When did the Yellowstone caldera erupt?
During the summer of 1988, about 250 separate fires broke out in
the greater Yellowstone eco-system. Most burned themselves out
without causing noticeable damage. Seven fires became much larger
than the others, and caused 95% of the nearly 800,000 acres of
damage that summer. The largest, named the Shoshone Fire, was first
noted on June 23, but it remained a minor event until about July
20.
Fire suppression after late July cost $120 million but did
almost nothing to even delay the spread of the fires. Snowfall on
September 11 finally ended the major damage, although the fires
were still smouldering into November.