Friday 3 July 2015

History of a volcanic mega explosion and its Legend

Scientists have concluded that huge Lake Toba found right in the center of North Sumatra was in fact created by one of the ancient earth’s mega explosions of a  supervolcano. A supervolcano is said to be capable of producing volcanic eruptions with ejecta or volcanic materials greater than 1,000 cubic kilometers (240 cubic miles), and thousand times larger than most historic volcanic eruptions. The colossal Mount Toba, along with the Yellowstone, Long Valley, and Valles Caldera in the United States; Taupo Volcano, North Island, New Zealand; and Aira Caldera, Kagoshima Prefecture, Kyushu, Japan,  are known as the six most highlighted supervolcanoes of  planet earth.

The Toba super-eruption that formed Lake Toba occurred between 69,000 and 77,000 years ago. The eruption was the latest in a series of at least three caldera-forming eruptions that occurred at the volcano, with earlier calderas having formed around 700,000 and 840,000 years ago. The last eruption was estimated to have Volcanic Explosivity Index (VEI) of 8, - described as mega-colossal,-  and is still believed to be the largest explosive eruption anywhere on earth in the last 25 million years.

The eruption spewed out about 2,800 cubic kilometers of volcanic materials, and the Pyroclastic flows of the eruption destroyed an area of 20,000 square kilometers (7,722 sq miles). To give an idea of its magnitude, consider that although the eruption took place in Indonesia, it deposited ash layers of approximately 15-cm (5.9-inch) thick over the entire South Asia.  At one site in central India, the Toba ash layer today is found to be up to 6 m (20 ft) thick.

Many scientists believe that the supervolcanic event plunged the planet into a 6-to-10-years  of  volcanic winter, which resulted in the world's human population being reduced to 10,000 or even a mere 1,000 breeding pairs, creating a bottleneck in human evolution. Some researchers argue that the Toba eruption produced not only catastrophic volcanic winters, but also an additional 1,000-years’ cooling episode.

The subsequent collapse formed a caldera that gradually filled with water and created what we now know as Lake Toba.  While, the rising caldera floor also formed the Samosir Island at the center of the lake, which was due to movements in the magma chamber beneath it

Along with the scientific explanations, locals have their own stories concerning the origin of Lake Toba. There are many variants of this legend, and here is one of them.

It is said that a long time ago, a poor young man lived alone in this area. This orphan made his living by farming and fishing. One day he captured a peculiar fish. Perplexed with the unusual shape, he touched it, and the fish became a beautiful princess. The princess told him that she was cursed for breaking a rule made by the gods. The gods decreed that the fish should take shape similar to a creature that touched her the first time; hence, the fish became human.

He proposed to her and she agreed on one condition, that he’d never divulge the secret of her origin. He agreed to this and they got married. Later on they had a son, and were happy even though they still had to work hard.


One day the boy was so hungry that he ate all of the food in the house, including his parents’ share. His father became so angry that he cursed his son, betraying his true parentage. Suddenly the wife and son vanished. The man regretted what he had done but there was no turning back. A spring came out from where the son and wife disappeared, which after some time became Lake Toba.

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