Seamounts and Canyons
While much of the seafloor is a flat, muddy plain, it’s interrupted by dramatic geological features: seamounts and submarine canyons. Similar to and often rivaling their counterparts on land, these seamounts and canyons are among the most important features in the ocean. That’s because they provide habitat for seafloor and water column organisms that scientists have found to be more diverse and abundant than most of the habitats that surround them.
Seamounts are underwater mountains that rise at least 1,000 meters (3,300 feet) above the seafloor. Most are remnants of extinct, underwater volcanoes. Some are active volcanoes. Seamounts can be found in every ocean basin and are typically on the edges of tectonic plates or in chains of seamounts formed by mid-plate hotspots (e.g., the Hawaiian Islands).
Submarine canyons are steep-sided underwater valleys that range in size and shape. Located on continental margins throughout the global ocean, these canyons connect the continental shelf with the deep ocean.
Seamounts rise from the seafloor; canyons cut into it. Their steep slopes affect the flow of the water around and within them. Focused currents transport food and wash away sediments in some areas, exposing hard, rocky surfaces. This results in a dependable food supply and varied physical landscape (e.g., walls, boulders, rocky ledges and outcrops, rubble fields, soft sediments) that enables life on seamounts and in canyons, on the seafloor and in the water column, to flourish.
In the deep ocean, some of the organisms that inhabit seamounts and canyons include deep-sea corals, sponges, and anemones, which are sessile (stationary), in addition to fish and invertebrates like crabs, sea spiders, urchins, sea stars, sea cucumbers, worms, shrimp, octopods, squid, and jellyfish that move freely across the seafloor and/or within the water column.
