Glacial Deposition

How the Ice Transports and Deposits material

Glaciers transport material (load) in three ways:

• Onglacial: carried on top of the glacier as it is eroded from the valley sides
• Englacial: material that has fallen through crevasses in the glacier
• Subglacial: material that is transported along the base of the glacier as it has become embedded in it

Landforms of Glacial Deposition

Moraine

Example: Glengesh, Co. Donegal

• A moraine is a long ridge of unsorted boulder clay formed by deposition, melting, mass movement, and freeze-thaw action.
• Lateral moraines form along both sides of a glacial valley as debris accumulates from the glacier's sides.
• Medial moraines occur when two lateral moraines merge in the center of a valley, creating a ridge.
• End or terminal moraines mark the furthest point reached by the glacier during its advance.
• Ground moraines consist of material found beneath the glacier, left behind as the glacier melts.

Drumlin:

Example: Clew Bay, Co. Mayo

• Drumlins are oval-shaped hills consisting of boulder clay.
• They are made of unstratified material and are impermeable.
• Drumlins indicate the direction of glacier movement.
• On OS maps, drumlins appear as small hills that are less than 50 meters high.

Erratics

Example: granite from Connemara found in the Burren, Co. Clare

Processes: deposition, plucking, melting

• Material transported by the glacier and are said to be 'out of place' when deposited
• Range from huge boulders to smaller rocks and pebbles