Their magma originates in the upper mantle or the lower crust and varies in composition .
Volcanoes come in all shapes and sizes.
The more common types are shield volcanoes, stratovolcanoes, and cinder cones. Shield volcanoes gained their name from the fact that their profile against the horizon looks like a shield laying on the ground. The flanks of a shield volcano have low slopes, sometimes only a few degrees from horizontal. Shield volcanoes are the largest volcanic features on earth. The largest shield volcano, Mauna Loa in the Hawaiian Islands, has a volume 300 times greater than that of the largest stratovolcano, Mount Fuji in Japan.