fromSFGATE
3 hours agoNot far from I-40, a Calif. desert hike 18 million years in the making
About 18.5 million years ago, giant volcanic eruptions forever changed the landscape of what is today a swath of protected California desert land, bound by two major interstates between Los Angeles and Las Vegas. The eruptions left behind unique rock formations, including cliffs and canyons made up of rhyolite tuff, a volcanic rock formed by different particles and rocks merging together from the heat of an eruption.
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