The formation of volcanoes is Magma under Earth's crust was inserted to the compression pressure cracks to the surface world. The force of the eruption or explosion caused by a volcanic eruption on the volcano's magma is steam, dust, debris and gases. It will be ejected from the crater. (lava ).Volcano are located around the Pacific Plate, in a region called at the Ring of Fire. In the Atlantic Ocean. Indonesia is area volcanoes most erupt because Indonesia near plate boundaries.