Submarine volcano

Submarine volcanoes are volcanoes which are under the surface of the world's oceans. These volcanoes occur in a range of forms. Many create cone-shaped seamounts or flat-topped guyots. 
Volcanoes in the ocean develop from cracks or holes in the earth's undersea surface. Changes in the ocean floor are caused when magma flows or erupts from a site which is under water. 
The presence of water alters the characteristics of a volcanic eruption.