WHEN PLATES MOVE

Why do plates move?
The plates can be thought of like pieces of a cracked shell that rest on the hot, molten rock of Earth's mantle and fit snugly against one another.

The heat from radioactive processes within the planet's interior causes the plates to move, sometimes toward and sometimes away from each other. It moves in a pattern called a convection cell that forms when warm material rises, cools, and eventually sinks. As the cooled material sinks, it is warmed and rises again.

When plates move
they collide or spread apart letting the quite hot molten material called lava to escape from the mantle. (p. 5) Even though plates move very slow, the motion is called plate tectonics, which has an immense impact on the Earth. (p. 7) When collisions occur, plate tectonics produce oceans, deep underwater valleys called trenches, continents, mountains, and volcanoes. As mountains and valleys are being formed, it also helps us understand why and where natural disasters such as earthquakes and volcanic activity can occur, which has affected humans for thousands of years. The movement creates 3 types of tectonic boundaries: convergent, divergent, and transform.

INTERESTING FACT
They move at a rate of one to two inches (three to five centimeters) per year.

1. Convergent Boundaries
A convergent boundary (also known as a destructive boundary) is an area on Earth where two or more lithospheric plates collide. One plate eventually slides beneath the other, a process known as subduction. The subduction zone can be defined by a plane where many earthquakes occur, called the Wadati–Benioff zone.


1.1 Oceanic-Oceanic Convergence
When two oceanic plates collide, the denser plate sinks below the lighter plate and eventually forms dark, heavy, basaltic volcanic islands.
1.2 Oceanic-Continental Convergence
When oceanic crust converges with continental crust, the denser oceanic plate plunges beneath the continental plate. The subduction occurs at the oceanic trenches. This causes earthquakes and forms a line of volcanoes known as a continental arc.
1.3 Continental-Continental Convergence
The two continental plates pit large slabs of crust against each other. This results in very little subduction, as most of the rock is too light to be carried very far down into the dense mantle. Instead, the continental crust at these convergent boundaries gets folded, faulted, and thickened, forming great mountain chains of uplifted rock.