The San Francisco Peaks loom large on the northern Arizona landscape and their distinctive profile is etched into the minds and hearts of area residents. As the state's highest mountain, they have beckoned desert travelers to the cool, pine-scented high country for millennia.
Rising 12,633 feet above sea level and almost a mile and a half above the surrounding Coconino Plateau, the Peaks are truly an awesome spectacle that tower over the Grand Canyon State.
But perhaps surprising to some, this ancient volcano once stood much higher than it does today. When its internal fire was nearly extinguished not quite half a million years ago, something happened to the top of the San Francisco Peaks. Geologists still debate exactly what caused this once stately cone to lose almost 3,000 vertical feet. But that didn't stop me, a Flagstaff geologist, and two Sedona artists from collaborating on an exciting project that allows us to see the mountain as it once looked.
As a geologic adviser, I provided Sedona photographer Tom Johnson and graphic artist Trevor Roberson with the scientific details of the Peaks history. We began our work by digitizing one of Tom's color photographs of the Peaks, taken near Rogers Lake southwest of Flagstaff during one of our more exceptionally wet winters.
Once the image was made computer friendly, Trevor began to weave his digital magic with some scientific coaching from me, who looked over his shoulder to make sure that the technical details were not lost in the artistic rendering.
What emerged is a captivating and intriguing glimpse of an unmistakably familiar landscape feature, but with a twist that is uniquely different. In this new view of the Peaks they have been rendered as they may have looked during the height of the last Ice Age almost 500,000 years ago.
A few liberties were taken to ensure that the recreation did not lose the distinctive shape and feel of the Peaks. For example, before the cone was destroyed and when eruptions were still spilling fresh lava down the volcano's flanks, there would not have been gullies cut into its side. However, Trevor and I decided to leave these modern day erosional features in the recreation because otherwise, the new image might have looked like any number of the world's other volcanoes.
Additionally, the amount of snow depicted is modern and not of an Ice Age amount.
INCOMPLETE BUT COMPELLING
The known history of the Peaks is incomplete but compelling. They are the tallest of more than 460 volcanoes in the San Francisco Volcanic Field.
Two million years ago they did not exist. But beginning then, cinders and lava erupted from a vent to build its foundation.
By half a million years ago, a large graceful stratovolcano, similar to modern day Mount. Fuji in Japan, stood tall upon the northern Arizona landscape. It rose to an elevation of about 15,300 feet above sea level, which would have been more than 8,000 feet above the future site of Flagstaff.
Mount Coconino (a name Flagstaff resident Marshall Scholing has suggested to me for the old cone) would have stood 800 feet higher than modern day Mount Whitney, currently the highest mountain in the lower 48 states.
The youngest flows on the top of Mount Humphreys have been dated at about 440,000 years old and these represent the time when the mountain began to go cold. Around that time, the Peaks probably looked like the cone shown in the recreation.
Sometime between then and about 220,000 years ago, which is the age of the next volcano that erupted on the floor of the already formed Inner Basin, the Peaks lost their top.
Ideas on how this may have occurred are inconclusive. One local volcanologist thinks that a Mount St. Helen's type of blast may have blown away the top. Another finds evidence that the mountain top collapsed — either from being top heavy or by falling into an empty magma chamber.
Both ideas are possible and could explain the existence of the Inner Basin, but it may be that only one is correct. We may never know.
However, as the debate continues residents can look with amazement and interest at this new image of a familiar and cherished icon.
Tom Johnson and I have plans to reproduce the image as a poster that would be available at places like the Museum of Northern Arizona book store. This image is the result of a fortuitous collaboration between a scientist and two creative artists. It allows all of us to better understand our long lost history and the origin of our stupendous scenery.