Long-term flow measurements (1961-2002) of the Arapaho, Taylor, and Fair rock glaciers, Front Range, Colorado

During the 1960s, several surveying networks were established on rock glaciers located in the Front Range of the Colorado Rocky Mountains. Most Surveys were updated every I to 5 years until approximately 1966, providing a short-term record of flow velocities; however, since these initial studies, the measurements have not been updated. Short-term and long-term flow velocities are needed to examine the evolution of rock glaciers. During the summer of 2002, 1 re-established surveying networks, and obtained a 40-plus year record of flow. Average rates of 7.3, 6.3, and 9.5 cm/year were calculated for the Arapaho, Taylor, and Fair rock glaciers, respectively. Compared to other rock glaciers, the displacements are small because Surveyed rocks are situated in a zone of compressive flow near the toes of the rock glaciers. Most displacements were within 10% of the projected estimates and were not significantly different from the earlier short-term measurements. Meteorological data do not show a clearly defined warming trend but indicate a slight increase in total precipitation. Rates of flow have remained consistent and Suggest that rock glaciers in the Front Range are adjusted to the current climate, unlike some rock glaciers in the European Alps. The rock glaciers, however, are not in a permanent steady state and are still likely adjusting to neoglacial environmental processes (within 4000 years B.P).