What Is a Geologic Fault?
A fault is a crack in the Earth's crust. Many faults are found along the edges of Earth's plates. Over many many years, the pieces of the Earth's crust can move along a fault in different directions. The moving rocks can cause earthquakes. Along some faults the pieces of the Earth's crust no longer move. These are called inactive faults.
There are different types of faults. The pictures below show what the most common types are like.
- Normal faults
- Normal faults happen in areas where the rocks are pulling apart.
- Reverse faults
- Reverse faults happen when rocks are pushed together.
- Thrust faults are a special type of reverse fault. They happen when the angle of the fault is close to flat.
- Transform (strike-slip) faults
- In these faults, one piece of crust is moving in one direction and another piece of crust is moving in the oposite direction.
- Strike slip faults do not make cliffs or fault scarps because the blocks of rock are not moving up or down.
Many faults are a combination of types.
What Is an Earthquake?
Where Do Earthquakes Happen?
Why Do Earthquakes Happen?
Seismic Waves: Moving and Shaking During an Earthquake
Movie: Designing Earthquake-resistant Buildings
Picture it: Take a look at a fault in Loma Pietra, California
Earthquakes... Indoors - streaming RealVideo (1 min. 6 sec.) from NSF
Shop Windows to the Universe Science Store!
The Fall 2010 issue of The Earth Scientist
, focuses on rocks and minerals, including articles on minerals and mining, the use of minerals in society, and rare earth minerals, and includes 3 posters!
You might also be interested in:
Many forces change the surface of the Earth over time. The largest force that changes our planet’s surface is movement of Earth's outer layer in a process called plate tectonics. As shown in this picture,...more
The ground underfoot might seem like it’s not going anywhere but it is. It moves. If it moves all of a sudden the ground shakes. That’s an earthquake! Earthquakes happen as pieces of the Earth’s crust...more
During an earthquake, the ground shakes making it difficult or impossible to stand up without falling. The land can also roll in waves – sinking in some places and rising in others. How does all this moving...more
Some faults look strong and like they wouldn’t cause an earthquake. But it turns out that they can slip and slide like weak faults causing earthquakes. Scientists have been looking at one of these faults...more
A team of scientists from the United States was invited to visit Haiti in late January 2010 to look into the cause of the magnitude 7 earthquake that happened there. While there, the geologists will collect...more
There has been no icy volcanism on Ganymede, nor continental drift, but it does seem that there have been movements of the surface. Examination of the surface of Ganymede reveals many kinds of faulting....more
Most people in San Francisco, CA were still asleep when an earthquake shook them awake early in the morning of April 18, 1906. It was a very strong earthquake. It lasted for only about a minute, but caused...more