An ice age is a long period in Earth's history when temperatures drop significantly, leading to the expansion of ice sheets and glaciers. These cold periods can last for millions of years and are characterized by lower global temperatures and changes in climate. The most recent ice age, known as the Quaternary Ice Age, began around 2.58 million years ago and continues today, with alternating glacial and interglacial periods. During an ice age, large areas of land, especially in the polar regions, become covered in ice. This can affect sea levels, ecosystems, and the distribution of plants and animals. The last major glacial period of the Quaternary Ice Age peaked about 20,000 years ago, when vast ice sheets covered parts of North America and Europe.