The underwater mountain is an isolated elevation of the seabed with a clearly defined apex and steep slopes. The relative height according to different definitions should exceed 500 [1] or 1000 m. [2]
Content
Structure and distribution
The tops of seamounts are conical or dome-shaped. The slopes of large mountains, as a rule, are curved upwards, their steepness rarely exceeds 14 °. For smaller objects this parameter can reach 35 °. In the horizontal section, the shape of seamounts is more often elliptical or simply elongated; perhaps this is due to the corresponding form of the fault , from which the lava flows. Rock samples raised from seamounts consist mainly of microcrystalline or glassy oceanic basalt , probably formed from underwater lava flows. The top and slopes of seamounts are usually covered with a layer of marine sediments.
Seamounts are found in all major ocean basins. By the end of the 1970s, more than 10,000 such objects were mapped in the Pacific Ocean alone. Almost every oceanographic expedition finds new seamounts, and their total number in the world is estimated at 20,000. [2]
Examples
Many seamounts are active underwater volcanoes , such as Loihi in Hawaii or Vailuluu off Manua Islands . Mountains of volcanic origin often form a group or are an archipelago sinking beneath the ocean surface. A classic example is the Imperial Mountains - a continuation of the Hawaiian Range , on which the Hawaiian Islands are located. This long chain of seamounts, stretching for thousands of kilometers to the north-west, demonstrates the movement of the plate above the Hawaiian hot spot . Some of the underwater mountains that are underwater volcanoes can become islands, as happened with Surtsey Island off the coast of Iceland or with Ferdinand Island south of Sicily . Not having obvious volcanic origin and detached mountains are less common - Eratosthenes , south of Cyprus or Horseshoe mountains west of the coast of Portugal, are examples.
One of the largest seamounts, the Great Meteor, is located in the North Atlantic . This mountain is a guyot (flat-topped submarine mountain), rising 4 km above the surrounding terrain and having a base diameter of 110 km. [2] The highest mountain on Earth (meaning not the height above sea level, but the distance from bottom to top) —Mauna Kea , its relative height (almost 10,210 m) consists of the underwater part (about 6 km) and height above sea level (4205 m). [3]
Danger
Since not all seamounts are mapped, they are a danger to navigation . For example, the underwater mountain Myurfield was named after the ship that collided with it in 1973. In 2005, the submarine USS San Francisco (SSN-711) collided with an uncharted submarine at a speed of 35 knots, as a result of which it almost sank and lost one sailor [4] .
Seamounts, which are active volcanoes, can make navigation difficult during eruptions. When the collapse of the seamount may occur tsunami . [five]
Notes
- ↑ Underwater (inaccessible link) - Dictionary of Natural Sciences. Glossary.ru
- ↑ 1 2 3 Seamount (English) . - article from Encyclopædia Britannica Online . The appeal date is January 12, 2010.
- ↑ Shield Volcanoes (English) . Usgs The appeal date is January 12, 2010. Archived April 15, 2012.
- ↑ Crew blamed for grounding US sub (eng.) . BBC (May 8, 2005). The date of circulation is January 13, 2010. Archived April 15, 2012.
- ↑ Tsunami sources in the Bay of Plenty (English) . National Institute of Water & Atmospheric Research (September 2007). The date of circulation is January 13, 2010. Archived April 15, 2012.
See also
- Guyot
- Underwater volcano
- Mid-Ocean Ridge
Links
- Seamount Catalog (eng.) . earthref.org. - Database of maps of seamounts. The appeal date is January 12, 2010. Archived April 15, 2012.
- Seamounts Online (eng.) . seamounts.sdsc.edu. - Database on the biology of seamounts. The appeal date is January 12, 2010. Archived April 15, 2012.
- Seamounts, deep sea corals and fisheries (English) . UNEP-WCMC. The appeal date is January 12, 2010. Archived on June 27, 2007.