Depositional Landforms

Formation

• Forms when a huge sheet of ie detaches from a glacier and melts in place leaving behind its load of unsorted gravel, mud and rock spread over a wide area
• According to the National Snow and Ice Reference centre, glacial till can form the basis for good farmland

Key Processes

• Fracturing of till sheet
• Basal sliding/deformation and lineation production (superimposed on till slab)
• Thawed- detatchment and sliding/deformation
• Frozen- Locked interface till/bedrock

Features and Characteristics

• A large relatively flat plain of till
• Sometimes the sediments in a till plain can contain large boulders. If these boulders are transported a great distance from their place of origin they are called erratics.
• An example is Northern Ohio.

Formation

• Glacial erratics are stones and rocks that were transported by a glacier and then left behind after the glacier melted

Key Processes

• The pieces of material which become erratics erode from a different landform
• These pieces are deposited away to an alternate area.

Features and Characteristics

• Erratics can be carried for hundreds of kilometers
• Erratics can range in size from pebbles to large boulders
• Scientists sometimes use erratics to help determine ancient glacier movement

Formation

The ice at the bottom of a glacier becomes overloaded with debris. This reduces its capacity to carry debris and deposition then occurs at the ice. Once this material has been deposited, it is streamlined by further ice advance. There could also be pre-existing sediment (older till from a previous glacial advance, for example) that is caught up in the streamlining process.

Key Processes

• Net subglacial deforming bed erosion
• Glacier moves over potentially deformable bed, coupling between glacier and underlying sediment- cakked subglacial glaciotectonic deformation

Features and Characteristics

• Vary widely in shape -> typically 5-25m in height and o.1 to 5km long. Extreme = 100m high, 100m wide
• Often occurs in groups (Basket and Eggs Topography)
• Occurs widely within moulded and streamlined scenary of Scottish Central Lowlands
• Examples are Around Horicon Marsh, Wisconsin, USA and South of Kendal, Lake District

Formation

• Lateral- glacier scraps along tearing off rock and soil from both sides of its path
• Medial- Formed when two glaciers meet- two lateral moraines from different glaciers pushed together
• Supraglacial- Lateral and medial can become supraglacial made of rocks and earth fallen on glacier from surrounding landscape
• Terminal- Debris that is scooped up and pushed to the front of the glacier depositedas large clumps of rocks, soil and sediment

Key Processes

• Abrasion forms lateral and deposition formes terminal

Features and Characteristics

• Material left behind by moving glacier (usually rock, soil)
• Scientists study terminal moraines to see where glaciers flowed and how quickly it moved
• Lateral leaves slight ridge on side when ice melts
• Example is Franz Josef, New Zealand (Terminal Moraine 430m high)