San Andreas Fault, California


The San Andreas Fault is one of the world’s biggest fault lines, making it a crucial part of any geological discussion.

Why Is It Famous?

The San Andreas Fault is famous for its incredible length, spanning almost 1,300 kilometers. Its fame also comes from the potential damage it can do if a major earthquake occurs.

What’s Nearby?

The San Andreas Fault sits across California, separating the North American and the Pacific tectonic plates. It creates a line from Cape Mendocino down to the border with Mexico.

Geological Description

The San Andreas Fault’s history began more than 30 million years ago with the collision of the North American and the Pacific tectonic plates. The main section of the fault has only been around for 5 million years or so. The San Andreas Fault is divided into Northern, Central, and Southern zones due to its size.

This is a transform fault, so the two plates rub each other side to side. The plates move slowly, only several inches each year. Geologists can spot the fault at a few locations via pressure ridges and scarps, including at the Olema Trough and the Carizzo Plain. In most cases, however, it is not noticeable unless you pay attention to the variations in rocks on either side of the fault line.

Events in Time

Professor Andrew Lawson from UC Berkeley first discovered the San Andreas Fault in 1895 within its Northern Zone. He named it after the San Andreas Valley that surrounds the fault.

In 1906, the fault made unfortunate history with the great San Francisco Earthquake. This earthquake led Professor Lawson and others to conclude that the fault line extends throughout southern California. Many in California worry about the possible consequences of a future earthquake along the fault line, especially since one has not occurred in a long time.

In Conclusion

The San Andreas Fault runs throughout California and caused the 1906 San Francisco earthquake. It has the potential for significant future damage if another earthquake occurs.