Glacial Deposition Landforms & Landscapes (Edexcel A Level Geography)

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Jacque Cartwright

Written by: Jacque Cartwright

Reviewed by: Bridgette Barrett

Glacial Deposition

  • When debris is deposited by the ice mass and not meltwater, it is called ice contact deposition

  • During the warmer summer months, glaciers begin to melt, and glacial till is deposited on the valley floor or sides of a moving glacier

  • Till is unsorted, irregular debris ranging from clay to stones to boulders of any size and shape

  • Features of ice contact deposition include erratics, moraines, and drumlins

Erratics

  • Erratics are random boulders of different sizes and types from the area where they are found

  • There is no pattern to their deposition, and they look completely out of place on the landscape

  • Glaciers pick up large rocks and carry them hundreds, sometimes thousands of kilometres from where they originate 

    • Erratics from Scandinavia have been found in boulder clay of the North East of England coastline

  • Erratics are carried deep in the ice and do not erode the same as till at the edges of the glacier

  • An example is the Great Stone of Fourstones, (Big Stone) on the moors of Tatham Fells, England

great-stone-of-fourstones
The Great Stone of Fourstones - erratics are random rocks that vary in size!

Moraines

  • Unsorted glacial till that is deposited in mounds are called moraines

  • Moraines are termed from their position on the glacier:

    • Terminal: Material deposited at the snout of the glacier

    • Lateral: Material is deposited along both sides of the glacier

    • Medial: Ridge of deposited material in the middle where two glaciers meet and continue to flow downhill together

    • Ground: Material dragged under the base of the glacier and deposited over a wide area on the valley floor

    • Recessional: They show the point of glacial retreat

    • Push: They form if the glacier advances after retreat

types-of-moraines
Main types of moraines

Drumlins

  • Drumlins are elongated, egg-shaped hills and made of glacial till

  • They form beneath the glacier when the glacier meets an obstruction and material is deposited as a ground moraine  

  • The moraine is then shaped by the moving ice, which follows the direction of the flow of ice

  • The largest ones can be over 1km in length, 0.5km wide, and 50m high

  • Multiple drumlins are known as swarms or baskets of eggs

  • As the material is deposited it builds up to have a round, blunt, and steep front (stoss) end 

  • The flow of ice over the top of the drumlin drags the material along and down creating the lee slope

  • The lee is gently sloped, elongated, and with a tapered tail 

  • The more elongated the drumlin the faster the ice was flowing

  • Examples include The Drumlin Field below Cam Fell in the Yorkshire Dales and Conway Valley, North Wales

drumlin

Lowland Deposition Features

  • Lowland ice contact depositional features include:

    • Till plain

    • Lodgement till

    • Ablation till

Till plains or ground moraine

  • When the ice mass retreats during the warmer months, till is deposited over a vast area across the valley floor 

  • Meltwater will also flow out of the glacier's snout forming meltwater rivers

  • These rivers carry large amounts of glacial till, which will undergo further erosion through attrition to become outwash 

  • This finer till is sorted and when the energy of the river reduces, the outwash is deposited in layers further down the valley on the outwash plain

Hogt~jhM_till-and-outwash
Glacial till                  Glacial outwash plain

Lodgement till

  • Found mainly with slow-moving glaciers which carry more debris sub-glacially

  • Lodgement till is subglacial unconsolidated material that is forced, or 'lodged' into the bedrock below

Ablation till

  • Ablation till includes supra and englacial material deposited as the glacier melts

transportation-of-glacial-till
Transportation of glacial till

Former Ice Extent Reconstruction

  • Landforms of glacial deposition are useful in understanding the direction and extent of ice cover - striations are deepest at initial point of contact

  • It also provides a record of past glacial changes over a longer timeframe than current observational records

  • Past temperatures and levels of precipitation can be measured with ice cores, indicating past glacial climates

  • Orientation of the landform can indication glacial direction and upland or lowland landforms can be a good indicator of actual ice mass - crag and tail as a macro feature needing a large ice mass to deform around resistant rock rather than flow over as in the meso landform of roches moutonnées 

  • Debris analysis can indicate distance travelled, as in the case of the Scandinavian erratics; or the rate of travel as in drumlin swarms, as slow moving glaciers carry more till

  • Morainic ridges indicate edges of ice sheets or glacial snouts in instances of glacial retreat

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Jacque Cartwright

Author: Jacque Cartwright

Expertise: Geography Content Creator

Jacque graduated from the Open University with a BSc in Environmental Science and Geography before doing her PGCE with the University of St David’s, Swansea. Teaching is her passion and has taught across a wide range of specifications – GCSE/IGCSE and IB but particularly loves teaching the A-level Geography. For the past 5 years Jacque has been teaching online for international schools, and she knows what is needed to get the top scores on those pesky geography exams.

Bridgette Barrett

Author: Bridgette Barrett

Expertise: Geography Lead

After graduating with a degree in Geography, Bridgette completed a PGCE over 25 years ago. She later gained an MA Learning, Technology and Education from the University of Nottingham focussing on online learning. At a time when the study of geography has never been more important, Bridgette is passionate about creating content which supports students in achieving their potential in geography and builds their confidence.