# Relationship between faults and plate boundaries

### Faults | HowStuffWorks

Nov 30, All faults are related to the movement of Earth's tectonic plates. The biggest faults mark the boundary between two plates. Seen from above. Intraplate faults generally don't penetrate very deep into the crust. Plate boundaries are where two distinct plates are adjacent. The San. Earthquakes happen due to the movement of the crust at fault lines. The movement of the plates on either side of the fault causes the edges to.

These faults occur where the crust is being pulled apart, at a divergent plate boundary. This content is not compatible on this device.

### What's the Difference Between a Fault and a Plate Boundary? | Yahoo Answers

The fault plane in a reverse fault is also nearly vertical, but the hanging wall pushes up, and the footwall pushes down. This sort of fault forms where a plate is being compressed.

A thrust fault moves the same way as a reverse fault, but at an angle of 45 degrees or less [source: In these faults, which are also caused by compression, the rock of the hanging wall is actually pushed up on top of the footwall at a convergent plate boundary. In a strike-slip fault, the blocks of rock move in opposite horizontal directions. These faults form when crust pieces slide along each other at a transform plate boundary.

The San Andreas Fault in California is one example of a transform plate boundary. With all these faults, rocks push together tightly, creating friction. If there's enough friction, they become locked, so that they won't slide anymore. Meanwhile, the Earth's forces continue to push against them, increasing the pressure and pent-up energy. If the pressure builds up enough, it will overcome the friction, the lock will give way suddenly, and the rocks will snap forward.

To put it another way, as the tectonic forces push on the "locked" blocks, potential energy builds.

## What's the Difference Between a Fault and a Plate Boundary?

If we instead apply compressive stress, this has the effect of squeezing and shortening the terrain. A fault will form that looks an awful lot like the normal fault in the previous example, but the motion on this fault is in the opposite direction. This fault is called a reverse fault because it is the "reverse," meaning opposite, of normal. Reverse faults tend to form scarps--a scarp is the piece of rock that has been thrust up higher than the original surface level. The third typical fault type is the strike-slip fault.

Strike-slip faults are distinct from the previous two because they don't involve vertical motion. They form via shear stress.

Plate Boundaries - The Different Types of Plate Boundaries - GCSE Geography

These are not as easy to recognize in cross-section unless there has been so much movement on the fault that there are completely different rock types on either side of the fault. Most strike-slip faults are close to vertical with respect to the bedding.

Faults at plate boundaries: Here are some animations of the lithosphere's sense of motion at plate boundaries. The first one is a mid-ocean ridge. Is the crust younger or older the farther it gets from the ridge? The strike-slip fault depicted above is what geologists call a "left-lateral" strike slip fault. If you stand on one side of the fault and look across to the other side, the other side is moving to your left. If you have a nice grove of orange trees and the fault happens to cut right through your grove, the rows of orange trees will gradually become offset as the fault continues to move.

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Each of these three types of faults is marked in a standard way on a geologic map. I've sketched those symbols below.

A normal fault is typically shown by a line representing the fault trace with a little perpendicular line to show the direction of the block that has slid down. Sometimes two parallel lines are drawn to represent plates moving apart instead. A reverse fault is a line with teeth on it. The teeth are drawn on the side of the overriding block. At a subduction zone plate boundary, the teeth are on the upper plate. A strike-slip fault is drawn as a line, usually but not always with a half-arrow on each side to show which direction the two sides of the fault are moving.

The example below shows a left-lateral fault. Fault symbol ID check! Can you identify the type of faulting occurring at each plate boundary in the map below? Check your answer here.