Pub. date: 2008 | Online Pub. Date: April 25, 2008 | DOI: 10.4135/9781412963893 | Print ISBN: 9781412958783 | Online ISBN: 9781412963893| Publisher:SAGE Publications, Inc.About this encyclopedia
Andrew J. Waskey
THERE ARE IDENTIFIABLE cycles in the weather patterns of the Earth. There are four seasons every year in the temperate zones. In the polar regions, there are seasons of light and dark, and in the tropical regions, there are seasons of wet monsoons and dry periods. These identifiable annual cycles are like the cycles of the climate of the Earth over vast eons of the geologic eras. Geologists estimate the age of the Earth at about 4 billion years old. For much of that time, it was a ball of gas, then the scene of enormous volcanic activity, and then weather activity dominated the whole of the Archaic or Pre-Cambrian eras of Earths history. During that time, repetitions of climate patterns may have occurred, but there were also dramatic changes. There was a time when oxygen came to be a major part of the atmosphere, when it was not as ...