How drumlins are formed?
Drumlins. DRUMLIN An oval-shaped hill, largely composed of glacial drift, formed beneath a glacier or ice sheet and aligned in the direction of ice flow. Their formation remains controversial (see below) but in spite of this they are extremely useful for reconstructing former ice sheets.
A glacial erratic is a piece of rock that differs from the size and type of rock native to the area in which it rests. "Erratics" take their name from the Latin word errare (to wander), and are carried by glacial ice, often over distances of hundreds of kilometres. They can be transported by ice rafting.
- An erratic is a piece of rock that has been eroded and transported by a glacier to a different area; it is left behind when the ice melts. Glacial erratics give us information about the direction of ice movement and distances of transport.
- A terminal moraine, also called end moraine, is a type of moraine that forms at the snout (edge) of a glacier, marking its maximum advance. The moraine is left as the marking point of the terminal extent of the ice.
- Drumlins are generally found in broad lowland regions, with their long axes roughly parallel to the path of glacial flow. Although they come in a variety of shapes, the glacier side is always high and steep, while the lee side is smooth and tapers gently in the direction of ice movement.
Glacial erratics. Definition: An erratic is a boulder transported and deposited by a glacier having a lithology different than the bedrock upon which it is sitting. Erratics are useful indicators of patterns of former ice flow. Of rock or sand reposeth, there to sun itself."
- End moraines are irregular ridges of glacial sediments that form at the margin or edge of the ice sheet. These landforms represent a stillstand of the ice, having formed as the ice margin remained in one position while internally the ice was bringing sediment forward and continuously depositing it at the margin.
- ALL GLACIAL DEPOSITS are DRIFT. Glaciers are powerful enough to carry tiny and huge rock debris, and when they drop it, the ice drops it indiscriminantly. Thus, material deposited by ice is unsorted or mixed in size. This non-sorted material is called TILL.
- Some of this debris is deposited at the edge of the corrie, building up the lip. These processes create a characteristic rounded, armchair shaped hollow with a steep back wall. When ice in a corrie melts, a circular lake is often formed at the bottom of the hollow.
Updated: 26th October 2019