Campground talk and slide show on volcanoes for Chiricahua National Monument

Abstract

The slides and the accompanying script presented here are based on a campground presentation at Chiricahua National Monument in 1994. Examples of eruptions at active volcanoes are used to help the audience visualize events that took place in the National Monument 27 million years ago. This presentation stresses the following themes: 1) The National Monument lies on the flank of an ancient volcano known as the Turkey Creek caldera. 2) This volcano produced giant explosive eruptions, much larger than any in the 20th century. Similar volcanoes that are still capable of producing giant eruptions exist today, and include examples in the United States. 3) We can learn how these giant volcanoes operate and what their typical "life histories" are by examining ancient analogues such as the Turkey Creek caldera that have been dissected by erosion. Studies of ancient volcanoes provide the conceptual framework for evaluating hazards at active volcanoes. 4) Large eruptions of the type that occurred in the Chiricahua Mountains are highly explosive. As a result, the molten rock, or magma, that feeds such eruptions is "blown to bits", producing volcanic ash and pumice instead of lava flows. 5) The volcanic history of Chiricahua National Monument can be reconstructed by geologic mapping and by "reading" the record of past eruptions from the layers of rock that were deposited by the volcano. The slides and script follow the format of the 1994 campground presentation. Slides are keyed to the script by number. Italic print is used to identify the subject and source of each slide, and to provide additional background information. This document is intended to be used by interpreters at the National Monument for presentations on geology. It may be used as a complete "packaged" talk or as background material for customized presentations. Additional information for the non-specialist on the geology of Chiricahua National Monument is available in a separate report (Pallister and others, 1993).