This video is part three of a four part series. As glaciers reach lower altitudes, temperatures rise and ice begins to melt. As this happens the ice cannot carry as much material so this is deposited. The main deposition features of glaciers are called moraines. These long, dark bands of debris are visible on top and along the edges of glaciers.
The material on the sides of the glacier are called lateral moraines. Where two glaciers merge, their lateral moraines meet in the middle of the larger combined glacier to form a medial moraine. The material deposited at the terminus of a glacier is called a terminal moraine. The terminal moraine may act as a dam for a ribbon lake.
Glaciers deposit a mixture of unsorted clay, sand, stones and boulders. The stones are angular because they have not yet been rounded by fluvial processes. This material is known as till. Glaciers deposit till on valley floors to form ground moraines. Ground moraines often have a hummocky appearance and can go on to form rolling hills and plains.
Another deposition feature is an erratic. An erratic is a boulder transported and deposited by a glacier having a lithology (rock type) different than the bedrock upon which it is sitting on.
Glaciers leave oval mounds of till called drumlins that range from 1 to 2 km long. They are commonly found in clusters.
Another feature is rock flour. This is a very fine sediment. Many glacial lakes such as Lake Pukaki near Mount Cook have a milky turquois colour due to glacial rivers washing this sediment in to them.
This video was filmed in the South Island of New Zealand.
30 сен 2024
