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Open-file Report - 541
A geologic study of the Capulin Volcano National Monument and surrounding areas, Union and Colfax Counties, New Mexico

William O. Sayre and Michael H. Ort


Capulin Volcano is a unique cinder cone in the National Park System. Its boca, or mouth, at its western flank, is more complex than most cinder cones. The volcano is very accessible, with a paved road to its rim, and it has become a well-established stop for both tourists and university geology field trips.

The eruption of Capulin volcano took place about 60,000 years ago over a period of a month to a few years. The first lava flows came out of small vents, followed by the eruption of cinder to make the volcanic edifice itself. After the cone grew to its present height, more lava was erupted from the western base of the volcano, forming the boca or mouth, consisting of several vents, lava lakes and lava tubes. These flows soon surrounded the volcano.

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