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As a volcano erupts in the Caribbean, meet Colorado’s lone active volcano

Dotsero volcano crater_courtesy Lee Siebert and Smithsonian Institution
Posted at 3:34 PM, Apr 09, 2021
and last updated 2023-11-07 17:57:56-05

EAGLE COUNTY, Colo. — As an ash cloud rose 6 miles above an erupting volcano in the Caribbean Friday morning, an active volcano sat quiet and still in the Rocky Mountains of Colorado. Could it see a similar fate anytime soon?

Spoiler: Nope. Not for a very, very, very long time. However, it is still considered an active volcano.

Colorado's Dotsero volcano is a sprawling indentation in the mountains just northeast of the unincorporated community of Dotsero in Eagle County off Interstate 70.

The United States Geological Survey (USGS) rates the threat of Dotsero erupting as "moderate," meaning it requires "basic real-time monitoring coverage," according to its website, and could impact air travel if it erupted.

It's a far cry from the high risk that led to the events in the eastern Caribbean Friday, where at 8:41 a.m. local time, the La Soufriere volcano on the island of St. Vincent exploded in a violent eruption. It sent an ash cloud as high as 6 miles into the sky. The local government had already started mandatory evacuations on Thursday.

Amid all the commotion in the Caribbean, Dotsero is still fast asleep. (You can even go hike it — see below for details on that.)

But they're very different volcanoes. In St. Vincent, eruptions have occurred several times in the same place, building a bigger and bigger construct, said Alison Graettinger, assistant professor of geosciences at University of Missouri-Kansas City and one of the premier volcanologists in the study of volcanoes like Dotsero. Experts watched the La Soufriere volcano build up over time leading up to Friday's eruption.

"With Dotsero, we don't expect the next eruption, if there were one, to come out of the exact same vent. It probably would be another small eruption nearby," she explained. "Because of the position of Dotsero being on the edge of the Colorado Plateau, there's a possibility for future eruptions, but it's much lower than in places like the Caribbean, where we know that magma is being made at depth regularly."

The Dotsero volcano crater is about 250 feet deep at low-rim points and about 2,460 feet wide, according to the USGS, though when it erupted it was likely wider and deeper.

It's the youngest volcano to erupt in Colorado and the last time it blew open was about 4,200 years ago, said Matt Morgan, senior research geologist and deputy director of the Colorado Geological Survey at the Colorado School of Mines. The estimated date of the last eruption was calculated using Carbon-14, which is often used to date geological samples, such as the charcoal fragments found within the lava flows of the Dotsero volcano.

That eruption all those years ago was two-fold, Morgan explained. Prior to the explosion, a scoria cone — or craggily volcanic rock like you'd use on a gas grill — built up from lava flows. Following that was a phreatomagmatic eruption, which is when the magma comes up through the crust and interacts with groundwater, producing explosive steam eruptions, Morgan said. This blasted the scoria cone around the surrounding area.

Graettinger said the magma in this kind of eruption carves what essential looks like a upside-down cone that is full of debris. When it erupts from the top, it throws rocks more sideways than up and out, creating the broad, low crater, also called a maar, that visitors can see today.

Dotsero volcano Google Maps

There's likely an outlet or fractures in the crater, as it doesn't typically hold water, Morgan said. Today, the crater is home to not only foliage, but also holds debris like car wrecks, tires, wheels, and trash.

While Morgan hasn't visited the crater, he's explored the lava flows below, which ran about 1.9 miles south of the crater, according to the U.S. Bureau of Land Management. Today, I-70 cuts across the flow.

“It's pretty neat," he said. "You don’t have to go all the way to Hawaii to see a really young and fresh, volcanic flow.”

OK, but what if it did erupt?

While the Dotsero volcano is quiet and calm now, Morgan described what we'd likely see should the volcano erupt in modern times.

"It’d probably spew out a little fountain, maybe some rock fragments would come out, maybe some ash," he said. "If it reacts with the groundwater, we'd see some steam and some explosive activity. But we're not talking anything near the scale of a (Mount) St. Helens, for instance, or Yellowstone, for sure."

The Colorado Department of Transportation would likely shut down I-70 in the area as it may have lava flow over it, he said. The river may be dammed. Local towns may evacuate, especially in low-lying areas where volcanic gas may flow. Earthquakes may be a concern. Flights may get diverted from the area, just in case. It would definitely cause a stir, but given its size, an eruption likely wouldn't become a life-threatening event.

"But if it were out in some isolated land, it might be something that could be educational without being threatening," Graettinger said.

Morgan echoed this statement.

"It’d be pretty exciting to stand there and watch it," Morgan said. "Some of the geologists that I work with would love to see an eruption like that. You can just imagine what some of the Native Americans saw back in the day. It would be pretty exciting, but nothing to really cause too much harm."

So, what are the signs that this volcano could rumble back to life?

One of the biggest factors is seismic activity or earthquakes, Morgan said, usually starting with low magnitudes in the 1s or 2s. He explained that at the Colorado Geological Survey, they have a seismic network installed across the state that could pinpoint those kinds of earthquakes. Should they notice that kind of activity, they'd deploy a more specific network in that area to get a better reading on what was going on below the surface, he said.

Another sign would be geothermal heat flow.

Currently, neither are happening around Dotsero, Morgan said.

It's still a relatively new volcano, so it has the potential to explode again in the far, far future, but for now, it's sleeping soundly.

"I think we're pretty lucky to have such a young feature like that here in Colorado," he said.

Want to visit the Dotsero volcano crater?

If you're hoping to explore the volcano, you're in luck — it's a relatively short and accessible hike.

Deb Stanley, a Denver7 content producer, has hiked the volcano and provided some insight on getting there and hiking into the crater.

Take note: The road accessing the crater is rough, and 4x4 high clearance vehicles are recommended.

To get there, take Interstate 70 to exit 133 (Dotsero) and turn right onto U.S. 6. Drive a couple hundred feet farther and then turn right onto the frontage road for the highway headed east. Just before the entrance to the trailer park, turn left around the north side of the park and continue east. The road will start climbing uphill until you reach a sign for Castle Peak, about 2.5 miles from the interstate. Park there — you'll see a small kiosk with information but there's no designated parking sign. Keep an eye out for trucks on the road.

The parking lot is at about 7,100 feet. The bottom of the crater is at about 6,800 feet and the highest point around its edge is around 7,300 feet.

From the parking area down to the bottom of the crater and back up is about 1.25 miles with a few hundred feet of elevation gain. This trek is not easy and isn't recommended for children. You will return the same way you go down, so turn around if you don't want to climb too far back up.

Hikers can also trek up the road toward the top of the crater and an old mining structure.

There are no garbage cans or restrooms at the crater, so come prepared to carry out whatever you bring in.

To learn more about active volcanoes around the world, visit the Smithsonian’s website here.