Copyright

What is a Normal Fault? - Definition & Example

What is a Normal Fault? - Definition & Example
Coming up next: Who was Alfred Wegener? - Biography, Facts, Theory & Accomplishments

You're on a roll. Keep up the good work!

Take Quiz Watch Next Lesson
 Replay
Your next lesson will play in 10 seconds
  • 0:01 What is Normal and…
  • 0:33 Normal Fault vs Reverse Fault
  • 1:02 Hanging Wall and Footwall
  • 2:36 Horst and Graben
  • 3:20 Additional Fun Fact
  • 3:45 Lesson Summary
Save Save Save

Want to watch this again later?

Log in or sign up to add this lesson to a Custom Course.

Log in or Sign up

Timeline
Autoplay
Autoplay
Speed

Recommended Lessons and Courses for You

Lesson Transcript
Instructor: Mary Ellen Ellis
A normal fault is no more typical, or better, than any other kind of fault. But it is responsible for certain mountain ranges and other interesting geological features in the earth's crust.

What is Normal and What is Not?

The term, 'normal fault' actually comes from coal mining, but more about that later. A fault, which is a rupture in the earth's crust, is described as a normal fault when one side of the fault moves downward with respect to the other side. The opposite of this, in which one side moves up, is called a reverse fault. To remember what a normal fault is, think about it this way: it seems more normal for earth to slide down (because of gravity) than it is for it to go up. Earth moving down is normal; moving up is reverse.

Normal Fault vs. Reverse Fault

Imagine a fault in the earth. It could be a small one in the middle of a continent, or it could be a large plate boundary. Think about what would happen if some force, like the movement of the earth's tectonic plates, pulled the earth apart on either side of the fault. What would happen? One side of the fault would have some wiggle room, causing it to slide downward. This is what happens at a normal fault. Now consider the opposite. When a fault is squeezed together, the earth gets pushed up, which is what happens at a reverse fault.

Hanging Wall and Footwall

We have terminology for the two sides of a fault. In a normal fault, the side that slides downward has a shape that makes it look like it is reaching, or hanging, out over the side, so we call it the hanging wall. The other side is shaped a little bit like a foot. We call that the footwall. The hanging wall slides down the footwall.

normal fault

In this picture of a normal fault, the valley is the hanging wall and the mountain is the footwall.

The motion between the two is not always smooth, and sometimes the walls get caught on each other. Pressure builds up and can be released with a great amount of energy, producing an earthquake. These are less common than earthquakes produced by strike-slip faults, which move past each other horizontally instead of vertically. The San Andreas Fault in California is an example of a strike-slip fault.

normal fault

In the image you can see a normal fault where the white line of rock has been disrupted. The hanging wall is to the left of the fault and the footwall to the right.

This sliding downward of normal faults creates rifts, valleys, and mountains. The rift basin at the bottom of the North Sea is an example of a normal fault in action. The Humboldt Fault in Kansas is another example of a normal fault. It produced a memorable earthquake in Kansas in 1867. There are multiple normal faults in Nevada and Utah that have produced the unique landscape of those states. The Sierra Nevada Fault is also normal and is a spectacular example of the kinds of mountains these faults can create.

To unlock this lesson you must be a Study.com Member.
Create your account

Register to view this lesson

Are you a student or a teacher?

Unlock Your Education

See for yourself why 30 million people use Study.com

Become a Study.com member and start learning now.
Become a Member  Back
What teachers are saying about Study.com
Try it risk-free for 30 days

Earning College Credit

Did you know… We have over 200 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Transferring credit to the school of your choice

Not sure what college you want to attend yet? Study.com has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

Create an account to start this course today
Try it risk-free for 30 days!
Create an account
Support