• Mount Toba is a super-volcano located on the Indonesian island of Sumatra. It has erupted at least four times over the past 1.2 million years, but it was the most recent eruption 74,000 years ago that interests researchers the most.
• Scientists are able to estimate the size of the eruption through several means: the size of the hole it left behind; the layer of ash, whose signature can be found worldwide; and the change to the climate, which can be gauged by ice cores.
• The crater left after the eruption of Mount Toba turned into Lake Toba, which stretches 60 miles long by 20 miles wide (96 x 32 km).
• Enough lava flowed out of the volcano to build two Mount Everests.
• In areas close to the volcano throughout what is now India and Pakistan, the ash reached an estimated depth of up to 9 yards (8 m). It’s likely that no humans and few creatures survived; it would have been a mass extinction of all living things in this region.
• Nearly all of Indonesia, Malaysia, and the Indian Ocean were covered with around 6 inches (15 cm) of ash.
• But all around the globe, there’s a thin telltale layer of potassium/argon crystals, which can be identified by mass spectrometers. Using a system similar to carbon dating, this layer can be traced back to Mount Toba’s eruption 74,000 years ago, give or take 600 years on either side.
• The eruption of Mount Toba was the largest eruption on Earth in 2 million years. The eruption lasted an estimated 14 days. The booming would have travelled around the world several times. The blast was 100 times bigger than Krakatoa and several thousand times bigger than Mt. St. Helens.
• The volcano spewed sulfuric acid and sulfur dioxide into the air in such amounts that it blotted out the sun.
• The eruption of Mount Tambora in 1815, while being the largest eruption in recent history, was much smaller than Mount Toba, perhaps only one-tenth the size. Yet it still led to untold thousands of deaths because the particulate matter in the atmosphere cooled the climate to such a degree that it was called “the year without summer.” Crops failed and people starved worldwide. The same would have happened following the eruption of Mount Toba, occurring at a point when the worldwide population of humans was perhaps only 100,000.
• It’s been estimated that the temperatures dropped 5 to 9° F (3 to 5° C) creating winter-like conditions for up to ten years following the eruption. Ice core samples from Greenland indicate that the climate cooled off for a period of nearly a thousand years afterwards, contributing to an ice age.
• However, the climate change precipitated by this blast wasn’t equal all over the globe. Temperature changes were far worse in the northern regions than at the equator. Human populations of Neanderthals in what is now Europe would have been devastated. But the archaeological record shows that the population of humans living in warm coastal areas of Africa were barely affected.
• Eruptions approaching the size of Toba are very rare, occurring on average less than once every million years or so. But understanding the climate consequences of such eruptions is critical to knowing the hazards posed by smaller magnitude eruptions. Eruptions much smaller than Toba still have the potential to dramatically affect human society around the world.
