best ias books

Landforms of Lowland Glaciation

Most of the glaciated lowlands have depositional features, but where rock masses project above the level surface, they result in striking features of erosion.

Roche Moutonnee

  • Basically a resistant residual rock hummock or mound, striated by the ice movement
  • Its upstream or stoss side is smoothened by abrasion & its downward or leeward side is roughened by plucking & is much steeper.
  • It is believed that plucking may have occurred on leeward side due to a reduction in pressure of the glacier moving over the stoss slope
  • Therefore providing the opportunity for water to refreeze on the lee side and pluck the rock away.

Roche Moutonnee


Crag & Tail

  • A crag and tail is a larger rock mass than a Roche moutonnee
  • Like a Roche moutonnee, it is formed from a section of rock that was more resistant than its surroundings.
  • Crag is a mass of hard rock with a steep slope on the upward side, which protects the softer leeward slope from being completely worn down by the oncoming ice.
  • It therefore has a gentle tail strewn with the eroded rock debris.

Crag & Tail


Boulder clay or Glacial till

  • This is an unsorted glacial deposit comprising a range of eroded materials such as boulders, sticky clays & fine rock flour.
  • It is spread out in sheets, not mounds, & forms gently undulating till or drift plains with monotonous landform.
  • The degree of fertility of such glacial plains depends very much on the composition of the depositional materials.

Boulder clay or Glacial till


Erratics

  • Boulders of varying size that are transported by ice & left stranded in the regions of deposition when the ice melted.
  • Called erratics because they are composed of the materials entirely different from those of the regions in which they have been transported.
  • Useful in tracing the source & direction of ice movements but their presence in large numbers causes hindrance in farming.
  • Also known as perched blocks as sometimes they are found perched in precarious positions as the ice dropped them.

 


Drumlins

  • Elongated whale back type hummocks composed wholly of boulder clay with elongation in the direction of ice flow i.e. on the downward side.
  • They are low hills upto 1.5 km long and 60 mm tall & appear steeper on the onset side & taper off at leeward side.
  • They are arranged diagonally & commonly referred as basket of eggs topography.

Drumlins


Eskers

  • Eskers are the sinuous ridges composed of glacial material mainly sands & gravel deposited by meltwater currents in glacial tunnels
  • Glacial tunnels marks the former sites of sub glacial melt water streams
  • Their orientation is generally parallel to the direction of glacial flow, and they sometimes exceed 100 kilometres in length.

Eskers


Outwash Plains

  • Made up of fluvio glacial deposits washed out from the terminal moraines by the streams of stagnant ice mass.
  • The melt waters sort & redeposit the material mainly consisted of layers of sand and other fine sediments.
  • Such plains with their sandy soils are often used for specialized kinds of agriculture, such as the potato.

 


Kettle lake

  • A depressions formed when the deposition takes place in the form of alternating ridges
  • Shallow, sediment filled body of water formed by retreating glaciers

kame & kettle topography


Kames

  • Small rounded hillocks of sand & gravel which cober part of the plain
  • Kames are often associated with kettles, and this is referred to as kame & kettle topography

Leave a Reply

Your email address will not be published. Required fields are marked *

*

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>