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What is a Drumlin?

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Drumlin's meaning is quite simple. Drumlins are elongated, oval-shaped or say teardrop-hills of rock, sand, and gravel. A drumlin is by and large made up of glacial drift, formed underneath an ice sheet or moving glacier and oriented in the direction of ice flow. There are no strict specifications with respect to the size of a drumlin but they tend to be up to a few kilometers up to 2 kilometers long and up to 50m in relief.


How Do Drumlins Form?

Drumlin glacier develops in the form of clusters apparently close to the terminus of glaciers. The mechanisms of formation are though disputed. They seemingly have significant interpretive value for rate and direction of glacial movement.

Drumlins are usually found in wide-ranging lowland regions, with their long axes approximately parallel to the path of glacial flow. Though they are observed in a multitude of shapes, the glacier side is always steep and high, while the lee side is tapered and smooth mildly in the direction of ice movement. Drumlins can hugely differ in size, with lengths from 1 to 2 km, heights from 50 to 100 feet, and widths from 400 to 600 m.


Regions of Formation of Drumlins

They are extensive in formerly glaciated regions and are particularly copious in Canada, Finland, Ireland, and Sweden.

Besides, Drumlins are mostly found in clusters with their numbering counting in the thousands. Often organized in belts, they impede drainage such that the small lakes and swamps may form between them. Large drumlin fields are situated in central New York and central Wisconsin; in northwestern Canada; and southwestern Nova Scotia.


Composition of Drumlins

Most drumlins are made up of till, but they may differ largely in their composition. Some contain substantial amounts of gravel, whereas others are composed of rock underlying the till surface (rock drumlins). Drumlins are most commonly linked with smaller, glacially streamlined bedrock forms referred to as roches moutonnées.


Eskers

Eskers are the geological structures that are formed when the glacial melted water carries the sediments and deposit through subglacial tunnels. Thus, they can give relevant information with regard to the shape and dynamics of glaciers and ice sheets whereas Drumlins are developed when the ice sheets move in streamline over the rock residue. These are elongated, oval shaped hills.


Drumlins and Eskers

Drumlins and Eskers by definition may seem similar, but there are still certain differences that you need to know about. These are as follows:-

Point of Difference

Drumlins

Eskers

Definition

Drumlins are described as both depositional and erosional landforms, though a depositional development emerges to be most common.

With the glaciers retreat the point of emergence for the water upstream leaves a narrow trail of sediment deposition, which emerges in the form of eskers.

Structure

These structures form in elongated drumlin landforms, in the direction of ice flow

Eskers are deposits of glaciofluvial from sediment carrying subglacial tunnels

Size

Drumlins are a few kilometres in length, width of a few hundred metres and a height of tens metres

Eskers may range from a few hundred feet to tens of miles in length, from 160 to 1,600 feet in width, and 16 to 160 feet in height.

Formation

These structures are created beneath the ice and are not formed by running water and sediment transport

These forms as the water appears from a tunnel at the bed of a glacier or an ice sheet and thus slows down. Because the sediment movement is dependent on the water velocity, the sediment will be deposited and the outcome is a highly localized deposition.


Bedrock

Bedrock, the sediment of solid rock which is essentially buried beneath the soil and other splintered or segregated substances (regolith). Bedrock is composed of igneous, metamorphic or sedimentary rock, and it often caters to as the parent substance (the source of rock and mineral particles) for soil and regolith. In Earth’s nitrogen cycle, bedrock is also a source of nitrogen. A bedrock accumulation which takes place at Earth’s surface is known as an outcrop.

FAQ (Frequently Asked Questions)

1. What is Meant By Kames?

Answer: Kames refers to the hummocky terrain which is formed by the substance that has been carried by glacier meltwater. The reason for the formation of hummocks is that when the sediments are being accumulated, loaves of ice get buried by the sediments and when that ice is melted a hummocky terrain is formed. A key here is that the accumulation of sediments from sediment transport would not be able to develop the erratic hummocky terrain as a principal feature, there need to be several other processes involved. Kames are thus generally a broad-range landform that does not mandatorily contain a preferred extension. As with eskers, the emergence of the water and sediment remains similar, the base of the glacier.

2. What are the Theories Associated With the Formation of Drumlin Landform?

Answer: Due to the inaccessibility of glacier beds no one has been able to notice a drumlin actively forming and so it will apparently be no surprise if their formation remains somewhat a mystery.


As a hypothesis, drumlins may have occurred by a successive build of sediment to develop the hill (i.e. accumulation or accretion) or pre-existing sediments may have been exhausted in regions leaving debris hills (i.e. erosion), or perhaps a process that smears these distinctions.


Observations of the nature of the bed of present-time ice sheets have exposed that the forward motion of ice, can in part, be attained by deformation of the smooth, soft sedimentary bed.


This resulted in the deforming of the bed model of glacier flow, which has further become the most widely accepted, but still unproven, process for the formation of drumlin. If the sediments of the bed are weak they may deform simply as an outcome of the shear stress executed by the overlying ice.