(Editor's Note: This story first appeared in the August 2004 issue of Mammoth Monthly magazine. Subscribe here.)

It's hard to imagine now, but there was a time when Mammoth's people didn't have a grasp on what was happening right underneath their feet.

All they knew for sure was that there were steam vents, evidence of recent volcanoes, the occasional big earthquake and occasional swarms of small ones. There was pumice all over the place and a subrange of mountains, the Glass Mountains, made up of black glass, not to mention the Obsidian Dome north of town.

Moreover, there was pinkish rock, Bishop Tuff, whose origins were unknown, and lots of yellowish rhyolites, also a mystery.

Roy Bailey changed all that.

Bailey, who died in 2003 at the age of 73, basically founded the Mammoth School of Rock. His discoveries gave us an understanding of the Mammoth area that is so accepted nowadays that there's hardly a mystery left.

"He was the guy who unraveled the story of what happened here," said David Hill, currently the U. S. Geologic Survey scientist in charge of this area.

"I think his principal legacy is his beautiful geologic map of the Long Valley Caldera and the Inyo and Mono Craters. It's really the foundation for so much work that came later."

Bailey, a native Rhode Islander who met his future wife, Patrice, on a trip to New Zealand when he was a student, gained his fundamental understanding of how calderas work while studying the Valles Caldera in the Jemez Mountains in New Mexico.

With that knowledge, he came to Mammoth and was able to put together the puzzle of the Long Valley Caldera and the magma chamber benearth the Resurgent Dome at the junction of Hwy. 203 and U.S. Hwy. 395.

"His mapping established the framework and the age sequence of all these things," said USGS scientist Wes Hildreth, who specializes in vulcanology and who finished Bailey's final professional paper on the area.

"Without that, the geophysicists … wouldn't know what the hell's going on."

Bailey, who lived in Santa Cruz during the winter and with Patrice in a Lakes Basin cabin in the summer, first did major work here in the 1970s. He built upon other scientists' work, namely that of Charles Gilbert, the famous geologist at the University of California-Berkeley who was a student at the Deep Springs School.

The result was his map, which is available online at the USGS Web site (www.usgs.gov).

It is a beautiful map, and if it weren't a scientific document one might mistake it for a work of pure art.

"He had an artist's eye," said Patrice, "and he applied that to his maps. He agonized over which colors worked best."

By following which colors represent what, the map offers explanations for just about everything that has happened -- from the huge cataclysm of the sinking caldera, the resulting spewing of the Bishop Tuff, the volcanic lava flow that today is the Volcanic Tablelands, all the way up to the eruptions of the Mono and Inyo Craters.

"He integrated all this into a coherent scenario," said Mammoth's Bob Drake, formerly a geologist at UC Berkeley.

In 2003, friends of Bailey gathered in the arboretum at the University of California-Santa Cruz and held a memorial service. They planted two New Zealand trees in his honor.

"He had a persistence and a doggedness about him," said Patrice, later, "and he was meticulous in his habits. He was patient and curious above all else, and he knew what the big questions were."

Roy Bailey Photo| The Map