A reef is a bar of rock, sand, coral or similar material, lying beneath the surface of water. Many reefs result from natural, abiotic processes—deposition of sand, wave erosion planing down rock outcrops, etc.—but the best known reefs are the coral reefs of tropical waters developed through biotic processes dominated by corals and coralline algae.
Artificial reefs (e.g. shipwrecks) sometimes have a role in enhancing the physical complexity of featureless sand bottoms, in order to attract a diverse assemblage of organisms, especially algae and fish.
Earth's largest reef system is the Great Barrier Reef in Australia, at a length of over 2,300 kilometres (1,400 miles).
There is a variety of biotic reef types, including oyster reefs and sponge reefs, but the most massive and widely distributed are tropical coral reefs. Although corals are major contributors to the framework and bulk material comprising a coral reef; the organisms most responsible for reef growth against the constant assault from ocean waves are calcareous algae, especially, although not entirely, coralline algae.
These biotic reef types take on additional names depending upon how the reef lies in relation to the land, if any. Reef types include fringing reefs, barrier reefs, and atolls. A fringing reef is a reef that is attached to an island. A barrier reef forms a calcareous barrier around an island resulting in a lagoon between the shore and the reef. An atoll is a ring reef with no land present. The reef front (ocean side) is a high energy locale whereas the internal lagoon will be at a lower energy with fine grained sediments.
Ancient reefs buried within stratigraphic sections are of considerable interest to geologists because they provide paleo-environmental information about the location in Earth's history. In addition, reef structures within a sequence of sedimentary rocks provide a discontinuity which may serve as a trap or conduit for fossil fuels or mineralizing fluids to form petroleum or ore deposits.
Corals, including some major extinct groups Rugosa and Tabulata, have been important reef builders through much of the Phanerozoic since the Ordovician Period. However, other organism groups, such as calcifying algae, especially members of the red algae Rhodophyta, and molluscs (especially the rudist bivalves during the Cretaceous Period) have created massive structures at various times. During the Cambrian Period, the conical or tubular skeletons of Archaeocyatha, an extinct group of uncertain affinities (possibly sponges), built reefs. Other groups, such as the Bryozoa have been important interstitial organisms, living between the framework builders. The corals which build reefs today, the Scleractinia, arose after the Permian–Triassic extinction event that wiped out the earlier rugose corals (as well as many other groups), and became increasingly important reef builders throughout the Mesozoic Era. They may have arisen from a rugose coral ancestor. Rugose corals built their skeletons of calcite and have a different symmetry from that of the scleractinian corals, whose skeletons are aragonite. However, there are some unusual examples of well-preserved aragonitic rugose corals in the Late Permian. In addition, calcite has been reported in the initial post-larval calcification in a few scleractinian corals. Nevertheless, scleractinian corals (which arose in the middle Triassic) may have arisen from a non-calcifying ancestor independent of the rugosan corals (which disappeared in the late Permian).
One useful definition distinguishes reefs from mounds as follows: Both are considered to be varieties of organosedimentary buildups – sedimentary features, built by the interaction of organisms and their environment, that have synoptic relief and whose biotic composition differs from that found on and beneath the surrounding sea floor. Reefs are held up by a macroscopic skeletal framework. Coral reefs are an example of this kind. Corals and calcareous algae grow on top of one another and form a three-dimensional framework that is modified in various ways by other organisms and inorganic processes. By contrast, mounds lack a macroscopic skeletal framework. Mounds are built by microorganisms or by organisms that don't grow a skeletal framework. A microbial mound might be built exclusively or primarily by cyanobacteria. Examples of biostromes formed by cyanobacteria occur in the Great Salt Lake in Utah, and in Shark Bay on the coast of Western Australia.
Cyanobacteria do not have skeletons, and individuals are microscopic. Cyanobacteria can encourage the precipitation or accumulation of calcium carbonate to produce distinct sediment bodies in composition that have relief on the seafloor. Cyanobacterial mounds were most abundant before the evolution of shelly macroscopic organisms, but they still exist today; stromatolites are microbial mounds with a laminated internal structure. Bryozoans and crinoids, common contributors to marine sediments during the Mississippian, for instance, produced a very different kind of mound. Bryozoans are small and the skeletons of crinoids disintegrate. However, bryozoan and crinoid meadows can persist over time and produce compositionally distinct bodies of sediment with depositional relief.
An artificial reef is a man-made underwater structure, typically built to promote marine life in areas with a generally featureless bottom, to control erosion, block ship passage, block the use of trawling nets, or improve surfing.
Many reefs are built using objects that were built for other purposes, for example by sinking oil rigs (through the Rigs-to-Reefs program), scuttling ships, or by deploying rubble or construction debris. Other artificial reefs are purpose built (e.g. the reef balls) from PVC or concrete. Shipwrecks may become artificial reefs when preserved on the sea floor. Regardless of construction method, artificial reefs generally provide hard surfaces where algae and invertebrates such as barnacles, corals, and oysters attach; the accumulation of attached marine life in turn provides intricate structure and food for assemblages of fish.Ashmore and Cartier Islands
The Territory of Ashmore and Cartier Islands is an uninhabited external territory of Australia consisting of four low-lying tropical islands in two separate reefs, and the 12 nautical mile territorial sea generated by the islands. The territory is located in the Indian Ocean situated on the edge of the continental shelf, about 320 km (199 mi) off the northwest coast of Australia and 144 km (89 mi) south of the Indonesian island of Rote.Ashmore Reef is called Pulau Pasir by Indonesians and Nusa Solokaek in the Rotenese language. Both names have the meaning "sand island".Atoll
An atoll ( , , , , or ), sometimes called a coral atoll, is a ring-shaped coral reef including a coral rim that encircles a lagoon partially or completely. There may be coral islands or cays on the rim. The coral of the atoll often sits atop the rim of an extinct seamount or volcano which has eroded or subsided partially beneath the water. The lagoon forms over the volcanic crater or caldera while the higher rim remains above water or at shallow depths that permit the coral to grow and form the reefs. For the atoll to persist, continued erosion or subsidence must be at a rate slow enough to permit reef growth upward and outward to replace the lost height.Blacktip reef shark
Not to be confused with the blacktip shark, Carcharhinus limbatus.
The blacktip reef shark (Carcharhinus melanopterus) is a species of requiem shark, in the family Carcharhinidae, easily identified by the prominent black tips on its fins (especially on the first dorsal fin and its caudal fin). Among the most abundant sharks inhabiting the tropical coral reefs of the Indian and Pacific Oceans, this species prefers shallow, inshore waters. Its exposed first dorsal fin is a common sight in the region. Most blacktip reef sharks are found over reef ledges and sandy flats, though they have also been known to enter brackish and freshwater environments. This species typically attains a length of 1.6 m (5.2 ft).
Blacktip reef sharks have extremely small home ranges and exhibit strong site fidelity, remaining within the same local area for up to several years at a time. They are active predators of small bony fishes, cephalopods, and crustaceans, and have also been known to feed on sea snakes and seabirds. Accounts of the blacktip reef shark's life history have been variable and sometimes contradictory, in part reflecting geographical differences within the species. Like other members of its family, this shark is viviparous, with females giving birth to two to five young on a biennial, annual, or possibly biannual cycle. Reports of the gestation period range from 7–9, through 10–11, to possibly 16 months. Mating is preceded by the male following closely behind the female, likely attracted by her chemical signals. Newborn sharks are found further inshore and in shallower water than adults, frequently roaming in large groups over areas flooded by high tide.
Timid and skittish, the blacktip reef shark is difficult to approach and seldom poses a danger to humans unless roused by food. However, people wading through shallow water are at risk of having their legs mistakenly bitten. This shark is used for its meat, fins, and liver oil, but is not considered to be a commercially significant species. The International Union for Conservation of Nature has assessed the blacktip reef shark as Near Threatened. Although the species as a whole remains widespread and relatively common, overfishing of this slow-reproducing shark has led to its decline at a number of locales.Capitol Reef National Park
Capitol Reef National Park is an American national park in south-central Utah. The park is approximately 60 miles (97 km) long on its north–south axis and just 6 miles (9.7 km) wide on average. The park was established in 1971 to preserve 241,904 acres (377.98 sq mi; 97,895.08 ha; 978.95 km2) of desert landscape and is open all year, with May through September being the highest visitation months.
Partially in Wayne County, Utah, the area was originally named "Wayne Wonderland" in the 1920s by local boosters Ephraim P. Pectol and Joseph S. Hickman. Capitol Reef National Park was designated a national monument on August 2, 1937, by President Franklin D. Roosevelt to protect the area's colorful canyons, ridges, buttes, and monoliths; however, it was not until 1950 that the area officially opened to the public. Road access was improved in 1962 with the construction of State Route 24 through the Fremont River Canyon.The majority of the nearly 100 mi (160 km) long up-thrust formation called the Waterpocket Fold—a rocky spine extending from Thousand Lake Mountain to Lake Powell—is preserved within the park. Capitol Reef is an especially rugged and spectacular segment of the Waterpocket Fold by the Fremont River. The park was named for its whitish Navajo Sandstone cliffs with dome formations—similar to the white domes often placed on capitol buildings—that run from the Fremont River to Pleasant Creek on the Waterpocket Fold. Locally, reef refers to any rocky barrier to land travel, just as ocean reefs are barriers to sea travel.Cay
A cay ( or ), also spelled caye or key, is a small, low-elevation, sandy island on the surface of a coral reef. Cays occur in tropical environments throughout the Pacific, Atlantic and Indian Oceans (including in the Caribbean and on the Great Barrier Reef and Belize Barrier Reef).Coral
Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically live in compact colonies of many identical individual polyps. Corals species include the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.
A coral "group" is a colony of myriad genetically identical polyps. Each polyp is a sac-like animal typically only a few millimeters in diameter and a few centimeters in length. A set of tentacles surround a central mouth opening. An exoskeleton is excreted near the base. Over many generations, the colony thus creates a large skeleton characteristic of the species. Individual heads grow by asexual reproduction of polyps. Corals also breed sexually by spawning: polyps of the same species release gametes simultaneously over a period of one to several nights around a full moon.
Although some corals are able to catch small fish and plankton using stinging cells on their tentacles, most corals obtain the majority of their energy and nutrients from photosynthetic unicellular dinoflagellates in the genus Symbiodinium that live within their tissues. These are commonly known as zooxanthellae. Such corals require sunlight and grow in clear, shallow water, typically at depths less than 60 metres (200 ft). Corals are major contributors to the physical structure of the coral reefs that develop in tropical and subtropical waters, such as the enormous Great Barrier Reef off the coast of Queensland, Australia.
Other corals do not rely on zooxanthellae and can live in much deeper water, with the cold-water genus Lophelia surviving as deep as 3,300 metres (10,800 ft). Some have been found as far north as the Darwin Mounds, northwest of Cape Wrath, Scotland, and others off the coast of Washington State and the Aleutian Islands.Coral Sea
The Coral Sea (French: Mer de Corail) is a marginal sea of the South Pacific off the northeast coast of Australia, and classified as an interim Australian bioregion. The Coral Sea extends 2,000 kilometres (1,200 mi) down the Australian northeast coast.
It is bounded in the west by the east coast of Queensland, thereby including the Great Barrier Reef, in the east by Vanuatu (formerly the New Hebrides) and by New Caledonia, and in the northeast approximately by the southern extremity of the Solomon Islands. In the northwest, it reaches to the south coast of eastern New Guinea, thereby including the Gulf of Papua. It merges with the Tasman Sea in the south, with the Solomon Sea in the north and with the Pacific Ocean in the east. On the west, it is bounded by the mainland coast of Queensland, and in the northwest, it connects with the Arafura Sea through the Torres Strait.The sea is characterised by its warm and stable climate, with frequent rains and tropical cyclones. It contains numerous islands and reefs, as well as the world's largest reef system, the Great Barrier Reef (GBR), which was declared a World Heritage Site by UNESCO in 1981. All previous oil exploration projects were terminated at the GBR in 1975, and fishing is restricted in many areas. The reefs and islands of the Coral Sea are particularly rich in birds and aquatic life and are a popular tourist destination, both nationally and internationally.Coral Sea Islands
The Coral Sea Islands Territory is an external territory of Australia which comprises a group of small and mostly uninhabited tropical islands and reefs in the Coral Sea, northeast of Queensland, Australia. The only inhabited island is Willis Island. The territory covers 780,000 km2 (301,160 sq mi), most of which is ocean, extending east and south from the outer edge of the Great Barrier Reef and includes Heralds Beacon Island, Osprey Reef, the Willis Group and fifteen other reef/island groups. Cato Island is the highest point in the Territory.Coral bleaching
Coral bleaching occurs when coral polyps expel algae that live inside their tissues. Normally, coral polyps live in an endosymbiotic relationship with this algae crucial for the health of the coral and the reef. The algae provides up to 90 percent of the coral's energy. Bleached corals continue
to live but begin to starve after bleaching. Some corals recover.
Above-average sea water temperatures caused by global warming is the leading cause of coral bleaching. According to the United Nations Environment Programme, between 2014 and 2016 the longest recorded global bleaching events killed coral on an unprecedented scale. In 2016, bleaching of coral on the Great Barrier Reef killed between 29 and 50 percent of the reef's coral. In 2017, the bleaching extended into the central region of the reef. The average interval between bleaching events has halved between 1980 and 2016.Coral reef
A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in groups.
Coral belongs to the class Anthozoa in the animal phylum Cnidaria, which includes sea anemones and jellyfish. Unlike sea anemones, corals secrete hard carbonate exoskeletons that support and protect the coral. Most reefs grow best in warm, shallow, clear, sunny and agitated water.
Often called "rainforests of the sea", shallow coral reefs form some of Earth's most diverse ecosystems. They occupy less than 0.1% of the world's ocean area, about half the area of France, yet they provide a home for at least 25% of all marine species, including fish, mollusks, worms, crustaceans, echinoderms, sponges, tunicates and other cnidarians. Coral reefs flourish in ocean waters that provide few nutrients. They are most commonly found at shallow depths in tropical waters, but deep water and cold water coral reefs exist on smaller scales in other areas.
Coral reefs deliver ecosystem services for tourism, fisheries and shoreline protection. The annual global economic value of coral reefs is estimated between US$30–375 billion and 9.9 trillion USD. Coral reefs are fragile, partly because they are sensitive to water conditions. They are under threat from excess nutrients (nitrogen and phosphorus), rising temperatures, oceanic acidification, overfishing (e.g., from blast fishing, cyanide fishing, spearfishing on scuba), sunscreen use, and harmful land-use practices, including runoff and seeps (e.g., from injection wells and cesspools).Coral reef fish
Coral reef fish are fish which live amongst or in close relation to coral reefs. Coral reefs form complex ecosystems with tremendous biodiversity. Among the myriad inhabitants, the fish stand out as colourful and interesting to watch. Hundreds of species can exist in a small area of a healthy reef, many of them hidden or well camouflaged. Reef fish have developed many ingenious specialisations adapted to survival on the reefs.
Coral reefs occupy less than one percent of the surface area of the world oceans, but still they provide a home for 25 percent of all marine fish species. Reef habitats are a sharp contrast to the open water habitats that make up the other 99% of the world oceans.
However, loss and degradation of coral reef habitat, increasing pollution, and overfishing including the use of destructive fishing practices, are threatening the survival of the coral reefs and the associated reef fish.Corallimorpharia
Corallimorpharia is an order of marine cnidarians closely related to stony or reef building corals (Scleractinia). They are mostly tropical, with a narrow column topped with a wide oral disc. The tentacles are usually short or very short, arranged in rows radiating from the mouth. Many species occur together in large groups. In many respects, they resemble the stony corals, except for the absence of a stony skeleton.
Corallimorpharians occur in a wide range of marine habitats, and are associated with phase shifts in coral reef ecosystems that result in a change from a hard-coral dominated reef to a soft-coral dominated one. Many species are also common invertebrates kept in marine aquaria.Florida
Florida ( (listen)) is the southernmost contiguous state in the United States. The state is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Atlantic Ocean, and to the south by the Straits of Florida. Florida is the 22nd-most extensive (65,755 sq mi or 170,300 km2), the 3rd-most populous (21,312,211 inhabitants), and the 8th-most densely populated (384.3/sq mi or 148.4/km2) of the U.S. states. Jacksonville is the most populous municipality in the state and the largest city by area in the contiguous United States. The Miami metropolitan area is Florida's most populous urban area. Tallahassee is the state's capital.
Florida's $1.0 trillion economy is the fourth largest in the United States. If it were a country, Florida would be the 16th largest economy in the world, and the 58th most populous as of 2018. In 2017, Florida's per capita personal income was $47,684, ranking 26th in the nation. The unemployment rate in September 2018 was 3.5% and ranked as the 18th in the United States. Florida exports nearly $55 billion in goods made in the state, the 8th highest among all states. The Miami Metropolitan Area is by far the largest urban economy in Florida and the 12th largest in the United States with a GDP of $345 billion as of 2017. This is more than twice the number of the next metro area, the Tampa Bay Area, which has a GDP of $145 billion. Florida is home to 51 of the world's billionaires with most of them residing in South Florida.The first European contact was made in 1513 by Spanish explorer Juan Ponce de León, who called it la Florida ([la floˈɾiða] "the land of flowers") upon landing there in the Easter season, known in Spanish as Pascua Florida. Florida was a challenge for the European colonial powers before it gained statehood in the United States in 1845. It was a principal location of the Seminole Wars against the Native Americans, and racial segregation after the American Civil War.
Today, Florida is distinctive for its large Cuban expatriate community and high population growth, as well as for its increasing environmental issues. The state's economy relies mainly on tourism, agriculture, and transportation, which developed in the late 19th century. Florida is also renowned for amusement parks, orange crops, winter vegetables, the Kennedy Space Center, and as a popular destination for retirees. Florida is the flattest state in the United States. Lake Okeechobee is the largest freshwater lake in the U.S. state of Florida.Florida's close proximity to the ocean influences many aspects of Florida culture and daily life. Florida is a reflection of influences and multiple inheritance; African, European, indigenous, and Latino heritages can be found in the architecture and cuisine. Florida has attracted many writers such as Marjorie Kinnan Rawlings, Ernest Hemingway and Tennessee Williams, and continues to attract celebrities and athletes. It is internationally known for golf, tennis, auto racing, and water sports. Several beaches in Florida have turquoise and emerald-colored coastal waters.About two-thirds of Florida occupies a peninsula between the Gulf of Mexico and the Atlantic Ocean. Florida has the longest coastline in the contiguous United States, approximately 1,350 miles (2,170 km), not including the contribution of the many barrier islands. Florida has a total of 4,510 islands that are ten acres or larger in area. This is the second-highest number of islands of any state of the United States; only Alaska has more. It is the only state that borders both the Gulf of Mexico and the Atlantic Ocean. Much of the state is at or near sea level and is characterized by sedimentary soil. Florida has the lowest high point of any U.S. state. The climate varies from subtropical in the north to tropical in the south. The American alligator, American crocodile, American flamingo, Roseate spoonbill, Florida panther, bottlenose dolphin, and manatee can be found in Everglades National Park in the southern part of the state. Along with Hawaii, Florida is one of only two states that has a tropical climate, and is the only continental state with either a tropical climate or a coral reef. The Florida Reef is the only living coral barrier reef in the continental United States, and the third-largest coral barrier reef system in the world (after the Great Barrier Reef and Belize Barrier Reef).Florida Reef
The Florida Reef (also known as the Great Florida Reef, Florida reefs, Florida Reef Tract and Florida Keys Reef Tract) is the only living coral barrier reef in the continental United States. It is the third largest coral barrier reef system in the world (after the Great Barrier Reef and Belize Barrier Reef). It lies a few miles seaward of the Florida Keys, is about 4 miles (6 to 7 km) wide and extends (along the 20 meter depth contour) 270 km (170 mi) from Fowey Rocks just east of Soldier Key to just south of the Marquesas Keys. The barrier reef tract forms a great arc, concentric with the Florida Keys, with the northern end, in Biscayne National Park, oriented north-south and the western end, south of the Marquesas Keys, oriented east-west. The rest of the reef outside Biscayne National Park lies within John Pennekamp Coral Reef State Park and the Florida Keys National Marine Sanctuary. Isolated coral patch reefs occur northward from Biscayne National Park as far north as Stuart, in Martin County. Coral reefs are also found in Dry Tortugas National Park west of the Marquesas Keys. There are more than 6,000 individual reefs in the system. The reefs are 5,000 to 7,000 years old, having developed since sea levels rose following the Wisconsinan glaciation.The densest and most spectacular reefs, along with the highest water clarity, are found to the seaward of Key Largo (in and beyond John Pennekamp Coral Reef State Park) and Elliott Key where the two long keys help protect the reefs from the effects of water exchange with Florida Bay, Biscayne Bay, Card Sound and Barnes Sound. The bays and sounds (all between the Florida Keys and the mainland) tend to have lower salinity, higher turbidity and wider temperature variations than the water in the open ocean. Channels between the Keys allow brackish water from the bays to flow onto the reefs (especially in the middle Keys), limiting their growth.Great Barrier Reef
The Great Barrier Reef is the world's largest coral reef system composed of over 2,900 individual reefs and 900 islands stretching for over 2,300 kilometres (1,400 mi) over an area of approximately 344,400 square kilometres (133,000 sq mi). The reef is located in the Coral Sea, off the coast of Queensland, Australia. The Great Barrier Reef can be seen from outer space and is the world's biggest single structure made by living organisms. This reef structure is composed of and built by billions of tiny organisms, known as coral polyps. It supports a wide diversity of life and was selected as a World Heritage Site in 1981. CNN labelled it one of the seven natural wonders of the world. The Queensland National Trust named it a state icon of Queensland.A large part of the reef is protected by the Great Barrier Reef Marine Park, which helps to limit the impact of human use, such as fishing and tourism. Other environmental pressures on the reef and its ecosystem include runoff, climate change accompanied by mass coral bleaching, dumping of dredging sludge and cyclic population outbreaks of the crown-of-thorns starfish. According to a study published in October 2012 by the Proceedings of the National Academy of Sciences, the reef has lost more than half its coral cover since 1985.The Great Barrier Reef has long been known to and used by the Aboriginal Australian and Torres Strait Islander peoples, and is an important part of local groups' cultures and spirituality. The reef is a very popular destination for tourists, especially in the Whitsunday Islands and Cairns regions. Tourism is an important economic activity for the region, generating over AUD$3 billion per year. In November 2014, Google launched Google Underwater Street View in 3D of the Great Barrier Reef.A March 2016 report stated that coral bleaching was more widespread than previously thought, seriously affecting the northern parts of the reef as a result of warming ocean temperatures. In October 2016, Outside published an obituary for the reef; the article was criticized for being premature and hindering efforts to bolster the resilience of the reef. In March 2017, the journal Nature published a paper showing that huge sections of an 800-kilometre (500 mi) stretch in the northern part of the reef had died in the course of 2016 due to high water temperatures, an event that the authors put down to the effects of global climate change. The percentage of baby corals being born on the Great Barrier Reef dropped drastically in 2018 and scientists are describing it as the early stage of a "huge natural selection event unfolding". Many of the mature breeding adults died in the bleaching events of 2016-17 leading to low coral birth rates. The types of corals that reproduced also changed, leading to a "long-term reorganisation of the reef ecosystem if the trend continues."Kingman Reef
Kingman Reef is a largely submerged, uninhabited triangular-shaped reef, 9.5 nautical miles (18 kilometers) east-west and 5 nmi (9 km) north-south, located in the North Pacific Ocean, roughly halfway between the Hawaiian Islands and American Samoa. It is the northernmost of the Northern Line Islands and lies 36 nautical miles (67 km) northwest of the next closest island (Palmyra Atoll), and 930 nautical miles (1,720 km) south of Honolulu.The reef encloses a lagoon up to 270 feet (82 m) deep in its western part. The total area within the outer rim of the reef is 29 sq mi (75 km2). There are two small strips of dry land composed of coral rubble and giant clamshells on the eastern rim with areas of 2 and 1 acre (8,100 and 4,000 m2) having a coastline of 2 miles (3 km). The highest point on the reef is less than 5 feet (1.5 m) above sea level, which is wetted or awash most of the time, making Kingman Reef a maritime hazard. It has no natural resources and supports no economic activity.Permian Basin (North America)
The Permian Basin is a large sedimentary basin in the southwestern part of the United States. The basin contains the Mid-Continent Oil Field province. This sedimentary basin is located in western Texas and southeastern New Mexico. It reaches from just south of Lubbock, past Midland and Odessa, south nearly to the Rio Grande River in southern West Central Texas, and extending westward into the southeastern part of New Mexico. It is so named because it has one of the world's thickest deposits of rocks from the Permian geologic period. The greater Permian Basin comprises several component basins; of these, the Midland Basin is the largest, Delaware Basin is the second largest, and Marfa Basin is the smallest. The Permian Basin covers more than 86,000 square miles (220,000 km2), and extends across an area approximately 250 miles (400 km) wide and 300 miles (480 km) long.The Permian Basin lends its name to a large oil and natural gas producing area, part of the Mid-Continent Oil Producing Area. Total production for that region up to the beginning of 1993 was over 14.9 billion barrels (2.37×109 m3). The cities of Midland, Texas, Odessa, Texas and San Angelo, Texas serve as the headquarters for oil production activities in the basin.
The Permian Basin is also a major source of potassium salts (potash), which are mined from bedded deposits of sylvite and langbeinite in the Salado Formation of Permian age. Sylvite was discovered in drill cores in 1925, and production began in 1931. The mines are located in Lea and Eddy counties, New Mexico, and are operated by the room and pillar method. Halite (rock salt) is produced as a byproduct of potash mining.Whitetip reef shark
The whitetip reef shark (Triaenodon obesus) is a species of requiem shark, in the family Carcharhinidae, and the only member of its genus. A small shark usually not exceeding 1.6 m (5.2 ft) in length, this species is easily recognizable by its slender body and short but broad head, as well as tubular skin flaps beside the nostrils, oval eyes with vertical pupils, and white-tipped dorsal and caudal fins. One of the most common sharks found on Indo-Pacific coral reefs, the whitetip reef shark occurs as far west as South Africa and as far east as Central America. It is typically found on or near the bottom in clear water, at a depth of 8–40 m (26–131 ft).
During the day, whitetip reef sharks spend much of their time resting inside caves. Unlike other requiem sharks, which rely on ram ventilation and must constantly swim to breathe, this shark can pump water over its gills and lie still on the bottom. At night, whitetip reef sharks emerge to hunt bony fishes, crustaceans, and octopus in groups, their elongate bodies allowing them to force their way into crevices and holes to extract hidden prey. Individuals may stay within a particular area of the reef for months or years, frequently returning to the same shelter. This species is viviparous, in which the developing embryos are sustained by a placental connection to their mother.
Whitetip reef sharks are rarely aggressive towards humans, though they may investigate swimmers closely. However, spear fishers are at risk of being bitten by one attempting to steal their catch. This species is caught for food, though ciguatera poisoning resulting from its consumption has been reported. The IUCN has assessed the whitetip reef shark as Near Threatened, noting its numbers are dwindling due to increasing levels of unregulated fishing activity across its range. The slow reproductive rate and limited habitat preferences of this species renders its populations vulnerable to overfishing.