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Transcript of Oceans
72% of the Earths surface. There are five oceans, The Indian, Southern, Atlantic, Pacific, and Arctic. The pacific ocean is the largest ocean it is 63.8 million square miles in area, the Indian is 28,350,000 miles in area, the Atlantic 41,100,000 sq miles in area, the Arctic is the smallest. The ocean is the most populated biome on earth, it is the least undiscovered place on earth. There are over 230,000 known species living in the oceans. Marine Life Marine biology is the scientific study of organisms in the ocean or other marine or brackish bodies of water. Given that in biology many phyla, families and genera have some species that live in the sea and others that live on land, marine biology classifies species based on the environment rather than on taxonomy. Marine biology differs from marine ecology as marine ecology is focused on how organisms interact with each other and the environment, and biology is the study of the organisms themselves.
Marine life is a vast resource, providing food, medicine, and raw materials, in addition to helping to support recreation and tourism all over the world. At a fundamental level, marine life helps determine the very nature of our planet. Marine organisms contribute significantly to the oxygen cycle, and are involved in the regulation of the Earth's climate. Shorelines are in part shaped and protected by marine life, and some marine organisms even help create new land.
Marine biology covers a great deal, from the microscopic, including most zooplankton and phytoplankton to the huge cetaceans (whales) which measure up to 30 meters (98 feet) in length.
The habitats studied by marine biology include everything from the tiny layers of surface water in which organisms and abiotic items may be trapped in surface tension between the ocean and atmosphere, to the depths of the oceanic trenches, sometimes 10,000 meters or more beneath the surface of the ocean. It studies habitats such as coral reefs, kelp forests, tidepools, muddy, sandy and rocky bottoms, and the open ocean (pelagic) zone, where solid objects are rare and the surface of the water is the only visible boundary.
A large proportion of all life on Earth exists in the oceans. Exactly how large the proportion is unknown, since many ocean species are still to be discovered. While the oceans constitute about 71% of the Earth's surface, due to their depth they encompass about 300 times the habitable volume of the terrestrial habitats on Earth.
Many species are economically important to humans, including food fish. It is also becoming understood that the well-being of marine organisms and other organisms are linked in very fundamental ways. The human body of knowledge regarding the relationship between life in the sea and important cycles is rapidly growing, with new discoveries being made nearly every day. These cycles include those of matter (such as the carbon cycle) and of air (such as Earth's respiration, and movement of energy through ecosystems including the ocean). Large areas beneath the ocean surface still remain effectively unexplored. Fish A fish is any member of a paraphyletic group of organisms that consist of all gill-bearing aquatic craniate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups. Most fish are ectothermic ("cold-blooded"), allowing their body temperatures to vary as ambient temperatures change, though some of the large active swimmers like white shark and tuna can hold a higher core temperature. Fish are abundant in most bodies of water. They can be found in nearly all aquatic environments, from high mountain streams (e.g., char and gudgeon) to the abyssal and even hadal depths of the deepest oceans (e.g., gulpers and anglerfish). At 32,000 species, fish exhibit greater species diversity than any other group of vertebrates.
Fish are an important resource for humans worldwide, especially as food. Commercial and subsistence fishers hunt fish in wild fisheries (see fishing) or farm them in ponds or in cages in the ocean (see aquaculture). They are also caught by recreational fishers, kept as pets, raised by fishkeepers, and exhibited in public aquaria. Fish have had a role in culture through the ages, serving as deities, religious symbols, and as the subjects of art, books and movies.
Because the term "fish" is defined negatively, and excludes the tetrapods (i.e., the amphibians, reptiles, birds and mammals) which descend from within the same ancestry, it is paraphyletic, and is not considered a proper grouping in systematic biology. The traditional term pisces (also ichthyes) is considered a typological, but not a phylogenetic classification.
The earliest organisms that can be classified as fish were soft-bodied chordates that first appeared during the Cambrian period. Although they lacked a true spine, they possessed notochords which allowed them to be more agile than their invertebrate counterparts. Fish would continue to evolve through the Paleozoic era, diversifying into a wide variety of forms. Many fish of the Paleozoic developed external armor that protected them from predators. The first fish with jaws appeared in the Silurian period, after which many (such as sharks) became formidable marine predators rather than just the prey of arthropods. Sea Kraits The Laticauda species are found throughout the south and southeast Asian islands spreading from India in the west, north as far as Japan, and southeast to Fiji. They are mostly found in coastal waters. A sea krait can grow up to 11 feet long (3.6 meters). Location Size Diet Behavior Laticauda females are oviparous, and they return to land to mate and lay eggs. Several males will form a mating ball around the female, twitching their bodies in what is termed 'caudocephalic waves'. Though these animals can occur in high densities in suitable locations, nests of eggs are very rarely encountered, suggesting specific nesting conditions need to be met. Breeding Laticauda species feed in the ocean, mostly eating moray and conger eels, and some squid, crabs, and fish. They have never been observed feeding on land. Laticauda species are often active at night, which is when they prefer to hunt. Though they possess highly toxic venom, Laticauda snakes are usually shy and reclusive, and in New Caledonia, where they are called tricot rayé ("stripey sweater"), children play with them. Bites are extremely rare, but must be treated immediately. Black-banded sea kraits, numbering in their hundreds, form hunting alliances with yellow goatfish and bluefin trevally, flushing potential prey from narrow crannies in a reef the same way some moray eels do. Species Katuali The katuali, which in the Nuien language means flat-tail sea snake (Laticauda schistorhynchus) is a sea snake, related to the sea krait, it is found only in the waters of the Pacific Island nation of Niue, being found nowhere esle on earth. It is unique to Nuie. It grows up to 1 meter in length, and is highly venomous, making it one of the most dangerous creatures on the planet. It has a fin-like tail, helping it to swim better. The colubrine sea krait, banded sea krait or yellow-lipped sea krait (Laticauda colubrina) is a species of sea snake found in tropical Indo-Pacific oceanic waters. Columbrine Sea Krait Ventral scales of this snake are large, one-third to more than one-half the width of the body; the nostrils are lateral; nasal scales are separated by internasals; 19 longitudinal rows of imbricate scales are found at midbody; no azygous prefrontal shield is present; rostral scales are undivided; ventrals number 225-243; subcaudals number 38–47 in males, females have 30–35 (ventral and subcaudal counts after Smith 1943:443). The upper lip is dark brown. Total length varies with sex: males are 910 mm (36 in), females are 1,070 mm (42 in); tail lengths are similar: 110 mm (4.3 in).Distribution:
This species is found in the Indian Ocean (East India, Sri Lanka, Myanmar, Thailand, Indonesia, the Philippines), off the coasts of Fujian and Taiwan, Andaman Islands, Bay of Bengal, coasts of Malay Peninsula to New Guinea, Japan, Polynesia, Melanesia, Solomon Islands ,Timor-Leste and New Caledonia. Blue-Lipped Sea Krait The black-banded sea krait, or Chinese sea snake (Laticauda semifasciata), known in Japan as erabu umi hebi ja:, and Okinawa as the irabu, is a member of the Laticauda genus of sea snakes. It is found in most of the warm waters of the western Pacific Ocean.
This high snake frequents coral reef areas. It has a short head, thick trunk, and no easily discernable neck. The tail is simply extended skin, spread wide like a fin, and unsupported by any projection. The stomach is comparatively wide. Massing together near the shore, they breed between narrow cracks in the reef and in caves. It is a nocturnal snake, rarely seen during the day. It requires oxygen to breathe, so breaks the surface at least once every six hours.
It is too slow to catch fish in a straight chase, so hunts for fish hiding in the coral. The bite is highly venomous and paralyzes the prey. Females lay their eggs on land.
Generally, the species is found in Fiji, southern Japan and Singapore. Their venom is ten times stronger than that of a cobra, making them extremely dangerous. Fortunately, this snake does not bite humans unless it feels threatened.
The erabu snake is a winter staple in southern Japan, where it is believed to replenish a female's womanhood. Irabu soup 'irabu-jiru ja: is said to taste like miso and a bit like tuna. This soup was a part of the royal court cuisine of Ryukyu Kingdom; it is thought to have analeptic properties. Black-banded Sea Krait Crocker's Sea Snake Crocker's sea snake (Laticauda crockeri) is a species of snake in the Laticaudinae family. It is endemic to a single brackish lake (Lake Tenago) on Rennell Island in the Solomon Islands.
It is currently listed as vulnerable by the IUCN due to its extremely limited distribution. Sea Turtles The green sea turtle (Chelonia mydas), also known as the green turtle, black (sea) turtle, or Pacific green turtle, is a large sea turtle of the family Cheloniidae. It is the only species in the genus Chelonia. Its range extends throughout tropical and subtropical seas around the world, with two distinct populations in the Atlantic and Pacific Oceans. The common name derives from the usually green fat found beneath its carapace.
This sea turtle's dorsoventrally flattened body is covered by a large, teardrop-shaped carapace; it has a pair of large, paddle-like flippers. It is usually lightly colored, although in the eastern Pacific populations parts of the carapace can be almost black. Unlike other members of its family, such as the hawksbill sea turtle and loggerhead sea turtle, C. mydas is mostly herbivorous. The adults commonly inhabit shallow lagoons, feeding mostly on various species of seagrasses.
Like other sea turtles, green sea turtles migrate long distances between feeding grounds and hatching beaches. Many islands worldwide are known as Turtle Island due to green sea turtles nesting on their beaches. Females crawl out on beaches, dig nests and lay eggs during the night. Later, hatchlings emerge and scramble into the water. Those that reach maturity may live to eighty years in the wild.
C. mydas is listed as endangered by the IUCN and CITES and is protected from exploitation in most countries. It is illegal to collect, harm or kill them. In addition, many countries have laws and ordinances to protect nesting areas. However, turtles are still in danger because of several human practices. In some countries, turtles and their eggs are hunted for food. Pollution indirectly harms turtles at both population and individual scales. Many turtles die caught in fishing nets. Also, real estate development often causes habitat loss by eliminating nesting beaches. This This To Are Sea Turtles Becoming Endangered? To awnser your question, Yes! Sea turtles are one of the most endangered animals in the world. Though they can be found in every ocean in the world, except the arctic, it is becoming harder and harder to find them. They are becoming endangered by getting tangled in human fishing nets, suffocationg in oil spills, and being illigally poached by humans for their shells. Now for the big question... Will the extinction of turtles effect our lives? The awnser is yes, because turtles are in the food chain and if they become extinct it will upset the balance of the food chain. A sea turtle is a tiger sharks favorite snack and if they become extinct the sharks will resort to other things like seals, manatees, and even... us. And sea turtles love to snack on jelly fish, which cause a huge threat to humans as they adaot very quickly and are very dangerous. So if we work together to save them they might go from... Jelly Fish Jellyfish are the major non-polyp form of individuals of the phylum Cnidaria. They are typified as free-swimming marine animals consisting of a gelatinous umbrella-shaped bell and trailing tentacles. The bell can pulsate for locomotion, while stinging tentacles can be used to capture prey. Jellyfish are found in every ocean, from the surface to the deep sea. A few jellyfish inhabit freshwater. Large, often colorful, jellyfish are common in coastal zones worldwide. Jellyfish have roamed the seas for at least 500 million years, and possibly 700 million years or more, making them the oldest multi-organ animal. Skates and Rays Batoidea is a superorder of cartilaginous fish commonly known as rays and skates, containing more than 500 described species in thirteen families. They are in the elasmobranchii category of fish, along with sharks.They are closely related to sharks, from which they can be distinguished by their flattened bodies, enlarged pectoral fins that are fused to the head, and gill slits that are placed on their ventral surfaces. Seabirds (also known as marine birds) 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. The first seabirds evolved in the Cretaceous period, and modern seabird families emerged in the Paleogene.
In general, seabirds live longer, breed later and have fewer young than other birds do, but they invest a great deal of time in their young. Most species nest in colonies, which can vary in size from a few dozen birds to millions. Many species are famous for undertaking long annual migrations, crossing the equator or circumnavigating the Earth in some cases. They feed both at the ocean's surface and below it, and even feed on each other. Seabirds can be highly pelagic, coastal, or in some cases spend a part of the year away from the sea entirely.
Seabirds and humans have a long history together: they have provided food to hunters, guided fishermen to fishing stocks and led sailors to land. Many species are currently threatened by human activities, and conservation efforts are under way. Sea Birds Sharks Sharks are a group of fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachimorpha (or Selachii), and are the sister group to the rays. However, the term "shark" has also been used for extinct members of the subclass Elasmobranchii outside the Selachimorpha, such as Cladoselache and Xenacanthus. Under this broader definition, the earliest known sharks date from more than 420 million years ago. Since that time, sharks have diversified into over 470 species. They range in size from the small dwarf lanternshark (Etmopterus perryi), a deep sea species of only 17 centimetres (6.7 in) in length, to the whale shark (Rhincodon typus), the largest fish in the world, which reaches approximately 12 metres (39 ft). Sharks are found in all seas and are common down to depths of 2,000 metres (6,600 ft). They generally do not live in freshwater although there are a few known exceptions, such as the bull shark and the river shark, which can survive in both seawater and freshwater. They breathe through five to seven gill slits. Sharks have a covering of dermal denticles that protects their skin from damage and parasites in addition to improving their fluid dynamics. They also have several sets of replaceable teeth. Well-known species such as the great white shark, tiger shark, blue shark, mako shark, and the hammerhead shark are apex predators—organisms at the top of their underwater food chain. Their predatory skill fascinates and frightens humans, even though their survival is threatened by human-related activities. The Ocean The Ocean is a very diverse and beautiful biosphere. An ocean (from Ancient Greek (Okeanos); the World Ocean of classical antiquity) is a body of saline water that composes a large part of a planet's hydrosphere. In the context of Earth, it refers to one or all of the major divisions of the planet's World Ocean – they are, in descending order of area, the Pacific, Atlantic, Indian, Southern (Antarctic), and Arctic Oceans. The word "sea" is often used interchangeably with "ocean", but strictly speaking a sea is a body of saline water (possibly a division of the World Ocean) partly or fully enclosed by land. Earth's global ocean is the largest confirmed surface ocean on all observable planets. Approximately 72% of the planet's surface (~3.6x108 km2) is covered by saline water that is customarily divided into several principal oceans and smaller seas, although some sources prove that the ocean only covers approximately 71% of the Earth's surface. In terms of the hydrosphere of the Earth, the ocean contains 97% of the Earth's water. Oceanographers have stated that out of 97%, only 5% of the ocean as a whole on Earth has been explored. Because it is the principal component of Earth's hydrosphere, the world ocean is integral to all known life, forms part of the carbon cycle, and influences climate and weather patterns. The total volume is approximately 1.3 billion cubic kilometres (310 million cu mi) with an average depth of 3,682 metres (12,080 ft). It is the habitat of 230,000 known species, although much of the ocean's depths remain unexplored and it is estimated that over two million marine species exist. The origin of Earth's oceans is still unknown, but oceans are believed to have formed in the Hadean period and may have been the impetus for the emergence of life. Extraterrestrial oceans may be composed of a wide range of elements and compounds. The only confirmed large stable bodies of extraterrestrial surface liquids are the lakes of Titan, although there is evidence for the existence of oceans elsewhere in the Solar System. Early in their geologic histories, Mars and Venus are theorized to have had large water oceans. The Mars ocean hypothesis suggests that nearly a third of the surface of Mars was once covered by water, though the water on Mars is no longer oceanic, and a runaway greenhouse effect may have boiled away the global ocean of Venus. Compounds such as salts and ammonia dissolved in water lower its freezing point, so that water might exist in large quantities in extraterrestrial environments as brine or convecting ice. Unconfirmed oceans are speculated beneath the surface of many dwarf planets and natural satellites; notably, the ocean of Europa is believed to have over twice the water volume of Earth. The Solar System's gas giant planets are also believed to possess liquid atmospheric layers of yet to be confirmed compositions. Oceans may also exist on exoplanets and exomoons, including surface oceans of liquid water within a circumstellar habitable zone. Ocean planets are a hypothetical type of planet with a surface completely covered with liquid. Pollution Problem Oceans are in trouble because of the pollution. People are just throwing trash on beaches, and oils are spilling in the oceans. The most recent oil spill was April 20, to July 15 2010, the ocean and it animals were not the only ones hurt by it. The spill left 11 people dead, countless marine life dead or struggling to stay alive, and damaged ore than $4.525 billion dollars in fines and other payments. People can recycle plastic bags to save sea turtles because plastic bags floating in the ocean look like jellyfish and they are a sea turtles favorite snack and they can get tangled and choked in the bags. Fish get tangled in netted buckets and sea birds get covered in oil and sink to the bottom of the ocean. Marine invertebrates are multicellular animals that inhabit a marine environment and are invertebrates, lacking a vertebral column. In order to protect themselves, they may have evolved a shell or a hard exoskeleton, but this is not always the case. As on land and in the air, invertebrates make up a great majority of all macroscopic life in the sea. Marine Inverts The Four Oceans The Indian Ocean The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded by Asia—including India, after which the ocean is named—on the north, on the west by Africa, on the east by Australia, and on the south by the Southern Ocean (or, depending on definition, by Antarctica.)
As one component of the World Ocean, the Indian Ocean is delineated from the Atlantic Ocean by the 20° east meridian running south from Cape Agulhas, and from the Pacific Ocean by the meridian of 146°55' east. The northernmost extent of the Indian Ocean is approximately 30° north in the Persian Gulf. The ocean is nearly 10,000 km (6,200 mi) wide at the southern tips of Africa and Australia, and its area is 73,556,000 km² (28,350,000 mi²), including the Red Sea and the Persian Gulf.
The ocean's volume is estimated to be 292,131,000 km³ (70,086,000 mi³). Small islands dot the continental rims. Island nations within the ocean are Madagascar (the world's fourth largest island), Comoros, Seychelles, Maldives, Mauritius, and Sri Lanka. The archipelago of Indonesia borders the ocean on the east. The 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 (or, depending on definition, to Antarctica) in the south, bounded by Asia and Australia in the west, and the Americas in the east.
At 165.25 million square kilometres (63.8 million square miles) in area, this largest division of the World Ocean – and, in turn, the hydrosphere – covers about 46% of the Earth's water surface and about one-third of its total surface area, making it larger than all of the Earth's land area combined. The equator subdivides it into the North Pacific Ocean and South Pacific Ocean, with two exceptions: the Galápagos and Gilbert Islands, while straddling the equator, are deemed wholly within the South Pacific. The Mariana Trench in the western North Pacific is the deepest point in the world, reaching a depth of 10,911 metres (35,797 ft).
The eastern Pacific Ocean was first sighted by Europeans early in the 16th century. Spanish explorer Vasco Núñez de Balboa crossed the Isthmus of Panama in 1513 and named it Mar del Sur (South Sea). The ocean's current name was given by Portuguese explorer Ferdinand Magellan during the Spanish expedition of world circumnavigation in 1521, who encountered favourable winds as he reached the ocean and called it Mar Pacifico in Portuguese, meaning "peaceful sea". The Atlantic Ocean The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about 106,400,000 square kilometres (41,100,000 sq mi), it covers approximately 20 percent of the Earth's surface and about 29 percent of its water surface area. The first part of its name refers to Atlas of Greek mythology, making the Atlantic the "Sea of Atlas". The oldest known mention of "Atlantic" is in The Histories of Herodotus around 450 BC (Hdt. 1.202.4): Atlantis thalassa (Greek: Ἀτλαντὶς θάλασσα; English: Sea of Atlas). The term Ethiopic Ocean, derived from Ethiopia, was applied to the southern Atlantic as late as the mid-19th century. Before Europeans discovered other oceans, the term "ocean" itself was synonymous with the waters beyond the Strait of Gibraltar that we now know as the Atlantic. The early Greeks believed this ocean to be a gigantic river encircling the world. The Atlantic Ocean occupies an elongated, S-shaped basin extending longitudinally between Eurasia and Africa to the east, and the Americas to the west. As one component of the interconnected global ocean, it is connected in the north to the Arctic Ocean (which is sometimes considered a sea of the Atlantic), to the Pacific Ocean in the southwest, the Indian Ocean in the southeast, and the Southern Ocean in the south. (Other definitions describe the Atlantic as extending southward to Antarctica.) The equator subdivides it into the North Atlantic Ocean and South Atlantic Ocean. The Arctic Ocean The Arctic Ocean, located in the Northern Hemisphere and mostly in the Arctic north polar region, is the smallest and shallowest of the world's five major oceanic divisions. The International Hydrographic Organization (IHO) recognizes it as an ocean, although some oceanographers call it the Arctic Mediterranean Sea or simply the Arctic Sea, classifying it a mediterranean sea or an estuary of the Atlantic Ocean. Alternatively, the Arctic Ocean can be seen as the northernmost part of the all-encompassing World Ocean. Almost completely surrounded by Eurasia and North America, the Arctic Ocean is partly covered by sea ice throughout the year (and almost completely in winter). The Arctic Ocean's temperature and salinity vary seasonally as the ice cover melts and freezes; its salinity is the lowest on average of the five major oceans, due to low evaporation, heavy freshwater inflow from rivers and streams, and limited connection and outflow to surrounding oceanic waters with higher salinities. The summer shrinking of the ice has been quoted at 50%. The US National Snow and Ice Data Center (NSIDC) uses satellite data to provide a daily record of Arctic sea ice cover and the rate of melting compared to an average period and specific past years. Prehistoric Oceans Marine animals that lived millions of years ago. These are animals that lived during the dinosaurs. The Marine animals long ago grew into huge monsters. The Megalodon, the largest shark ever known, lived during the Cenozoic Era (late Oligocene to early Pleistocene). Megalodon fossils have been excavated from many parts of the world, including Europe, Africa and both North and South America, as well as Puerto Rico, Cuba, Jamaica, Australia, New Zealand, Japan, Malta, Grenadines and India. Megalodon teeth have been excavated from regions far away from continental lands, such as the Mariana Trench in the Pacific Ocean. The earliest megalodon remains were reported from late Oligocene strata, circa 28 million years old. Although fossils are mostly absent in strata extending beyond the Tertiary boundary, they have been reported from subsequent Pleistocene strata. It is believed that megalodon became extinct in the Pleistocene, probably about 1.5 million years ago. There are also animals called living fossils. These animals are animals that have been living on earth since they evolved. Example of a living fossil are, The Coelacanth, a fish that was thought to be extinct until one was caught of the coast of South Africa, and many others. Ocean Ecosystems Ocean Destruction Marine ecosystems are among the largest of Earth's aquatic ecosystems. They include oceans, salt marsh and intertidal ecology, estuaries and lagoons, mangroves and coral reefs, the deep sea and the sea floor. They can be contrasted with freshwater ecosystems, which have a lower salt content. Marine waters cover two-thirds of the surface of the Earth. Such places are considered ecosystems because the plant life supports the animal life and vice-versa. See food chains.
Marine ecosystems are very important for the overall health of both marine and terrestrial environments. According to the World Resource Center, coastal habitats alone account for approximately 1/3 of all marine biological productivity, and estuarine ecosystems (i.e., salt marshes, seagrasses, mangrove forests) are among the most productive regions on the planet. In addition, other marine ecosystems such as coral reefs, provide food and shelter to the highest levels of marine diversity in the world.
Marine ecosystems usually have a large biodiversity and are therefore thought to have a good resistance against invasive species. However, exceptions have been observed, and the mechanisms responsible in determining the success of an invasion are not yet clear. Tsunami A tsunami (plural: tsunamis or tsunami; from Japanese: 津波, lit. "harbour wave"; English pronunciation: /suːˈnɑːmi/ soo-nah-mee or /tsuːˈnɑːmi/ tsoo-nah-mee) is a series of water waves caused by the displacement of a large volume of a body of water, typically an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater explosions (including detonations of underwater nuclear devices), landslides, glacier calvings, meteorite impacts and other disturbances above or below water all have the potential to generate a tsunami.
Tsunami waves do not resemble normal sea waves, because their wavelength is far longer. Rather than appearing as a breaking wave, a tsunami may instead initially resemble a rapidly rising tide, and for this reason they are often referred to as tidal waves. Tsunamis generally consist of a series of waves with periods ranging from minutes to hours, arriving in a so-called "wave train". Wave heights of tens of metres can be generated by large events. Although the impact of tsunamis is limited to coastal areas, their destructive power can be enormous and they can affect entire ocean basins; the 2004 Indian Ocean tsunami was among the deadliest natural disasters in human history with over 230,000 people killed in 14 countries bordering the Indian Ocean.
The Greek historian Thucydides suggested in his late 5th century BC, History of the Peloponnesian War, that tsunamis were related to submarine earthquakes,but the understanding of a tsunami's nature remained slim until the 20th century and much remains unknown[clarify]. Major areas of current research include trying to determine why some large earthquakes do not generate tsunamis while other smaller ones do; trying to accurately forecast the passage of tsunamis across the oceans; and also to forecast how tsunami waves would interact with specific shorelines. Waves In fluid dynamics, wind waves or, more precisely, wind-generated waves are surface waves that occur on the free surface of oceans, seas, lakes, rivers, and canals or even on small puddles and ponds. They usually result from the wind blowing over a vast enough stretch of fluid surface. Waves in the oceans can travel thousands of miles before reaching land. Wind waves range in size from small ripples to huge waves over 30 m high.
When directly being generated and affected by the local winds, a wind wave system is called a wind sea. After the wind ceases to blow, wind waves are called swell. Or, more generally, a swell consists of wind generated waves that are not—or are hardly—affected by the local wind at that time. They have been generated elsewhere, or some time ago. Wind waves in the ocean are called ocean surface waves.
Wind waves have a certain amount of randomness: subsequent waves differ in height, duration and shape, with a limited predictability. They can be described as a stochastic process, in combination with the physics governing their generation, growth, propagation and decay—as well as governing the interdependence between flow quantities such as: the water surface movements, flow velocities and water pressure. The key statistics of wind waves (both seas and swells) in evolving sea states can be predicted with wind wave models.
Tsunamis are a specific type of wave not caused by wind but by geological effects. In deep water, tsunamis are not visible because they are small in height and very long in wavelength. They may grow to devastating proportions at the coast due to reduced water depth.