1.1. Toba Catastrophe
Lake Toba is located in Sumatra, Indonesia (Figure 1). The Toba Eruption was the last of three major eruptions, which occurred over the past million years, creating a volcanic caldera1. The most recent eruption, also known as the Youngest Toba Tuff erupted around 73,000 (± 4000) years ago2. This created a global catastrophe that effected many species, including humans. Many researchers have linked this even to the most recent bottleneck in human evolution resulting in a dramatic drop in the human population to only about 3,000 to 10,000 in a very short period of time3.
1.2 Definition of Supereruption
The term “supereruption” was introduced after the Toba eruption in 1992 to describe the devastating effects that occurred5. To this date, there is no strict definition however; an eruption that can produce over 300 cubic kilometers of magma would have global consequences and therefore, be considered ‘super’6. The volume of magma that erupted from Toba was much greater than any other eruption previously recorded2. The fragmental deposit from such a large eruption can produce volumes of 1000km3 or greater7. Therefore, according to this definition, the latest eruption of Toba can definitely be considered a supereruption.
1.3 Comparison to Yellowstone Eruptions
Figure 2 compares the volume of material erupted from several different eruptions and it is clear the Yellowstone eruptions were of significant size. Three of the eruptions from the Yellowstone hotspot, situated under the continental portion of the North American Plate, were considered supereruptions because of their size8. The largest is called the Huckleberry Ridge Tuff (Figure 2). This resulted in the creation of a caldera because the volcanic eruption was so large, it emptied its magma stores so quickly that it collapsed8. The formation of this caldera did not stop the volcanic eruptions, it simply created a resurgent dome which is seen at Lake Toba as well9. Toba is in fact the largest resurgent cauldron in the world10. In both the Yellowstone and Toba eruptions, rhyolite was present, providing evidence that in both cases, a large amount of alterations were experienced by the magma as it made its way up to the surface12. This created the perfect combination of ingredients for a massive eruption to occur. Yellowstone and Toba were both massive eruptions that had a significant impact on the world. However, the effects produced by Yellowstone do not even compare to those of Toba as seen in Figure 2.
1.4 Overview of Report
The geological settings of Toba will first be discussed in this report. This includes the involvement of the tectonic plates as well as the interaction and the history of formation that resulted in such a massive eruption to occur. Following this, the supereruption itself will be discussed in detail, also known as the Youngest Toba Tuff. Finally, this report will touch on the global effects that occurred from this eruption...