Wednesday, September 14, 2005
How well prepared are people to disastrous situations?
History cannot forget Indonesia’s Krakatau eruption in 1883, which was preceded by an earthquake of 8.7 magnitude. Already, during the last eight months, the volcanoes like Telang in Sumatra, Barren Island in Andaman region have been activated after the series of earthquakes.
More than a dozen earthquakes preceded the major earthquake of Sumatra, which had a magnitude of 9 in December, 2004 that triggered tsunami in Indian ocean killing thousands of people. Over 20 earthquakes preceded the March 2005 earthquake of Sumatra, which had a magnitude of 8.7 and already, over 200 earthquakes of over 5.5 and 6.5 magnitude have been recorded in the Sumatra region, said D Chandrasekharam, an IIT professor and volcanologist.
He said, in various data published after December 2004, the Indian plate was constantly being drawn below the Sumatra plate.
“What is happening to the material that is being subducted below Sumatra?,” Chandrasekharam asked, answering it himself, “the answer could be that the subducting material must be melting, thus promoting continued subduction. This process of melting would result in seismic activity.”
This phenomenon is true in all subduction zones, the scientist said. The rate of subduction during the pre-December 2004 earthquake was estimated at 6.7 cm per year, while it was estimated more than 6.7 cm per year after the December 2004 earthquake, Chandrasekharam said.
He further said, the accumulation of melted material cannot stay below the earth’s crust for a long period. As the volcanoes in this region have already been activated, close monitoring is essential.
“These are relatively small volcanoes compared to those like Krakatau, Toba and Sorikmarapi. The Krakatau eruption of 1883 was preceded by an earthquake of 8.7 magnitude,”Chandrasekharam said.
Toba and Sorikmarapi lie just below the area, where all the present earthquakes are located (Nias and Northern Sumatra). More than 130 active volcanoes are present in Indonesia, which is more than any other country on earth. They comprise the axis of the Indonesian island arc system, which is generated by northeastward subduction of the Indo-Australian plate.
Toba is a stratovolcano, which erupted about 74,000 years ago, ejecting 2,800 cubic metres of tuff into the sky, which created a major disaster over the entire Asian continent. Now, this is a dormant volcano.
Michael Rampino,of New York University warned, a massive volcanic eruption capable of causing as much devastation as the cosmic bodies occurs every 50,000 years.
The young Toba tuff has an estimated volume of 2,800 cubic kilometres (km) and erupted about 74,000 years ago, he said.
There have been no eruptions at Toba in a historical time, but the area is seismically active with major earthquakes in 1892, 1916, 1920-1922, and 1987.
A recent article, (Zeynab El Fatah from northern Sumatra), in the Victory New magazine said, Rampino’s research pointed out that Toba blasted a crater 100 km long and sent 3 billion tonne of sulphur dioxide into the atmosphere and a dense volcanic cloud around the globe.
According to the department of science and technology officials, the India Meteorological Department (IMD) and its Indonesian counterpart are exchanging information on earthquakes.
After the tsunami experience of December 26, 2004, the IMD is in touch with the Japanese Meteorological Agency and the Pacific Tsunami Warning System in Hawaii with the help of the ministry of external affairs.
Department of science and technology (DST), will be working with their Japanese counterparts, on earthquakes in the Indian ocean region, the officials said, adding that the tsunami warning system will be in place within two years.
The Geological Survey of India (GSI) has carried out seismic observations in the Andaman and Nicobar islands. According to the GSI, it is conducting some study on the ocean bottom features for a better placement of tsunami warning system.
“So far, there is no such proposal for working with Indonesia and that too, on volcanoes,” they said. However, DST has a project proposal with IIT Mumbai to work on volcanoes in the Andaman and Nicobar islands.