A destructive plate boundary, also referred to as a convergent plate boundary, occurs when oceanic crust collides with continental. The oceanic crust, although made of denser basalt, subducts beneath the more buoyant yet far thicker granitic continental crust. This process tends to lead to tectonic activity including earthquakes and volcanic formation from both friction and the melted material rising, and also incorporates some water.
Folding occurs when initially horizontal layers of material become permanently distorted through other geologic forces. In most cases folding occurs from slow, consistent forces that are within a rock's level of tolerance, but can also occur in pre-lithified sedimentary strata. An example of a mountain range formed by folding is the Ridge and Valley Appalachians in the eastern United States
