Earthquakes in Sedona and Beyond
Above: Mount Humphreys, San Francisco Peaks photo by Sedona photographer Ted Grussing. See additional aerial photos by Ted here.
Sedona and Northern Arizona are high desert places filled with magnificent, other-worldly rock formations. Many were created by the effects of erosion and tectonic movement over vast stretches of time; others, monuments of ages past, are the result of sudden, violent forces, such as volcanic eruptions. I thought about this topic while reflecting on a recently asked question: “Do we experience earthquakes here in Sedona?” The answer is: “Yes! Sometimes…”
A small earthquake was felt in Sedona in October 2015. The epicenter was located about seven miles north of Sedona near picturesque, ponderosa pine-forested Munds Park, according to the Arizona Geological Survey in Tuscon.
"The location is quite close to the Oak Creek fault zone, a down-to-the-east normal fault with 700 feet of vertical displacement in the past 10 million years or so," said Phil Pearthree, chief of Environmental Geology at the Arizona Geological Survey.
More than 1000 people reported the quake which reached a magnitude 4.7 on the Richter scale. It was felt all the way up to Flagstaff, where one man reported his whole apartment was “swaying back and forth!”
There were no reports of injury or damage, but it’s a sobering reminder that the ground in Northern Arizona is very much alive, in a constant state of flux and change.
Remarkably, just 20 miles north of Sedona lies the majestic, oft snow-covered Humphreys Peak, the highest mountain in Arizona at over 12,600 feet above sea level. It is the centerpiece of what is known as the San Francisco fields, a region dotted by approximately 600 volcanos spread over 1800 square miles. Despite its awe-inspiring stature and role as centerpiece amid stunning Flagstaff views, Humphreys is a mere shadow of its former self; it is, in fact, a remnant of the mammoth San Francisco mountain that exploded millennia ago, collapsing from an original height speculated to be almost 16,000 feet.
About 6 million years ago, the first volcanoes in the San Francisco Volcanic Field began to erupt near the location of the town of Williams, Arizona. Williams is located near the intersection of State Route 64 (leading to the Grand Canyon) and I-40 (paralleling the old Route 66), and loosely marks the lower left corner of the sprawling volcanic field. The band of erupting volcanos migrated east over time, past Humphreys Peak, and on toward the valley of the Little Colorado River, extending about 50 miles from west to east. Geology experts postulate that when a future eruption occurs (not if, but when!), it would likely be on the east side of the volcanic field, in a relatively remote and unpopulated area.
Returning to my original story about earthquakes in or around Sedona: in 2005 there was a 5.1 magnitude earthquake about 50 miles southwest of the 2015 epicenter. The fact is, earthquakes in and around Sedona are infrequent and small.
However, I’m reminded of a story about Flagstaff and earthquakes.
Between 1906 and 1912, three magnitude 6 earthquakes hit near Flagstaff, causing large-scale evacuations. These quakes are the largest historical earthquakes in Arizona recorded to date.
A series of 52 earthquakes in September, 1910, caused a construction crew in the Coconino National Forest (near Flagstaff) to leave the area. According to the USGS, boulders rolled down into their camp from the nearby mountains, and the ground constantly shook. The shaking grew in intensity until September 23, when a strong shock was felt throughout northern Arizona causing resident Native Americans to evacuate an area north of the San Francisco Peaks.