Long before any recorded human history in Yellowstone National Park, a massive volcanic eruption spewed an immense volume
ash that covered all of the western U.S., much
the Midwest, northern Mexico and some areas of the eastern Pacific Coast. The eruption dwarfed that of Mt. St. Helens
1980 and left a huge caldera. Yellowstone typically erupts every 600,000
900,000 years with the last event occurring 640,000 years ago. Its eruptions are among the largest known to have ever occurred
Earth, producing drastic climate change
the aftermath. The park was named
the yellow rocks seen
the Grand Canyon of the Yellowstone - a deep gash in the Yellowstone Plateau that was formed
floods during previous ice ages and
river erosion from the Yellowstone River.
Source: http://en.wikipedia.org/wiki/Yellowstone_National_Park
