Dotsero

Dotsero Crater is an elongate, 2,300 ft (700 m) long by 1,300 ft (400 m) wide, maar incised into sedimentary strata of the side of a mountain, called Blowout Hill, and local, irregular, mountainous topography. At an elevation of 7,316 ft (2,230 m), its north rim lies about 330 ft (100 m) higher than its south rim. Dotsero Crater is about 1,300 ft (400 m) deep. It is part of a maar and scoria cone complex in which the associated scoria cones are constructed along a NNE-SSW line on either side of the maar and is perched near the upper edge of steep sided canyons about 1,000 ft (300 m) above the valley floor of the Eagle River. The axis of the maar and scoria cone complex aligns with the axis of a local syncline. Associated with the maar and scoria cones is a lahar and 2 mi (3.2 km)-long lava flow. Dotsero Crater lies northeast of Dotsero, Colorado near the junction of the Colorado River and the Eagle River.

History of Study

In 1888, the Dotsero Crater was first researched and described by P. H. Van Diests as part of his regional work on Colorado volcanic craters. Van Diest's research was followed by R. E. Lakes, along with descriptions of Upper Carboniferous gypsiferous deposits in the same area, in 1890. Lakes noted the highly explosive character of the volcanic deposits of the Dotsero Crater and proposed that it erupted "...within the human period." Much later in 1933, R. E. Landon attempted to establish the age of the Dotsero Crater 's volcanics by studying their relation to the topography of the area, including local terraces of the Eagle River. He concluded that this crater erupted during the Holocene Period; that this crater is a sinkhole; and the Eagle River was dammed by the Dotsero Crater's lava flow. In 1963, F. F. Giegengack studied the pyroclastic deposits and lava flow associated with Dotsero Crater and their relationships to local Quaternary terraces, fans, and deposits. He concluded that this crater erupted during the Late Wisconsin age; its lava flow did not dam the Eagle River; and Dotsero Crater is definitely a volcanic crater. His and earlier research about Dotsero Crater is summarized by J. A. Rizo in 1971.

E. E. Larson and others in 1975 and P. T. Leat and others in 1989 briefly discussed the role of Dotsero Crater as part of regional volcanism in northwest Colorado in terms of both volcano-tectonism and geochemistry. Both papers provide only a very limited descriptions of the primary volcanic deposits at Dotsero Crater, some of which have since been altered or destroyed by either erosion, quarrying, or a combination of both. In 2011, M. C. Rowe and others investigated the compositional evolution of the Dotsero Crater's magmas using the geochemistry and petrography of melt inclusions. They recognized that this crater is a maar and proposed that the eruption began with construction of scoria cones and lava flow, followed by maar-forming activity. Finally, in 2018, M. R. Sweeney and others described in detailed the volcanic deposits and geologic context of Dotsero Crater. From their observations, they concluded that the eruption of Dotsero Crater progressed from initial effusive magmatic volcanism through a period of explosive phreatomagmatic maar-forming volcanism to a final period of explosive magmatic volcanism. They also concluded from the character and distribution of volcanic deposits that the locally irregular and mountainous pre-eruptive topography strongly influenced the accumulation of volcanic deposits around the crater.

Eruption information

This Holocene volcano erupted in the year 2220 ± 300 years B.C. When Dotsero did erupt, it created small scoria cones that were constructed along a NNE-SSW line on either side of the maar. The eruption date is based upon radiocarbon dating of wood found underneath some of the scoria.

Dotsero, and all volcanoes that have erupted in the past 10,000 years, are more likely to become active again. The United States Geological Survey considers it a moderate threat to impact air travel if it were to erupt.

Interstate 70 cuts across the lava flow. At the base of the volcano is a mobile home park.

References