Module - Plate Tectonics
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Who developed the continental drift hypothesis
Alfred Wegener
What was the name of the supercontinent that began breaking apart about 200 million years ago
Pangaea
What did Wegener say happened to the continents
They drifted to their present positions
According to Wegener what did continents do to the ocean crust
They broke through the ocean crust
What is one piece of evidence involving the shape of continents
The fit of South America and Africa
What fossil evidence supported Wegener’s hypothesis
Identical fossils found on widely separated land
What rock evidence supported Wegener’s hypothesis
Rock types and mountain structures match across continents
What paleoclimatic evidence supported Wegener’s hypothesis
Glacial deposits found in the Southern Hemisphere including Africa South America India and Australia
What was the main objection to Wegener’s hypothesis
He could not provide a mechanism for continental movement
What is the lithosphere
The Earth’s rigid outer shell made of several plates
Where are most tectonic plates located
Beneath the ocean
What is the largest tectonic plate
The Pacific plate
What is the asthenosphere
A hotter weaker layer beneath the lithosphere that allows plate movement
Where do major plate interactions occur
Along plate boundaries
What happens at divergent plate boundaries
Two plates move apart
Where are most divergent boundaries found
Along oceanic ridge crests
What process occurs at divergent boundaries
Seafloor spreading
What forms when divergent boundaries occur on continents
Rift valleys
What happens at convergent plate boundaries
Plates collide and the lithosphere is subducted into the mantle
What forms at convergent boundaries
Ocean trenches
What happens in oceanic continental convergence
Denser oceanic crust subducts forming magma and volcanic mountains
What are examples of continental volcanic arcs
Andes and Cascades
What happens in oceanic oceanic convergence
One oceanic plate subducts forming volcanic island arcs
What are examples of volcanic island arcs
Aleutian Mariana and Tonga