Visual Glossary

Normal fault

We classify faults by how the two rocky blocks on either side of a fault move relative to each other. The one you see here is a normal fault. A normal fault drops rock on one side of the fault down relative to the other side. Take a look at the side that shows the fault and arrows indicating movement. See the block farthest to the right that looks kind of like a foot? That's the foot wall. Now look at the block on the other side of the fault. See how it's resting or hanging on top of the foot wall block? That's the hanging wall.

Now, consider this: if we hold the foot wall stationary, gravity will normally want to pull the hanging wall down, right? Faults that move the way you would expect gravity to move them normally are called normal faults! Not so hard, is it?

Take a look where the fault has ruptured the Earth surface. Notice that movement along the fault has produced an elongate cliff? That fault-generated cliff is called a fault scarp.