Abstract:

Climatic data collected over the last 20 or 30 years make it possible to classify the Fildes Peninsula (62°08'-62°20'S, 58°45'-58°58'W, with about 30 km2 of ice-free area) of King George Island and the Vestfold Hills (68°22'-68°40'S, 77°55'-78°30'E, with 400 km2 of ice-free area) being of two types of climate: Antarctic maritime climate with mild low temperature, long summer, moisture and high precipitation, aad Antarctic continental climate which is characterized by very low temperature, short summer, low precipitation and violent winds. It is obvious that periglacial landforms in the Fildes Peninsula (more than 25 types are found and distributed everywhere) are much more developed than in the Vest-fold Hills (with 12 types only and limited in some favored places). This is a conformity with the environment of these two places. For the Vestfold Hills, low temperature coupled with comparatively short periods of freeze-thaw activity (47 days yearly) and widespread dryness in regolith, detemined the extent for the development of periglacial landforms, while mild low temperatures coupled with long periods of freeze-thaw activity (more than 110 days a year) and wetland in the Fildes Peninsula are quite fitted for the active periglacial processes. Measurement of seasonal changes in patterned ground is the best way for establishing their activity status. Horizontal displacements of large sorted circles were monthly or seasonally monitored by the author and ANARE expeditioners from February 1981 to March 1985 in the Vestfold Hills and by CHINARE expeditioners from February 1985 to February 1988 in the Fildes Peninsula. Distinct seasonal activity is evident in the behaviours of the large sorted circles under observations. Expansion takes place in February and March with the expansion upwards of the permafrost, and contraction occurs during the development of annual active layer in November and January. Over winter the circles are stable. Over four seasons in Vestfold Hills and three seasons in Fildes Peninsula, mean annual extention rate varies between 1.2 mm and 6.2 mm and between 5.1 mm and 32 mm respectively, i.e. difference in extention rate is 4-5 times between these two places.