Moving in a southwesterly direction at the rate of one inch (2.5 cm) per year, the North American continental plate has passed over a shallow chamber of partially molten rock, leaving behind a trail of volcano tracks.

Over the course of 16.5 million years, approximately 15-20 massive eruptions have left immense calderas (craters) to dot the landscape from the Nevada-Oregon border through Idaho’s Snake River Plain to Yellowstone National Park. Eventually the movement of the plate brought the Yellowstone area into contact with the shallow body of magma and the stage was set for more volcanic fireworks!