The Holly Jolly of December. Precambrian Era ENVIRONMENT Climatic conditions

A major factor controlling the climate during the Precambrian was the tectonic arrangement of continents. At times of supercontinent formation (at 2.5 billion, 2.1 to 1.8 billion, and 1.0 billion to 900 million years ago), the total number of volcanoes was limited; there were few island arcs (long, curved island chains associated with intense volcanic and seismic activity), and the overall length of oceanic spreading ridges was relatively short. This relative shortage of volcanoes resulted in low emissions of the greenhouse gas carbon dioxide (CO2). This contributed to low surface temperatures and extensive glaciations. In contrast, at times of continental breakup, which led to maximum rates of seafloor spreading and subduction (at 2.3 to 1.8 billion, 1.7 to 1.2 billion, and 800 to 500 million years ago), there were high emissions of CO2 from numerous volcanoes in oceanic ridges and island arcs. The atmospheric greenhouse effect was enhanced, warming Earth’s surface, and glaciation was absent. These latter conditions also applied to the Archean Eon prior to the formation of continents.