The Eruption of Toba - Case Study Example

The Eruption Of Toba Lake Toba is a super volcanic lake. The length of the lake is 100 kilometers with a width that is 30 kilometers, while its depth is 505 meters (1,666 feet). The surface elevation of the island of Sumatra is around 900 meters which equates to 2,953 feet. Lake Toba is the largest lake of Indonesia, and it also is the largest volcanic lake of the world. The eruption at Lake Toba is estimated to be around 8VEI and it is estimated that it occurred around 69,000 to 77,000 years ago. The general belief is that the volcanic eruption that occurred caused volcanic winters and thereafter the temperatures around the African and the Indian regions have been noted to fall quiet alot. Some geologists believe that the volcanic eruption also resulted in the extinction of the human race that existed at that time. However, there is a belief that this theory does not hold true because many of the species of the animals that are said to be sensitive to the change in temperature did exist at that time. The other belief is that it caused a change in the genetic setup of the human beings that lived in the area at that time. This volcanic eruption is considered to be the largest known eruption in the last 25 million years and caused a major change in climate at that time. The volcanic winter which occurred as a result of the eruption resulted in decrease in temperature to around 3 to 5 °C (5 to 9 °F), and up to 15 °C (27 °F) in higher latitudes (Causey 48-59). TOBA CATASTROPHE THEORY According to this theory the winter caused because of this super volcanic eruption lasted for around 6-10 years and the cooling of the lava was a long process that stretched around 1000 years. It was suggested by Ann Gibbons that the super volcanic eruption that took place resulted in a bottleneck in the human race. A few other scientists suggested the same but then again many other scientists subsequently failed to identify any link or develop enough evidence to support the theory. According to a theory there were not just one but a series of three eruptions that spanned over the period of 1 million years. The crater that was formed because of the super volcanic eruption was 100 × 30 km2 area wide. The crater is known as the Caldera Complex and the volume of the eruption was estimated to be around 2,000 km3 and 3,000 km3. The mass that was collected after this eruption was estimated to be larger than the erupted mass that had been ever collected in the past 100 years of volcanic eruption history. The ash layer that was deposited from the Toba eruption that took is said to be around 15cm thick and it was spread over the whole of South Asia. A layer of ash was also deposited over the Indian Ocean, and the Arabian and South China Sea. Even the deep sea rocks that were later retrieved from the South of China sea are said to have the after effects of the volcanic eruption and this has proven that the estimation that was done about the spread of the volcanic mass was an underestimation. And therefore the mass was estimated to have a more far reaching effects than it had even been calculated (Gunn 40). Some of the scientists believe that the eruption happened at the time when the last of the glacial period was setting in. They believe that the super volcanic eruption that occurred was not responsible for the cooling effect on the climate, but it acted as a trigger for the glacial period. The glacial period was setting in was at a very low speed, but when the super eruption at Toba occurred the whole process was quickened and the glacial period occurred. There are many conflicting opinion about this theory but the general assumption is that the super eruption at Toba caused a lot of dramatic changes in the weather and the temperatures dropped dramatically thereafter. There were also a lot of ash deposits found in the atmosphere as well as in the ocean. The ice samples that were found from the Greenland also showed abnormality in the temperatures and the deposition that had occurred. The abnormality that had occurred was due to abrupt changes in the temperatures that occurred at the same time the super volcanic eruption took place (Smith 57). It has been assumed that the genetic bottleneck that occurred at that time is considered to have been caused by the volcanic eruption of Toba. The genetic bottleneck is said to have occurred around 50,000 years ago. This theory claims that the human population decreased to around 3000 to 10,000 individuals. There is evidence as well that the existing humans today have descended from the few thousand pairs that had survived at that time. The believers of the genetic bottleneck theory suggest that the eruption at the Toba Mountain had also caused a major loss in vegetation. The geological setting of Sumatra in Indonesia and also the neighboring Java makes it prone to natural disasters such as volcanoes, cyclones and tsunamis. The latest eruption which occurred at this island was in 2010. But the greatest ever explosion to occur in the world has been the Toba volcanic explosion some seventy-four thousand years ago. This Island still has many active volcanoes that have been deemed dangerous. The Toba volcano is termed as the super volcano as is to date it is the last volcano to erupt in this category. This eruption resulted in release of some thousand cubic kilometers of magma. This eruption not only caused changes in the tectonic settings but also caused great changes in the climate as well. One of the most unique things about this volcanic eruption was that it resulted in the formation of the world’s latest and largest caldera (Officer & Page 50). The caldera is the largest one till date. It is known as the world’s largest quaternary caldera. It was formed not only because of this volcanic eruption but in fact it took time to evolve the formation of the caldera was completed with this eruption. This formation had started some one million years then finally the Toba explosion completed the formation. The Samosir Island is a result of this explosion and it also caused formation of volcanic domes. Its results also include the venting of the ash rock equivalent to 2500-300cubic kilometers on the north east as well as the south west of the lake Toba. Post affects also include the formation of a volcano to the north west of the lake which geologist found is only a few hundred years old. This shows that how huge the explosion would have been that its affect are still bringing about geographical changes. These findings were made due to lack of vegetation around this volcano which certifies the findings that it is a recently created volcano. Ignimbrites are materials which resulted in the eruption along with ash, magma and harmful and poisonous gases. Ignimbrites caused great deal of pollution as well for it released 10-12 kilograms of Sulphur gas into the atmosphere. One of the characteristics of such super explosions is that super volcanoes such as Toba are not simple conical shaped mountains. Toba basically, now is a beautiful lake but it is considerably large for the size of the lake. Animal life, human life, vegetation, and climate are greatly affected by such eruptions but thankfully such explosions do not occur with much frequency and happen after fifty thousand years and may also take even more time. Since all of the ash, volcanic gases and other dust particles that were released due to the eruption caused a veil to be formed which blocked the solar light and radiations and prevented them from reaching the surface of the earth, the absence of the heat resulted in lowering of the temperatures. This is why the vegetation is greatly damaged for without sunlight photosynthesis cannot occur. Scientists and researchers after a deep and detailed study conducted over a long period concluded that effect on the sea’s ecosystem as well as the surface due to Toba eruption continued as a cycle for a period of six years. Most of the people to survive the ordeal were in the tropical regions which remained considerably hot as compared to other places. Even in the region surrounding the Indian Ocean there was a mass extinction that has been recorded. The rocks that have been collected show the effect of ash cloud in this region. This whole event has also been named as the youngest Toba Tuff or YTT. Toba is located at the center of the Sumatra Island and is no more an active volcano mainly because most of its part was blown when it erupted and then collapsed to form a caldera which was filled with water forming an unusually large lake. Since it happened way back calculating its actual impact is not possible but it has been estimated that this eruption was twenty eight thousand times the explosion that occurred due to the eruption of Saint Helen. The archaeologists and geologists have found that effects of this explosion on the Greenland ice cores are quite prominent, because there are a lot of ash deposits to be found. The ash deposit that is found in the Indian ocean and the South China ocean has been associated with the super volcanic eruption that had occurred in the form of Toba explosion, the ash deposit is said to be thousand feet in thickness. The resultant volcanoes that formed on the surface of the lake are still active and show activity with the most recent being some hundred years for the vegetation is sparse around the volcano, the magma that flowed destroyed the top soil causing loss in vegetation. The relation between the bottleneck and the eruption is not yet determined and reaching a conclusion has not yet been possible. Toba tuffs collapsed along the regional line causing the budge in the eastern side. The reason of the explosion was mainly the collapse of the line across the western marginal fault lines. The Toba volcano comes in the Pacific ring of fire. The place where two tectonic plates meet is known as the fault lines and Sumatra is located there which makes it very prone to natural disasters. The volcanoes still present there are dangerous but still not that horrific and disastrous as the super volcanoes. The pressure that built up over time caused the light crust formed over it to explode releasing all the gases, ash and dust. Since they are not like the typical mountains we see that they basically are cauldron shaped features on surface of the earth that tend to have magma and other features similar to a volcano but due to the formation of crust the pressure of the rocks and molten lave increases till it reaches beyond the point of bearing by the crust, the crust erupts due to high temperatures and pressures that are building up inside the mountain and the magma flows out. All of the research about the super volcanic eruption has been made is through the help of DNA samples of the remains that had been found and by closely studying the sediments layers and Toba tuffs using radioactive means to determine the date and constituents of the explosions. After the recent Tsunami, about seventy or sixty volcanoes became active again. However, the Toba volcano is buried deep and safe underneath the ocean and rest of it which exploded is now a lake. Though it seems that for now we have no imminent danger there but since the nature of Earth is highly unpredictable therefore we can say that we are not safe. We do have reports and researches suggesting that any explosion similar to that of Toba is not possible for another ten thousand years or even more than that but still all we can do is hope to be safe from such disasters which cannot be challenged or stopped. Works Cited Causey, Andrew. "go Back to the Batak, Its Safe There: Tourism in North Sumatra During Perilous Times." Indonesia and the Malay World. 35.103 (2007): 257-271. Print. Gunn, Angus M. Encyclopedia of Disasters: Environmental Catastrophes and Human Tragedies. Westport, Conn: Greenwood Press, 2008. Print. Officer, Charles B, and Page, Jake. Tales of the Earth. New York: Oxford University Press, 1993. Print. Smith, Joseph. "Natural Hazards: Geology, Engineering, Agriculture, and Sociopolitical/humanitarian Considerations for the Twenty-First Century." International Geology Review. 42.7 (2000): 617-656. Print. Read More