The Earth Moves: The Crust in Action

Help the Earth is spinning too fast!!

How is crust formed?Divergent Boundary

Crust is formed at mid-oceanic ridges. As the lava is extruded from the mantle it is rapidly cooled by the surrounding oceanic water, which slowly moves away from the ridge as more lava emerges.

Three ways to destroy crust!

Subduction Zone

Oceanic and Continental crust subduction zone. The ocean crust is being destroyed as it is pushed back into the mantle.ANCIENT CRUST

How to destroy crust #2!Subduction Zone #2

Continental and Continental crust subduction zone. One continental crust is being forced under the other. This is what has formed many mountain ranges. The force of the two crusts pushing together pushes up the mountain range. Of course the crust being forced into the mantle is destroyed.

Destroying Crust #3Subduction Zone #3 Oceanic crust to

Oceanic crust. One crust is pushing the other down into the mantle. Where this is happening, you often get an arc of volcanic islands as is illustrated on the picture. ANCIENT CRUST

What causes the movement?

Convection Currents

The cells of superheated rock begin to rise in a column and cannot fall in the same place as it is rising, which creates the circular movement known as convection currents. This current occurs in the mantle and moves the relatively small crust.

How do we know it convects?

All things that we have heated eventual convect and start that circular motion called a convection current.

You can test this at home with the supervision of an adult.

Take a pan of water and heat it to boiling. Place a small amount of rice into the boiling liquid and watch it sink and rise in a circular motion.

Do plates move in other ways?

Faulting

When plates move side by side and rub their edges together, we refer to the area as a fault line or fault. This is one way in which a fault can manifest when it causes an earthquake. The earthquake is caused by the sudden release of pressure. This slip causes the shaking and destruction.

Perhaps the most famous of faults in the United States is the San Andreas Fault in southern California.

Moving Plate make Earthquakes!!

This movement against each other builds up pressure and eventually is released in a jerking motion as the rock spurs holding it together break.

How do we detect earthquakes?

We use a tool known as a seismograph.

Because a magnet moving inside a coil creates a current within the coil, the movement of the ground during an

earthquake can be converted into an electrical signal.

This signal could then be used to modify the projection of light onto photographic

paper, or to move a needle across paper and trace out the wiggles of the Earth's shaking.

To Review!!!!!!!!!!!How and where is crust formed?

At mid-oceanic ridges, where lava is forced up and rapidly cooled by the ocean, pushing older crust further away from the rift valley.

Crust is destroyed at what zone?

The Subduction Zone

What three types of crustal interaction take place in those subduction zones?

Oceanic to Oceanic, Oceanic to Continental, and Continental to Continental.

What is the current called which moves the plates?

Convection current

What other ways do plates move?

Faulting

What causes earthquakes?

The building of pressure between the plates.