Raet is the largest terminal moraine in Scandinavia. It was formed during the end of the last glacial period, 12,800–11,500 years ago, in one of the latest advances of the glaciers. As the glacier retreated towards the end of this period, it could stop for hundreds of years before moving forward again. Material that the glacier brought from the inland, such as particles of rocks, gravel, sand and clay, gathered where the edge of the ice laid still for some time. Such deposits, which are partly deposited on land and partly in ocean, are called terminal moraine.