Toba, Indonesia

For quite some time, the theory that the Toba eruption ~74,000 years ago caused a "genetic bottleneck" in human populations has been floated. This theory, by no means, is accepted by all geologists and anthropologists, but we can agree on one thing: Toba was one of the largest eruptions that has occurred since humans left Africa, erupting over 2,500 cubic kilometers of volcanic material. Some recent research has shown that the acid signature of volcanic aerosols likely from Toba can be found in ice on both polar icecaps, supporting the global influence of the eruption. The above Landsat image of Toba shows the scale of the caldera - it is 100 kilometers from end to end on the long axis! How big is that? It would fit snugly between Columbus and Dayton here in Ohio.

Image: NASA / Wikipedia