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Karst Verification on the White River Plateau, Colorado


By Erin Dundas, Cave and Karst Resource Technician, White River National Forest

Situated on the White River Plateau, the high alpine meadows of the Flat Tops are characterized by a high density of significant karst features. These features include deep epikarst fissures, large sinkholes, extensive cave networks, and paleokarst towers dating back to an age when the land that is now Colorado had a tropical climate. The most extensive and well-developed of these features form in the Leadville Limestone, with some less significant features extending into underlying units. The heavily fractured nature of these soluble rock units makes the hydrology of the area very complex and creates a geological environment conducive to forming unique karst features, such as the Hanging Lake travertine system.

A group of people standing in front of trees.
The expedition team for the Flat Tops Expedition. From left to right: Jim Baichtal, Marjorie Jerez, Neil Hooker, Lorraine Negron, Erin Dundas, Caroline Bedwell, Lima Soto, and Brad Ellis.

In mid-July of 2022, a team of geologists from the Eagle Ranger District of the White River National Forest set out with Jim Baichtal, the former Forest Geologist and karst expert from the Tongass National Forest, and Lima Soto, the Forest Service’s National Cave and Karst Program Lead, to verify potential karst features previously identified using LiDAR datasets and ArcGIS processing. This method proved to be incredibly effective for locating karst features on the ground and prioritizing areas of highest significance. The Flat Tops cover a very large land area and locating sinkholes by walking transects can be nearly impossible. Many of the deep sinkholes that the team located on the ground with the LiDAR maps were invisible until the team was nearly on top of them and likely would have been missed without the maps pointing the team directly to them.

Over the course of the team’s weeklong expedition, it was able to identify and record hundreds of karst features. Many of the features that the team located were large insurgence basins with water lines indicating that they fill and drain during high runoff periods, but the occasional discovery of a cave or a large sinkhole created the most excitement among the team members. A few areas in particular had an abundance of very deep sinkholes, some with caves continuing horizontally at the bottom, ranging from an estimated 30-70 feet deep. The success of this expedition left the group feeling very positive about continuing the verification process and making more significant discoveries in the future.

 
A large sinkhole taking in water.
A large sinkhole that is taking in water from a smaller adjacent sinkhole/insurgence. This sinkhole was located using LiDAR mapping and was not visible from the nearby trail.
A stream draining into a small sinkhole.
A stream draining into a small sinkhole, adjacent to the large sinkhole in the previous photograph.