The Largest Volcanic Eruption Ever

I'm not sure if there is any agreement on the largest eruption ever. Almost certainly it was some pre-historic eruption from one of the large rhyolite calderas that occur in association with subduction zones. Some candidates are the Toba eruption in Sumatra, the Taupo eruption in New Zealand, the Oruanui eruption in New Zealand, the Long Valley (Calif.) eruption that produced the Bishop tuff, or perhaps some Yellowstone eruption. Each of these covered huge areas with ash and if it were to happen today would be catastrophic.

Probably the largest eruption since we've been paying close attention would be that of Tambora in Indonesia in 1815.