Cryogenic structure of the active layers of selected Pergelic Cryaquepts were studied in the Fairbanks and Delta areas of interior Alaska. The study was conducted in April and early May when all active layers were completely frozen. The purposes of the study were to determine the relationship between pedogenic and cryogenic structure; to find the boundary between the active layer and the permafrost; and to predict the settlement of the soil.

Cryogenic structure of the B horizons generally changed very rapidly over a short distance. Lens-shaped cryogenic structure dominated the upper part of the B horizon, whereas the lower part of the cryogenic structure changed to massive with hoar-frost ice between soil plates. Moisture content of the B horizon decreased from 40-50% in the upper part of the B horizon to 15-20% in the middle and lower parts of the horizon. There is an increase in moisture content of the thin layer in contact with the permafrost. The upper layer of the permafrost (BCf or Cf horizons) contains different kinds of ice lenses; belt-shaped, microlayering, and layering cryogenic structure. The moisture content in the upper permafrost layer ranges from 100-200%. The volume of ice is more than 60%. The upper permafrost layers have very important engineering and pedogenic significance.

C. L. Ping
Palmer Reserach Center
Agricultural and Forestry Experiment Station
University of Alaska Fairbanks
533 E. Fireweed Avenue
Palmer, AK  99645
Tel:  907-746-9462
FAX:  907-746-2677
Email:  PFCLP@ORION.ALASKA.EDU