New Mexico Rock Glacier Inventory: Analysis of Geomorphology and Paleogeography

• Main Author: Kinworthy, Bryan
• Format: Text
• Language: English
• Published: UNM Digital Repository 2016
• Subjects: rock glacier; permafrost; periglacial; paleoclimate; Ice
• Online Access: https://digitalrepository.unm.edu/geog_etds/27; https://digitalrepository.unm.edu/context/geog_etds/article/1026/viewcontent/Thesis_FINAL_v3.pdf

Rock glaciers are large masses of rock debris and interstitial ice that flow or have flowed downhill by permafrost creep. The formation and distribution of rock glaciers is restricted to climates conducive to permafrost development and lithology vulnerable to weathering for source rock. Subsurface ice is insulated from solar radiation, allowing rock glacier formation in lower latitudes and elevations than ice glaciers. Thus rock glaciers provide a useful geomorphic indicator of past and present climate change in regions absent of ice glaciers such as the U.S. Southwest. This study inventories 424 rock glaciers covering 18.36km2 in the state of New Mexico, identifies environmental parameters that control their formation, and estimates dates for periods of periglacial activity. New Mexico rock glaciers exist in a broad latitudinal range between 33°N in southern New Mexico to 37°N at the Colorado border. The distribution of rock glaciers is controlled predominantly by elevation, mean annual air temperature (MAAT), slope, and geology; precipitation and solar irradiance are also minor controls. Tertiary intrusive bedrock was found to create extremely dense distributions of rock glaciers. High elevation rock glaciers with extremely cold MAATs are more likely to be located outside areas shaded from solar irradiance, and may require increased ice temperature for internal deformation. A bimodal histogram of minimum elevation and MAAT suggests at least two pulses of periglacial activity. Rock glaciers that likely formed during the late to terminal Wisconsin (35 — 12kya) reach minimum elevations of ~2,400m, whereas those formed during the Neoglacial (4.9kya — 0.12kya) flow to ~3,450m. MAATs suggest some inventoried rock glaciers may still contain subsurface ice or remain active.