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Sunday, August 20, 2023

Fauna of the United States

The bald eagle is the national bird of the United States and appears on its Great Seal. The bald eagle's range includes all of the contiguous United States and Alaska.

The fauna of the United States of America is all the animals living in the Continental United States and its surrounding seas and islands, the Hawaiian Archipelago, Alaska in the Arctic, and several island-territories in the Pacific and in the Caribbean. The U.S. has many endemic species found nowhere else on Earth. With most of the North American continent, the U.S. lies in the Nearctic, Neotropic, and Oceanic faunistic realms, and shares a great deal of its flora and fauna with the rest of the American supercontinent.

An estimated 432 species of mammals characterize the fauna of the continental U.S. There are more than 800 species of bird and more than 100,000 known species of insects. There are 311 known reptiles, 295 amphibians and 1154 known fish species in the U.S. Known animals that exist in all of the lower 48 states include white-tailed deer, bobcat, raccoon, muskrat, striped skunk, barn owl, American mink, American beaver, North American river otter and red fox. The red-tailed hawk is one of the most widely distributed hawks not only in the U.S., but in the Americas.

Huge parts of the country with the most distinctive indigenous wildlife are protected as national parks. In 2013, the U.S. had more than 6770 national parks or protected areas, all together more than 1,006,619 sq. miles (2,607,131 km2). The first national park was Yellowstone National Park in the state of Wyoming, established in 1872. Yellowstone National Park is widely considered to be the finest megafauna wildlife habitat in the U.S. There are 67 species of mammals in the park, including the gray wolf, the threatened lynx, and the grizzly bear.

Western United States

The raccoon is widespread throughout the lower 48 states.
Mountain lions live throughout the western U.S.

The ecoregions and ecology found in the Western United States are extremely varied. For instance, large areas of land are made up of everything from sand dunes in the Central Basin and Range ecoregion, which makes up much of the State of Nevada, to the ecology of the North Cascades in Washington state, which has the largest concentration of active alpine glaciers in the lower 48. The densely forested areas found in Northern California, Oregon, Washington, Idaho, and Montana have mostly species adapted to living in temperate climates, while Southern California, Nevada, Arizona, southern Utah, and New Mexico have a fauna resembling its position in the dry deserts with temperature extremes.

The western continental coast of the U.S., just as the East Coast, varies from a colder-to-warmer climate from north to south. Few species live throughout the entire West Coast, however, there are some, including the bald eagle that inhabits both the Alaskan Aleutian Islands and the California Channel Islands. In most of the contiguous Western U.S. are mule deer, white-tailed antelope squirrels, cougars, American badgers, coyotes, hawks and several species of snakes and lizards are common.

While the American black bear lives throughout the U.S., the brown bears and grizzly bears are more common in the northwest and in Alaska. Along the West Coast there are several species of whales, sea otters, California sea lions, eared seals and northern elephant seals. In the dry, inland desert areas of states such as California, Nevada, Arizona and New Mexico there are some of the world's most venomous lizards, snakes and scorpions. The most notorious might be the Gila monster and Mohave rattlesnake, both found in deserts in the Southwest. The Sonoran Desert has eleven species of rattlesnakes - more than anywhere else in the world.

Along the southwestern border there are jaguars and ocelots. Other mammals include the Virginia opossum, which occurs throughout California and coastal areas in Oregon and Washington. The North American beaver and mountain beaver live in forested areas of Washington, Oregon and Northern California. The kit fox lives throughout Arizona, New Mexico and Utah, while the gray fox occurs throughout the Western U.S.

The red fox occurs mostly in Oregon and Washington, while the island fox is a native to six of the eight Channel Islands in Southern California. These islands are also famous for their marine life and endemic species such as the Channel Islands spotted skunk, Garibaldi, island fence lizard, island scrub jay, bald eagle, and their non-native Catalina Island bison herd. The raccoon and spotted skunk occur throughout the Western U.S., while the ring-tailed cat occurs throughout Arizona, New Mexico, Western Texas, Utah, Colorado, and most of California. The American black bear occurs in most western states, including Washington, Oregon, California, Arizona and Colorado.

Channel Islands

The Channel Islands National Park consists of five out of the eight California Channel Islands. The Channel Islands are part of one of the richest marine biospheres of the world. Many unique species of plants and animals are endemic to the Channel Islands, including fauna such as the island fox, Channel Islands spotted skunk, island scrub jay, ashy storm-petrel, island fence lizard, island night lizard, Channel Islands slender salamander, Santa Cruz sheep, San Clemente loggerhead shrike and San Clemente sage sparrow. Other animals in the islands include the California sea lion, California moray, bald eagle, Channel Islands spotted skunk and the non-native Catalina Island bison herd.

Southern United States

The South has a large variety of habitats that range from the Mississippi River basin in Arkansas and Mississippi to the Southern Appalachian Mountains. As far north as the hills of Tennessee and Virginia, all the way down to the Everglades in the southern end of Florida. From the eastern-most point on the Outer Banks of North Carolina, as far west as the deserts and prairies of West Texas and Oklahoma. The warmer climate allows for rich biodiversity ranging from cypress swamps in Louisiana to the thick bays and the longleaf pine biome of the South Carolina Lowcountry. It is riddled along the way with countless salt marshes in every coastal state from the Carolinas, through Georgia to Texas, including the Mobile Delta that lies in the borders of Alabama.

The American alligator is endemic to eight states in the Southeast, and is the official state reptile of Florida, Louisiana and Mississippi.

The Southern United States is home to a multitude of reptiles and amphibians. The American alligator lives in much of the South - including every coastal state from North Carolina to Texas, along with the inland states of Arkansas and Tennessee- while the less widespread American crocodile is only found in southern Florida. The Alligator snapping turtle and more than forty other species of turtle are found in the southern U.S. including the eastern box turtle, red-eared slider, and the softshell turtle. Snakes in the region include the eastern copperhead, eastern diamondback rattlesnake, timber rattlesnake, pigmy rattlesnake, cottonmouth, and eastern coral snake, all of which are venomous. Some of the other reptiles and amphibians thriving in the South include the Carolina anole, razor-backed musk turtle, broad-headed skink, American bullfrog, southern toad, spring peeper and the coal skink.

Mammals of the region include the elk, the largest of which that was wiped out in the 1800s, but has been reintroduced and is making promising recoveries in Virginia, North Carolina, Tennessee, and Arkansas. There still remain resident populations in parts of Texas and Oklahoma. The American black bear is native to much of the South, but are prevalent in Virginia, the Carolinas, Tennessee, Georgia, Florida, Arkansas, and Oklahoma. The Florida panther is the largest feline in the South and is exclusive to the wetlands of South Florida. White-tailed deer, bobcat, coyote, wild boar, red and grey fox are other mammals that inhabit parts of every state in the region. Wild horses roam parts of the South in small groups, which are remnants of horses brought by settlers in the 1400s and 1500s. These are mostly in coastal habitats.

Many water-dwelling mammals inhabit the South including the American beaver, muskrat, river otter, and nutria, which is an invasive species and has decimated plant life in the swamps of Louisiana. Weasels and mink also prefer being near water. Rabbits are common in the South; the eastern cottontail is found throughout the region, while the desert cottontail and black-tailed jackrabbit is primarily found in Texas, and Oklahoma. The swamp rabbit is found in wetlands of states like Mississippi, Alabama, Louisiana and Arkansas, while the marsh rabbit resides along the coastal regions of the Carolinas, Georgia, Florida, and Alabama. Squirrels are also abundant. The eastern grey squirrel and eastern fox squirrel can both be found in every southern state. The southern range of the American red squirrel dips into the higher elevations of Virginia and North Carolina. Other common mammals are the Virginia opossum, raccoon striped and spotted skunk, groundhog and in parts of the South, the nine-banded armadillo.

There are over 1,100 species of bird in the Southern U.S. ranging from upland birds, to waterfowl. The South is home to many coastal birds including gulls, rails, gallinules, skimmers, grebes, sandpipers, cranes, and herons. Upland birds include wild turkey and ruffed grouse. Various game bird species such as the bobwhite quail and the woodcock. The eastern whip-poor-will and the Chuck-will's-widow belong to the nighthawk family and are found in every southern state. Songbirds make up the largest portion of birds found in this region.

Central United States

The pronghorn is the fastest land mammal in the Western Hemisphere and can reach speeds up to 55 mph.

In the prairie in the Central United States lives mostly animals adapted for living in grasslands. Indigenous mammals include the American bison, eastern cottontail, black-tailed jackrabbit, plains coyote, black-tailed prairie dog, muskrat, opossum, raccoon, prairie chicken, wild turkey, white-tailed deer, swift foxes, pronghorn antelope, the Franklin's ground squirrel and several other species of ground squirrels.

Reptiles include bullsnakes, common collared lizard, common snapping turtle, musk turtles, yellow mud turtle, painted turtle, western diamondback rattlesnake and the prairie rattlesnake. Some of the typical amphibians found in the region are the three-toed amphiuma, green toad, Oklahoma salamander, lesser siren and the plains spadefoot toad. In the Rocky Mountains and other mountainous areas of the inland is where the bald eagle is most observed, even though its habitat includes all of the Lower 48, as well as Alaska.

Rabbits live throughout the Great Plains and neighboring areas; the black-tailed jackrabbit is found in Texas, Oklahoma, Nebraska and Kansas, the white-tailed jackrabbit in the Dakotas, Minnesota and Wisconsin, the swamp rabbit in swampland in Texas, and the eastern cottontail is found in Texas, Oklahoma, Kansas, Nebraska, the Dakotas, and every state in the Eastern U.S.

The groundhog is a common species in Iowa, Missouri, and eastern portions of Kansas, Nebraska and Oklahoma.

The groundhog is widespread throughout Illinois, Iowa, Missouri, and Minnesota. Virginia opossum is found is states such as Missouri, Indiana, Iowa, Oklahoma, Nebraska and Kansas.

The nine-banded armadillo is found throughout the South and states such as Missouri, Kansas and Oklahoma. The muskrat is found throughout the Central U.S., excluding Texas, while the American beaver is found in every central state.

The American bison is the heaviest land animal in North America and can be as tall as 6.5 feet (2.0 m) and weigh over a ton.

Maybe the most iconic animal of the American prairie, the American buffalo, once roamed throughout the central plains. Bison once covered the Great Plains and were critically important to Native-American societies in the Central U.S. They became nearly extinct in the 19th century, but have made a recent resurgence in the Great Plains. Today, bison numbers have rebounded to about 200,000; these bison live on preserves and ranches.

Some of the species that occupy every central state include the red fox, bobcat, white-tailed deer, raccoon, eastern spotted skunk, striped skunk, long-tailed weasel, and the American badger and beaver. The wild boar is common in the South, while the American mink lives in every central state with the exception of Texas. The least weasel is found around the Great Lakes as well as states such as Nebraska, the Dakotas, Minnesota, Iowa, Illinois, Michigan, and Wisconsin.

The gray fox is found in Iowa, Missouri, Oklahoma, Texas and also around the Great Lakes region. The ring-tailed cat is found in the southern region, including in Texas, Missouri, and Oklahoma. There are many species of squirrels in the central parts of the U.S., including the fox squirrel, eastern gray squirrel, Franklin's ground squirrel, southern flying squirrel, and the thirteen-lined ground squirrel. Voles include the prairie vole, woodland vole and the meadow vole. The plains pocket gopher lives throughout the Great Plains. Shrews include the cinereus shrew, southeastern shrew, North American least shrew, and the Elliot's short-tailed shrew.

Eastern United States

The White-tailed deer is common in all eastern states.

In the Appalachian Mountains and the Eastern United States are many animals that live in forested habitats. They include deer, rabbits, rodents, squirrels, hares, woodpeckers, owls, foxes and bears. The New England region is particularly famous for its crab and the American lobster living along most of the Atlantic Coast. The bobcat, raccoon and striped skunk live in every eastern state, while the American alligator lives in every coastal state between North Carolina and Texas.

Some species of mammals found throughout the Eastern U.S. includes the red fox and gray fox, the North American beaver, North American porcupine, Virginia opossum, eastern mole, coyote, white-tailed deer, American mink, North American river otter, and long-tailed weasel. The American black bear lives throughout most of New England, New York, New Jersey, Pennsylvania, Maryland, the Virginias, and parts of the Carolinas and Florida.

The American beaver is found throughout the U.S., except for Florida, Nevada and Hawaii.

Shrews are common: the cinereus shrew, long-tailed shrew and American water shrew are widespread in the New England region, while the North American least shrew and southeastern shrew are common in the southeastern states. The American pygmy shrew, smoky shrew, and northern short-tailed shrew are found from the Appalachian Mountains to New England. The star-nosed mole lives throughout the Eastern U.S., while the hairy-tailed mole is more common from the Appalachians to New England in the north.

Hares are also common: the snowshoe hare thrives from the Appalachians to New England, the Appalachian cottontail is only found in the Appalachians, the New England cottontail is only found in New England, while the eastern cottontail is widespread throughout the east. While the white-footed mouse and muskrat are common throughout the east, with the exception of Florida, the meadow vole is found from the Appalachians to New England and the southern red-backed vole is found in New England.

The striped skunk lives throughout the continental United States.

The brown rat and the house mouse were both introduced and their habitat range throughout the Eastern U.S. Weasels such as the fisher and short-tailed weasel are found in the northeast. The eastern chipmunk, fox squirrel, eastern gray squirrel and the woodchuck are found throughout the region, while the southern flying squirrel and northern flying squirrel are more common in the southeast, the American red squirrel is more common in the northeast. The least weasel is native to the Appalachian Mountains.

The wild boar is the wild ancestor of the domestic pig and has spread through much of the southeastern region as an invasive species. The Canada lynx is found in parts of New England. Species of bats found throughout the east includes the eastern pipistrelle, silver-haired bat, eastern red bat, hoary bat, big brown bat, little brown bat, northern long-eared myotis, and in most regions the eastern small-footed myotis, gray bat and Indiana bat.

Of the marine life, the harbor seal is the most widely distributed species of seal and found along the east coast, while the hooded seal, bearded seal, grey seal, ringed seal, and harp seal are found in the northwest. Whales are common along Atlantic coastline. Whale species found along the entire coastline includes the Gervais' beaked whale, common minke whale, fin whale, sei whale, blue whale, humpback whale, sperm whale, dwarf sperm whale, pygmy sperm whale, killer whale, Cuvier's beaked whale, True's beaked whale, and the Blainville's beaked whale.

The northern bottlenose whale and the long-finned pilot whale are also common along the New England coast. Dolphins are common; species found along the entire coastline includes the Risso's dolphin, short-beaked common dolphin, striped dolphin, Atlantic spotted dolphin and the common bottlenose dolphin. Dolphin species found in New England include white-beaked dolphin and Atlantic white-sided dolphin, while species roaming the southeastern parts of the coastline include the Fraser's dolphin, pantropical spotted dolphin, Clymene dolphin, spinner dolphin, and the rough-toothed dolphin.

Several sea turtles live along the Atlantic coast, including the hawksbill sea turtle, Kemp's ridley sea turtle, and loggerhead sea turtle. The green sea turtle and leatherback sea turtle are more common species along the southeastern coastline. Land turtles and tortoises found throughout most of the Eastern United States are the common snapping turtle, painted turtle, spotted turtle, diamondback terrapin, spiny softshell turtle, eastern mud turtle, northern red-bellied cooter, common musk turtle, eastern box turtle, and the yellow- and red-eared slider. While common species in the northeast include Blanding's turtle, wood turtle, and bog turtle, common species in the southeastern U.S. include gopher tortoise, pond slider, Escambia map turtle, Barbour's map turtle, eastern river cooter, striped mud turtle, loggerhead musk turtle, and the Florida softshell turtle. The smooth softshell turtle is for instance found in the Ohio River and the Allegheny River in Pennsylvania.

The American black bear occurs in most states.

Some of the snake species found in much of the Eastern U.S. includes the eastern racer, De Kay's snake, northern copperhead, ringneck snake, timber rattlesnake, eastern hog-nosed snake, milk snake, northern water snake, western rat snake, northern redbelly snake, plainbelly water snake, midland water snake, scarlet kingsnake, common kingsnake, queen snake, smooth earth snake, ribbon snake, and the common garter snake. Snake species mostly found in the northeast includes the smooth green snake, northern ribbon snake, and the eastern worm snake.

Snakes limited to the southeast includes the southeastern crown snake, pinesnake, eastern diamondback rattlesnake, coral snake, pygmy rattlesnake, southern copperhead, water moccasin, eastern coral snake, eastern indigo snake, southern hognose snake, coachwhip snake, banded water snake, brown water snake, green water snake, Nerodia clarkii clarkii, salt marsh snake, mole kingsnake, pine woods snake, glossy crayfish snake, striped crayfish snake, short-tailed snake, swamp snake, rim rock crown snake, rough earth snake, southern black racer, rough green snake, western rat snake, eel moccasin, and the mud and corn snakes. The eastern fence lizard is common throughout the Eastern United States, with the exception of New York and New England.

The gray wolf once roamed the Eastern U.S., but is now extinct from this region. The eastern cougar as well was once as widespread as the cougar in the western parts of the country, but was deemed extinct by the U.S. Fish and Wildlife Service in 2011. Eastern elk once lived throughout the east, but was extirpated in the 19th century and declared as extinct by the U.S. Fish and Wildlife Service in 1880. Moose as well once roamed throughout the east, but is currently only found in northern New England. Due to its highly prized fur, the sea mink was hunted to extinction in 1903.

Hawaiian Islands

A green sea turtle (honu in Hawaiian) swimming by coral reefs in Kona.

Much of the fauna in Hawaii has developed special adaptations to their home and evolved into new species. Today, nearly 90% percent of the fauna in Hawaii are endemic, meaning that they exist nowhere else on Earth.[15] Kauaʻi is home to the largest number of tropical birds, as it is the only island free of mongooses. The Javan mongoose is widespread throughout the archipelago, except on the islands of Lanaʻi and Kauaʻi.

Famous birds include ʻiʻiwi, nukupuʻu, Kauaʻi ʻamakihi and ʻōʻū. Unfortunaly, most of these birds and now extinct. The hoary bat is found in the Kōkeʻe State Park on Kauaʻi, wild horses live in the Waipio Valley, wild cattle by the Mauna Kea and the Australian brush-tailed rock-wallaby live by the Kalihi Valley on Oʻahu. The Hawaiian monk seal, wild goats, sheep and pigs live throughout most of the archipelago.

In Hawaii, three species of sea turtles are considered native: honu, honu’ea and the leatherback sea turtle. Two other species, the loggerhead sea turtle and the olive ridley sea turtle, are sometimes observed in Hawaiian waters. The Hawaiian green sea turtle is the most common sea turtle in Hawaiian waters. As well as turtles, the sea life consist of more than forty species of shark and the Hawaiian spinner dolphin is widespread. Hawaii's coral reefs are home to over 5000 species, and 25 percent of these are found nowhere else in the world.

Alaska

Grizzly bears are found throughout Alaska, parts of Montana and on the Canada–US border in Idaho. They are also found in Yellowstone National Park.

The wildlife of Alaska is abundant, extremely diverse and includes for instance polar bears, puffins, moose, bald eagles, Arctic foxes, wolves, Canadian lynx, muskox, snowshoe hare, mountain goats, walrus and caribou. Life zones in Alaska range from grasslands, mountains, tundra to thick forests, which leads to a huge diversity in terrain and geology throughout the state.

Alaska has also over 430 species of birds and the largest population of bald eagles in the nation. From pygmy shrews that weigh less than a penny to gray whales that weigh 45 tons, Alaska is the "Last Frontier" for animals as well as people. Many species endangered elsewhere are still abundant in Alaska.

Aleutian Islands

The Aleutian Islands are home to an abundance of large bird colonies; more than 240 bird species inhabit in Alaska's Aleutian Archipelago. Large seabird colonies are present on islands like Buldir Island, which has 21 breeding seabird species, including the Bering Sea-endemic red-legged kittiwake. Large seabird colonies are also present on Kiska Island, Gareloi Island, Semisopochnoi Island, Bogoslof Island, and several others.

The islands are also frequented by vagrant Asiatic birds, including the common rosefinch, Siberian rubythroat, bluethroat, lanceolated warbler, and the first North American record of the intermediate egret. Other animals in the Aleutian Chain include the Arctic fox, American mink, Porcupine caribou, northern sea otter, horned puffin, tufted puffin, Steller sea lion, spotted seal, ringed seal, northern fur seal and many more.

Territories

American Samoa

The blue-crowned lorikeet is a parrot found throughout the Samoan islands.

Because of its remote location, diversity among the terrestrial species is low. The archipelago has a huge variety in animals and more than 9,000 acres is a national park: National Park of American Samoa. The park stretches over three of the six islands in the archipelago: Tutuila, Ofu-Olosega and Ta‘ū. Eight mammal species have been recorded at American Samoa, of which none of them are critically endangered.

The mammals include several species of native bats, including the Samoa flying fox and insular flying fox. The avifauna includes 65 species of bird where the more unusual distinctive ones are the blue-crowned lorikeet, the spotless crake, the many-colored fruit dove, the wattled honeyeater, tropical pigeons, the samoan starling, white tern, black noddy and the red-tailed tropicbird.

There are many reptiles in the islands, including five species of geckos, eight species of skinks and two species of snakes: the Pacific boa and the Australoasian blindsnake. The marine life is magnificent and much concentrated around the colorful coral reefs. The Samoan ocean is a home to sea turtles as hawksbill sea turtle, olive ridley sea turtle, leatherback sea turtle and the green sea turtle. Five species of dolphins live in the area: spinner dolphin, rough-toothed dolphin, bottlenose dolphin, pantropical spotted dolphin and striped dolphin.

Guam

Shortly after World War II, the brown tree snake was introduced to the island of Guam and caused much of the endemic wildlife to become extinct. Due to an abundance of prey species and lack of predators, the brown tree snake's population exploded and reached nearly 13,000 snakes per square mile at most. Ten out of twelve endemic bird species, ten lizards and two bats all became extinct as a result of the introduction of the brown tree snake. In recent years, a lot has been done by the U.S. government to decrease the number of brown tree snakes on the island. For instance in 2013, a $1 million program by the U.S. Fish and Wildlife Service dropped more than 2000 mice filled with poison on the island. In 2013, more than two million brown tree snakes were estimated to be on the island. Other introduced species include the Philippine deer, the Asiatic water buffalo, the marine toad and the giant African land snail. Several native species of skinks, geckos and a monitor lizard are still found on the island.

Northern Mariana Islands

The Commonwealth of Northern Mariana Islands is home to 40 indigenous and introduced bird species. Some endemic bird species are the Mariana fruit dove, the Mariana swiftlet, the Rota white-eye, the Tinian monarch, the bridled white-eye and the golden white-eye. Other common, but introduced species, include the collared kingfisher, the rufous fantail, the fairy tern and the uniform swiftlet. The Mariana fruit bat is endemic to both Guam and the Northern Mariana Islands. The sambar deer is the largest mammal and lives on several of the islands. The Mariana monitor, ranging up to 3 feet long, is also present on the island of Rota. The oceans are home to more than a thousand species of marine life, including for instance the coconut crabs, the mahi-mahi, the barracuda, tridacna, marlin and tuna.

Puerto Rico

The Mona ground iguana is the largest native terrestrial lizard in Puerto Rico and is an endangered species.

Puerto Rico has 349 bird species, 83 mammals, 25 amphibians, 61 reptiles and 677 species of fish. Birds found nowhere else on earth include for instance the Puerto Rican owl, the Puerto Rican woodpecker, the Puerto Rican tody, the green mango, the Puerto Rican emerald, the Puerto Rican lizard cuckoo, the Puerto Rican nightjar and many more. All current endemic 13 land mammals are bats, which includes for instance the greater bulldog bat, the Antillean ghost-faced bat and the Parnell's mustached bat. Extinct native mammals include the plate-toothed giant hutia and the Puerto Rican cave rat. Reptiles unique to Puerto Rico include the Puerto Rican boa, the guanica blindsnake, the Mona Island iguana, the Puerto Rican worm lizard, the Puerto Rican galliwasp and the Nichols’ dwarf gecko. Amphibians native to the island include the Puerto Rican crested toad, the common coqui, the locust coqui, the wrinkled coqui, the forest coqui, the elfin coqui and the bronze coqui. Endemic fish include the Puerto Rican snake eel and the Puerto Rico coralbrotula.

Virgin Islands

The Virgin Islands National Park covers approximately 60% of the Island of St. John and nearly all of Hassel Island. The national park has more than 140 species of birds, 302 species of fish, 7 species of amphibians and 22 species of mammals. The tropical Virgin Islands are home to a huge variety of wildlife, including many unique species endemic to the archipelago. There are three species of sea turtles in the USVI that inhabit the local waters and utilize beaches for nesting: the green sea turtle, the hawksbill sea turtle and the leatherback sea turtle. Several species of sharks, manatees and dolphins roam the seas.

Effects of nuclear explosions

The 14-kiloton test shot Charlie of Operation Buster–Jangle at the Nevada Proving Grounds on 30 October 1951. The red/orange color seen here in the cap of the mushroom cloud is largely due to the fireball's intense heat in combination with the oxygen and nitrogen naturally found in air. Oxygen and nitrogen, though generally unreactive toward each other, form NOx species when heated to excess, specifically nitrogen dioxide, which is largely responsible for the color. There was concern in the 1970s and 1980s, later proven unfounded, regarding fireball NOx and ozone loss.

The effects of a nuclear explosion on its immediate vicinity are typically much more destructive and multifaceted than those caused by conventional explosives. In most cases, the energy released from a nuclear weapon detonated within the lower atmosphere can be approximately divided into four basic categories:

Depending on the design of the weapon and the location in which it is detonated, the energy distributed to any one of these categories may be significantly higher or lower. The physical blast effect is created by the coupling of immense amounts of energy, spanning the electromagnetic spectrum, with the surroundings. The environment of the explosion (e.g. submarine, ground burst, air burst, or exo-atmospheric) determines how much energy is distributed to the blast and how much to radiation. In general, surrounding a bomb with denser media, such as water, absorbs more energy and creates more powerful shockwaves while at the same time limiting the area of its effect. When a nuclear weapon is surrounded only by air, lethal blast and thermal effects proportionally scale much more rapidly than lethal radiation effects as explosive yield increases. This bubble is faster than the speed of sound. The physical damage mechanisms of a nuclear weapon (blast and thermal radiation) are identical to those of conventional explosives, but the energy produced by a nuclear explosion is usually millions of times more powerful per unit mass and temperatures may briefly reach the tens of millions of degrees.

Energy from a nuclear explosion is initially released in several forms of penetrating radiation. When there is surrounding material such as air, rock, or water, this radiation interacts with and rapidly heats the material to an equilibrium temperature (i.e. so that the matter is at the same temperature as the fuel powering the explosion). This causes vaporization of the surrounding material, resulting in its rapid expansion. Kinetic energy created by this expansion contributes to the formation of a shockwave which expands spherically from the center. Intense thermal radiation at the hypocenter forms a nuclear fireball which, if the explosion is low enough in altitude, is often associated with a mushroom cloud. In a high-altitude burst, where the density of the atmosphere is low, more energy is released as ionizing gamma radiation and X-rays than as an atmosphere-displacing shockwave.

Direct effects

Blast damage

Overpressure ranges from 1 to 50 psi (6.9 to 345 kilopascals) of a 1 kiloton of TNT air burst as a function of burst height. The thin black curve indicates the optimum burst height for a given ground range. Military planners prefer to maximize the range at which 10 psi, or more, is extended over when attacking civilian targets, thus a 220 m height of burst would be preferred for a 1 kiloton blast. To find the optimum height of burst for any weapon yield, the cube root of the yield in kilotons is multiplied by the ideal H.O.B for a 1 kt blast, e.g. the optimum height of burst for a 500 kt weapon is ~ 1745 m.
An estimate of the size of the damage caused by the 16 kt and 21 kt atomic bombings of Hiroshima and Nagasaki.

The high temperatures and radiation cause gas to move outward radially in a thin, dense shell called "the hydrodynamic front". The front acts like a piston that pushes against and compresses the surrounding medium to make a spherically expanding shock wave. At first, this shock wave is inside the surface of the developing fireball, which is created in a volume of air heated by the explosion's "soft" X-rays. Within a fraction of a second, the dense shock front obscures the fireball and continues to move past it, now expanding outwards, free from the fireball, causing a reduction of light emanating from a nuclear detonation. Eventually, the shock wave dissipates to the point where the light becomes visible again giving rise to the characteristic double flash due to the shock wave–fireball interaction. It is this unique feature of nuclear explosions that is exploited when verifying that an atmospheric nuclear explosion has occurred and not simply a large conventional explosion, with radiometer instruments known as Bhangmeters capable of determining the nature of explosions.

For air bursts at or near sea-level, 50–60% of the explosion's energy goes into the blast wave, depending on the size and the yield of the bomb. As a general rule, the blast fraction is higher for low yield weapons. Furthermore, it decreases at high altitudes because there is less air mass to absorb radiation energy and convert it into a blast. This effect is most important for altitudes above 30  km, corresponding to less than 1 percent of sea-level air density.

The effects of a moderate rain storm during an Operation Castle nuclear explosion was found to The General Effects of the Atomic Bombs on Hiroshima and Nagasaki. Describes effects, particularly blast effects, and the response of various types of structures to the weapons' effects

Much of the destruction caused by a nuclear explosion is due to blast effects. Most buildings, except reinforced or blast-resistant structures, will suffer moderate damage when subjected to overpressures of only 35.5 kilopascals (kPa) (5.15 pounds-force per square inch or 0.35 atm). Data obtained from the Japanese surveys found that 8 psi (55 kPa) was sufficient to destroy all wooden and brick residential structures. This can reasonably be defined as the pressure capable of producing severe damage.

The blast wind at sea level may exceed one thousand km/h, or ~300 m/s, approaching the speed of sound in air. The range for blast effects increases with the explosive yield of the weapon and also depends on the burst altitude. Contrary to what one might expect from geometry, the blast range is not maximal for surface or low altitude blasts but increases with altitude up to an "optimum burst altitude" and then decreases rapidly for higher altitudes. This is due to the nonlinear behavior of shock waves. When the blast wave from an air burst reaches the ground it is reflected. Below a certain reflection angle, the reflected wave and the direct wave merge and form a reinforced horizontal wave, this is known as the 'Mach stem' (named after Ernst Mach) and is a form of constructive interference. This phenomenon is responsible for the bumps or 'knees' in the above overpressure range graph.

For each goal overpressure, there is a certain optimum burst height at which the blast range is maximized over ground targets. In a typical air burst, where the blast range is maximized to produce the greatest range of severe damage, i.e. the greatest range that ~10 psi (69 kPa) of pressure is extended over, is a GR/ground range of 0.4 km for 1 kiloton (kt) of TNT yield; 1.9 km for 100 kt; and 8.6 km for 10 megatons (Mt) of TNT. The optimum height of burst to maximize this desired severe ground range destruction for a 1 kt bomb is 0.22  km; for 100 kt, 1  km; and for 10 Mt, 4.7  km.

Two distinct, simultaneous phenomena are associated with the blast wave in the air:

  • Static overpressure, i.e., the sharp increase in pressure exerted by the shock wave. The overpressure at any given point is directly proportional to the density of the air in the wave.
  • Dynamic pressures, i.e., drag exerted by the blast winds required to form the blast wave. These winds push, tumble and tear objects.

Most of the material damage caused by a nuclear air burst is caused by a combination of the high static overpressures and the blast winds. The long compression of the blast wave weakens structures, which are then torn apart by the blast winds. The compression, vacuum and drag phases together may last several seconds or longer, and exert forces many times greater than the strongest hurricane.

Acting on the human body, the shock waves cause pressure waves through the tissues. These waves mostly damage junctions between tissues of different densities (bone and muscle) or the interface between tissue and air. Lungs and the abdominal cavity, which contain air, are particularly injured. The damage causes severe hemorrhaging or air embolisms, either of which can be rapidly fatal. The overpressure estimated to damage lungs is about 70 kPa. Some eardrums would probably rupture around 22 kPa (0.2 atm) and half would rupture between 90 and 130 kPa (0.9 to 1.2 atm).

Blast winds: The drag energies of the blast winds are proportional to the cubes of their velocities multiplied by the durations. These winds may reach several hundred kilometers per hour.

Thermal radiation

Nuclear weapons emit large amounts of thermal radiation as visible, infrared, and ultraviolet light, to which the atmosphere is largely transparent. This is known as "Flash". The chief hazards are burns and eye injuries. On clear days, these injuries can occur well beyond blast ranges, depending on weapon yield. Fires may also be started by the initial thermal radiation, but the following high winds due to the blast wave may put out almost all such fires, unless the yield is very high, where the range of thermal effects vastly outranges blast effects, as observed from explosions in the multi-megaton range. This is because the intensity of the blast effects drops off with the third power of distance from the explosion, while the intensity of radiation effects drops off with the second power of distance. This results in the range of thermal effects increasing markedly more than blast range as higher and higher device yields are detonated.

Thermal radiation accounts for between 35–45% of the energy released in the explosion, depending on the yield of the device. In urban areas, the extinguishing of fires ignited by thermal radiation may matter little, as in a surprise attack fires may also be started by blast-effect-induced electrical shorts, gas pilot lights, overturned stoves, and other ignition sources, as was the case in the breakfast-time bombing of Hiroshima. Whether or not these secondary fires will in turn themselves be snuffed out as modern noncombustible brick and concrete buildings collapse in on themselves from the same blast wave is uncertain, not least of which, because of the masking effect of modern city landscapes on thermal and blast transmission are continually examined. When combustible frame buildings were blown down in Hiroshima and Nagasaki, they did not burn as rapidly as they would have done had they remained standing. The noncombustible debris produced by the blast frequently covered and prevented the burning of combustible material. Fire experts suggest that unlike Hiroshima, due to the nature of modern U.S.  city design and construction, a firestorm in modern times is unlikely after a nuclear detonation. This does not exclude fires from being started, but means that these fires will not form into a firestorm, due largely to the differences between modern building materials and those used in World War II-era Hiroshima.

There are two types of eye injuries from the thermal radiation of a weapon:

Flash blindness is caused by the initial brilliant flash of light produced by the nuclear detonation. More light energy is received on the retina than can be tolerated, but less than is required for irreversible injury. The retina is particularly susceptible to visible and short wavelength infrared light since this part of the electromagnetic spectrum is focused by the lens on the retina. The result is bleaching of the visual pigments and temporary blindness for up to 40 minutes.

Burns visible on a woman in Hiroshima during the blast. Darker colors of her kimono at the time of detonation correspond to clearly visible burns on the skin which touched parts of the garment exposed to thermal radiation. Since kimono are not form-fitting attire, some parts not directly touching her skin are visible as breaks in the pattern, and the tighter-fitting areas approaching the waistline have a much more well-defined pattern.

A retinal burn resulting in permanent damage from scarring is also caused by the concentration of direct thermal energy on the retina by the lens. It will occur only when the fireball is actually in the individual's field of vision and would be a relatively uncommon injury. Retinal burns may be sustained at considerable distances from the explosion. The height of burst and apparent size of the fireball, a function of yield and range will determine the degree and extent of retinal scarring. A scar in the central visual field would be more debilitating. Generally, a limited visual field defect, which will be barely noticeable, is all that is likely to occur.

When thermal radiation strikes an object, part will be reflected, part transmitted, and the rest absorbed. The fraction that is absorbed depends on the nature and color of the material. A thin material may transmit a lot. A light-colored object may reflect much of the incident radiation and thus escape damage, like anti-flash white paint. The absorbed thermal radiation raises the temperature of the surface and results in scorching, charring, and burning of wood, paper, fabrics, etc. If the material is a poor thermal conductor, the heat is confined to the surface of the material.

The actual ignition of materials depends on how long the thermal pulse lasts and the thickness and moisture content of the target. Near ground zero where the energy flux exceeds 125 J/cm2, what can burn, will. Farther away, only the most easily ignited materials will flame. Incendiary effects are compounded by secondary fires started by the blast wave effects such as from upset stoves and furnaces.

In Hiroshima on 6 August 1945, a tremendous firestorm developed within 20 minutes after detonation and destroyed many more buildings and homes, built out of predominantly 'flimsy' wooden materials. A firestorm has gale-force winds blowing in towards the center of the fire from all points of the compass. It is not peculiar to nuclear explosions, having been observed frequently in large forest fires and following incendiary raids during World War II. Despite fires destroying a large area of the city of Nagasaki, no true firestorm occurred in the city, even though a higher yielding weapon was used. Many factors explain this seeming contradiction, including a different time of bombing than Hiroshima, terrain, and crucially, a lower fuel loading/fuel density in the city than that of Hiroshima.

Nagasaki probably did not furnish sufficient fuel for the development of a firestorm as compared to the many buildings on the flat terrain at Hiroshima.

As thermal radiation travels, more or less, in a straight line from the fireball (unless scattered) any opaque object will produce a protective shadow that provides protection from the flash burn. Depending on the properties of the underlying surface material, the exposed area outside the protective shadow will be either burnt to a darker color, such as charring wood, or a brighter color, such as asphalt. If such a weather phenomenon as fog or haze is present at the point of the nuclear explosion, it scatters the flash, with radiant energy then reaching burn sensitive substances from all directions. Under these conditions, opaque objects are therefore less effective than they would otherwise be without scattering, as they demonstrate maximum shadowing effect in an environment of perfect visibility and therefore zero scatterings. Similar to a foggy or overcast day, although there are few if any, shadows produced by the sun on such a day, the solar energy that reaches the ground from the sun's infrared rays is nevertheless considerably diminished, due to it being absorbed by the water of the clouds and the energy also being scattered back into space. Analogously, so too is the intensity at a range of burning flash energy attenuated, in units of J/cm2, along with the slant/horizontal range of a nuclear explosion, during fog or haze conditions. So despite any object that casts a shadow being rendered ineffective as a shield from the flash by fog or haze, due to scattering, the fog fills the same protective role, but generally only at the ranges that survival in the open is just a matter of being protected from the explosion's flash energy.

The thermal pulse also is responsible for warming the atmospheric nitrogen close to the bomb and causing the creation of atmospheric NOx smog components. This, as part of the mushroom cloud, is shot into the stratosphere where it is responsible for dissociating ozone there, in exactly the same way as combustion NOx compounds do. The amount created depends on the yield of the explosion and the blast's environment. Studies done on the total effect of nuclear blasts on the ozone layer have been at least tentatively exonerating after initial discouraging findings.

Indirect effects

Electromagnetic pulse

Gamma rays from a nuclear explosion produce high energy electrons through Compton scattering. For high altitude nuclear explosions, these electrons are captured in the Earth's magnetic field at altitudes between twenty and forty kilometers where they interact with the Earth's magnetic field to produce a coherent nuclear electromagnetic pulse (NEMP) which lasts about one millisecond. Secondary effects may last for more than a second.

The pulse is powerful enough to cause moderately long metal objects (such as cables) to act as antennas and generate high voltages due to interactions with the electromagnetic pulse. These voltages can destroy unshielded electronics. There are no known biological effects of EMP. The ionized air also disrupts radio traffic that would normally bounce off the ionosphere.

Electronics can be shielded by wrapping them completely in conductive material such as metal foil; the effectiveness of the shielding may be less than perfect. Proper shielding is a complex subject due to the large number of variables involved. Semiconductors, especially integrated circuits, are extremely susceptible to the effects of EMP due to the close proximity of the PN junctions, but this is not the case with thermionic tubes (or valves) which are relatively immune to EMP. A Faraday cage does not offer protection from the effects of EMP unless the mesh is designed to have holes no bigger than the smallest wavelength emitted from a nuclear explosion.

Large nuclear weapons detonated at high altitudes also cause geomagnetically induced current in very long electrical conductors. The mechanism by which these geomagnetically induced currents are generated is entirely different from the gamma-ray induced pulse produced by Compton electrons.

Radar blackout

The heat of the explosion causes air in the vicinity to become ionized, creating the fireball. The free electrons in the fireball affect radio waves, especially at lower frequencies. This causes a large area of the sky to become opaque to radar, especially those operating in the VHF and UHF frequencies, which is common for long-range early warning radars. The effect is less for higher frequencies in the microwave region, as well as lasting a shorter time – the effect falls off both in strength and the affected frequencies as the fireball cools and the electrons begin to re-form onto free nuclei.

A second blackout effect is caused by the emission of beta particles from the fission products. These can travel long distances, following the Earth's magnetic field lines. When they reach the upper atmosphere they cause ionization similar to the fireball, but over a wider area. Calculations demonstrate that one megaton of fission, typical of a two-megaton H-bomb, will create enough beta radiation to blackout an area 400 kilometres (250 mi) across for five minutes. Careful selection of the burst altitudes and locations can produce an extremely effective radar-blanking effect.

The physical effects giving rise to blackouts are those that also cause EMP, which itself can cause power blackouts. The two effects are otherwise unrelated, and the similar naming can be confusing.

Ionizing radiation

About 5% of the energy released in a nuclear air burst is in the form of ionizing radiation: neutrons, gamma rays, alpha particles and electrons moving at speeds up to the speed of light. Gamma rays are high-energy electromagnetic radiation; the others are particles that move slower than light. The neutrons result almost exclusively from the fission and fusion reactions, while the initial gamma radiation includes that arising from these reactions as well as that resulting from the decay of short-lived fission products.

The intensity of initial nuclear radiation decreases rapidly with distance from the point of burst because the radiation spreads over a larger area as it travels away from the explosion (the inverse-square law). It is also reduced by atmospheric absorption and scattering.

The character of the radiation received at a given location also varies with the distance from the explosion. Near the point of the explosion, the neutron intensity is greater than the gamma intensity, but with increasing distance the neutron-gamma ratio decreases. Ultimately, the neutron component of the initial radiation becomes negligible in comparison with the gamma component. The range for significant levels of initial radiation does not increase markedly with weapon yield and, as a result, the initial radiation becomes less of a hazard with increasing yield. With larger weapons, above 50 kt (200 TJ), blast and thermal effects are so much greater in importance that prompt radiation effects can be ignored.

The neutron radiation serves to transmute the surrounding matter, often rendering it radioactive. When added to the dust of radioactive material released by the bomb itself, a large amount of radioactive material is released into the environment. This form of radioactive contamination is known as nuclear fallout and poses the primary risk of exposure to ionizing radiation for a large nuclear weapon.

Details of nuclear weapon design also affect neutron emission: the gun-type assembly Hiroshima bomb leaked far more neutrons than the implosion-type 21 kt Nagasaki bomb because the light hydrogen nuclei (protons) predominating in the exploded TNT molecules (surrounding the core of the Nagasaki bomb) slowed down neutrons very efficiently while the heavier iron atoms in the steel nose forging of the Hiroshima bomb scattered neutrons without absorbing much neutron energy.

It was found in early experimentation that normally most of the neutrons released in the cascading chain reaction of the fission bomb are absorbed by the bomb case. Building a bomb case of materials which transmitted rather than absorbed the neutrons could make the bomb more intensely lethal to humans from prompt neutron radiation. This is one of the features used in the development of the neutron bomb.

Earthquake

The seismic pressure waves created from an explosion may release stress within nearby plates or otherwise cause an earthquake event, an underground explosion concentrates this pressure wave and a localized earthquake event is more probable, these waves, the first and fastest wave, equivalent to a normal earthquakes P wave can inform the location of the test, the S wave and the Rayleigh wave follow, these can all be measured in most circumstances by seismic station across the globe and comparisons with actual earthquakes can be used to help determine estimated yield via differential analysis, by the modelling of the high-frequency (>4 Hz) teleseismic P wave amplitudes. However, theory does not suggest that a nuclear explosion of current yields could trigger fault rupture and cause a major quake at distances beyond a few tens of kilometers from the shot point.

Summary of the effects

The following table summarizes the most important effects of single nuclear explosions under ideal, clear skies, weather conditions. Tables like these are calculated from nuclear weapons effects scaling laws. Advanced computer modelling of real-world conditions and how they impact on the damage to modern urban areas has found that most scaling laws are too simplistic and tend to overestimate nuclear explosion effects. As it is only simplistic and unclassified scaling laws that are commonly encountered, that do not take important things like varying land topography into account to ease calculation time and equation length. The scaling laws that were used to produce the table below, assume among other things, a perfectly level target area, no attenuating effects from urban terrain masking, e.g. skyscraper shadowing, and no enhancement effects from reflections and tunneling by city streets. As a point of comparison in the chart below, the most likely nuclear weapons to be used against countervalue city targets in a global nuclear war are in the sub-megaton range. Weapons of yields from 100 to 475 kilotons have become the most numerous in the US and Russian nuclear arsenals; for example, the warheads equipping the Russian Bulava submarine-launched ballistic missile (SLBM) have a yield of 150 kilotons. US examples are the W76 and W88 warheads, with the lower yield W76 being over twice as numerous as the W88 in the US nuclear arsenal.


Effects Explosive yield / height of burst
1 kt / 200 m 20 kt / 540 m 1 Mt / 2.0 km 20 Mt / 5.4 km
Blast—effective ground range GR / km
Urban areas completely levelled (20 psi or 140 kPa) 0.2 0.6 2.4 6.4
Destruction of most civilian buildings (5 psi or 34 kPa) 0.6 1.7 6.2 17
Moderate damage to civilian buildings (1 psi or 6.9 kPa) 1.7 4.7 17 47
Railway cars thrown from tracks and crushed
(62 kPa; values for other than 20 kt are extrapolated using the cube-root scaling)
≈0.4 1.0 ≈4 ≈10
Thermal radiation—effective ground range GR / km
Fourth degree burns, Conflagration 0.5 2.0 10 30
Third degree burns 0.6 2.5 12 38
Second degree burns 0.8 3.2 15 44
First degree burns 1.1 4.2 19 53
Effects of instant nuclear radiation—effective slant range1 SR / km
Lethal2 total dose (neutrons and gamma rays) 0.8 1.4 2.3 4.7
Total dose for acute radiation syndrome2 1.2 1.8 2.9 5.4

1 For the direct radiation effects the slant range instead of the ground range is shown here because some effects are not given even at ground zero for some burst heights. If the effect occurs at ground zero the ground range can be derived from slant range and burst altitude (Pythagorean theorem).

2 "Acute radiation syndrome" corresponds here to a total dose of one gray, "lethal" to ten grays. This is only a rough estimate since biological conditions are neglected here.

Further complicating matters, under global nuclear war scenarios, with conditions similar to that during the Cold War, major strategically important cities, like Moscow, and Washington are likely to be hit not once, but numerous times from sub megaton multiple independently targetable re-entry vehicles, in a cluster bomb or "cookie-cutter" configuration. It has been reported that during the height of the Cold War in the 1970s Moscow was targeted by up to 60 warheads. The reasons that the cluster bomb concept is preferable in the targeting of cities is twofold, the first is down to the fact that large singular warheads are much easier to neutralize as both tracking and successful interception by anti-ballistic missile systems than it is when several smaller incoming warheads are approaching. This strength in numbers advantage to lower yield warheads is further compounded by such warheads tending to move at higher incoming speeds, due to their smaller, more slender physics package size, assuming both nuclear weapon designs are the same (a design exception being the advanced W88). The second reason for this cluster bomb, or ‘layering’ (using repeated hits by accurate low yield weapons), is that this tactic along with limiting the risk of failure, also reduces individual bomb yields, and therefore reduces the possibility of any serious collateral damage to non-targeted nearby civilian areas, including that of neighboring countries. This concept was pioneered by Philip J. Dolan and others.

Other phenomena

Mushroom cloud height depending on yield for ground bursts.
0 = Approx. altitude at which a commercial aircraft operates
1 = Fat Man
2 = Castle Bravo

Gamma rays from the nuclear processes preceding the true explosion may be partially responsible for the following fireball, as they may superheat nearby air and/or other material. The vast majority of the energy that goes on to form the fireball is in the soft X-ray region of the electromagnetic spectrum, with these X-rays being produced by the inelastic collisions of the high-speed fission and fusion products. It is these reaction products and not the gamma rays which contain most of the energy of the nuclear reactions in the form of kinetic energy. This kinetic energy of the fission and fusion fragments is converted into internal and then radiation energy by approximately following the process of blackbody radiation emitting in the soft X-ray region.

As a result of numerous inelastic collisions, part of the kinetic energy of the fission fragments is converted into internal and radiation energy. Some of the electrons are removed entirely from the atoms, thus causing ionization, others are raised to higher energy (or excited) states while still remaining attached to the nuclei. Within an extremely short time, perhaps a hundredth of a microsecond or so, the weapon residues consist essentially of completely and partially stripped (ionized) atoms, many of the latter being in excited states, together with the corresponding free electrons. The system then immediately emits electromagnetic (thermal) radiation, the nature of which is determined by the temperature. Since this is of the order of 107 degrees, most of the energy emitted within a microsecond or so is in the soft X-ray region. Because temperature depends on the average internal energy/heat of the particles in a certain volume, internal energy or heat is due to kinetic energy.

For an explosion in the atmosphere, the fireball quickly expands to maximum size, and then begins to cool as it rises like a balloon through buoyancy in the surrounding air. As it does so it takes on the flow pattern of a vortex ring with incandescent material in the vortex core as seen in certain photographs. This effect is known as a mushroom cloud.

Sand will fuse into glass if it is close enough to the nuclear fireball to be drawn into it, and is thus heated to the necessary temperatures to do so; this is known as trinitite.

At the explosion of nuclear bombs lightning discharges sometimes occur.

Smoke trails are often seen in photographs of nuclear explosions. These are not from the explosion; they are left by sounding rockets launched just prior to detonation. These trails allow observation of the blast's normally invisible shock wave in the moments following the explosion.

The heat and airborne debris created by a nuclear explosion can cause rain; the debris is thought to do this by acting as cloud condensation nuclei. During the city firestorm which followed the Hiroshima explosion, drops of water were recorded to have been about the size of marbles. This was termed black rain, and has served as the source of a book and film by the same name. Black rain is not unusual following large fires and is commonly produced by pyrocumulus clouds during large forest fires. The rain directly over Hiroshima on that day is said to have begun around 9 a.m. with it covering a wide area from the hypocenter to the north-west, raining heavily for one hour or more in some areas. The rain directly over the city may have carried neutron activated building material combustion products, but it did not carry any appreciable nuclear weapon debris or fallout, although this is generally to the contrary to what other less technical sources state. The "oily" black soot particles, are a characteristic of incomplete combustion in the city firestorm.

The element einsteinium was discovered when analyzing nuclear fallout.

A side-effect of the Pascal-B nuclear test during Operation Plumbbob may have resulted in the first man-made object launched into space. The so-called "thunder well" effect from the underground explosion may have launched a metal cover plate into space at six times Earth's escape velocity, although the evidence remains subject to debate.

In 1942, there was speculation among the scientists developing the first nuclear weapons in the Manhattan Project that a sufficiently large nuclear explosion might ignite the Earth's atmosphere: heat from the explosion might fuse pairs of atmospheric nitrogen atoms, forming carbon and oxygen while releasing further energy which would sustain the reaction until all the world's atmospheric nitrogen was consumed. Hans Bethe was assigned to study this hypothesis from the project's earliest days, and eventually concluded that such a reaction could not sustain itself on a large scale due to cooling of the nuclear fireball through an inverse Compton effect. Richard Hamming was asked to make a similar calculation just before the first nuclear test, and reached the same conclusion. Nevertheless, the notion has persisted as a rumor for many years, and was the source of apocalyptic gallows humor at the Trinity test where Enrico Fermi took side bets on atmospheric ignition.

Survivability

Survivability is highly dependent on factors such as if one is indoors or out, the size of the explosion, the proximity to the explosion, and to a lesser degree the direction of the wind carrying fallout. Death is highly likely and radiation poisoning is almost certain if one is caught in the open with no terrain or building masking effects within a radius of 0–3 km from a 1 megaton airburst, and the 50% chance of death from the blast extends out to ~8 km from the same 1 megaton atmospheric explosion.

To highlight the variability in the real world, and the effect that being indoors can make, despite the lethal radiation and blast zone extending well past her position at Hiroshima, Akiko Takakura survived the effects of a 16 kt atomic bomb at a distance of 300 meters from the hypocenter, with only minor injuries, due mainly to her position in the lobby of the Bank of Japan, a reinforced concrete building, at the time. In contrast, the unknown person sitting outside, fully exposed, on the steps of the Sumitomo Bank, next door to the Bank of Japan, received lethal third-degree burns and was then likely killed by the blast, in that order, within two seconds.

With medical attention, radiation exposure is survivable to 200 rems of acute dose exposure. If a group of people is exposed to a 50 to 59 rems acute (within 24 hours) radiation dose, none will get radiation sickness. If the group is exposed to 60 to 180 rems, 50% will become sick with radiation poisoning. If medically treated, all of the 60–180 rems group will survive. If the group is exposed to 200 to 450 rems, most if not all of the group will become sick. 50% of the 200–450 rems group will die within two to four weeks, even with medical attention. If the group is exposed to 460 to 600 rems, 100% of the group will get radiation poisoning. 50% of the 460–600 rems group will die within one to three weeks. If the group is exposed to 600 to 1000 rems, 50% will die in one to three weeks. If the group is exposed to 1,000 to 5,000 rems, 100% of the group will die within 2 weeks. At 5,000 rems, 100% of the group will die within 2 days.

Nuclear explosion impact on humans indoors

Researchers from the University of Nicosia simulated (Ioannis W. Kokkinakis and Dimitris Drikakis , "Nuclear explosion impact on humans indoors", Physics of Fluids 35, 016114 (2023), using high-order Computational Fluid Dynamics (CFD), an atomic bomb explosion from a typical intercontinental ballistic missile and the resulting blast wave to see how it would affect people sheltering indoors.

They found that the blast wave was enough in the moderate damage zone to topple some buildings and injure people caught outdoors. However, sturdier buildings, such as concrete structures, can remain standing. The team used advanced computer modelling to study how a nuclear blast wave speeds through a standing structure. Their simulated structure featured rooms, windows, doorways, and corridors and allowed them to calculate the speed of the air following the blast wave and determine the best and worst places to be. The study showed that high airspeeds remain a considerable hazard and can still result in severe injuries or even fatalities.

Furthermore, simply being in a sturdy building is not enough to avoid risk. The tight spaces can increase airspeed, and the involvement of the blast wave causes air to reflect off walls and bend around corners. In the worst cases, this can produce a force equivalent to multiple times a human’s body weight. The most dangerous critical indoor locations to avoid are windows, corridors, and doors. The above study received considerable interest from the international press.

Entropy (information theory)

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