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Great Blue Hole
The Great Blue Hole is a giant marine sinkhole off the coast of Belize. It lies near the center of Lighthouse Reef, a small atoll from the mainland and Belize City. The hole is circular in shape, across and deep. It has a surface area of . It was formed during several episodes of quaternary glaciation The Quaternary glaciation, also known as the Pleistocene glaciation, is an alternating series of glacial and interglacial periods during the Quaternary period that began 2.58 Ma (million years ago) and is ongoing. Although geologists describe ... when sea levels were much Last glacial period, lower. Analysis of stalactites found in the Great Blue Hole shows that formation took place 153,000, 66,000, 60,000, and 15,000 years ago. As the ocean began to rise again, the cave was flooded. The Great Blue Hole is a part of the larger Belize Barrier Reef, Belize Barrier Reef Reserve System, a UNESCO World Heritage Site. Exploration The site was made famous by Jacques Cousteau, w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Belize City
Belize City is the largest city in Belize and was once the capital of the former British Honduras. According to the 2010 census, Belize City has a population of 57,169 people in 16,162 households. It is at the mouth of the Haulover Creek, which is a distributary of the Belize River. The Belize River empties into the Caribbean Sea from Belize City on the Philip Goldson Highway on the coast of the Caribbean. The city is the country's principal port and its financial and industrial hub. Cruise ships drop anchor outside the port and are tendered by local citizens. The city was almost entirely destroyed in October 1961 when Hurricane Hattie swept ashore. It was the capital of British Honduras (as Belize was then named) until the government was moved to the new capital of Belmopan in 1970. History Belize City was founded as "Belize Town" in 1638 by English lumber harvesters. It had been a small Maya city called Holzuz. Belize Town was ideal for the English as a central post b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Karst
Karst is a topography formed from the dissolution of soluble rocks such as limestone, dolomite, and gypsum. It is characterized by underground drainage systems with sinkholes and caves. It has also been documented for more weathering-resistant rocks, such as quartzite, given the right conditions. Subterranean drainage may limit surface water, with few to no rivers or lakes. However, in regions where the dissolved bedrock is covered (perhaps by debris) or confined by one or more superimposed non-soluble rock strata, distinctive karst features may occur only at subsurface levels and can be totally missing above ground. The study of ''paleokarst'' (buried karst in the stratigraphic column) is important in petroleum geology because as much as 50% of the world's hydrocarbon reserves are hosted in carbonate rock, and much of this is found in porous karst systems. Etymology The English word ''karst'' was borrowed from German in the late 19th century, which entered German much earlier ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Yucatán Peninsula
The Yucatán Peninsula (, also , ; es, Península de Yucatán ) is a large peninsula in southeastern Mexico and adjacent portions of Belize and Guatemala. The peninsula extends towards the northeast, separating the Gulf of Mexico to the north and west of the peninsula from the Caribbean Sea to the east. The Yucatán Channel, between the northeastern corner of the peninsula and Cuba, connects the two bodies of water. The peninsula is approximately in area. It has low relief, and is almost entirely composed of porous limestone. The peninsula lies east of the Isthmus of Tehuantepec, the narrowest point in Mexico separating the Atlantic Ocean, including the Gulf of Mexico and Caribbean Sea, from the Pacific Ocean. Some consider the isthmus to be the geographic boundary between Central America and the rest of North America, placing the peninsula in Central America. Politically all of Mexico, including the Yucatán, is generally considered part of North America, while Guatemala an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hammerhead Shark
The hammerhead sharks are a group of sharks that form the family Sphyrnidae, so named for the unusual and distinctive structure of their heads, which are flattened and laterally extended into a "hammer" shape called a cephalofoil. Most hammerhead species are placed in the genus ''Sphyrna'', while the winghead shark is placed in its own genus, ''Eusphyra''. Many different, but not necessarily mutually exclusive, functions have been postulated for the cephalofoil, including sensory reception, manoeuvering, and prey manipulation. The cephalofoil gives the shark superior binocular vision and depth perception. Hammerheads are found worldwide in warmer waters along coastlines and continental shelves. Unlike most sharks, some hammerhead species usually swim in Shoaling and schooling, schools during the day, becoming solitary hunters at night. Description The known species range from in length and weigh from . One specimen caught off the Florida coast in 1906 weighed over . They are u ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bull Shark
The bull shark (''Carcharhinus leucas''), also known as the Zambezi shark (informally zambi) in Africa and Lake Nicaragua shark in Nicaragua, is a species of requiem shark commonly found worldwide in warm, shallow waters along coasts and in rivers. It is known for its aggressive nature, and presence mainly in warm, shallow brackish and freshwater systems including estuaries and lower reaches of rivers. Bull sharks are euryhaline and can thrive in both salt and fresh water. They are known to travel far up rivers, and have been known to travel up the Mississippi River as far as Alton, Illinois, about from the ocean, but few freshwater interactions with humans have been recorded. Larger-sized bull sharks are probably responsible for the majority of nearshore shark attacks, including many incidents of shark bites attributed to other species. Unlike the river sharks of the genus '' Glyphis'', bull sharks are not true freshwater sharks, despite their ability to survive in freshwa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Caribbean Reef Shark
The Caribbean reef shark (''Carcharhinus perezi'') is a species of requiem shark, belonging to the family Carcharhinidae. It is found in the tropical waters of the western Atlantic Ocean from Florida to Brazil, and is the most commonly encountered reef shark in the Caribbean Sea. With a robust, streamlined body typical of the requiem sharks, this species is difficult to tell apart from other large members of its family such as the dusky shark (''C. obscurus'') and the silky shark (''C. falciformis''). Distinguishing characteristics include dusky-colored fins without prominent markings, a short free rear tip on the second dorsal fin, and tooth shape and number. Measuring up to long, the Caribbean reef shark is one of the largest apex predators in the reef ecosystem, feeding on a variety of fishes and cephalopods. They have been documented resting motionless on the sea bottom or inside caves, unusual behavior for an active-swimming shark. If threatened, it may perform a threat di ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Midnight Parrotfish
The midnight parrotfish (''Scarus coelestinus'') is a species of parrotfish that inhabits coral reefs mainly in the Caribbean, Bahamas, and Florida. The typical size is between 30 and 60 cm, but it can grow to almost 1 m. It has been observed as far north as Maryland and as far south as Brazil. Usually found between 3 and 80 m deep, it swims over reefs and sandy areas, where it feeds on algae by scraping it with its teeth fused into a beak. Coloring & Morphology The midnight parrotfish has a deep blue body with light blue patches along its sides and head. The exact location of light blue patches differs between each fish, but all midnight parrotfish have a light blue patch on the underside of the beak. Unlike other parrotfish species, the midnight parrotfish retains its coloring through its juvenile and adult stages of life. Both male and female midnight parrotfish exhibit this coloring. The parrotfish gains its name from its hard beak it uses to scrape its food from hard ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anoxic Waters
Anoxic waters are areas of sea water, fresh water, or groundwater that are depleted of dissolved oxygen. The US Geological Survey defines anoxic groundwater as those with dissolved oxygen concentration of less than 0.5 milligrams per litre. Anoxic waters can be contrasted with hypoxic waters, which are low (but not lacking) in dissolved oxygen. This condition is generally found in areas that have restricted water exchange. In most cases, oxygen is prevented from reaching the deeper levels by a physical barrier, as well as by a pronounced density stratification, in which, for instance, heavier hypersaline waters rest at the bottom of a basin. Anoxic conditions will occur if the rate of oxidation of organic matter by bacteria is greater than the supply of dissolved oxygen. Anoxic waters are a natural phenomenon, and have occurred throughout geological history. The Permian–Triassic extinction event, a mass extinction of species from the world's oceans, may have resulted from w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrogen Sulfide
Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The underground mine gas term for foul-smelling hydrogen sulfide-rich gas mixtures is ''stinkdamp''. Swedish chemist Carl Wilhelm Scheele is credited with having discovered the chemical composition of purified hydrogen sulfide in 1777. The British English spelling of this compound is hydrogen sulphide, a spelling no longer recommended by the Royal Society of Chemistry or the International Union of Pure and Applied Chemistry. Hydrogen sulfide is toxic to humans and most other animals by inhibiting cellular respiration in a manner similar to hydrogen cyanide. When it is inhaled or it or its salts are ingested in high amounts, damage to organs occurs rapidly with symptoms ranging from breathing difficulties to convulsions and death. Despite this, the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sonar
Sonar (sound navigation and ranging or sonic navigation and ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigation, navigate, measure distances (ranging), communicate with or detect objects on or under the surface of the water, such as other vessels. "Sonar" can refer to one of two types of technology: ''passive'' sonar means listening for the sound made by vessels; ''active'' sonar means emitting pulses of sounds and listening for echoes. Sonar may be used as a means of acoustic location and of measurement of the echo characteristics of "targets" in the water. Acoustic location in air was used before the introduction of radar. Sonar may also be used for robot navigation, and SODAR (an upward-looking in-air sonar) is used for atmospheric investigations. The term ''sonar'' is also used for the equipment used to generate and receive the sound. The acoustic frequencies used in sonar systems vary from very low (infrasonic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trimix (breathing Gas)
Trimix is a breathing gas consisting of oxygen, helium and nitrogen and is used in deep commercial diving, during the deep phase of dives carried out using technical diving techniques, and in advanced recreational diving. The helium is included as a substitute for some of the nitrogen, to reduce the narcotic effect of the breathing gas at depth. With a mixture of three gases it is possible to create mixes suitable for different depths or purposes by adjusting the proportions of each gas. Oxygen content can be optimised for the depth to limit the risk of toxicity, and the inert component balanced between nitrogen (which is cheap but narcotic) and helium (which is not narcotic and reduces work of breathing, but is more expensive and increases heat loss). The mixture of helium and oxygen with a 0% nitrogen content is generally known as heliox. This is frequently used as a breathing gas in deep commercial diving operations, where it is often recycled to save the expensive helium c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cave Diving
Cave-diving is underwater diving in water-filled caves. It may be done as an extreme sport, a way of exploring flooded caves for scientific investigation, or for the search for and recovery of divers or, as in the 2018 Thai cave rescue, other cave users. The equipment used varies depending on the circumstances, and ranges from breath hold to surface supplied, but almost all cave-diving is done using scuba equipment, often in specialised configurations with redundancies such as sidemount or backmounted twinset. Recreational cave-diving is generally considered to be a type of technical diving due to the lack of a free surface during large parts of the dive, and often involves planned decompression stops. A distinction is made by recreational diver training agencies between cave-diving and cavern-diving, where cavern diving is deemed to be diving in those parts of a cave where the exit to open water can be seen by natural light. An arbitrary distance limit to the open water s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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