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New USGS Geologic Map of Mount Mazama and Crater Lake Caldera, Oregon

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Crater Lake Institute News
Crater Lake, Oregon
November 24, 2008

By Rob Mutch

A spectacular new map, years in the making, is now available from the United States Geological Survey (USGS) Volcano Hazards Team of Menlo Park, CA:

Dr. Charles Bacon, a USGS geologist who has conducted research at Crater Lake National Park for decades, has worked many years on the map project.

New USGS map showing Crater Lake

We asked Dr. Bacon about the new map:

Robert Mutch (Crater Lake Institute): Charlie, how long have you been working on this map project?

Dr. Bacon: This project was started in 1979. Most of the fieldwork was done 1979-1988, with some additions through 1995. The Publication was caught up in the digital revolution. Putting everything into digital form, writing all of the geologic map unit descriptions, adding the caldera floor geology, and USGS internal technical review was completed in 2002. I had been working on a number of papers throughout the time I was working on the map. Waiting in line in the publications group for map edits and final production consumed the years leading up to publication."

Robert Mutch (Crater Lake Institute): How influential was the work of previous geologists such as Howell Williams, Clarence Dutton, and Diller and Patton?

Now for Sale

The new map, and companion CD,  is now available in print at the Crater Lake Natural History Association.

Dr. Bacon: Howel Williams' monograph, of course, was a guide to every subsequent worker at Crater Lake. In my own work, although I looked at Williams' book, I made my own observations and came to my own conclusions. The Diller and Patton Professional Paper is a marvelous book and was a tremendous accomplishment for the time. It is of historical interest, and many of the things in it have held up. I never really looked into what Dutton did. As I said earlier, I knew Howel Williams. He was a charming and dynamic individual. Unfortunately, I had very little opportunity to talk with Willie after I had started fieldwork, but I did get in a conversation or two. He was very encouraging. Recall that he died in early 1980, shortly before Mount St. Helens awoke."


Crater Lake National Park encompasses most of the area of the geologic map. Knowledge of the geology and eruptive history of the Mount Mazama edifice, greatly enhanced by the caldera wall exposures, gives exceptional insight into how large volcanoes of magmatic arcs grow and evolve.

Learn more about the Geology of Crater Lake National Park through articles, books, images, news, and more

The new 1:24,000 scale geologic map is unusual because it portrays bedrock (outcrop), surficial, and lake floor geology. Caldera wall geology is depicted in detail on the accompanying geologic panoramas. Also included is a 1:50,000 scale bedrock geologic map and a 45 page pamphlet.

The new map may be obtained as downloadable files at and will be available in printed form with CD-ROM as SIM Map 2832.

The map consists of several downloadable files: four large map sheets in PDF format, a 49-page pamphlet for the maps, a ArcInfo database consisting of files and containing a map and topographic base data in a single zipped folder. In addition, there is a collection of photographs of the area covered.


New USGS map showing Crater Lake




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