Age : Present to 1.8 million years ago
The Quaternary, also known as the Ice Age, comprises a series of periods of widespread glaciation separated by more temperate climatic conditions (interglacials). There have been at least seven glacial-interglacial cycles, although only the last three or four of these have resulted in ice sheets spreading across Britain. During the ice ages, glaciers developed in upland areas such as the Lake District, carving out U-shaped valleys and at times large ice sheets advanced over lowland Britain. Areas beyond the ice sheet margins were much like the Arctic tundra. The climate of the interglacials was temperate, similar to that of today and at times warmer.
At the time of glacial maxima, sea-level was up to 120m lower and the English Channel and most of the North Sea were land. As ice melted sea-level rose, which at times would have been higher than it was today resulting in the formation of raised beaches around the coast.
During the warmer interglacials the fauna resembled that of modern-day Africa with hippopotamus, elephant, hyena and lion being present in southern Britain. During the cold glacial episodes woolly mammoths, woolly rhinoceros and reindeer roamed over much of southern England.
Vast amounts of sediment were eroded and transported by the actions of ice, water and wind during the Quaternary. Typically, material deposited from beneath glaciers and ice sheets, known as till or boulder clay, mantles the surface rocks of much of northern England and the midlands. Following the melting of ice sheets and glaciers large volumes of sand and gravel were transported along river valleys or deposited along the margins of the ice bodies. In some areas large ice-dammed lakes formed in which clays and sands were laid down. In southern England, away from the main ice sheets, the processes of freezing and thawing led to the formation of dry valleys on the Chalk and limestone outcrops and the deposition of weathered material in valleys.