Seasonal frost mounds occur in the North Fork Pass area in response to increased hydraulic potentials in perennial, spring-fed groundwater systems. Geochemical and isotope analyses indicate that local precipitation is the source of water for flow systems discharging from the springs. The direct measurement of pressure potentials in a number of frost blisters and icing blisters, undertaken in March 1982, gave values ranging from 30 and 81 kPa for mounds approximately 2.0 m high. These pressures exceed theoretical, calculated values and are attributed to the tensile strength of the soil and (or) ice overburden. In genetic terms, seasonal frost mounds should be clearly differentiated from other morphologically similar features such as palsas.