Conservative plate margins and their characteristics
A conservative plate margin occurs when two plates move parallel to one another. Normally, one plate will be moving in the opposite direction to the other plate and this will very often cause a build up of friction. When one of these large build ups of friction is finally over come, the energy is released into the plate causing it to shudder. This shudder of the plate is known as an earthquake and is the main characteristic of a conservative margin. The point at which the earthquake occurs within the plate is called the epicentre. Directly above the epicentre, on the earth surface is the focus. Frequent Seismic activity is very common at conservative margins. Volcanism is not associated with constructive plate margins and both plates are neither created nor destroyed. A conservative margin is also sometimes referred to as a slip margin or a passive margin or transform boundary.
Probably the most famous example of a conservative margin is the San Andreas Fault that runs through California, on the West coast of North America. The fault line has been active for about 20 million years, it is roughly 800 miles long and is over 15 km deep! On one side of the fault is the Pacific Plate moving northwards and on the other side of the plate is the North American plate moving southwards. Therefore the plates are moving parallel to one another in opposite directions. The last major earthquake experienced along the San Andreas Fault was in 2004 when a magnitude 6 earthquake struck and happened as a result of a fault movement of about 18 inches. These earthquakes are known as Parkfield earthquakes because the Fault line runs through a small town called Parkfield. Between 1857 and 1966, an earthquake of magnitude 6 occurred here every 21 to 24 years and this occurred 6 successive times. Earthquakes may occur here regularly because of it the town’s midway position along the fault line.