Glaciation refers to the process during which large areas of the Earth's surface are covered by ice sheets and glaciers. This phenomenon occurs when temperatures drop significantly over long periods, allowing snow to accumulate and compact into ice. Glaciation has shaped many landscapes, creating features such as valleys, fjords, and lakes. During the last major glaciation, known as the Last Glacial Maximum, which occurred around 20,000 years ago, vast regions of North America and Europe were covered by ice. As the climate warmed, these glaciers began to melt, leading to rising sea levels and changes in ecosystems. Glaciation plays a crucial role in understanding Earth's climate history.