The entire park is an enormous volcanic caldera, hence the thousands of hot vents, geysers, bubbling pools, and clouds of steam in the lower park.
When the Yellowstone caldera has exploded, in the distant past, it has thrown so much matter into the sky that it has darkened the globe for years — think 28 to 250 times larger than Mount Pinatubo.
The smallest Yellowstone eruption in the past was 280 times larger than Mount St. Helens.
The biggest?
If it happened again, it would end most life on earth.
The evidence of earthquakes and landslides are all over the park, as is massive volcanic flows ranging from basalt to mud and ash.
Over the whole thing has come glaciation under 4,000 foot sheets of ice — ice sheets that only receded about 11,000 years ago.
The bison and elk and native Americans came after the Sequoias, but before the Toyota Rad-4s.
As far as the park is concerned, nothing here is old but the rock and water itself.
The three pictures, above, are of the same place, but with the basalt columns — which represent a single layer — emphasized.
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