Explanation:

The continental crust is made mostly of rocks with a composition similar to granite , whereas the oceanic crust is made mostly of rocks with a composition of basalt. The oceanic crust, which, on average, is only about six kilometers thick, is primarily made up of the igneous rock basalt. Basalt tends to come from lava that flows smoothly and quietly from a volcanic vent, unlike the viscous lava typical of the violent eruptions of many continental volcanoes.