Glacial till is a heterogeneous mixture of unsorted and unstratified sediment deposited directly by glacial ice. It is characterized by its unique properties and features, which can be used to distinguish it from other types of sediment.
1. Texture and Composition:
* Unsorted: Till contains a wide range of particle sizes, from clay and silt to boulders.
* Unstratified: The sediment is not layered or sorted by size.
* Angular and Subangular: The particles are often angular or subangular, due to the grinding action of the glacier.
* Variety of Rock Types: Till can contain a diverse range of rock types, reflecting the geology of the area where the glacier originated.
2. Physical Characteristics:
* Clayey Matrix: Till often has a clayey matrix that binds the larger particles together.
* Dense and Compact: The sediment is typically dense and compact, due to the weight of the overlying ice.
* Poorly Drained: Till can be poorly drained, leading to the formation of wetlands or bogs.
3. Morphological Features:
* Drumlins: Elongated hills of till that are streamlined in the direction of ice flow.
* Eskers: Winding ridges of till deposited by meltwater flowing within or beneath the glacier.
* Kames: Conical hills of till deposited by meltwater in depressions on the glacier surface.
4. Field Observations:
* Location: Till is typically found in areas that were once glaciated, such as the northern United States, Canada, and Europe.
* Landform: The presence of glacial landforms, such as drumlins, eskers, and kames, can indicate the presence of till.
* Soil Profile: Till soils are often poorly developed, with a thick layer of unsorted sediment.
5. Laboratory Analysis:
* Grain Size Analysis: Can determine the range of particle sizes in the sediment.
* Mineralogical Analysis: Can identify the different rock types present in the till.
* Geochemical Analysis: Can provide insights into the origin and transport history of the till.
Note: It is important to consider the context of the location and the surrounding geology when identifying glacial till. Other types of sediment, such as alluvium or colluvium, can sometimes resemble till.
