Geology Reference
In-Depth Information
Present extent of
continuous permafrost
Present extent of
discontinuous permafrost
Southern limit of discontinuous
permafrost in Little Ice Age
Southern limit of
late-Pleistocene permafrost
Figure 11.14.
Changes in permafrost distribution since the Late Pleistocene in northern China.
Compiled from data in Brown (2001), Vandenberghe et al (2004), Qiu and Cheng (1995).
11.5.6. Extent in the Southern Hemisphere
In the southern hemisphere, the majority of Pleistocene frost-action phenomena have been
described from the southern parts of South America and Southern Africa. There are also
reports from Tasmania and New Zealand. Because of its wide-ranging nature, it is diffi cult
to evaluate the signifi cance of this information. For example, most of the frost-action
phenomena described from Tasmania and New Zealand (tors, talus, blockstreams, hum-
mocks, bedded scree) (Derbyshire, 1973; Soons and Price, 1990) appear not to require
permafrost. Only in southern Patagonia and Tierra del Fuego, Argentina, have unambigu-
ous features of past permafrost and intense frost action been identifi ed (Galloway, 1985;
Grosso and Corte, 1989, 1991; Rabassa et al., 2004; Vogt and del Valle, 1994). There, a
cold lowland steppe-like ecozone developed to the east of the ice-covered Fuegian moun-
tains. On the Falklands Plateau, no evidence for permafrost has yet been identifi ed in the
Falkland Islands. It seems reasonable to conclude that the southern hemisphere mid-
latitudes did not experience the same magnitude of temperature depression as the north-
ern hemisphere. Derbyshire (1973) suggests a temperature depression of only 6.5 °C for
the last cold period in Tasmania. Presumably, this was because the presence of the South-
ern Oceans and the strong zonal westerly winds isolated the southern continents from the
effects of the huge Antarctic ice mass to the south.
11.6. CONCLUSIONS
Estimates as to the global extent of the Late-Pleistocene periglacial domain are diffi cult.
Periglacial environments varied in time and space; some were characterized by both
