Jonathan Perkins
Can wind carve canyons?
One of the topics of my dissertation work with Dr. Noah Finnegan is examining how wind can shape landscapes in very dry, windy environments. At the margins of the Atacama desert in northeast Chile, the western slope of the Central Andes is subject to erosion by both wind and water. The four million year old Puripicar ignimbrite, a 1400 cubic km (i.e., Yellowstone-sized) pyroclastic flow deposit located just north of San Pedro de Atacama, provides a natural experiment to look at the contribution of both wind and water in incising bedrock canyons.
In a recent paper in the journal Nature Geoscience, we compare wind-shielded and wind-affected canyons along the Puripicar and show that winds here can carve canyons an order of magnitude faster than rivers. Canyons subject to wind abrasion are longer, wider, and more aerodynamically shaped than their fluvial counterparts. A neat implication of this work is in thinking about how other dry, windy landscapes in the solar system like Mars may also experience these effects.
Not only are canyons within the Puripicar ignimbrite incising by wind, the entire landscape is disappearing over time. Here the frontal escarpment is being shaped into rounded erosional prows called megayardangs. Image credit: Kerri Johnson
Figure 1. Satellite images showing evidence for wind abrasion along Martian bedrock canyons. White arrows indicate wind direction; black arrows indicate the direction of water flow. a. HiRISE image PSP_002486_1860 of a channel network near Ascraeus Mons. Islands between the branching channels are evolving into megayardangs. b. HiRISE image ESP_013097_1850 shows a canyon entering Crommelin Crater whose headwaters are evolving into a yardang field. c. Image of Kasei Valles (ESA ID 292688)
Above the canyons atop this four million year old volcanic landscape, wind abrasion has helped carve an extensive network of linear channels that extend for kilometers downwind.