The Petrified Forest of Calistoga, California
"...you are in a grove of redwoods, some millions of years ago, with strange creatures scurrying around under a dense growth of trees and ferns. Smoke has been sighted coming from the towering volcano to the northeast, and a few earthquakes have rumbled through the forest in the past days, but nothing else is unusual. Suddenly, a puff of smoke arises from the side of the volcano, growing larger and larger in seconds and towering upward, shooting streamers of ash and bombs of lava outward.
Then all is still, the violence of the explosion gone, and more ash is falling, smaller now, from a high cloud from the rumbling distant volcano. For days and weeks, the eruption continues, with more layers of ash burying the prone forest. Streams erode the surface, depositing gravel in their channels. Glassy lava flows erupt from domes of sticky lava. For perhaps a million years, more eruptions lay down ash, lava flows and ash with glass so hot that it is welded into hard layers."
Excerpted from the work "Volcanos in Eruption" by Terry Wright, Phd.