Author(s):
David R. Butler - Texas State University - San Marcos
George P. Malanson - University of Iowa
Abstract:
Active Frost Processes and Fine-Scale Polygonal Patterned Ground on Turf-Banked Terrace Treads, Eastern Glacier National Park, Montana
Fine-scale geomorphic/pedogenic processes at alpine treeline may facilitate or preclude the initial stages of conifer invasion of alpine tundra. Turf-banked terraces are widespread relict landforms above treeline in eastern Glacier National Park. On the treads of these terraces, active frost processes churn the upper several centimeters of fine-grained and produce environments inimical to seedling survival.
Fifteen U.S. 1 cent pieces (pennies) were placed on three turf-banked terraces in the summer of 2003. When revisited in 2004, all pennies had been frost heaved/churned, and in some cases had been subducted into and underneath the surface. On terrace tread 1, 11 of 15 pennies were recovered, all had moved and some were standing vertically. On tread 2, 12 of the original 15 were recovered and all but 3 of those had undergone extensive movement. On the 3rd tread, all pennies were recovered, and all had undergone movement. Overturning of pennies was common on all three turf-banked terrace treads. Fifteen pennies were placed on two additional treads in 2004 for additional future monitoring.
