Glacial Deposits
- Dropstones:
- These are curious-looking boulders ound in sedimentary deposits. They measure up to ten feet (3 meters) in diameter. It is believed that they were carried on drift ice and deposited where the ice melted. This place may have been covered by the sea at one time.
- Drumlins:
- These are aligned, elongated hillocks created from thick deposits of glacial till. They are composed of clay till and, sometimes, sand and gravel sediments. They are steepest on the side facing the glacier, and gently sloping on the other side.
- Erratic Boulders:
- These are rocks ranging in size from pebbles to massive boulders that have been strewn in mountainous regions. They have been carried by glaciers for 500 or more miles (800 km). An indicator boulder is a glacial erratic of known origin used to locate the source area and the transport distance of any given glacial till. A boulder fan is a fan-shaped area containing distinctive erratics.
- Eskers:
- These are long, narrow ridges of stratified glacial meltwater deposits of sand and gravel. They usually occur in areas once occupied by the ground moraine of a continental glacier. In length, they may extend up to 500 miles (800 km). However, they are seldom more tha 1,000 feet (303 meters) in width and 150 feet (45 meters) in height.
- Frost Polygons:
- These are seen as snow retreats in Arctic and alpine regions where the soil is exposed to seasonal freezing and thawing cycles. They create a honeycomb network. The shapes are a wide range of sizes, depending on their composition.
- Glacial Varves:
- These are regularly banded deposits, developed by cyclic sedimentation, with fine-grained, dark laminae alternating with coarse-grained lighter layers. They develop on the floors of cold freshwater lakes that are fed by glacial meltwater streams.
- Kames:
- These are low, conical mounds of stratified sand and gravel at the end of an ice sheet or the margin of a melting glacier. They form in similar places as eskers.
- Loess Deposits:
- These are windblown sediments that have accumulated in thick deposits of a finely-grained, loosely consolidated sheets. They are made up of particles of quartz, feldspar, horneblende, mica, and clay. They lie downwind from glaciated areas. Dune deposits of desert sand are found with them.
- Moraines:
- These are accumulations of rock material carried by a glacier and deposited in a regular pattern. The material ranges from sand to boulders. Ground moraine is an irregular layer of till deposited under a glacier. A terminal moraine is a ridge of debris deposited at the forward melting point of a glacier. A lateral moraine is the debris from erosion and avalanches along the edges of a glacier.
- Tillites:
- Glacial till is nonstratified material deposited directly by glacial ice. It is made up of clay and medium boulders. Tillites are sedimentary rocks formed by the compacting and cementing of glacial tills.
