Plate Boundaries Flashcards
What are the four different plate boundaries?
Constructive
Destructive
Collision
Conservative
What is the constructive plate boundary?
Two plates under the ocean are pulled apart by the convection currents in the soft rock below them. Liquid rock (magma) rises between the plates. It hardens to basalt which forms new ocean. So the ocean floor is getting wider - by about 2cm a year. This process causes earthquakes and volcanoes.
What is the destructive plate boundary?
Two plates are pushing against each other but one is heavier and so gets pushed under at an ocean trench. The rock jolts and grinds its way down, causing earthquakes at the same time it heats up. Some rock melts, and forces its way up through the Andes to form a volcano.
What is the collision plate boundary?
The crust gets pushed and folded upwards to form a mountain. The movement of the rock causes earthquakes but no rock gets pushed down and melted - so no volcanoes.
What is the conservative plate boundary?
Two plates can either be moving in the same direction, but one is moving faster than the other, or two plates can be moving in a different direction. With either one of these scenarios, parts of the plates get stuck, then lurch free which causes earthquakes. But no rock rock is pushed down and melted so no volcanoes.
