Socorro Island
Encyclopedia
Socorro Island is a small volcanic island in the Revillagigedo Islands
Revillagigedo Islands
The Revillagigedo Islands or Revillagigedo Archipelago are a group of four volcanic islands in the Pacific Ocean, known for their unique ecosystem...

, a Mexican
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

 possession lying some 600 kilometers off the country's western coast at 18°48'N, 110°59'W. The size is 16.5 by 11.5 km, with an area of 132 km².

Geology

The island rises abruptly from the sea to 1050 meters (3,445 ft) in elevation at its summit. Isla Socorro is a shield volcano
Shield volcano
A shield volcano is a type of volcano usually built almost entirely of fluid lava flows. They are named for their large size and low profile, resembling a warrior's shield. This is caused by the highly fluid lava they erupt, which travels farther than lava erupted from more explosive volcanoes...

. It most recently erupted in 1993, which was a submarine flank eruption off the coast from Punta Tosca. Some of its earlier eruptions have been around 1848 and 1896, and in 1905 and 1951. Mount Evermann (Spanish: Cerro Evermann) is the name given to the summit dome complex, in honor of ichthyologist Barton Warren Evermann
Barton Warren Evermann
Barton Warren Evermann was an American ichthyologist. He was born in Monroe County, Iowa, and graduated from Indiana University in 1886. For 10 years, he served as teacher and superintendent of schools in Indiana and California. He was professor of biology at the Indiana State University in...

. The island's surface is broken by furrows, small craters, and numerous ravines, and covered in lava dome
Lava dome
|250px|thumb|right|Image of the [[rhyolitic]] lava dome of [[Chaitén Volcano]] during its 2008–2009 eruption.In volcanology, a lava dome is a roughly circular mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano...

s, lava flows and cinder cone
Cinder cone
According to the , Cinder Cone is the proper name of 1 cinder cone in Canada and 7 cinder cones in the United States:In Canada: Cinder Cone In the United States:...

s.

There is a naval station 18.728°N 110.952°W, established in 1957, with a population of 250 (staff and families), living in a village with a church, that stands on the western side of Bahia Vargas Lozano, a small cove with a rocky beach, about 800 meters east of Cabo Regla, the southernmost point of the island. The station is served by a dock, a local helipad and airport Isla Socorro, located six kilometers to the north, at 18.773°N 110.931°W. The airport, with IATA code SOC and ICAO code MMSC, has a 1700 meter long runway and positions for two airplanes and two helicopters.

There is a freshwater
Freshwater
Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...

 spring about 5 km northwest of Cabo Regla, at the shoreline of Ensenada Grayson (or Caleta Grayson), an inlet. This is brackish or even covered by the sea at high tide. Apart from some temporary pools and maybe one that is more permanent, a small freshwater seep exists most of the time some 45 meters (50 yard) inland at Bahia Lucio Gallardo Pavon (Binner's Cove), 800 meters NW of the naval station.

History

No evidence of human habitation on Socorro exists before its discovery by Spanish explorers. Hernando de Grijalva and his crew discovered an uninhabited island on December 28, 1533 and named it Isla de los Inocentes, only nine days after the discovery of Santo Tomé island. The description and location may correspond to that of San Benedicto
San Benedicto Island
San Benedicto, formerly Santo Tomás, is an uninhabited island, and third largest island of the Revillagigedo Islands, located in the Pacific at ....

. In 1542, Ruy González de Villalobos, while exploring new routes across the Pacific, rediscovered Inocentes and renamed it Isla Anublada ("Cloudy Island") due to the clouds frequently forming on the northern slopes of Mount Evermann, and again in 1608, Martín Yañez de Armida, in charge of another expedition, visited Santo Tomé and changed its name to Isla Socorro after Our Lady of Perpetual Help (Virgen del Perpetuo Socorro).

At the beginning of the twentieth century, Barton Warren Evermann
Barton Warren Evermann
Barton Warren Evermann was an American ichthyologist. He was born in Monroe County, Iowa, and graduated from Indiana University in 1886. For 10 years, he served as teacher and superintendent of schools in Indiana and California. He was professor of biology at the Indiana State University in...

, director of the California Academy of Sciences
California Academy of Sciences
The California Academy of Sciences is among the largest museums of natural history in the world. The academy began in 1853 as a learned society and still carries out a large amount of original research, with exhibits and education becoming significant endeavors of the museum during the twentieth...

 in San Francisco promoted the scientific exploration of the island. The most comprehensive biological collections were obtained at this time. The volcano on Socorro was renamed in his honor.

In September 1997, the island was struck by Hurricane Linda
Hurricane Linda (1997)
Hurricane Linda was the strongest eastern Pacific hurricane on record. Forming from a tropical wave on September 9, 1997, Linda steadily intensified and reached hurricane status within 36 hours of developing. It rapidly intensified, reaching winds of and an estimated central pressure...

, one of the strongest hurricanes ever recorded.

Ecology

The lowlands of Socorro - except on the northern, more humid side - are covered with thick shrubland, consisting mainly of endemic Croton masonii and a cactus
Cactus
A cactus is a member of the plant family Cactaceae. Their distinctive appearance is a result of adaptations to conserve water in dry and/or hot environments. In most species, the stem has evolved to become photosynthetic and succulent, while the leaves have evolved into spines...

, probably Engelmann's Prickly Pear (Opuntia engelmannii). Above 650 metres (2,132.5 ft) and on the northern side, a richer vegetation occurs. This includes small trees such as Ficus
Ficus
Ficus is a genus of about 850 species of woody trees, shrubs, vines, epiphytes, and hemiepiphyte in the family Moraceae. Collectively known as fig trees or figs, they are native throughout the tropics with a few species extending into the semi-warm temperate zone. The Common Fig Ficus is a genus of...

 cotinifolia
, Black Cherry (Prunus serotina), and the endemic Guettarda
Guettarda
Guettarda is a plant genus in the family Rubiaceae. Most of these plants are known by the common name Velvetseed. Estimates of the number of species range from about 50 to 162. Most of the species are neotropical. Twenty are found in New Caledonia and one reaches Australia...

 insularis
, which bear epiphytic orchids (Epidendrum
Epidendrum
Epidendrum , abbreviated Epi in horticultural trade, is a large neotropical genus of the orchid family. With more than 1,100 species, some authors describe it as a mega-genus. The genus name refers to its epiphytic growth habit...

 nitens
, E. rigidum
Epidendrum rigidum
Epidendrum rigidum is an epiphytic reed-stemmed Epidendrum orchid common throughout the Neotroical lowlands, below 600 m. Epidendrum rigidum is an epiphytic reed-stemmed Epidendrum orchid common throughout the Neotroical lowlands, below 600 m. Epidendrum rigidum is an epiphytic...

and the endemic Pleurothallis unguicallosa).

The native land fauna
Fauna
Fauna or faunæ is all of the animal life of any particular region or time. The corresponding term for plants is flora.Zoologists and paleontologists use fauna to refer to a typical collection of animals found in a specific time or place, e.g. the "Sonoran Desert fauna" or the "Burgess shale fauna"...

 is depauperate, with birds predominating and mammals absent. There is one endemic species of iguanid
Iguanidae
Iguanidae is a family of lizards, composed of iguanas and related species.-Classification of Iguanidae:Two different classification schemes have been used to define the structure of this family. These are the "traditional" classification and the classification presented by Frost et al. .Frost et...

 lizard (Urosaurus
Urosaurus
The North American genus Urosaurus belongs to the New World Iguanian family Phrynosomatidae. They can be distinguished from members of the genus Sceloporus by the presence of a gular fold and granular lateral scales...

 auriculatus
) and the land crab
Land crab
Gecarcinidae is a family of true crabs that are adapted for terrestrial existence, commonly known as land crabs. Similar to all other crabs, land crabs possess a series of gills. In addition, the part of the carapace covering the gills is inflated and equipped with blood vessels. These organs...

 Gecarcinus planatus which occurs on islands throughout the region.

Sheep, cats and rodent
Rodent
Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....

s were introduced to the island by human activity; more recently, the locust
Locust
Locusts are the swarming phase of short-horned grasshoppers of the family Acrididae. These are species that can breed rapidly under suitable conditions and subsequently become gregarious and migratory...

 Schistocerca piceifrons has also established itself on the island. Unlike the mammals on Guadalupe Island
Guadalupe Island
Guadalupe Island, or Isla Guadalupe is a volcanic island located 241 kilometers off the west coast of Mexico's Baja California peninsula and some 400 kilometers southwest of the city of Ensenada in Baja California state, in the Pacific Ocean...

 or Clarión
Clarion Island
Isla Clarión, formerly called Santa Rosa, is the second largest, westernmost and most remote of the Revillagigedo Islands, west of Socorro Island and over from the Mexican mainland and an area ². It has three prominent peaks. The westernmost and tallest peak, Monte Gallegos, is high...

, their impact on the local flora
Flora
Flora is the plant life occurring in a particular region or time, generally the naturally occurring or indigenous—native plant life. The corresponding term for animals is fauna.-Etymology:...

 was minor, but cat predation had a drastic effect since the mid-1970s due to the fauna's island tameness
Island tameness
Island tameness is the tendency of many populations and species of animals living on isolated islands to lose their wariness of potential predators, particularly of large animals. The term is partly synonymous with ecological naïvete, which also has a wider meaning referring to the loss of...

 and the locusts swarm twice a year and seriously damage vegetation during that time. There have been no recorded extinctions of plants on Socorro; several birds have been drastically affected by cat predation however and one taxon
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...

 appears to have gone extinct.

Socorro is an important breeding location for several seabird
Seabird
Seabirds are birds that have adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same environmental problems and feeding niches have resulted in similar adaptations...

s, many of which have here one of their most north(east)ernmost breeding colonies. The present status of these birds is not well known, and they presumably have suffered from cat predation. In 1953, the following taxa were present:
  • Wedge-tailed Shearwater
    Wedge-tailed Shearwater
    The Wedge-tailed Shearwater, Puffinus pacificus is a medium-large shearwater in the seabird family Procellariidae. It is one of the shearwater species that is sometimes referred to as a Muttonbird, like the Sooty Shearwater of New Zealand and the Short-tailed Shearwater of Australia...

    , Puffinus pacificus (or Ardenna pacifica)
  • Western Red-billed Tropicbird
    Red-billed Tropicbird
    The Red-billed Tropicbird, Phaethon aethereus, also known as the Boatswain Bird is a tropicbird, one of three closely related seabirds of tropical oceans.-Distribution and habitat:...

    , Phaethon aethereus mesonauta - breeding suspected but not verified
  • Nazca Booby
    Nazca Booby
    The Nazca Booby, Sula granti, is a booby which is found in the eastern Pacific Ocean, namely on the Galápagos Islands where it can be seen by eco-tourists, and on Clipperton Island...

    , Sula granti - breeding suspected but not verified
  • Northeast Pacific Brown Booby
    Brown Booby
    The Brown Booby is a large seabird of the booby family, Sulidae. The adult brown booby reaches about in length. Its head and upper body are covered in dark brown, with the remainder being a contrasting white. The juvenile form is gray-brown with darkening on the head, wings and tail...

    , Sula leucogaster brewsteri - breeding suspected but not verified
  • East Pacific Great Frigatebird
    Great Frigatebird
    The Great Frigatebird is a large dispersive seabird in the frigatebird family. Major nesting populations are found in the Pacific and Indian Oceans, as well as a population in the South Atlantic....

    , Fregata minor ridgwayi - breeding suspected but not verified; a doubtfully distinct subspecies
    Subspecies
    Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...

  • East Pacific Sooty Tern
    Sooty Tern
    The Sooty Tern, Onychoprion fuscatus , is a seabird of the tern family . It is a bird of the tropical oceans, breeding on islands throughout the equatorial zone. Colloquially, it is known as the Wideawake Tern or just wideawake...

    , Onychoprion fuscatus crissalis - a doubtfully distinct subspecies
  • East Pacific Brown Noddy
    Brown Noddy
    The Brown Noddy or Common Noddy is a seabird from the tern family. The largest of the noddies, it can be told from the closely related Black Noddy by its larger size and plumage, which is dark brown rather than black...

    , Anous stolidus ridgwayi


Non-endemic landbirds and shorebirds occur mostly as vagrants or use the island as a stopover during migration
Bird migration
Bird migration is the regular seasonal journey undertaken by many species of birds. Bird movements include those made in response to changes in food availability, habitat or weather. Sometimes, journeys are not termed "true migration" because they are irregular or in only one direction...

; the Northern Mockingbird
Northern Mockingbird
The Northern Mockingbird, Mimus polyglottos, is the only mockingbird commonly found in North America. This species was first described by Linnaeus in his Systema naturae in 1758 as Turdus polyglottos....

 has become established in the late 20th century. Among those that are recorded not infrequently are Great Blue Heron
Great Blue Heron
The Great Blue Heron is a large wading bird in the heron family Ardeidae, common near the shores of open water and in wetlands over most of North and Central America as well as the West Indies and the Galápagos Islands. It is a rare vagrant to Europe, with records from Spain, the Azores and England...

, Hudsonian Curlew, Spotted Sandpiper
Spotted Sandpiper
The Spotted Sandpiper is a small shorebird, 18–20 cm long. Together with its sister species, the Common Sandpiper they make up the genus Actitis...

 and Wandering Tattler
Wandering Tattler
The Wandering Tattler, Tringa incana , is a medium-sized wading bird. It is similar in appearance to the closely related Gray-tailed Tattler, T. brevipes...

. Opposed to the situation on smaller and more isolated Clarión, wind-blown or vagrant birds seem to consititute the bulk of the records, including species such as Brown Pelican
Brown Pelican
The Brown Pelican is the smallest of the eight species of pelican, although it is a large bird in nearly every other regard. It is in length, weighs from and has a wingspan from .-Range and habits:...

, Osprey
Osprey
The Osprey , sometimes known as the sea hawk or fish eagle, is a diurnal, fish-eating bird of prey. It is a large raptor, reaching more than in length and across the wings...

, Peregrine Falcon
Peregrine Falcon
The Peregrine Falcon , also known as the Peregrine, and historically as the Duck Hawk in North America, is a widespread bird of prey in the family Falconidae. A large, crow-sized falcon, it has a blue-gray back, barred white underparts, and a black head and "moustache"...

, Semipalmated Plover
Semipalmated Plover
The Semipalmated Plover is a small plover.This species weighs and measures in length and across the wings. Adults have a grey-brown back and wings, a white belly, and a white breast with one black neckband...

, Willet
Willet
The Willet, Tringa semipalmata , is a large shorebird in the sandpiper family. It is a good-sized and stout scolopacid, the largest of the shanks...

, Sanderling
Sanderling
The Sanderling is a small wader. It is a circumpolar Arctic breeder, and is a long-distance migrant, wintering south to South America, South Europe, Africa, and Australia...

, Belted Kingfisher
Belted Kingfisher
The Belted Kingfisher is a large, conspicuous water kingfisher, the only member of that group commonly found in the northern United States and Canada. It is depicted on the 1986 series Canadian $5 note. All kingfishers were formerly placed in one family, Alcedinidae, but recent research suggests...

 and Buff-bellied Pipit
Buff-bellied Pipit
The Buff-bellied Pipit , or American Pipit as it is known in North America, is a small songbird found on both sides of the northern Pacific. It was first described by Marmaduke Tunstall in his 1771 Ornithologia Britannica...

. It may be that this puzzling observation is due to the presence of the Red-tailed Hawks and cats, which has at least made the local Urosaurus
Urosaurus
The North American genus Urosaurus belongs to the New World Iguanian family Phrynosomatidae. They can be distinguished from members of the genus Sceloporus by the presence of a gular fold and granular lateral scales...

more wary than its relative on Clarión, and might deter passing birds from stopping on Socorro.

Endemism

Being the largest of the Revillagigedo Islands and closer to mainland than Clarion
Clarion Island
Isla Clarión, formerly called Santa Rosa, is the second largest, westernmost and most remote of the Revillagigedo Islands, west of Socorro Island and over from the Mexican mainland and an area ². It has three prominent peaks. The westernmost and tallest peak, Monte Gallegos, is high...

, Socorro sports a rich array of endemic taxa, mainly plants and landbirds.

Animals
  • Socorro Parakeet
    Socorro Parakeet
    The Socorro Parakeet is a subspecies of the Green Parakeet. It was formerly considered a distinct species, and some taxonomists still consider it so. It is endemic to Socorro Island in the Revillagigedo Islands, Mexico. Its natural habitat is subtropical or tropical moist lowland forests...

    , Aratinga brevipes (Endangered)
  • Socorro Red-tailed Hawk
    Red-tailed Hawk
    The Red-tailed Hawk is a bird of prey, one of three species colloquially known in the United States as the "chickenhawk," though it rarely preys on standard sized chickens. It breeds throughout most of North America, from western Alaska and northern Canada to as far south as Panama and the West...

    , Buteo jamaicensis socorroensis
  • Socorro Common Ground Dove
    Common Ground Dove
    The Common Ground Dove is a small bird that inhabits the southern United States, parts of Central America, the Caribbean and northern South America. The Common Ground Dove is considered to be the smallest dove that inhabits the United States...

    , Columbina passerina socorroensis
  • Socorro Elf Owl, Micrathene whitneyi graysoni (probably extinct since c.1970)
  • Socorro Mockingbird
    Socorro Mockingbird
    The Socorro Mockingbird, Mimus graysoni, is an endangered mockingbird endemic to Socorro Island in Mexico's Revillagigedo Islands. The specific epithet commemorates the American ornithologist Andrew Jackson Grayson....

    , Mimodes graysoni (Critically endangered
    Critically endangered
    Version 2010.3 of the IUCN Red List of Threatened Species identified 3744 Critically Endangered species, subspecies and varieties, stocks and subpopulations.Critically Endangered by kingdom:*1993 Animalia*2 Fungi*1745 Plantae*4 Protista-References:...

    )
  • Socorro Yellow-crowned Night Heron
    Yellow-crowned Night Heron
    The Yellow-crowned Night Heron , also called the American Night Heron or squawk, is a fairly small heron, similar in appearance to the Black-crowned Night Heron...

    , Nycticorax violaceus gravirostris (or Nyctanassa violacea gravirostris)
  • Socorro Tropical Parula
    Tropical Parula
    The Tropical Parula is a small New World warbler. It breeds from southernmost Texas and northwest Mexico south through Central America to northern Argentina, including Trinidad and Tobago. This widespread and common species is not considered threatened by the IUCN.This passerine is not migratory,...

    , Parula pitiayumi graysoni
  • Socorro Towhee, Pipilo (maculatus) socorroensis
  • Townsend's Shearwater
    Townsend's Shearwater
    Townsend's Shearwater, Puffinus auricularis, is a rare seabird of the tropics from the family Procellariidae.Its relationships are unresolved. Its closest relatives are probably, but not certainly, the Hawaiian Shearwater and possibly the Manx Shearwater...

    , Puffinus auricularis (Critically endangered; recently extirpated from San Benedicto and probably Clarión)
  • Socorro Wren
    Socorro Wren
    The Socorro Wren is a species of bird in the Troglodytidae family.It is endemic to Socorro Island, Mexico. It was formerly placed in Thryomanes but was moved to Troglodytes considering "manners, song, plumage, etc." and by biogeography and mtDNA NADH dehydrogenase subunit 2 sequence analysis.Its...

    , Troglodytes sissonii (Near Threatened
    Near Threatened
    Near Threatened is a conservation status assigned to species or lower taxa that may be considered threatened with extinction in the near future, although it does not currently qualify for the threatened status...

    )
  • Socorro Dove
    Socorro Dove
    The Socorro Dove is a dove that is extinct in the wild. It was endemic to Socorro Island in the Revillagigedo Islands off the west coast of Mexico. The last sighting in its natural habitat was in 1972. There are not more than 200 and probably fewer than 100 purebred birds in captivity...

    , Zenaida graysoni (Extinct in the wild
    Extinct in the Wild
    Extinct in the Wild is a conservation status assigned to species or lower taxa, the only known living members of which are being kept in captivity or as a naturalized population outside its historic range.-Examples:...

    )
  • Urosaurus auriculatus (Endangered)


Plants
Brickellia peninsularis var. amphithalassa, Cheilanthes peninsularis var. insularis, Nicotiana stocktonii, Spermacoce nesiotica and Zapoteca formosa ssp. rosei are near-endemics, being restricted to Socorro and Clarión. Whether Teucrium townsendii ssp. affine is the same plant as those on San Benedicto is not conclusively determined.

Visiting information

Socorro Island is a popular scuba diving
Scuba diving
Scuba diving is a form of underwater diving in which a diver uses a scuba set to breathe underwater....

 destination known for underwater encounters with dolphin
Dolphin
Dolphins are marine mammals that are closely related to whales and porpoises. There are almost forty species of dolphin in 17 genera. They vary in size from and , up to and . They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, mostly eating...

s, shark
Shark
Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....

s, manta ray
Manta ray
The manta ray is the largest species of the rays. The largest known specimen was more than across, with a weight of about . It ranges throughout waters of the world, typically around coral reefs...

s and other pelagic animals. Since there is no public airport on the island, divers visit here on live-aboard dive vessels. The most popular months are between November and May when the weather and seas are calmer.

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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