Imprint of Climate Zonation on Marine Sediments

Abstract

The main factor in all processes on the surface of Earth, including geological ones involving sedimentation, is commonly thought to be the energy from the sun, which provides for exogenic forcing. However, major changes in geography (such as the distribution of land and sea and elevations) are wrought by endogenic forcing, that is, forcing that comes from the mantle and drives tectonics, including plate motions. In addition, there is astronomic forcing, which works through the Earth’s orbital features, through impact, or by cosmic radiation. Milankovitch forcing is orbital and modifies solar forcing. Apparently it is responsible for much of the ice-age fluctuations. Exogenic (solar) forcing directly involves the radiation balance (which is part of the everyday climate system), that is, the equilibrium between incoming solar heat and outgoing radiation from the Earth, an equilibrium that keeps the planet at a given average temperature (Fig. 9.1). The latest (and most rapid) of changes are from human activities, presumably to be counted as “exogenic” since they work by enhancing solar input (i.e., blocking output of heat radiation to space). The changes are commonly (quite properly) categorized as “anthropogenic,” emphasizing human causation.