Environmental Engineering Reference
In-Depth Information
U-shaped
valley
Moraine-dammed
lakes
Hanging
valley
Arete
Cirque
Kettle
FIGURE 7.75
Aerial oblique showing many landforms resulting from the activities of a mountain glacier in the Andes
Mountains of Bolivia.
Driftless area
Illinoian
Holocene
Wisconsinin
Nebraskin and Kansan
FIGURE 7.76
Drift borders at the time of a maximum advance of the various Pleistocene glaciers and at the beginning of the
Holocene in North America.
retreat to their present extent covering less than 10%. The extent of Pleistocene glaciation
in the United States is given in Figure 7.76 and in Europe is given in
Figure 7.69.
The effect on the land was great. The Great Lakes as well as the Finger Lakes of New
York State are thought to be primarily the result of glacial excavation. The mountain
ranges of the Northeast have been reduced and rounded by abrasion and many peaks
show striations on their rocky summits. The Ohio and Missouri Rivers flow near the
southernmost extent of glaciation and are called ice-marginal rivers. The grasslands of the
Great Plains are the result of the rich deposits of loess, picked up by the winds from the
outwash plains and redeposited to blanket and level out the landform.
