LANDFORMS OF GLACIATION

During the Pleistocene period, approximately 30,000 years ago, colossal ice sheets covered extensive temperate latitudes, spanning 12 million square miles and transforming landscapes across North America, Europe, Greenland, and the high mountains of Eurasia. Today, remnants of these frozen giants persist in major ice caps, notably Greenland (covering 720,000 square miles) and Antarctica (encompassing 5 million square miles).

1. Formation and Characteristics of Glaciers

• Marie Byrd Land in Antarctica boasts an ice cap reaching a staggering 14,000 feet in thickness.
• From the central dome of these ice caps, glaciers radiate outward, creeping in all directions.
• Glacial ice sheets reach polar waters, forming ice shelves that extend into the ocean.
• These shelves, eventually breaking into icebergs, only reveal a fraction (1/9th) of their mass above the water's surface.
• The process of glaciation is intricately tied to the snowline, varying in height from 9,000 feet for the Alps to 17,000 feet for Mount Kilimanjaro.
• Snow accumulation, melt, and refreezing contribute to the formation of hard granular masses known as neve (French) or firn (German).
• Gravity then guides this neve toward valleys, initiating the flow of glaciers or ice rivers.

2. Types of Glaciers and Their Movement

• Glaciers, broadest at their source and tapering like tongues, are not liquid but exhibit movement under pressure.
• This movement is most pronounced in the middle, with friction restraining the sides and bottom.
• The velocity of glacier movement varies, ranging from 3 feet per day in the Alps to 50 feet per day in Greenland and a few inches per day in Antarctica.
• One of Europe's longest glaciers, the Aletsch Glacier in Bernese Oberland, Switzerland, spans 10 miles but is surpassed in size by glaciers in Alaska and the Himalayas.
• Piedmont glaciers, formed at the foot of mountain ranges, converge to create extensive ice masses, exemplified by the Malaspina Glacier (65 miles long, 25 miles wide, and covering 1,600 square miles).

3. Landforms of Highland Glaciation

 The glacial processes manifest in distinctive landforms resulting from erosion and deposition:

Erosional Features

• Corrie, Cirque, or Cwm: Glacial movement carves depressions in upland slopes, evolving into steep, horseshoe-shaped basins with corrie lakes or tarns at their base.
• Arete or Pyramidal Peak: Conjoined peaks form pyramidal structures, such as Striding Edge on Helvellyn in Westmorland or the Matterhorn in Switzerland.
• U-shaped trough: Glacial erosion sculpts valleys with wide, flat floors, deepening them and blunting interlocking spurs, creating truncated spurs. Trough lakes like Loch Ness and Lake Ullswater exemplify this form.
• Hanging Valleys: Main valleys erode faster than tributaries, leaving hanging tributaries above, potentially forming sources of hydropower.

Depositional Features

• Moraines: Rocks transported by glaciers result in lateral, end (terminal), or medial moraines.
• Fjords: Steep-sided inlets, like those on the Norwegian and South Chilean coasts, form when the lower end of a glacial trough is submerged by the sea.

4. Landforms of Glaciated Lowlands

 Depositional features shaped by valley glaciers and continental ice shelves include:

• Residual Hummocks: Roche Moutonnees are Smooth on the upstream side and rough on the downstream side, resembling sheepskin wigs.
• Protective Rock Formations: Crag and tail are hard rock formations with steep upstream slopes protecting softer leeward slopes from erosion.
• Unsorted Glacial Deposits: Boulder Clay and glacial Till are Extensive sheets of unsorted glacial deposits, contributing to featureless landscapes, such as those in East Anglia and Northern Mid-West USA.
• Stranded Boulders: Erratics are Boulders stranded after glaciers melt, composed of materials different from the local region. Perched blocks are sizeable rocks left atop moraines or Roche moutonnees.
• Distinctive Ridge Structures: Drumlins are Elongated, oval hummocks, resembling whalebacks, composed of boulder clay with steeper onset sides and tapering leeward ends.
• Sinuous Meltwater Ridges: Eskers are Long, sinuous ridges of sand and gravel, indicating sub-glacial meltwater stream paths.
• Terminal Features: Terminal Moraines are Accumulations of rock debris at the furthest extent of glacier movement, like the Baltic Heights in the North European Plain.
• Outwash Plains are Fluvio-glacial deposits washed from terminal moraines, forming plains with kames (small hillocks) and kettle topography when collapsed kame deltas create depressions.

5. Impact on Human Activities

The geological legacy of glaciation profoundly influences human endeavours:

• Agricultural Implications: Regions with glacial histories exhibit diverse soil conditions, from thin and barren surfaces to fertile glacial lake beds. Erratics can obstruct farming, while former glacial lake beds support heavy cropping.
• Cultural and Economic Significance: Glacially carved valleys and gaps, like the Hudson-Mohawk Gap, serve as natural routes connecting interior regions to coastal areas. Eskers, kames, and outwash plains are excavated for sand and gravel, essential resources for construction and metal casting.
• Environmental Recreation: Glacial landscapes, especially in Scandinavia, Switzerland, and Canada, attract tourists for activities such as skiing, mountain climbing, and sightseeing.
• Hydropower Generation: Regions with abundant glacial features, like Scandinavia, Switzerland, and Canada, utilize glacial meltwater streams and waterfalls to harness hydropower for industries.