AT U R EÊSF U N R Y What Is a Tsunami What Is a Tsunami Atsunami is a huge wave that can flood the land with devastating effects The word tsunami is Japanese for harbour wave It is an appropriate name since it is when a tsunami hits a harbor or other area used by people that its destructive power is felt A tsunami can flood towns and villages with little warning destroying all in its path and killing people and animals When the wave retreats everything can be swept out to sea A tsunami floods houses in Oahu Hawaii in 1957 Tsunamis through time Tsunamis have probably been around as long as the sea One of the earliest descriptions was left by the Greek historian Thucydides who described a tsunami in the Mediterranean Sea near Greece in 426 BCE The sea returned in a huge wave and invaded a great part of the town and retreated leaving some of it still underwater so that what was once land is now sea such of the 4
AT U R EÊSF U N R Y inhabitants perishing as could not run up to the higher ground in time Thucydides linked the tsunami to recent earthquakes in the area modern scientists would do the same What causes tsunamis Tsunamis are caused by a disturbance in or under the sea that makes a large volume of water move suddenly Most are caused by earthquakes though landslides volcanic eruptions and even meteorites falling into the sea can cause tsunamis Waves flow outward in a circle from the point where the disturbance happens like ripples spreading from a stone dropped in a pond CASE STUDY When the sea and sky fell Modern geologists point to evidence of a tsunami caused by a meteorite striking the Tasman Sea between 500 and 850 years ago This may explain a legend told by the people of Burragorang in New South Wales Australia One steamy hot night the people lay unable to sleep in their camp Just after sunset the sky shuddered heaved and tumbled crashing down on them The Milky Way split and stars fell including a gigantic burning blue star that tore the ground apart showering the people with chunks of earth and rock Later other tribes told of the whole ocean falling on them from above It then rained for weeks and the whole land was flooded The native peoples believed these events were caused by an angry ancestor in the sky A tsunami can have devastating effects if it strikes an area where people live and work W h a t I s a T s u n a m i 5
AT U R EÊSF U N R Y The Tsunami Zone The Tsunami Zone Tsunamis can happen anywhere but most occur around the Pacific Ocean Volcanic eruptions and earthquakes are very common around the edges of the Pacific both inland and just off the coast and these can trigger tsunamis that spread across the whole ocean Inland tsunamis Tsunamis can even happen in an inland sea or lake Many tsunamis have formed in the Mediterranean Sea which is mostly enclosed by Europe and North Africa Earthquakes and volcanic activity around Italy and Greece have caused some disastrous tsunamis through history including some believed to have destroyed ancient Greek and Minoan cities thousands of years ago Smaller bodies of water such as lakes and rivers can also be affected by tsunamis In 2011 the severe earthquake that struck Japan caused a tsunami that flowed up many rivers causing damage far inland from the coast The eruption of Mount St Helens in Washington State in 1980 caused a tsunami on nearby Spirit Lake The Ring of Fire is a zone prone to earthquakes and volcanic eruptions that circles the Pacific Ocean Landfall A tsunami can strike land a long way from the event that causes it even on the other side of the ocean In 1946 a tsunami that struck the Hawaiian Islands in the middle of the Pacific Ocean was caused by an earthquake in the Aleutian Trench off the coast of Alaska five hours earlier The earthquake was over 2,400 miles 4,000 kilometers from Hawaii 6
AT U R EÊSF U N R Y When a tsunami strikes a region that didn’t feel the earthquake it can seem to come from nowhere When it reaches the shore quickly and near to the source of the earthquake or eruption it brings new devastation to an area hit only minutes before EARTHÊS JIGSAW PUZZLE The surface or crust of the Earth is divided into chunks called tectonic plates that fit together in a giant jigsaw puzzle The crust is made up of seven large plates and several smaller ones The Pacific Ocean is held on a single vast plate Within the earth semi-liquid red-hot rock moves very slowly around the globe dragging the plates with it At the joins between plates they rub or push against each other These are geologically active areas where earthquakes and volcanic eruptions happen A lone man watches the approach of the tsunami that swept him away on Hilo’s Pier 1 in Hawaii in 1946 T h e T s u n a m i Z o n e 7
