50 Interesting Facts About Tsunami You Probably Don't Know

A tsunami is usually caused by an earthquake but can also be caused by a volcanic eruption, landslide, rapid changes in atmospheric pressure, or a meteorite. A tsunami is not just one big wave, but a series of waves called a “wave train.” The time period between waves is called the “wave period” and can be between a few minutes and two hours. The first wave is usually not the strongest, and later waves, such as the fifth or sixth, may be significantly larger. Greek historian Thucydides (460–395 B.C.) in his History of the Peloponnesian Warwas the first to associate tsunamis with underwater earthquakes. In the deepest part of the ocean, tsunami waves are often only 1 to 3 feet tall. Sailors may not even realize that tsunami waves are passing beneath them. The Indonesia 9.0 earthquake in 2004 released more energy than all the earthquakes on the planet in the last 25 years combined. A segment of seafloor the size of the state of California moved upward and seaward by more than 30 feet, displacing huge amounts of water. Approximately 99% of all tsunami-related fatalities have occurred within 160 miles (250 km) of the tsunami’s origin or within 30 minutes of when the tsunami was generated. Consequently, anyone in a coastal area who feels a strong earthquake should take that as a natural warning that a tsunami may be imminent and leave low-lying coastal areas. Tsunamis are typically caused by thrust-type subduction-zone earthquakes Earthquake-induced tsunamis are created along subduction zones, or when a lighter tectonic plate is forced above a heavier plate. The sudden rise or fall of the ocean floor displaces the entire overlying water column. This rise and fall of the ocean level above the earthquake generates a tsunami. A tsunami will generally not form if the tectonic plates instead split apart or slide past each other. The states in the U.S. at greatest risk for tsunamis are Hawaii, Alaska, Washington, Oregon, and California. While no one has witnessed a tsunami caused by a meteorite, many scientists think that a meteorite may have created a tsunami that wiped out life on Earth more than 3.5 billion years ago. Scientists believe that an asteroid struck the Indian Ocean about 4,800 years ago. The tsunami that resulted is theorized to have been approximately 600 feet (180 m) high. One of the largest earthquakes in history occurred over 100 miles off the coast of Chile on May 22, 1960. Just 15 minutes after the 9.5 quake, 80-foot waves struck the coast. Fifteen hours later, tsunami waves struck Hawaii and, finally, 22 hours after the earthquake, the tsunami struck Japan—10,000 miles from where the earthquake took place. While waves generated by wind may travel anywhere from around 2 to 60 miles (3.2 to 97 km) per hour, tsunami waves can travel at speeds of 600 miles (970 km) per hour, the speed of a jet plane. The farthest distance inland (horizontally) reached by tsunami waters is referred to as the area of inundation. The highest point (vertically) that this water reaches is called the run-up. The Indian Ocean tsunami of 2004 killed more than 216,000 people, possibly as many as 283,000. Victims included not only local people but also approximately 9,000 tourists from Australia, Sweden, the United Kingdom, and the U.S. who were spending their Christmas vacations at beach resorts in Southeast Asia.g Palm trees with their long, bare trunks are well adapted to life on the shore and often survive tsunamis intact. A “mega-tsunami” is a tsunami with extremely high waves and is usually caused by a landslide. A mega-tsunami occurred at Lituya Bay, Alaska, in 1958, creating the tallest tsunami ever recorded at 1,700 feet (534 m) high. Miraculously, only two people died. Scientists hypothesize that the next mega-tsunami may occur in the Canary Islands. The mega tsunami could cross the Atlantic Ocean and devastate U.S. coastal cities like New York, Boston, and Miami with waves reaching more than 100 feet high. When an enormous earthquake hit Lisbon in 1755, the city’s terrified citizens rushed to the shore for safety. They were amazed to see seawater rushing away from the shore. Minutes later, a tsunami arrived. Ninety thousand residents were killed. Experts suggest evacuating to a place at least 50 feet above sea level during a tsunami Reports show that those who use their cars to escape tsunamis often get stuck in traffic jams or encounter other obstacles and are, therefore, more likely to be swept away. Reports show that the best way to escape is on foot, climbing up any steep slopes nearby as quickly as possible. People often die after the first tsunami wave because they return to their homes too soon or go to the beach to help stranded people or animals, only to be engulfed by another tsunami wave. If caught by a tsunami wave, it is better not to swim, but rather to grab a floating object and allow the current to carry you. Seiches (SAYSH uhz) are like tsunamis, but instead of occurring in seas and oceans, they occur in enclosed bodies of water, such as lakes or inland seas. They are usually smaller and less harmful than tsunamis. Wind is the most common cause of seiches. Up to half an hour before a tsunami strikes, the ocean can (but not always) suddenly appear to drain away. The withdraw of the water is called the “drawback” and is the trough of the tsunami reaching the shore. Tsunami means “harbor wave” in Japanese (tsu = harbor + nami = wave), reflecting Japan’s tsunami-prone history. When a tsunami crashes into coastal areas, it is typically moving at about 22 mph (35 km/hr). The speed as it moves inland changes dramatically depending on the slope of the beach and the shore environment. The force of the tsunami backwash can be just as strong and in some cases stronger than the initial impact.g The costliest tsunami ever to strike the western United States and Canada occurred on March 28, 1964, when an 8.4 earthquake struck Alaska. Waves reached as high as 21 feet and killed more than 120 people. Damages reached $106 million. The state at greatest risk for a tsunami is Hawaii. Hawaii experiences about one tsunami a year and a damaging tsunami every seven years. California, Oregon, and Washington have a damaging tsunami about every 18 years. Many who were killed in the 2004 Indian Ocean tsunami were women and children. Many women were reportedly waiting along the beaches for their husbands to return from fishing, and children were simply too weak to fight the strong currents. About one third of the dead were children and, in many locations, four times as many women as men were killed. The 2004 Indian Ocean tsunami uncovered the remains of Mahabalipuram The Indian Ocean tsunami in 2004 uncovered the lost city Mahabalipuram, the capital of a powerful kingdom that traded with China, Roma, Greece, Arabia, and Egypt some 1,500 years ago. It is said that the capital was kodalkol or “swelled by the sea” at the height of its glory. Tsunamis can poison fresh-water surface and groundwater systems as well as soil by leaving large amounts of salt behind. Consequently, thousands of people can die of starvation and disease long after the tsunami is gone. While tsunamis have been recorded in every ocean on Earth, about 80% of all tsunamis occur in the Pacific “Ring of Fire.” Only two large tsunamis are known to have struck Europe: one struck Crete and surrounding Mediterranean coasts in 1530 B.C., and one struck Lisbon, Portugal in 1755. A tsunami hits land with thousands of times the power of a regular wave. Regular waves are caused by wind pushing water at the surface of the ocean or other body of water. Tsunami waves are created by an event that affects the entire water column, from the ocean floor to its surface. Tsunami waves do not look like normal waves because they do not break and curl as normal waves do. They come as rapid floods of water or in the form of a bore, which is a large, steep wave that looks like a wall of water. Some animals may have the ability to detect impending natural disasters Hours before the Indian Ocean tsunami, people reported seeing elephants and flamingos heading for higher ground. Dogs and zoo animals refused to leave their shelters. After the tsunami, very few dead animals were found.b As a tsunami wave approaches shallow water near land, it slows down to about 20-30 miles (30-50 km) per hour. As it slows, all the water that had been traveling so fast pulls up, causing the wave to grow higher and higher. By the time it hits shore, a tsunami wave can reach 100 feet high, or as tall as a 10-story building. Tsunamis were sometimes called tidal waves, but this is misleading because tsunamis have nothing to do with tides. Some geologists suggest the ancient tsunamis are the source of ancient legends, such as the great biblical flood, the parting of the Red Sea during the exodus of the Israelites from Egypt, and the destruction of the Minoan civilization on the island of Crete. In the Pacific region, nearly 500,000 people have died from tsunamis over the last 2,000 years. The 2004 Indian Ocean tsunami alone exerted a death toll now estimated at more than 280,000. The plural form of the term can be either “tsunami” or “tsunamis.” Tsunamis are known from ancient times, dating back almost 4,000 years in China. Of the three major oceans, only the Pacific Ocean has an integrated multinational tsunami warning system. There was no tsunami warning system in the Indian Ocean in 2004, though experts had previously recommended one be installed. Because of its long history of devastating tsunamis, Japan had the most advanced tsunami warning system in the world prior to the 2011 tsunami, which consisted of more than 1,500 seismometers and more than 500 water-level gauges. Japan’s tsunami warning system costs $20 million a year to run. As of March 25 2011, there have been over 21,911 dead and missing in the Japan tsunami (over 10,000 confirmed dead; 17,440 missing) and 2,755 injured. The World Bank estimates that rebuilding the tsunami-affected areas of Japan will cost $232 billion and will take at least five years. A 9.0 earthquake 81 miles off the coast of Sendai caused the massive 2011 tsunami The earthquake that caused the 2011 Japan tsunami is the world’s fifth-largest earthquake since 1900. It has been 1,200 years since an earthquake of this magnitude struck the plate boundary of Japan. Over 180,000 people were evacuated after an earthquake and tsunami damaged the main cooling systems and generators at the Fukushima Daiichi nuclear complex in Japan in 2011. After the 2011 Japan tsunami, a tide of bodies washed ashore on the peninsula in Miyagi Prefecture. The 2011 Japan tsunami is estimated to become the world’s most expensive disaster in history. Tsunamis retain their energy, meaning they can travel across entire oceans with limited energy loss. A tsunami that travels thousands of miles across the ocean is called a transoceanic tsunami or teletsunami. A tsunami that only reaches the coast near the point of its origin is a local tsunami.[SOURCE]

42 Amazing Facts About our Planet Earth

Earth can be seen as a living, breathing organism: it regulates temperature, burns energy, continually renews its skin, and experiences changes to its face as it ages with time. Researchers in the the field of astrobiology have found that Earth’s current conditions are temporary and that Earth’s stable climate is an anomaly that will end in the next billion years. Under the oceans, there are the earth’s largest mountain ranges that circle the planet like the stitching on a baseball. More than 80% of the Earth’s surface is volcanic. Holes drilled as deep as 5 miles into the Earth’s reveal that the rock temperature increases about 37 degrees Fahrenheit per 320 feet. Even on the deepest sea floor, rock remains slightly above freezing. A belief of some Native Americans was that the earth is supported by a giant tortoise, which made the earth tremble each time it took a step. Earth and the planet Theia were twin planets sharing an orbit until they collided and Earth absorbed Theia Earth was originally born as a twin to the planet Theia, which was about half as wide as Earth and roughly the size of Mars. The two planets shared an orbit for several million years until they collided. Earth absorbed Theia, and the remaining debris eventually coagulated into Earth’s moon. The mass donated by Theia gave Earth the gravity necessary to sustain a substantial atmosphere. The theory of Pangaea states that all of Earth’s current continents were originally a single supercontinent that existed some 200 million years ago during the Paleozoic and Mesozoic eras. The northern part of the supercontinent, North America and Eurasia, was called Laurasia—and Gondwana, the southern part, was made up of Australia, South America, Africa, Antartica, and India. India later broke away and moved north to join Asia. Pangaea was not the beginning position of the land on Earth, but one of as many as six lost worlds that have come and gone. Pangea was preceded by Pannotia about 550-650 million years ago and by Rhodinia around 1.8 billion years ago. Before them, at intervals of roughly 500 million years, Nuna, Kenorland, and Ur existed and then broke up. Pangea broke up starting along the line that would become the mid-Atlantic ridge when the existing fracture at the southern end of South America/Africa widened and opened the rift like a zipper. As these new continents moved apart, they pushed and folded up the Earth’s crust and created great mountain ranges. The Earth’s plates move just a few inches a year—about as fast as a person’s fingernails grow. This continental pattern predicts that 250 million years from now, a new supercontinent will be born. The beginning of the Industrial Revolution marked the beginning of humanity's affecting Earth’s environment by producing enough carbon dioxide to affect the atmosphere's global balance and chemical composition. If a person extends his or her arm and index finger completely, the beginning of Earth is represented by the end of the nose and the present is the fingertip. Passing a file over the fingernail once would erase all of human history. The metaphor of rock being like Earth’s blood works because Earth’s levels of air and water are kept in balance by rock’s continuous circulation. The amount of carbon dioxide in water and atmosphere and the amount of solar energy the planet receives are two factors that control the destiny of life on Earth and the planet itself. Too much of the greenhouse effect is detrimental to human life—but without some greenhouse effect, Earth’s global temperature would be 0 degrees Fahrenheit (-18 degrees Celsius) rather than 59 degrees F (15 degrees C). The Amazon rainforest is home to one third of Earth’s land species Earth’s Amazon rainforest is home to one third of the planet’s land species, illustrating Earth’s ability to sustain itself within a concentrated area. Strong evidence suggests that the universe began with the Big Bang about 13 billion years ago, and two thirds of its history passed before our own solar system was formed. During this time, stars evolved and died, supplementing the basic hydrogen, helium, and trace of lithium that the universe began with and providing more complex atoms such as carbon, oxygen, silicon, magnesium, and nitrogen. The way Earth was formed allows for its many unique traits that have developed and will develop during its life. Earth, which can be viewed as a metal ball coated with rock, hurtles through space at 66,000 miles (107,000 km) per hour. The word “planet” comes from the Greek word planetai for “wanderer.” Earth began as sticky dust which clumped, like snowflakes, into a planetesimal, or a body that is about a half mile in diameter. Earth is made up of hydrogen gas, stardust, and gravity. The gas and dust floating in space were drawn together by gravity and they formed into a spinning disc. As this disc collided with and absorbed rock bodies, the Earth formed. Astronomers believe the formation of Earth was relatively quick. Orbiting debris smashed into the newly formed Earth, and gravity and radioactive processes heated its interior to nearly 2000 degrees Fahrenheit. A solid inner core formed as iron and nickel were absorbed into the center. This inner core was surrounded by a molten outer core, and then less dense silicates formed the mantle and crust. The name “Earth” comes from Old English and Old High Germanic words (eorthe anderda, respectively) for “ground” or “soil,” and it is the only name for a planet of the solar system that does not come from Greco-Roman mythology. One half to three quarters of Earth’s mass is made up of matter that would have made separate planets if not for Earth’s cannibalism. Earth is called a terrestrial planet because it is made almost entirely of rock and metal. Because Earth formed inside the snow line—meaning it was close enough to the sun that water, carbon, and nitrogen were all in a gaseous state—the elements so essential to supporting life had to be supplied in some other way. They were carried to the Earth by dirty snowballs—asteroids that retained water in hydrated minerals. Later those hydrated minerals were heated and the trapped water was released. The Earth had the energy to release trapped water from the energy supplied by the collisions that had delivered the minerals in the first place. Without the gravitational pull of the moon, Earth would not be habitable The birth of Earth’s moon is singularly important because it stabilizes Earth’s tilt. Without the moon, Earth would still have wild changes in climate and be uninhabitable. The stabilizing tug of the moon tempers Earth, resulting in the minor tip that causes summer and winter seasons. To put the size of each of these bodies in perspective, think of the Earth’s moon as a tennis ball and Earth as the size as a basketball. The sun’s diameter is about 109 times greater than Earth’s, whereas Earth is just about four times larger in diameter than the moon. The great impacts that gave Earth its mass had the potential to blow away the fragile atmosphere that was forming and turn the oceans into steam. Despite these threats, Earth went through a normal birthing process for a habitable planet. Had Earth formed in a more gentle way, the result would have been a cold and dead planet, because the energy of the falling bodies would have been small enough that the bodies would bounce back into space. Because Earth was hit by huge, hurtling chunks of rock and ice, they cratered so deeply into the interior of the planet that their heat, water, and future atmospheric gases were anchored there and retained by gravity. Earth’s ocean of magma was created by bodies crashing into the planet a bit later in its development.j Within 10 million years of Earth’s birth, its average interior temperature was hot enough to melt virtually the entire planet, which caused the core to sink to the middle of the planet and left the mantle a bubbling, viscous layer. The great heat of Earth’s core and magma ensured that Earth would have an atmosphere and oceans. It also created plate tectonics, which meant its oceans would be partitioned by dry land. Heat and pressure began creating rock lighter than the ocean floor that would eventually emerge as floating continents. Earth’s unique mix of land and ocean makes the Earth relatively stable by cycling carbon dioxide. Carbon dioxide cycling moderates temperature swings that would otherwise occur. Earth’s greatest source of heat, besides the sun, is its interior, which conducts a hundred billion billion calories of energy to the surface each year—or 1.5 microcalories per .155 square inch of the earth’s surface each second. So much energy radiates from inside the Earth that it could satisfy all human energy needs three times over. As the earth cooled after it had finished growing, the lithosphere—the hard, outermost layer between the mantle and the Earth’s crust—cracked like an eggshell and split into seven large and twelve small floating islands with jagged edges. These islands are the tectonic plates that move continuously over the viscous mantle, rubbing, pushing, and trying to mount one over the other. Although Earth’s plates are made of solid rock, they buckle and twist like slabs of warm clay when they collide. The Earth’s plates were divided into land masses and oceans because of the difference in the thickness and composition of the planet’s two types of crust. Continental crust, mostly composed of relatively lightweight granite, is about 18 to 30 miles thick. The much denser basalt that makes up the oceanic crust is only 5 or 6 miles thick. Because they are more buoyant, the continents “float” higher on the mantle than the ocean floors do. Earth’s earthquakes, volcanoes, and mountains are evidence of a living and changing planet Earthquakes, volcanoes, and mountains are all formed by Earth’s moving plates. Other planets and moons in our solar system have volcanoes, but they do not have mountain ranges like Earth’s because only Earth has plate tectonics. Plate tectonics contributed to making Earth habitable by creating volcanoes as well. The water vapor and other gases emitted by volcanoes during Earth’s early years helped to create Earth’s oceans and atmosphere. When a tectonic plate lingers over a hot spot for a while and then moves on, a volcanic island is formed. A hot spot is a column of basalt that punctures the earth’s crust and allows magma to escape from the interior. The movement of a tectonic plate over a hot spot forms a chain of volcanic islands, called a seamount. One well known example of a seamount is a chain of ancient volcanoes that were once over the hot spot that is now under Hawaii. The Himalayas are examples of the movement of tectonic plates against each other.[SOURCE]