ICE AGE

also called Glacial Age, any geologic period during which thick ice sheets cover vast areas of land. Such periods of large-scale glaciation may last several million years and drastically reshape surface features of entire continents. A number of major ice ages have occurred throughout Earth history. The earliest known took place during Precambrian Time dating back more than 570 million years. The most recent periods of widespread glaciation occurred during the Pleistocene Epoch (1,600,000 to 10,000 years ago). A lesser, recent glacial stage called the Little Ice Age began in the 16th century and advanced and receded intermittently over three centuries. Its maximum development was reached about 1750, at which time glaciers were more widespread on Earth than at any time since the principal Quaternary Ice Ages.