2
The tell-tale sign of an ancient supervolcano is a giant crater known as a caldera. The photo you
see here is a caldera that is now Lake Toba, in Indonesia. The largest volcanic lake in the world,
it was created by a super eruption 75,000 years ago.
This aerial view from a NASA satellite gives you a sense of the Toba caldera, is 18 miles wide
and 60 miles long.
The geysers and hydrothermal pools are some of the most beautiful sites above ground at
Yellowstone. But things are quite different beneath the surface.
What’s down there? First, there’s a large magma chamber, as shown here in a picture from
National Geographic. This chamber contains enough magma to fill the Grand Canyon eleven
times over.
But second, even though this chamber is huge, it’s dwarfed in comparison to a giant magma
plume that extends more than 20 miles into the earth. When the Yellowstone supervolcano erupts
again, all this magma will be devastating.