Seamount is a volcano that forms on the ocean floor. There may be as many as 1 million volcanoes on the Pacific Ocean floor alone, roughly 750 times the number on dry land. Seamounts occur throughout the ocean, wherever magma (melted rock inside the earth) rises to the sea floor and erupts. These submerged volcanoes form in deep basins, in areas near the continents, and at the mid-ocean ridges where lava (magma that has erupted) hardens into new sea floor material.