What type of stress is associated with convergent boundaries

In the mid-oceanic ridges in the Atlantic and Pacific oceans, molten basalt released under the water hardens into pillow-like blobs, creating new oceanic crust. Hydrothermal vents release hot, mineral-laden water, which resembles black smoke. In some cases, the edges of the plates slide past each other, neither significantly pressing together, nor pulling apart.

Here the movement causes a lateral shear. Where movement causes horizontal displacement, it is called a "strike-slip" fault. The movement isn't smooth; the plates build up stress which eventually releases in a sudden movement, causing earthquakes like the San Fransisco event.

The San Fransisco earthquake provides a vivid example of dangers arising from crustal movement. When movement occurs along a fault, nearby structures suffer damage. As you can see, the fault has had the effect of dropping the block on the right with respect to the block on the left.

If you saw something like this in the field, you'd be able to tell how much offset there was on the fault by measuring how much the layers had moved across the fault. 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. 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. See in the animation below how the various fault types move. Animation is silent and comes from IRIS. Each of these three types of faults is marked in a standard way on a geologic map. Compression squeezes rocks together, causing rocks to fold or fracture.

Rocks that are pulled apart are under tension. Rocks under tension lengthen or break apart. Rocks Are Stressed Stress causes rocks to deform, meaning the rocks change size or shape. There are different kinds of stress that rocks experience, and these determine how the rocks deform. Tensional stress is when rock is stretched apart. Compressional stress is when rock is pressed together. Compression stress squeezes rocks together. Compression causes rocks to fold or fracture Figure below.

This chapter deals with two types of geological activity that occur because of plate tectonics: mountain building and earthquakes. First, we will consider what can happen to rocks when they are exposed to stress. Stress is the force applied to an object. In geosciences, stress is the force per unit area that is placed on a rock. Four types of stresses act on materials. A deeply buried rock is pushed down by the weight of all the material above it.

Since the rock cannot move, it cannot deform called confining stress. Compression squeezes rocks together, causing rocks to fold or fracture. Compression is the most common stress at convergent plate boundaries. Rocks that are pulled apart are under tension. Rocks under tension lengthen or break apart. Tension is the major type of stress at divergent plate boundaries.

When forces are parallel but moving in opposite directions, the stress is called shear. Shear stress is the most common stress at transform plate boundaries. Sedimentary rocks are important for deciphering the geologic history of a region because they follow certain rules. First, sedimentary rocks are formed with the oldest layers on the bottom and the youngest on top.