Climatic factors on the Archean earth

Abstract

There is no strong evidence for extreme climates during the Archean. Galciogenics rokcs are rare, while evaporites are about as widespread as in later geological periods. Sedimentary rocks suggest processes of erosion and weathering not particularly anomalous. This findings is surprising in the light of simple physical reasons to believe that the sun was less bright.Although the area of exposed land was probably low, the albedo change associated with more extensive oceans could hardly have been large enough to prevent glaciation. A stronger atmospheric greenhouse is indicated. Carbon dioxide was the most likely candidate gas. A variety of arguments suggest that it was much more abundant. Methane is another possible contributor to the greenhouse. While abiotic sources of this gas were probably negligible then as now, biogenic sources could have sustained methane mixing ratios in the range 10-4 to 10-6.Other climatic factors of uncertain impact include more rapid rotation of the earth -- the lenght of the day was probably about fifteen hours throughout most of Archean time - and little or no continental land areas, which would have reduced the importance of landsea circulations while permitting less restricted zonal flow of ocean currents.