and Europe
Sea-floor spreading: Process that occurs at a mid-ocean ridge, that continually ______ more ________ to the ocean floor.
Sea-floor spreading: Process that occurs at a mid-ocean ridge, that continually ADDS more MATERIALS/CRUST to the ocean floor.
Why does subduction occur (explain using density)?
The oceanic rock is cooler and more dense. When it collides with continental crust, gravity pulls the more dense oceanic crust back into the mantle.
What drives the motion of Earth's tectonic plates?
Convection currents in the mantle
At this boundary, plates slip past each other and move in opposite directions:
Transform Boundary
Give an example of the fossil evidence Wegener used to support his theory of Continental Drift:
Glossopteris: Fern-like plant fossil found on multiple continents now separated by oceans, indicates the land was once connected.
Lystrosaurus and Mesosaurus: FRESHWATER reptiles found on continents now separated by SALTWATER oceans. These reptiles would not have been able to survive swimming across oceans, so the reptiles must have lived on a single landmass.
Describe evidence scientists have found for sea-floor spreading.
Ocean material- pillow lava: form when molten material quickly cools after erupting underwater
Magnetic Stripes- Mirror image pattern on both sides on the Mid-Ocean Ridge shows the crust spread from the ridge at the same time
Drilling Samples- Rock samples show that the further away the rock sample was taken, the older it was. Younger rocks found closer to the ridge
Why is the Pacific Ocean getting smaller?
The Pacific Ocean has more deep-ocean trenches, where crust is being destroyed through subduction.
There aren't as many mid-ocean ridges to create new crust.
So the Pacific Ocean is getting smaller.
Faults
Name the landforms/results of a divergent boundary
Rift valley (on land)
Mid ocean ridge (ocean)
Earthquakes
Give an example of the climate evidence Wegener used to support his theory of Continental Drift:
Tropical plant fossils found on an Arctic island- that land must have been somewhere warmer in the past
Glacier scratches found on South Africa- in order for glaciers to exist the land must have been somewhere colder
Name the landforms/results that occur at a convergent boundary:
Mountains (on land)
Trenches (ocean)
Volcanoes (when there is subduction)
Earthquakes