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Geology of Mojave National Preserve: Hole in the Wall
Colorful, sculptured volcanic rocks at Mojave National Preserve's Hole in the Wall.
Visitors to Mojave National Preserve are fascinated by the brightly colored,
fantastically sculpted rocks at Hole in the Wall. Little do they know
that these intricate forms hold the key to a devastating and violent episode
in Mojave's geological past.
About 18.5 million years ago, a powerful
volcanic eruption blasted outward from the nearby
Woods Mountains. Propelled by the force of rapidly rising and expanding
gasses, a ground-hugging
cloud of ash and rock fragments spread out at near
super-sonic speeds across the countryside. Some of the rocks thrown
out by the blast are
14-20 meters (60 feet) across - the largest ever
Hot, suffocating ash buried every living thing
in the path of the blast. An area of over 600
km2 was covered
with ash and rock fragments so hot that they
welded together after they reached the ground. The toasted and fossilized
remains of birds,
mammals, and plants lie entombed beneath the
volcanic tuff that
forms the colorful cliffs of Hole in the Wall.
Records of many more catastrophic volcanic
blasts can be seen as you drive through the Preserve.
Dig deeper into Hole in the Wall's violent past.
Skip forward to Cinder Cones National Natural Landmark
Citation: McCurry, M., Lux, D. R., and Mickus, K. L., 1995. Neogene Structural Evolution of the Woods Mountains Volcanic Center, East Mojave National Scenic Area: San Bernadino County Museum Association Quarterly, v. 42, no. 3, p.75-80.