So where are they? http://earthquake.usgs.gov/learning/topics/plate_tectonics/plates.php
Constructive plate margin Also called a tensional or divergent boundary This type of boundary is found mainly under the oceans. Here, two plates move apart. This lets the mantle rise up and reach the surface to make new crust (=construct).
There is a constructive plate boundary running down through the middle of the Atlantic Ocean and forms what we call the Mid Atlantic ridge. This is formed as the Eurasian plate and the North American plate move apart.
Here you might get earthquakes. You will also find lots of eruptions as magma comes up to the surface e.g. Iceland The crust on either side of the margin buckle to form ridges and also has lots of faults in it, caused by the massive pressures that the moving plates cause .
Conservative plate margin <ul><li>Here two plates are moving sideways past each other. Crust is neither being formed nor destroyed . This often causes earthquakes. </li></ul>
At the San Andreas fault in California, the North American plate and the Pacific plate are sliding past each other. They are moving in the same direction but the North American plate is moving slightly faster. The Pacific plate is moving north westwards at 6cm a year whilst the North American plate is only moving at 1cm per year. Pressure builds up along the fault until one plate jerks past the other causing an earthquake. The movement has also caused the land to become ridge and crumpled