Chapter 4 Summary and Analysis

When the Wisconsinan Glaciation finally ended about 18,000 years ago, global warming begins. Glaciers melt, sea levels rise dramatically, and streams become raging rivers. In Europe, Britain is separated from the European Continent by the English Channel; ice disappears from Central Germany and most of Russia; the Alps recede. To our Stone Age ancestors, this is welcome relief. The climate has warmed before, but the warmth has never been so persistent. People begin to migrate toward the north and south poles.

About 12,000 years ago, however, an ice sheet about the size of a large Canadian province slides into the North Atlantic Ocean, causing disastrous waves and reducing temperatures to glaciation time levels. This event, known as the Younger Dryas, causes more than 1,000 years of cooling. By 10,000 years ago, temperatures begin to warm again. This warm period is called the Holocene Epoch, although...