Explain what occurs at a conservative plate boundary and provide an example.

A Conservative plate boundary is where two crustal plates slide past each other, and the movement of the plates is parallel to the plate margin. The plates move with relative horizontal movement which is either sinistral (left) or dextral (right). The plates can either be moving in opposite directions, or in the same direction at differing speeds. The movement of the plates rubbing together side by side creates a build-up of pressure (stresses) between the plate edges. Frictional forces lock the blocks of lithosphere together, until these forces are overcome, and there is a sudden release of friction. This triggers shallow-focus earthquakes, which are occasionally of considerable magnitude. These earthquakes can displace landscapes and man-made features such as roads and rivers. At Conservative plate boundaries, lithosphere is neither created nor subducted, and therefore there is no volcanic activity. An example of a conservative plate boundary is the San Andreas Fault which marks the junction between the North American and Pacific plates. The Pacific Plate (on the west) is moving northwest relative to the North American Plate (on the east). The Pacific plate is moving at a faster rate of 8 cm/year, compared to the North American plate moving at 2.3cm/year. The movements of the San Andreas Fault produced the famous earthquakes of 1906 and 1989 in San Francisco, and if current rates of movement are maintained, LA will be adjacent to San Francisco in approximately 20 million years.