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8.4 Note-taking Guide B
1. The place where two plates push together; one plate sinking beneath another;
continental-continental collision, oceanic-continental subduction, oceanic-continental
subduction.
2. Where two continental plates push together; how mountains form.
3. Denser oceanic plate sinks into the asthenosphere; sinking plate is melted; sometimes
the melted rock rises back to the surface and forms volcanoes; if both are oceanic plates,
the older sinks; if continental and oceanic plates meet, the oceanic plate sinks because it
is more dense.
4. Deep-ocean trench forms along coastline. Coastal mountains form as continental plate
buckles, folds, and rises up. Some mountains become volcanoes as magma rises up.
5. Students should draw mountains on the left plate, near the point where the plates meet.
The X can be put anywhere between the mountains and the trench, an oceanic-continental
subduction boundary.
6. The plate on the right; Oceanic plates are more dense, therefore they sink beneath
continental plates.
7. Boundaries occur mainly on the sea floor, a few on land.
8. Geologists can use the theory to understand the geologic history of Earth. Rocks
reveal how the Appalacian Mountains and U. S. Northeast coast formed. Geologists can
also use the theory to predict major geologic events along plate boundaries.