Glaciers
47
Figure 2.14. Plateau ice cap of Myrdalsj6kull (Iceland). Photo: F. Guti6rrez.
Vatnaj6kull, in Iceland, the most characteristic example. The plain ice caps are located
in areas of little relief, such as the Barnes ice cap on Baffin Island in the Arctic.
Cirque glaciers occur in the valley heads of mountainous areas (Fig. 2.15). They are
small ice masses located in amphitheatres, generally of steep walls, hectometric dimensions and thicknesses of tens of metres. During a glaciation period they are the first to be
developed and last ones to disappear.
Valley glaciers are laterally confined by rocky walls. If their feeding comes from
cirques we are speaking of valley glaciers of the alpine type (Embleton and King, 1975a)
(Fig. 2.16). They flow radially from the great massifs and can be fed by secondary valley
glaciers. A clear hierarchy is given by the relation between valley width and number of
tributaries. The glacier mass is long, narrow, and generally finishes in a single ice tongue
or terminus. The longitudinal slopes are variable. Some glaciers exceed 100 km in
length. At the present time they are common in high mountains. In the peripheral zone of
the icecaps the ice masses can escape from the margins giving origin to valley glaciers or
outlet glaciers (Figs 2.17 and 2.18), which are like appendices arising from the edge of
ice caps. When the front of valley glaciers is constituted by an extensive plain the ice
spreads out considerably over it, increasing in width and producing a piedmont glacier.
The most classical example is the Malaspina Glacier in Alaska extending as a wide lobe
in the coastal plains of the Pacific. It constitutes the ablation zone of the lower Seward
Glacier, being 600 m thick and occupying a great depression that reaches 250 m below
sea level (Benn and Evans, 1998). Its compressive flow produces an intense deformation
of the debris bands and medial moraines (Sharp, 1958) (Fig. 2.19).
47
Figure 2.14. Plateau ice cap of Myrdalsj6kull (Iceland). Photo: F. Guti6rrez.
Vatnaj6kull, in Iceland, the most characteristic example. The plain ice caps are located
in areas of little relief, such as the Barnes ice cap on Baffin Island in the Arctic.
Cirque glaciers occur in the valley heads of mountainous areas (Fig. 2.15). They are
small ice masses located in amphitheatres, generally of steep walls, hectometric dimensions and thicknesses of tens of metres. During a glaciation period they are the first to be
developed and last ones to disappear.
Valley glaciers are laterally confined by rocky walls. If their feeding comes from
cirques we are speaking of valley glaciers of the alpine type (Embleton and King, 1975a)
(Fig. 2.16). They flow radially from the great massifs and can be fed by secondary valley
glaciers. A clear hierarchy is given by the relation between valley width and number of
tributaries. The glacier mass is long, narrow, and generally finishes in a single ice tongue
or terminus. The longitudinal slopes are variable. Some glaciers exceed 100 km in
length. At the present time they are common in high mountains. In the peripheral zone of
the icecaps the ice masses can escape from the margins giving origin to valley glaciers or
outlet glaciers (Figs 2.17 and 2.18), which are like appendices arising from the edge of
ice caps. When the front of valley glaciers is constituted by an extensive plain the ice
spreads out considerably over it, increasing in width and producing a piedmont glacier.
The most classical example is the Malaspina Glacier in Alaska extending as a wide lobe
in the coastal plains of the Pacific. It constitutes the ablation zone of the lower Seward
Glacier, being 600 m thick and occupying a great depression that reaches 250 m below
sea level (Benn and Evans, 1998). Its compressive flow produces an intense deformation
of the debris bands and medial moraines (Sharp, 1958) (Fig. 2.19).