Igneous deposits produced by this feature are extrusive in nature. Common plutonic features. Plumes that are able to reach the Earth's surface produce volcanoes . Most of the continental volcanoes found on our planet are located along the edge of the continents where oceanic crust is being actively subducted. In North America, the zone of active volcanoes is located on the west coast where the subduction of the Pacific plate occurs.
Volcanoes add mass to the continents when magma produces lava flows , tephra , and volcanic ash .
Unlike continental crust, oceanic crust is actively being created at the various mid-oceanic ridges . The newly added rock then horizontally pushes previously created ocean crust away from the rift in a conveyor belt fashion. When the oceanic crust encounters a slab of continental crust it becomes subducted because of its greater density. This process causes the oceanic crust to return to the mantle were it is re-melted into magma . The process also causes the movement of continental crust across the surface of the Earth.