Geography Reference
In-Depth Information
Alaska, glacial troughs have filled with seawater, resulting in steep-sided ocean inlets called
fiords.
Glaciated mountains have a spectacularly rugged look about them. Perhaps not surprisingly, there-
fore, such areas tend to be major magnets of travel and tourism. Also, one must remember that these
landforms were created by erosion, which leads one to ask where all the removed material went. The
answer is that it was deposited downslope, forming or mixing in with soil or, in the case of fiords,
ocean bottom.
Continental glaciers
Continental glaciers
build up over large land masses in general, as opposed to mountains in
particular. At the height of the last Ice Age, some 20,000 years ago, they covered substantial
portions of North America, as well as fair portions of Eurasia. The present ice caps of Green-
land and Antarctica (see Chapter 8), which are more than 2-miles thick in some places, offer
insight into continental glacier scale and movement.
In North America, massive ice sheets (as seen in Figure 7-7) slowly built up over many years in what
is now Canada. Eventually, the unimaginable weight and volume caused the ice to “ooze” outward
in response to the pressure, at which point, the ice technically became a glacier. As the ice sheet
advanced, its immense weight weathered the underlying Earth and
gorged out
(eroded) low-lying
landforms through which it passed. Thus were formed, for example, the beds of the Great Lakes,
the Finger Lakes (New York State), and numerous other future water bodies. Much of Canada was
scoured by that process, which explains the relative lack of soil today over parts of that country, as
well as the presence of thousands of lakes.
Eventually, of course, all of the eroded material being carried or pushed along by the ice got depos-
ited, particularly as climates warmed and the ice sheets waned. In some places, these deposits of rock,
sand, and other debris (called
glacial till
) merely coated the surface. In others, however, major ac-
cumulations occurred, resulting in landforms called
moraines.
Long Island and Cape Cod are note-
worthy examples. These were created by the bulldozing effect of the ice sheets and the transporting
and deposition of debris beneath them.
