Water And Oceanography

Undersea Volcanoes Seamounts



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Seamounts are mountains rising from the deep ocean floor, which don’t reach the surface waters of the sea. Seamounts are usually found rising at between 1,000-4,000 meters (3,280-13100 ft.) from the ocean floor. Seamounts are believed to form from extinct volcanoes. There are approximately 100,000 seamounts in the ocean floors of the planet, and an estimated 30,000 lie in the Pacific Ocean; however, there are many smaller and deeper seamounts that haven’t been analyzed, therefore the exact number may be unknown. Many seamounts are separated from one another by long distances, and each of them hosts an abundance of flora and fauna.

Seamount formation

Most seamounts are of volcanic origin, therefore, they tend to be found on the oceanic crust near mid-ocean ridges, mantle plumes and island arcs. Volcanoes near mid-ocean ridges and plate boundaries form by decompression of melting rock that floats up to the surface, while volcanoes near subducting zones from when the subducting plate adds volatiles to the rising plate. The majority of seamounts are found in the Pacific Ocean, and the remaining are largely distributed across the Atlantic and Indian oceans. Seamounts are usually found in groups of submerged archipelagos, while others can be found in isolation, such as the Eratosthenes in the Mediterranean.

Ecological importance

Seamounts are a very important ecosystem. The physical processes between seamounts and the ocean currents bring together an array of marine life, including corals, fish, plankton, and marine mammals. Their location, above the ocean floor, causes ocean current disturbances. Due to this water movement, seamounts often support large plankton populations, providing an abundant feeding resource for other marine animals. This in turn attracts predators, making seamounts important biological ecosystems. Seamounts often protrude upwards into shallower ocean zones, attracting marine species not usually found on the deep ocean floor.

Biodiversity

Seamounts provide spawning grounds for various animals, including the black stripe cardinal and black oreo fish. Marine mammals, tuna, sharks and cephalopods gather together around seamounts to feed. Where a seamount reaches shallower ocean waters, some species of sea birds can be observed feeding on seamount marine life. The nature of their volcanic structure makes them unique ecologically, producing a variety of fauna that does not exist on the ocean floor. The volcanic rocks on the slopes of seamounts are densely populated by corals. In tropical zones, extensive coral growth forms coral atolls in the late life of a seamount.

Stopping points for migrating animals           

Due to its rich biodiversity, seamounts serve as stopping points for migratory marine animals, such as whales. Recent research suggests that whales may use seamounts as navigational aids throughout their long ocean migrations. Elephant seals and beaked whales tend to feed at seamounts, while bottlenose dolphins Dall’s porpoise and pilot whales make periodic stops for food. According to panda.org, some seamounts offer grounds to spawn and feed for many fish species, while turtles and whales periodically stop at shallow seamounts for food and shelter during their long migrations.

Fishing

The significant attracting effect that seamounts exert on fish populations has not gone unnoticed by the commercial fishing industry. Seamounts have been extensively fished since the second half of the twentieth century, producing a significant depletion of some marine species. The list of fish species in seamounts is surprisingly long. According to seaaroundus.org, many species have identified to be at great risk, especially in the world’s southern oceans where fisheries are outside of the current governing laws of any country. Fleets of fishing boats roam these ocean regions with relative impunity. Dealing with this problem is of immediate priority before the sustainability of these oceanic ecosystems is seriously compromised.

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ARTICLE SOURCES AND CITATIONS
  • InfoBoxCallToAction ActionArrowhttp://ocean.si.edu/ocean-news/seamounts-underwater-oases
  • InfoBoxCallToAction ActionArrowhttp://wwf.panda.org/about_our_earth/blue_planet/open_ocean/surface_waters/
  • InfoBoxCallToAction ActionArrowhttp://www.seaaroundus.org/report/seamounts/11_rwatson_tmorato/rw_tm_text.pdf