"Four thousand years ago, a volcano erupted and left a mark that's barely visible today. But the Dotsero volcano, now a pile of ash and reddened soil on the east end of Glenwood Canyon north of Interstate 70 and the Eagle River, has appeared on the radar screen of the U.S. Geological Survey, which recently rated the threats of volcanoes across the country.
"This is the first comprehensive report on volcanoes since Mount St. Helens" erupted 25 years ago, said Clarice Ransom, spokesman for the USGS in Reston, Va.
Dotsero is rated as a moderate threat for its potential to spew volcanic ash into the air at such altitudes that it could disrupt airplane traffic. Sunset Crater in Arizona is also a moderate threat.
"Where you sit in Colorado, that part of the U.S. is heavily trafficked by jet airplanes," said Jim Quick, USGS program coordinator for volcanic hazards. "If Dotsero should erupt with an explosive event, it would put ash up to flight altitudes and threaten aircraft."
Quick explained that the USGS evaluated volcanoes in the United States as well as its territories, and scientists believe any volcano that has erupted in the last 10,000 years, during the geologic Holocene Era, could become active again.
The report identified a handful that are not well-monitored but could present a danger. Four are currently erupting: Mount St. Helens; Anatahan, in the Marianas Islands of the western Pacific; Mount Spurr, in Alaska; and Kilauea, in Hawaii. Thirteen were rated as very high threats, including nine in the Cascade Mountains and four in Alaska, and 19 were identified as having a high potential to disrupt airplane flights with volcanic ash, primarily in Alaska and the Marianas. Another 21 volcanoes need individual monitoring, including the Yellowstone caldera, which underlies most of Yellowstone National Park, the report said.
Dotsero is not one of those, however. The volcano is not likely to erupt in our lifetime.
"The probability of it happening in a human lifetime is pretty low," Quick said. "But at some time in future? That's harder to judge, especially in the absence of monitoring."
"In terms of your and children's lifetimes, I wouldn't worry too much" about Dotsero, Quick added.
Quick explained that Dotsero is a "maar," or explosive volcano.
"Because it's a maar it ended up with a moderate threat rating. Because it has erupted we feel it could happen again," he said.
Dotsero also produced "lahars," mudflows of water and volcanic ash that traveled about one and a half miles downstream of the volcano and diverted the flow of the Eagle River to the south side of the valley.
"(They) can be quite devastating downstream," Quick said. Such lahars, or mudflows, from the eruption of Mount St. Helens 25 years ago dammed a river and resulted in extensive damage to buildings.
"They have the density and viscosity of wet concrete," Quick said of the mudflows.
Volcanic flow from the Dotsero crater was cut by I-70 and is visible on the south side of the highway. The crater itself is north of the interstate, above the trailer park. (May 11, 2005 by Donna Gray)" (
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"Dotsero is a 700-meter (2,300 ft) wide by 400-meter (1,300 ft) deep maar volcano located in Dotsero, Colorado near the junction of the Colorado River and the Eagle River. It is classified as a scoria cone with evaporitic rock, basaltic tephra, and oxidized sandstone. Erupting approximately 4200 years ago, it is the youngest volcano in Colorado. It is currently dormant.
Eruption information
This Holocene volcano erupted in the year 2220 ± 300 years B.C. When Dotsero blew, it created small scoria cones that were constructed along a NNE-SSW line on either side of the maar.[1] The eruption date is based upon radiocarbon dating of wood found underneath some of the scoria. It is one of the youngest eruptions in the continental U.S. and it produced an explosion crater, a lahar, and a 3-kilometer (1.9 mi) long lava flow. Scientists think that the volcanoes that have erupted int the past 10,000 years could become active again. Interstate 70 cuts across the lava flow." (from (
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This volcano is a Maar volcano and estimated eruption was 2200 BC ± 300 years. The coordinates above are from the photo. The lava field is from roughly mile marker 132 to 134. Coordinates of the summit (on provate property) are 39.661°N 107.056°W. (from (
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