How Does Plate Motion Affect the Rock Cycle?

How Does Plate Motion Affect the Rock Cycle?

A Review for Our Unit Exam

Plate Tectonics

• Plate tectonics is the movement of the Earth's crust through convection currents that occur in the mantle.

• Notice that some plates are pulling apart, but others are crashing into each other in this picture.

Igneous Rocks

• Igneous rocks form from the cooling of magma or lava.

• When two plates pull apart, hot magma rises to the surface.

• When magma cools and solidifies at the surface, it becomes new igneous rock.

• New rocks are created here!

Melting Rocks

• Sometimes when two plates collide, one will sink beneath the other.

• As you sink into the Earth, it gets hotter and the sinking crust rock melts.

• Rocks are destroyed here!

Igneous Rocks Again

• When plates collide the sinking plate melts into magma.

• The magma rises to the surface and solidifies into new igneous rock.

• Over time, this forms a volcano.

• New rocks are created here!

Metamorphic Rocks

• Metamorphic rocks form when existing rocks experience a lot of heat or pressure.

• The heat does not melt them, but it "bakes" them and changes them.

• The pressure squeezes them and the atoms in the rock reorganize and change into new substances.

Mountains

• When two continental plates crash into each other, mountains can form

• All the rocks pushing on each other creates a lot of pressure.

• All the rocks grinding past each other creates friction and heat.

• Because of all the pressure and heat, you would expect to find metamorphic rocks in mountains!

Contact Metamorphism

• Metamorphic rocks can also form if the rocks get close to magma.

• The heat from the magma "bakes" the rock and changes it.

Sedimentary Rocks

• When plates smash into each other, the Earth's surface builds up into volcanoes or mountains.

• Wind, water, and ice work to break apart the rocks into pieces.

• These pieces of rock collect someplace else and eventually are pressed and stuck together, forming new sedimentary rock!

The rock cycle summarizes all the changes than can happen to rock material.

What if the Earth cooled and convection in the mantle stopped?

• The plates would stop moving.

• No new igneous or metamorphic rocks would form.

• Mountains and volcanoes would be broken down by weathering and erosion.

• The surface would be much flatter.