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Tsunamis are giant waves that are usually triggered by an earthquake. For example, the 2004 Aceh earthquake and ensuing tsunami killed about 250,000 people, and the Tohoku tsunami that struck off the coast of Japan in 2011 killed more than 15,000 people.
Although the tsunami triggered by the earthquake is classified as very dangerous sort, previous studies mentions that the resulting tsunami wave heights are usually less than 150 meters. This was disclosed by Dallas Abbott, a geologist at the Lamont-Doherty Earth Observatory in Palisades property of Columbia University in Palisades, New York.
However, researchers today continues to uncover new evidence of the existence of the giant tsunami which makes tsunamis was as though mediocre. Scientists have recently revealed that the mega tsunami as high as 50-story skyscrapers, even more, never hit the Santiago island off the west coast of Africa, about 73,000 years ago.
More recently, Abbott and his colleagues found that the giant dunes of the island nation of Madagascar possibilities generated by a mega tsunami with a height of about 90 meters that occurred about 8,000 years ago.
"It's interesting that we might have this sedahsyat event is still within reach of human history," said Abbott told Live Science. "It will demonstrate that men had survived the catastrophic events are quite powerful."
The researchers examined a set of hills located along the southern coast of Madagascar. The dunes are shaped like the letter V is usually arranged along such lines in military uniform epaulet - the greatest height of about 185 meters above sea level with a length of over 40 kilometers.
Previous research assumes that most of the material forming these hills the wind carried away. But Abbott and his colleagues suspect that the material on this hill was taken by the giant tsunami early.
The researchers analyzed 22 samples from the two sets of Madagascar and surrounding hills, which they collected in 2006. They focused on minerals such as calcium carbonate which is often found in the shells.
The researchers found that the level of calcium carbonate in the dunes is generally greater than 40 percent. However, the level of calcium carbonate in areas beyond the dunes are only ranged from 0 to 9 percent.
"The dunes are the result of wind usually 100 percent quartz sand," said Abbott, as quoted by Live Science, Friday (01/15/2016). "The dunes contain many carbonate. The sand just outside the area basically does not contain carbonates."
The dunes also contain intact microscopic marine fossils in abundance.
"If these fossils were blown inland by the wind, they may be shattered due to bounce on the surface," said Abbot. "But if it was taken by the water, the possibility of the fossil remains intact. We found a complete intact micro fossils, mostly. You mungin look a little worn at the edges, but it was probably due to the effects of wind after being taken by the water. You will not find fosil- fossil was broken into pieces. "
In addition, the presence of magnesium in the fossil showed that the fossil, at a time, immersed in brackish water warm and shallow. "They did not just dwell exposed on the beach - they were excavated, somehow," said Abbott again.
Triggered Comet?
The researchers speculate that perhaps a giant tsunami triggered by a comet or asteroid that crashed into the Indian Ocean. This cosmic collision that likely produced Burckle crater, the hole with a width of about 29 km which is located about 1,450 km in southeast Madagascar, at a depth of about 3,800 meters below sea level.
"There are other material content around the Indian Ocean shows that craters and dunes Madagascar is evidence of a cosmic collision," said Abbott. "In Western Australia, you can find sand rich in carbonate height up to 150 meters above sea level and is located 7 kilometers on the island. These sites could be formed at the same time as that in Madagascar, although we do not yet have enough evidence . "
Yet another Abbot added, "It is difficult to confirm that Burckle is the impact crater. That's the problem with underwater crater - it is hard to verify its origin."
There is a possibility that the mega tsunami that hit Madagascar is not triggered by the collision of a cosmic collision, but the consequences of the events in the mainland as a massive landslide. "However, the effects of a massive landslide usually quite local," said Abbott. "If the events of Madagascar and Australia occurred in the same period in the Indian Ocean, then the possibility of a collision is kosmiklah cause."
Abbot mention that the research in the future, will be collected more samples from Madagascar to be analyzed. Experiments in the wind tunnel at the micro fossils will also be done to see if the fossil remains intact after bouncing, or breaks as expected.
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