WILLIAM PENGELLY CAVE STUDIES TRUST

The Ice Age

Devon's geographic situation placed it south of the ice sheets but the climate was severe. Biting winds swept the permanently frozen ground where only grasses, sedges, dwarf birches and arctic willows grew. This tundra landscape became the home of Reindeer, Mammoth, Woolly Rhinoceros and Wolverine, the remains of which have been found in Kents Cavern Torquay and Tornewton Cave near Totnes.

At the start of the Pleistocene Period, 1.5 millions years ago, the climate of the Northern Hemisphere began to deteriorate and the Polar ice caps gradually spread southward over Europe, The Great Ice Age had begun. Why the earth's climate should change so dramatically has been the subject of intense research and the generally accepted theories attribute these changes to variations in the earth's orbital geometry.

As it became warmer ice retreated northwards and grasses, sedges and forests gradually replaced the tundra. Forests of Firethorn and Oak flourished providing food and shelter to Straight-Tusked Elephant, Hippopotamus, Rhinoceros, Deer and Bison. This was the setting around the Dart Valley 100 000 years ago and the remains of these animals can be seen in Joint Mitnor Cave.

There were twenty major phases of intense cold known as the Glacial Periods, during which vast sheets of ice up to a 1000 metres thick spread over Britain as far as the Thames Valley and Bristol Channel.

These Glacials were seperated by short-lived warmer periods - The Interglacials, when the ice melted and retreated northwards.

River Terraces

River Terraces were created by the building up of river gravel beds.

When the sea-level rose the river flow became slower, depositing sheets of gravel (1); then, during the glacial periods the sea-level fell and the river cut down into the gravel leaving a terrace on either side (2). As the sea-level lowered in each succesive phase throughout the Ice Age a series of terraces were formed, of which the highest is the earliest (3, 4, 5).

The Huge Quantities of water locked up in the ice sheets depleted the sea. So during the Glacial periods the sea level dropped by up to a hundred metres.

During the warm Interglacial periods the ice melted and released the water back into the sea and the sea level rose.

The corresponding changes in the shore level created Raised Beaches.