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Tsunamis - Causes,Survive During and Preventive Measures

Tsunamis - Causes,Survive During and Preventive Measures
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A tsunami could even be a series of ocean waves that sends surges of water, sometimes reaching heights of over 100 feet (30.5 meters), onto land. These walls of water can cause widespread destruction once they crash ashore.



Tsunami waves don't resemble normal undersea currents or sea waves because their wavelength is far longer. Instead of appearing as a breaking wave, a tsunami may instead initially resemble a rapid flood tide. For this reason, it's often mentioned as a tidal wave, although this usage isn't favored by the scientific community because it'd give the misunderstanding of a causal relationship between tides and tsunamis. Tsunamis generally contain a series of waves, with periods, starting from minutes to hours, arriving during a so-called "wave train".Wave heights of tens of meters are often generated by large events. Although the impact of tsunamis is restricted to coastal areas, their destructive power is often enormous, and that they can affect entire ocean basins. The 2004 Indian Ocean tsunami was among the deadliest natural disasters in human history, with a minimum of 230,000 people killed or missing in 14 countries bordering the Indian Ocean.

The Ancient Greek historian Thucydides suggested in his 5th century BC History of the Peloponnesian War that tsunamis were associated with submarine earthquakes, but the understanding of tsunamis remained slim until the 20th century and much remains unknown. Major areas of current research include determining why some large earthquakes don't generate tsunamis while other smaller ones do; accurately forecasting the passage of tsunamis across the oceans, and forecasting how tsunami waves interact with shorelines.

What are Tsunamis?

Tsunamis are ocean waves triggered by large earthquakes that occur near or under the ocean, volcanic eruptions, submarine landslides, and by onshore landslides during which large volumes of debris fall into the water. Scientists don't use the term "tidal wave" because these waves aren't caused by tides. Tsunami waves are unlike typical ocean waves generated by wind and storms, and most tsunamis don't "break" just like the curling, wind-generated waves of fashionable surfers. Tsunamis typically contain multiple waves that rush ashore sort of a fast-rising tide with powerful currents. Tsunami waves can travel much farther inland than normal waves. When tsunamis approach the shore, they behave sort of a very fast-moving tide that extends far inland. If a tsunami-causing disturbance occurs on the brink of the coastline, a resulting tsunami can reach coastal communities within minutes. A rule of thumb is that if you see the tsunami, it's too late to outrun it. Even small tsunamis (for example, 6 feet in height) are related to extremely strong currents, capable of knocking someone off their feet. As a result of complex interactions with the coast, tsunami waves can persist for several hours.

As with many natural phenomena, tsunamis can home in size from micro-tsunamis detectable only by sensitive instruments on the ocean bottom to mega-tsunamis which may affect the coastlines of entire oceans, like the Indian Ocean tsunami of 2004. If you hear a tsunami warning or if you are feeling strong shaking at the coast or see very unusual wave activity (e.g., the ocean withdrawing faraway from shore), it is important to maneuver to status and stand back from the coast until wave activity has subsided (usually several hours to days).

What Causes a Tsunami?

These awe-inspiring waves are typically caused by large, undersea earthquakes at tectonic plate boundaries. When the ocean floor at a plate boundary rises or falls suddenly, it displaces the water above it and launches the rolling waves which can become a tsunami.

Most tsunamis–about 80 percent–happen within the Pacific Ocean’s “Ring of fireside,” a geologically active area where tectonic shifts make volcanoes and earthquakes common.

Tsunamis also can be caused by underwater landslides or volcanic eruptions. They may even be launched, as they often were in Earth’s ancient past, by the impact of an outsized meteorite plunging into an ocean.

Tsunamis race across the ocean at up to 500 miles (805 kilometers) an hour—about as fast as a jet airplane. At that pace, they will cross the whole expanse of the Pacific in but each day. And their long wavelengths mean they lose little or no energy along the way.

What Happens When It Hits Land

A tsunami’s trough, the low point beneath the wave’s crest, often reaches shore first. When it does, it produces a vacuum effect that sucks coastal water seaward and exposes harbor and sea floors. This retreating of seawater is a crucial wake-up call of a tsunami because the wave’s crest and its enormous volume of water typically hit shore five minutes approximately later. Recognizing this phenomenon can save lives.

A tsunami is usually composed of a series of waves, called a series, so its destructive force could even be compounded as successive waves reach the shore. People experiencing a tsunami should remember that the danger might not have passed with the primary wave and will await the official word that it's safe to return to vulnerable locations.

Some tsunamis don't appear on shore as massive breaking waves but instead resemble a quickly surging tide that inundates coastal areas.

The best defense against any tsunami is an early warning that permits people to hunt higher ground. The Pacific Tsunami Warning System, a coalition of 26 nations headquartered in Hawaii, maintains a web of seismic equipment and water level gauges to spot tsunamis stumped. Similar systems are proposed to guard coastal areas worldwide

IF YOU ARE UNDER A TSUNAMI WARNING:

  1. First, protect yourself from an Earthquake. Drop, Cover, then Hold On.
  2. Get to status as far inland as possible.
  3. Be aware of signs of a tsunami, like a sudden rise or draining of ocean waters.
  4. Listen to emergency information and alerts.
  5. Evacuate: DO NOT wait! Leave as soon as you see any natural signs of a tsunami or receive a politician tsunami warning.
  6. If you're during a boat, leave to sea.

HOW TO STAY SAFE WHEN A TSUNAMI THREATENS

Prepare NOW

  1. If you reside near or regularly visit a coastal area, study the danger of tsunami within the area. Some at-risk communities have maps with evacuation zones and routes. If you're a visitor, ask about community plans.
  2. Learn the signs of a possible tsunami, like an earthquake, a loud roar from the ocean, or unusual ocean behavior, like a sudden rise or wall of water or sudden draining of water showing the ocean bottom.
  3. Know and practice community evacuation plans and map your routes from home, work, and play. Pick shelters 100 feet or more above water level, or a minimum of one mile inland.
  4. Create a family emergency communication plan that has an out-of-state contact. Plan where to meet if you get separated.
  5. Sign up for your community’s warning system. The Emergency Alert System (EAS) and National Oceanic and Atmospheric Administration (NOAA) Weather Radio also provide emergency alerts.
  6. Consider earthquake insurance and a flood policy through the National Flood Insurance Program (NFIP). Standard homeowner’s insurance doesn't cover flood or earthquake damage.

Survive During

  1. If you're during a tsunami area and there's an earthquake, then first protect yourself from the earthquake. Drop, Cover, and Hold On. Drop to your hands and knees. Cover your head and neck with your arms. Hold on to any sturdy furniture until the shaking stops. Crawl as long as you'll reach better cover, but don't undergo a neighborhood with more debris.
  2. When the shaking stops, if there are natural signs or official warnings of a tsunami, then move immediately to a secure place as high and as far inland as possible. Listen to the authorities, but don't await tsunami warnings and evacuation orders.
  3. If you're outside of the tsunami hazard zone and receive a warning, then stay where you're unless officials tell you otherwise.
  4. Leave immediately if you're told to try to so. Evacuation routes are often marked by a wave with an arrow within the direction of the upper ground.
  5. If you're within the water, then grab onto something that floats, like a raft, trunk, or door.
  6. If you're during a boat, then face the direction of the waves and head bent sea. If you're during a harbor, then go inland.

Be Safe AFTER

  1. Listen to local alerts and authorities for information on areas to avoid and shelter locations.
  2. Avoid wading in floodwater, which may contain dangerous debris. Water may be deeper than it appears.
  3. Be aware of the risk of electrocution. Underground or downed power lines can electrically charge water. Do not touch electrical equipment if it's wet or if you're standing in water.
  4. Stay away from damaged buildings, roads, and bridges.
  5. Document property damage with photographs. Conduct a listing and get in touch with your insurance firm for assistance.
  6. Save phone calls for emergencies. Phone systems are often down or busy after a disaster. Use text messages or social media to speak with family and friends.

10 worst tsunamis in history:

1. Sumatra, Indonesia – 26 December 2004

2. North Pacific Coast, Japan – 11 March 2011

3. Lisbon, Portugal – 1 November 1755

4. Krakatau, Indonesia – 27 August 1883

5. Enshunada Sea, Japan – 20 September 1498

6. Nankaido, Japan – 28 October 1707

7. Sanriku, Japan – 15 June 1896

8. Northern Chile – 13 August 1868

9. Ryuku Islands, Japan – 24 April 1771

10. Ise Bay, Japan – 18 January 1586
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