Davidson Seamount
Encyclopedia
Davidson Seamount is a seamount
Seamount
A seamount is a mountain rising from the ocean seafloor that does not reach to the water's surface , and thus is not an island. These are typically formed from extinct volcanoes, that rise abruptly and are usually found rising from a seafloor of depth. They are defined by oceanographers as...

 (underwater volcano
Submarine volcano
Submarine volcanoes are underwater fissures in the Earth's surface from which magma can erupt. They are estimated to account for 75% of annual magma output. The vast majority are located near areas of tectonic plate movement, known as ocean ridges...

) located off the coast of Central California, 80 mi (129 km) southwest of Monterey and 75 mi (121 km) west of San Simeon. At 26 mi (42 km) long and 8 mi (13 km) wide, it is one of the largest known seamounts in the world. From base to crest, the seamount is 7480 ft (2,280 m) tall, yet its summit is still 4101 ft (1,250 m) below the sea surface. The seamount is biologically diverse, with 237 species and 27 types of deep-sea coral having been identified.

Discovered during the mapping of California's coast in 1933, Davidson Seamount is named after geographer George Davidson
George Davidson (geographer)
George Davidson was an geodesist, astronomer, geographer, surveyor and engineer in the United States.-Biography:Born May 9, 1825 in England, he came to the U.S. in 1832 with his parents, who settled in Pennsylvania...

 of the U.S. National Geodetic Survey
U.S. National Geodetic Survey
National Geodetic Survey, formerly called the U.S. Coast and Geodetic Survey , is a United States federal agency that defines and manages a national coordinate system, providing the foundation for transportation and communication; mapping and charting; and a large number of applications of science...

. Studied only sparsely for decades, NOAA expeditions to the seamount in 2002 and 2006 cast light upon its unique deep-sea coral
Deep water coral
The habitat of deep water corals, also known as cold water corals, extends to deeper, darker parts of the oceans than tropical corals, ranging from near the surface to the abyss, beyond where water temperatures may be as cold as 4°C...

 ecosystem. Davidson Seamount is populated by a dense population of large, ancient corals, some of which are over 100 years of age. The data gathered during the studies fueled the making of Davidson Seamount into a part of the Monterey Bay National Marine Sanctuary
Monterey Bay National Marine Sanctuary
The Monterey Bay National Marine Sanctuary is a US Federally protected marine area offshore of California's central coast around Monterey Bay....

 in 2009.

Geology

A seamount
Seamount
A seamount is a mountain rising from the ocean seafloor that does not reach to the water's surface , and thus is not an island. These are typically formed from extinct volcanoes, that rise abruptly and are usually found rising from a seafloor of depth. They are defined by oceanographers as...

 such as Davidson is an underwater volcano
Submarine volcano
Submarine volcanoes are underwater fissures in the Earth's surface from which magma can erupt. They are estimated to account for 75% of annual magma output. The vast majority are located near areas of tectonic plate movement, known as ocean ridges...

; this one rises over 3280 ft (1,000 m) above the surrounding ocean floor. Although there are over 30,000 seamounts in the Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...

 alone, only about 0.1% of them have been explored. The aqueous environment of the seamount means that it behaves differently to volcanoes on land. Its surface is composed mostly of blocky lava flows, although some pillow lava
Pillow lava
Pillow lavas are lavas that contain characteristic pillow-shaped structures that are attributed to the extrusion of the lava under water, or subaqueous extrusion. Pillow lavas in volcanic rock are characterized by thick sequences of discontinuous pillow-shaped masses, commonly up to one metre in...

, which is the typical lava type of a seamount, prevails at the deeper flank. The summit is composed of layered deposits of volcanic ash
Volcanic ash
Volcanic ash consists of small tephra, which are bits of pulverized rock and glass created by volcanic eruptions, less than in diameter. There are three mechanisms of volcanic ash formation: gas release under decompression causing magmatic eruptions; thermal contraction from chilling on contact...

 and pyroclastic material
Pyroclastic rock
Pyroclastic rocks or pyroclastics are clastic rocks composed solely or primarily of volcanic materials. Where the volcanic material has been transported and reworked through mechanical action, such as by wind or water, these rocks are termed volcaniclastic...

. These rocks indicate mildly explosive eruptions of gas-rich lava near the summit of the volcano. The base of Davidson is probably buried in a deep layer of muds.

At 26 mi (42 km) long and 8 mi (13 km) wide, Davidson Seamount is impressively large. If it were on land, it would dominate the landscape in a way similar to how Mount Shasta
Mount Shasta
Mount Shasta is located at the southern end of the Cascade Range in Siskiyou County, California and at is the second highest peak in the Cascades and the fifth highest in California...

 dominates the horizon of northern California. Put in perspective, the size of the seamount is enough to fill Monterey Bay
Monterey Bay
Monterey Bay is a bay of the Pacific Ocean, along the central coast of California. The bay is south of San Francisco and San Jose, between the cities of Santa Cruz and Monterey....

 from the Santa Cruz
Santa Cruz, California
Santa Cruz is the county seat and largest city of Santa Cruz County, California in the US. As of the 2010 U.S. Census, Santa Cruz had a total population of 59,946...

 boardwalk to Monterey's Fishermen's Wharf.

Davidson Seamount is part of a group of seamounts off the continental margin, including Guide
Guide Seamount
Guide Seamount is a seamount in the eastern Pacific Ocean, about 16.6±0.5 million years old. It is similar in shape and orientation to the nearby Davidson, Pioneer, Rodriguez, and Gumdrop seamounts. It is named for the U.S. National Geodetic Survey survey ship the US&GS Guide.Guide Seamount is...

, Pioneer
Pioneer Seamount
Pioneer Seamount is an undersea mountain, or seamount, in the Pacific Ocean off the coast of central California.-Location:Pioneer Seamount is located at 37° 21.1' North Latitude, 123° 26.1' West Longitude, at the base of the continental slope of North America about 95 kilometers off the coast just...

, Gumdrop
Gumdrop Seamount
Gumdrop Seamount is a small seamount located on the flank of Pioneer Seamount, off the coast of Central California. It is the northern-most of the related seamounts in the region, which includes Davidson, Guide, Pioneer, and Rodriguez seamounts...

, and Rodriguez
Rodriguez Seamount
Rodriguez Seamount is a seamount and guyot located about off the coast of Central California. It is structurally similar to the nearby Guide, Pioneer, Gumdrop, and Davidson seamounts, all located roughly between 37.5° and 34.0° degrees of latitude. This group of seamounts is morphologically...

 seamounts, all located roughly between 37.5° and 34.0° degrees of latitude
Latitude
In geography, the latitude of a location on the Earth is the angular distance of that location south or north of the Equator. The latitude is an angle, and is usually measured in degrees . The equator has a latitude of 0°, the North pole has a latitude of 90° north , and the South pole has a...

. This group is morphologically unique, and very similar to one another. All the seamounts in the group are complex northeast-southwest trending structures, consisting of parallel ridges separated by sediment-filled troughs. The ridges constructed run parallel to an ancient spreading center
Plate tectonics
Plate tectonics is a scientific theory that describes the large scale motions of Earth's lithosphere...

 which has since been replaced in its role by the San Andreas Fault
San Andreas Fault
The San Andreas Fault is a continental strike-slip fault that runs a length of roughly through California in the United States. The fault's motion is right-lateral strike-slip...

 system. They are unique in this origin, as they are formed from the remnants of an old ocean-ridge spreading center
Mid-ocean ridge
A mid-ocean ridge is a general term for an underwater mountain system that consists of various mountain ranges , typically having a valley known as a rift running along its spine, formed by plate tectonics. This type of oceanic ridge is characteristic of what is known as an oceanic spreading...

. A series of "knobs" are aligned with the ridges; however the distinctive summit crater
Volcanic crater
A volcanic crater is a circular depression in the ground caused by volcanic activity. It is typically a basin, circular in form within which occurs a vent from which magma erupts as gases, lava, and ejecta. A crater can be of large dimensions, and sometimes of great depth...

, evident in many oceanic volcanoes, is absent. This lack of a collapse crater suggests that magma was never stored in a chamber within the structure, as with most other volcanoes.

Analysis of argon–argon dating studies indicate that Davidson formed between 9 and 15 million years ago, 5 to 12 million years after the formation of the overlaying oceanic crust.

Ecology

Studies have indicated that a seamount functions as an "oasis of life," with a higher species count and more biodiversity
Biodiversity
Biodiversity is the degree of variation of life forms within a given ecosystem, biome, or an entire planet. Biodiversity is a measure of the health of ecosystems. Biodiversity is in part a function of climate. In terrestrial habitats, tropical regions are typically rich whereas polar regions...

 then the surrounding seafloor. Although previous analysis has stressed the exceptionally of the seamount habitat, recent biological analysis, much of it centered on Davidson Seamount, has indicated that this does not necessarily translate into a higher endemic percentage. However, it is believed that they provide a refuge for rare species that have difficulty surviving elsewhere.

There are reasons that seamounts are biologically important. They rise high in the water column, creating complex current patterns that support life on, around, and above the seamount. The surface of the seamount also provides a substrate upon which organisms can attach themselves and grow. This in turn supports the species that feed on them, in turn supporting the whole ecological food web
Food web
A food web depicts feeding connections in an ecological community. Ecologists can broadly lump all life forms into one of two categories called trophic levels: 1) the autotrophs, and 2) the heterotrophs...

. Scientists have found that seamounts often provide a habitat for endemic species that are not found anywhere else.

Davidson Seamount is among the best biologically described seamounts worldwide. Six major expeditions to the volcano have yielded over 60,000 species observations. scientists have observed and recorded 168 species of megafauna
Megafauna
In terrestrial zoology, megafauna are "giant", "very large" or "large" animals. The most common thresholds used are or...

 on the seamount. Of these, about 7% of the species at Davidson are endemic, meaning they live only at Davidson. 71% of the species can be confidently classified as cosmopolitan
Cosmopolitan distribution
In biogeography, a taxon is said to have a cosmopolitan distribution if its range extends across all or most of the world in appropriate habitats. For instance, the killer whale has a cosmopolitan distribution, extending over most of the world's oceans. Other examples include humans, the lichen...

 (widespread), and sufficient data exists for 22% of the observed species to strongly suggest that their range is not limited to seamounts. The remaining 7% have only been seen in video footage. Interestingly, 13 species have been identified in other areas, but never in other seamounts.

The seamount is populated by a large variety of deep-sea coral
Deep water coral
The habitat of deep water corals, also known as cold water corals, extends to deeper, darker parts of the oceans than tropical corals, ranging from near the surface to the abyss, beyond where water temperatures may be as cold as 4°C...

s, most of which in turn provide a habitat for other species. It has in the past been called "An Oasis in the Deep", hosting a vast coral forest, large sponge field, crab
Crab
True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...

s, deep-sea fish, basket star
Basket star
Basket stars are a group of brittle stars. They are treated as a suborder Euryalina or order Euryalida. Many of them have characteristic many-branched arms. They generally live in deep sea habitats.The life span in the wild is up to 35 years. They weigh around 11 lbs, or 5 kg...

s, and a number of rare benthic species, some of which have yet to be studied properly or even named. These are all cold-water species, as the temperature even at the top of the seamount is just above freezing—around 2 °C (36 °F), as compared to 14 °C (57 °F) at the ocean's surface.

Despite its size, the top of Davidson Seamount remains over 4500 ft (1,372 m) below the ocean's surface. This great depth means that the habitats that the seamount supports have not been significantly disturbed by human activity; anchor
Anchor
An anchor is a device, normally made of metal, that is used to connect a vessel to the bed of a body of water to prevent the vessel from drifting due to wind or current. The word derives from Latin ancora, which itself comes from the Greek ἄγκυρα .Anchors can either be temporary or permanent...

ing and trawling typically does not occur below a depth of 1500 ft (457 m), and waste disposal and discharge occurs much closer to shore.

In comparisons drawn to the nearby Monterey Bay National Marine Sanctuary
Monterey Bay National Marine Sanctuary
The Monterey Bay National Marine Sanctuary is a US Federally protected marine area offshore of California's central coast around Monterey Bay....

, the two were shown to be very different biologically. Species that are rare in Monterey Bay are common on Davidson, and vice versa.

Deep-sea coral

The ecology on Davidson Seamount is dominated by an extensive "forest" of ancient deep-sea coral
Deep water coral
The habitat of deep water corals, also known as cold water corals, extends to deeper, darker parts of the oceans than tropical corals, ranging from near the surface to the abyss, beyond where water temperatures may be as cold as 4°C...

 and sponges, some of which are over 100 years old. Although these species also grow elsewhere, they are generally sparsely distributed and far smaller and younger than the coral growth on Davidson. Conversely, sea cucumber
Sea cucumber
Sea cucumbers are echinoderms from the class Holothuroidea.They are marine animals with a leathery skin and an elongated body containing a single, branched gonad. Sea cucumbers are found on the sea floor worldwide. There are a number of holothurian species and genera, many of which are targeted...

s, which are very common on the walls of Monterey Canyon
Monterey Canyon
Monterey Canyon, or Monterey Submarine Canyon, is a submarine canyon in Monterey Bay, California. It is the subject of ongoing study by the scientists at the Monterey Bay Aquarium Research Institute, the Moss Landing Marine Laboratories, and other oceanographic institutions.Monterey Canyon begins...

, are all but absent on Davidson, an example of the polarity between Davidson and Monterey Bay.

Researchers speculate that Davidson Seamount is an ideal habitat for deep-sea corals and sponges because it has favorable bottom rock (bare lava rock), a steady food supply (supplied by a water current favoring the seamount; see the section above), and has not been disturbed by strong bottom currents than often bother other seafloor areas.

Craig McClain, one of the scientists studying the seamount, told PhysOrg:
Research also suggests that seamounts such as Davidson Seamount may be ecologically valuable to rare species that use them as breeding grounds. The seamounts are likely to be a source of larvae
Larvae
In Roman mythology, lemures were shades or spirits of the restless or malignant dead, and are probably cognate with an extended sense of larvae as disturbing or frightening...

 that maintains the population of the species in nearby, sub-optimal areas, known as "sink
Sink (geography)
A geographic sink is a depression within an endorheic basin where water collects with no visible outlet. Instead of discharging, the collected water is lost due to evaporation and/or penetration...

s." Sinks are low-lying areas in which species can live, but do so very poorly; if they are not replenished by nearby population centers, such as at Davidson, they could disappear from the area entirely. DNA studies
Genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....

 may in the future help scientists prove seamounts are indeed sources of larvae for their surrounding seafloor.

Exploration

Davidson Seamount was initially discovered and mapped in 1933. Davidson Seamount was the first underwater volcano to be classified as "seamount" by the United States Board of Geographic Names, in 1938, and was named in honor of the United States Coast and Geodetic Survey scientist George Davidson
George Davidson (geographer)
George Davidson was an geodesist, astronomer, geographer, surveyor and engineer in the United States.-Biography:Born May 9, 1825 in England, he came to the U.S. in 1832 with his parents, who settled in Pennsylvania...

, one of the key figures in the survey of America's west coast.

Because of its great depth, for a long time Davidson Seamount had been preceded only by a sparse few investigations. Davidson is interesting to volcanologist
Volcanology
Volcanology is the study of volcanoes, lava, magma, and related geological, geophysical and geochemical phenomena. The term volcanology is derived from the Latin word vulcan. Vulcan was the ancient Roman god of fire....

s because of its unique geology, and to biologist
Biologist
A biologist is a scientist devoted to and producing results in biology through the study of life. Typically biologists study organisms and their relationship to their environment. Biologists involved in basic research attempt to discover underlying mechanisms that govern how organisms work...

s for its unique ecology. In 2002 the NOAA sponsored the first modern in-depth study of the seamount. The team included scientists, educators, and resource managers, with the goal of documenting species, taking geologic samples, and describing the ocean environment. The expedition documented many rare, previously undiscovered species that exist nowhere else, not even on nearby seamounts, including ancient coral gardens that are vulnerable to human activity.

Recent expeditions to Davidson have focused on its ecology, and specifically on the variety of deep-sea coral
Coral
Corals are marine animals in class Anthozoa of phylum Cnidaria typically living in compact colonies of many identical individual "polyps". The group includes the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.A coral "head" is a colony of...

s, some over 100 years old, that live on its banks. These large colonies are extremely fragile to human interaction. Davidson's proximity to scientific research institutions has helped its exploration, as multiple dives, mappings, and studies have made it one of the better-studied seamounts in the world.
In 2006, another exploration, a collaboration of the Monterey Bay National Marine Sanctuary, the Monterey Bay Aquarium Research Institute
Monterey Bay Aquarium Research Institute
The Monterey Bay Aquarium Research Institute is a not-for-profit oceanographic research center in Moss Landing, California affiliated with the Monterey Bay Aquarium. It was founded in 1987 by David Packard of Hewlett-Packard fame...

 (MBARI), and Moss Landing Marine Labaratories was undertaken, mainly to test a model that had been developed to predict the availability of coral and to advance the understanding of the seamount's deep-sea coral. The NOAA outlined a set of 4 goals for the expedition:
  • Understand why deep-sea corals live where they do on the seamount
  • Determine the age and growth patterns of the bamboo coral
    Bamboo coral
    Bamboo coral, family Isididae, is a family of mostly deep-sea coral of the phylum Cnidaria, class Anthozoa, and subclass Octocorallia. It is a commonly recognized inhabitant of the deep sea, due to the clearly articulated skeletons of the species. Deep water coral species such as this are...

  • Improve the species list and taxonomy of corals from the seamount
  • Share the exciting experience with the public through television and the Internet


Scientific data on the water currents
Ocean current
An ocean current is a continuous, directed movement of ocean water generated by the forces acting upon this mean flow, such as breaking waves, wind, Coriolis effect, cabbeling, temperature and salinity differences and tides caused by the gravitational pull of the Moon and the Sun...

 and food availability of the seamount was collected, as was information on the age
Ageing
Ageing or aging is the accumulation of changes in a person over time. Ageing in humans refers to a multidimensional process of physical, psychological, and social change. Some dimensions of ageing grow and expand over time, while others decline...

 and growth pattern
Cell growth
The term cell growth is used in the contexts of cell development and cell division . When used in the context of cell division, it refers to growth of cell populations, where one cell grows and divides to produce two "daughter cells"...

s of the corals themselves. The British Broadcasting Corporation (BBC
BBC
The British Broadcasting Corporation is a British public service broadcaster. Its headquarters is at Broadcasting House in the City of Westminster, London. It is the largest broadcaster in the world, with about 23,000 staff...

) filmed the cruise for their series, Planet Earth
Planet Earth (TV series)
Planet Earth is a 2006 television series produced by the BBC Natural History Unit. Five years in the making, it was the most expensive nature documentary series ever commissioned by the BBC, and also the first to be filmed in high definition...

. A total of 70 hours of observations and 102 deep-sea animal and rock specimens were collected during the cruise. The expedition, which lasted from January 26 through February 4, made use if the MBARI's research vessel
Research vessel
A research vessel is a ship designed and equipped to carry out research at sea. Research vessels carry out a number of roles. Some of these roles can be combined into a single vessel, others require a dedicated vessel...

 Western Flyer and the ROV Tiburon.

As a marine sanctuary

Following the information learned from the 2002 and 2006 expeditions, there was public support for the making of Davidson Seamount into a marine sanctuary
Marine Protected Area
Marine Protected Areas, like any protected area, are regions in which human activity has been placed under some restrictions in the interest of conserving the natural environment, it's surrounding waters and the occupant ecosystems, and any cultural or historical resources that may require...

. A key group of research scientists, fishermen, officials, educators, and marine biologists was formed in 2006 to discuss whether or not to make Davidson Seamount a National Marine Sanctuary under the National Marine Sanctuaries Act, and if so whether to make it its own sanctuary, or incorporate it into the nearby Monterey Bay National Marine Sanctuary
Monterey Bay National Marine Sanctuary
The Monterey Bay National Marine Sanctuary is a US Federally protected marine area offshore of California's central coast around Monterey Bay....

. The group decided that the seamount was eligible for sanctuary designation, and the majority of the group recommended its incorporation into the nearby Monterey Bay sanctuary.

The Monterey Bay advisory group concurred with the findings, and submitted its approval to the NOAA, with whom the final decision rested. In a press release dated November 20, 2008, the NOAA finalized its approval of the plans, and expanded Monterey Bay by a total of 775 sq mi (2,007 km²) to include Davidson Seamount in its protected area. After a management plan was created, Davidson Seamount was incorporated into Monterey Bay in 2009, 7 years after it was originally proposed.

External links

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