Glaciers modify earth surface by degradation and aggradation; typical landforms are produced by glacial erosion and deposition.
After the glacial ice melts, streams are formed and certain landforms are produced by the combined action of both river and glacier which are termed as pro-glacial or fluvio-glacial landforms.
(i) Glacial valley:
In contrast to river valleys, the glacial valleys are broad with relatively smooth and steep sided walls – forming ‘U’ shaped vallyes.
(ii) Hanging valley:
The base of the tributary glaciers generally lie at a higher level than the trunk glaciers because of lower eroding capacity. After snow melts away, the valley floor of the tributaries exist much above the floor of the trunk valley. This gives rise to hanging valleys with steep cliffs which in many instances form water falls.
One of the most typical features of all mountain glaciers is the development of amphi-theatre like depressions at the head of the glaciers with that of the snow field due to head ward erosion. These depressions are cirques, corries or CWM.
The valley floor of glacier is smooth and polished with nearly vertical walls. Similar basins are also formed in sub-polar regions, but they lack steep head walls. Cirque may be individual, compound or complex. Due to retreat of glaciers, it gives rise to lake.
(iv) Glacial trough:
Less resistant rocks are easily eroded by the glacier forming broad elongated basins. These commonly head at the edge of the cirques. After glaciers melt, they commonly give rise to trough lakes.
Head-ward erosion at the cirque walls and in case of compound cirques, high, sharp and steep sided peaks are left out in form of horns.
In mountainous terraines at the head of cirques glacial erosion, frost action and gravity collectively play their role to form serrated or saw-toothed ridges which are known as aretes.
These are peaks of resistant rocks that stand out in the snow field and are not covered by ice.
(viii) Fjords / Fiords:
These are long straight or broadly curved valleys filled with sea water. These are formed by glacial erosion beyond the sea level now covered with sea-water. They occur extensively in Scandinavia. Greenland, Alaska, Newzealand and other regions. Norway is called the land of five ‘F’s out of which one is fiord. During Pleistocene the glaciers carved their valleys much deeper than the sea level before melting. After the retreat of glacial ice the sea water covered the valleys forming fjords or fiords.
(ix) Roches moutonnee:
The bed rocks are smoothened and striated due to glacial erosion. Hard and resistant rocks often survive glacial erosion, where as surrounding weaker rocks are easily eroded, as a result of which the remnants of erosion are left out as small elongated hills, the upstream sides of which have gentle slopes and the leeward side is relatively steeper. These are called as roches moutonnee and occur profusely resembling herds of sheep. They are prominent features of continental glaciated regions.
(x) Ice-scoured plain:
In continental glaciated regions almost a low land is formed with basins, lakes, knobs etc. due to effective glacial erosion. This low land is termed as ice – scoured plain. These are common in Canadian – Shield, Scandinavia and Russia.