Sedona Sinkholes Focus Hikers Attention Below the Red Rocks
February 20, 2015
by Louise Gelotte
On a phenomenally beautiful day in early January the Tracker group of the Sedona Westerners arrived at Posse Ground eagerly anticipating another special interest hike in our stunning Red Rock classroom. No one knew that within a month a new sink hole opening up in Oak Creek Canyon would make this topic even more relevant to all participants. Our remarkable instructor Paul Lindberg, geological engineer, has delighted Sedona Westerners for years with enjoyable and instructive Earth Science hikes. Lindberg claimed he's been leading these hikes since the Pleistocene!
Everyone in the group knew about the Devils Kitchen sinkhole accessed by the Soldier Pass hiking trail and also visited by jeep tours. But, most of the group was alarmed to learn that there were six other exposed sinkholes around the city of Sedona, which included the two that the Tracker Group would visit on this day, Nolan Draw and Red Canyon.
In 1990, after the 1989 collapse of Devils Kitchen sinkhole, the U.S. Forest Service, concerned for the safety of visitors, asked Lindberg to conduct a geologic study of the hazards of the Nolan Draw sinkhole. Lindberg then decided to do a detailed study of all seven sinkholes in the Sedona area and in 2010 submitted a report to the Arizona Geological Survey containing maps, photos and statistics, that would serve as a baseline for future monitoring.
As the group hiked to Nolan Draw, Lindberg pointed out an interesting feature on the ground. There were three small openings in a row indicating that something had dropped beneath and may prove to be an extension of the Nolan Draw sinkhole. Lindberg appealed to Sedona Westerners to make note of any features like this, along with GPS coordinates, that they might encounter while hiking, since there could be other sinkholes unknown to him. Because of its remoteness, hikers were curious about how this sinkhole was discovered. In the late 1980's, forest rangers came out to Nolan Draw thinking that the depression on the topographic map was an old cattle tank. They discovered something much more dramatic, a sinkhole with a collapsed area 4.6 times larger than its surface opening. Lindberg observed that this was an older sinkhole because of its well rounded rock edges. There were also two mysterious potholes on the rim indicating that once there had been a lot of water forcefully cascading over the edge.
All Sedona sinkholes exist because of the deep-buried Redwall limestone layer about 800 feet below our boots. Groundwater flowing through this layer dissolves some of the limestone, thus creating huge caves. As the cave becomes larger, its ceiling can no longer support the weight of the overlying rocks and collapses. This process of collapse continues progressively upward toward the surface.
Paul Lindberg explains Nolan Draw sinkhole.
The Trackers enjoyed lunch a safe distance from Nolan Draw. Then it was time to explore the next sinkhole, Red Canyon. This dramatic sinkhole has been by far the largest one in the Sedona area. The Trackers first viewed this feature from the top admiring the 100 foot sheer drop of the sandstone walls. Next, they were able to walk down into this sinkhole and detect the many trees growing from the floor, including hackberry and Arizona walnut.
Last, Lindberg took his students to a "bonus" fledgling sinkhole, named 4543 by him, because of its location. In sharp contrast to Red Canyon, this was the smallest known sinkhole in Sedona. During periods of atmospheric pressure change, substantial amounts of air either entered or exhausted through this blowhole.
On the ride home, members of the Tracker group pondered the idea that in millions of years from now, when the cave system beneath our feet was no longer wet, visitors may travel to Sedona to observe one of the great cavern systems of the world, rivaling Mammoth Cave in Kentucky! Once again, a Tracker hike with Paul Lindberg provided the Westerners with a lot to contemplate.
More information about sinkholes and the unique geologic setting of Oak Creek Canyon can be found in the recently released book “Legacy of the Oak Creek Watershed”, by the Oak Creek Watershed Council including Paul Lindberg.
If you are interested in joining the club, please go to our website at http://sedonawesterners.org or just come to one of our monthly meetings. The next one will be on Thursday, March 5, 2015 at 7 pm at the Sedona Elks Club, 110 Airport Road.