Cataclysmic Landslide Created 'flat And Tranquil' Valley Enjoyed Today In Zion National Park

The Sentinel, a sandstone formation on Zion Canyon’s west wall, was once much larger. But over the course of a cataclysmic minute 4,800 years ago, it disgorged 10 billion cubic feet of broken Navajo and Kayenta sandstone that poured up and down the canyon. Debris flows reached speeds of 180 mph before settling into a plug two miles long and a mile wide, according to new research from the University of Utah. Rising 300 feet above the canyon bottom, the slide blocked the Virgin River, forming a t... <iframe src="http://www.sltrib.com/csp/mediapool/sites/sltrib/pages/garss.csp" height="1" width="1" > </frame>