Dotsero

Geography & Climate

Dotsero is located in United States, within the Basin and Range Volcanic Province of the broader North America Volcanic Regions. Situated at 39.66° N, 107.04° W in the Northern Hemisphere, the volcano lies within a temperate climate zone. At 2,230 meters above sea level, Dotsero rises above the surrounding terrain into montane or subalpine conditions. The elevation creates distinct ecological zones along its flanks, from forested lower slopes to exposed rocky terrain near the summit. The volcanic landform is characterized as a minor (basaltic), which describes the physical shape and structure of the volcanic edifice as observed from the surface.

Geological Context

Dotsero is situated along a rift zone, where tectonic plates are pulling apart. As the crust thins and fractures, magma rises to fill the gap, creating volcanic activity. Rift volcanism typically produces more fluid lava flows rather than explosive blasts, which means communities near Dotsero in United States generally face slower-moving hazards like lava flows and ground fissures rather than sudden pyroclastic events. However, rift volcanoes can still generate significant ash emissions and gas releases that affect local air quality. The dominant rock type is basalt / picro-basalt, a dark, fine-grained volcanic rock that forms from rapidly cooling, low-viscosity lava. Basaltic eruptions tend to be less explosive and produce fluid lava flows that can travel long distances. While less immediately dangerous than explosive eruptions, basaltic lava flows can destroy structures and infrastructure in their path, and volcanic gases released during these eruptions can affect air quality over a wide area.

Eruption History Summary

Dotsero has 1 recorded eruption in the geological database, spanning from 2200 BCE to 2200 BCE. The most powerful recorded event was an explosive event producing ash plumes up to several kilometers in 2200 BCE, reaching VEI 2 on the Volcanic Explosivity Index.

GVP Reference Summary

A small maar and scoria cone complex at Dotsero is located near the junction of the Colorado and Eagle Rivers west of the Gore Range. Highway I-70 cuts across a lava flow, but the most prominent feature of the complex is a 700 m wide and 400 m deep maar that was erupted about 4,150 radiocarbon years ago along a ridge consisting of evaporites and reddish oxidized sandstones of Pennsylvanian age. Small scoria cones were constructed along a NNE-SSW line on either side of the maar. Small lahars preceded eruption of a basaltic lava flow that traveled 3 km down two narrow V-shaped valleys and spread out onto the floodplain of the Eagle River, diverting the river to the south side of the valley. Older Pleistocene basaltic lava flows occur nearby at Willow Peak, McCoy, and Triangle Peak.

— Smithsonian Institution, Global Volcanism Program