Seamount

A seamount is like a really tall mountain, but instead of being on land, it's under the water in the ocean. Seamounts are formed by hot magma (really hot melted rock) coming up from the Earth's mantle and forming a big pile on the ocean floor. Over millions of years, as the tectonic plates (kind of like puzzle pieces that make up the Earth's crust) move around, seamounts can sometimes become islands or they can sink back down into the ocean. Seamounts are really important because they provide habitats for all kinds of sea creatures, from tiny plankton all the way up to big fish and whales.