Indonesia's Toba supervolcano – the site of the world's largest volcanic lake in Sumatra –came alive late last month, producing hot steam and foul smelling gas. The recent activity has raised fears of a major eruption after 75,000 years.
Toba Volcano, according to reports in the Indonesian media, is presently producing large emissions of steam and the ground in the area around the volcano is giving off foul odors of gas. Locals have also reported feeling the ground hot under their feet.
The latest activity is reportedly spreading panic among residents of the Toba area.
According to Dutchsinse, Toba supervolcano has a larger eruptive power than the Yellowstone supervolcano in Wyoming, United States.
Researchers say that Toba was responsible for two major global environment altering events in the last 2 million years, erupting on four different occasions in the Quaternary Period: 840,000 years ago, 700,000 years ago and finally about 75,000 years ago.
The last eruption that occurred 75,000 years ago was the largest of the four eruptions and has been characterized by the extent of its ashfall in the so-called Young Toba Tuff (YTT). The eruption led to formation of the Toba caldera -- Earth's largest Quaternary caldera -- in its present form.
The caldera, as it is known today, began forming about 1 million years ago during the Pleistocene epoch, when the first eruptions occurred.
"Toba caldera [the crater] produced the largest eruption in the last 2 million years. The caldera is 18 x 60 miles (30 by 100 km) and has a total relief of 5,100 feet (1700 m)."
To put the magnitude of the last Toba supervolcanic eruption into perspective, scientists estimate that the volume of the ash ejected was about 2,800 cubic kilometers, compared with the May, 1980 eruption of Mount St. Helens which produced only 1 cubic kilometer of ash.
The eruption is estimated to be 100 times greater than Indonesia's 1815 Mount Tabora eruption that caused the 1816 "Year Without Summer" in the northern hemisphere.
The last supervolcanic eruption of Yellowstone, about 600,000 years ago, produce only 1,000 cubic kilometers of ash.
"The Young Toba Tuff [ash ejected during eruption] has an estimated volume of 2,800 cubic kilometers (km) and was erupted about 74,000 years ago. The Huckleberry Ridge Tuff, erupted at Yellowstone 2.2 million years ago, has a volume of 2,500 cubic km. The Lava Creek Tuff, erupted at Yellowstone 600,000 years ago, has a volume of 1,000 cubic km. The May 1980 eruption of Mount St. Helens produced 1 cubic km of ash."
Eruptions in the magnitude of hundreds of cubic kilometers of ash are very rare indeed and are categorized as supervolcanic eruptions.
Scientific researchers believe that the last massive eruption of the volcano, 75,000 years ago, caused a dramatic change in global climate that led to a global volcanic winter. The volcanic winter caused a large part of global human population to die off, leaving only about 15,000 humans, thus causing a global population bottleneck that narrowed the genetic variability of the human race and restricted the direction of subsequent evolutionary history of the human species.
The scientific hypothesis that a massive eruption of the Toba volcano 75,000 years ago caused a global human population bottleneck and mass extinction of species is known as the Toba catastrophe theory/hypothesis.
The Toba catastrophe theory – which has been challenged by other researchers – states that the eruption event 75,000 years ago caused a global volcanic winter that lasted about a decade. The cooling effect on global environment lasted much longer, according to some authorities, 1,000 years.
There are fears that the supervolcano could have awakened once again after 75,000 years. According to a report by the Indonesian news site Merdeka, villagers of Sitoluama, in the District of Laguboti, Toba Samosir, noticed on Wednesday, May 27, that ceramic floors in their homes were feeling hot under their feet and that hot steam and smelly gas were coming out of the ground.
A resident of the area, Purasa Silalahi, told local reporters on Saturday, May 30, that he noticed vapors in his house about ten kilometers from Balige, Toba Samosir regency capital.
"Hot steam and gas was coming out of the pores of the soil it is feared to threaten the safety of people around, so we report them to the government."
Purasa said his house has become very hot due to the vapors. He attempted to trace the source of the vapor by digging the ground next to his house. But after he had dug to a shallow depth more smoke began issuing from the ground and Purasa hastened to cover up the hole out of fear of aggravating the situation.
Head of the Environment Agency in Toba Samosir, Parulian Siregar, confirmed that his agency received reports from locals who complained about hot vapors rising from the ground around their homes.
"We are trying to coordinate with the Department of Mines and Energy of North Sumatra and stakeholders to determine the definite vapor source, including handling solutions."
The June 6 eruption of Mount Sinabung, about 25 miles from the Lake Toba, came after the late May reports about Toba.
Dutchsinse reports that the authorities in Western Indonesia have issued an alert due to fears that Mount Sinabung could produce a "mega-eruption."
The Indonesian government ordered the evacuation of thousands of residents in the area around Mt. Sinabung after scientists warned that a major eruption could occur.
[Images: Wikimedia Commons]