# Chapter 5 Lesson 2 The Moving Crust

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Chapter 5 Lesson 2 The Moving Crust
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Earth’s surface is broken into several large pieces called tectonic plates.

A fault is a crack in the crust where the plates meet.

These plates are constantly slowly moving
These plates are constantly slowly moving. This movement creates changes in the Earth’s surface.

A fault-block mountain forms when one plate slides on top of another plate as they push together.

If two plates push together and both plates push up, a fold occurs.
Folded Mountains

When a sudden movement along a fault occurs, an earthquake takes place
When a sudden movement along a fault occurs, an earthquake takes place. This is cause by pressure being built up for a long time along a fault.

The energy released during an earthquake travels in waves through the earth. These are called seismic waves.

Scientists use an instrument called a seismograph to measure seismic waves.

The magnitude of an earthquake is how strong the earthquake is
The magnitude of an earthquake is how strong the earthquake is. The Richter Scale is how the magnitude of earthquakes are rated.

If an earthquake takes place below the ocean, and is powerful enough, it can cause a giant wave called a tsunami.

A volcano is a mountain that builds up around an opening in the Earth’s crust.

Most volcanoes occur at the edges of tectonic plates where magma (melted rock) pushes towards the surface.

A volcanic eruption can send out melted rock (lava), gases, ash, or rocks into the air.