The Great Lakes on the United States and Canadian border
The
five Great Lakes of North America make up the largest group of freshwater
lakes on the Earth and they are also known for their contribution to the
Earth's ecology and their diversity and beauty. Lying on or near the
Canadian/US border, the Great Lakes consist of Lake Superior, Lake
Michigan, Lake Huron, Lake Erie and Lake Ontario.
They formed at the end of the last ice age, roughly 10,000 years ago when
the Laurentide ice sheet retreated and the meltwater filled the valley
that had been gouged out by glaciers. As the glaciers melted and began
receding, their leading edges left behind high ridges, some of which can
be seen today in the cliffs of Door County, Wisconsin, and the Bruce
Peninsula in Ontario, as well as at Niagara Falls.
The five lakes contain more than 20 per cent of the world's entire
freshwater supply - 22,812 cu km (5,473 cu miles). All five of the lakes
are among the world's 18 largest lakes by area and volume. The combined
surface area of the lakes is 151,681 sq km (94,250 sq miles) - larger than
England, Scotland and Wales together.
Lake Superior is the largest and deepest of the Great Lakes - larger in
fact, than the entire Czech Republic. Lake Michigan is the second largest
lake in volume, while the shallower Lake Huron is the second largest in
area. Lake Erie, the shallowest, is the smallest in volume while Lake
Ontario is the smallest in area. It is also at a much lower altitude than
the other lakes.
The primary outlet of the five interconnected lakes is the Saint Lawrence
River, eventually flowing through Quebec, past the Gaspe Peninsula and
into the northern Atlantic Ocean. In the days before mass rail freight
this link allowed the development of the large industrial cities on and
near the lakes' shores. Now, tourism is important to the economy on both
sides of the border, as is commercial fishing.
Because of their size, the lakes actually have an effect on the region's
climate, which is known as the lake effect. In summer, their waters
absorb heat and keep the surrounding areas cool, then during autumn as
they slowly lose heat, they stave off the cold of winter. However, it is
during winter that their most spectacular effect is seen - lake effect
snow. Dry continental air masses, which usually come from the west,
absorb moisture from the lakes. As soon as they reach colder air over the
land to the east, they dump the snow, sometimes to depths of several
feet. This can produce the strange effect of snow falling from an
apparently clear sky.
There are several national parks on the shores of the lakes and a wide
range of activities is available. As well as water-based activities such
as yachting, canoeing and kayaking, fishing and scuba diving, the
surrounding land is great for biking, birding, hiking and camping. The
birdlife that may be found in the unpopulated areas includes bald eagles
and peregrines, while the remote wilderness areas contain black bears,
grey wolves, elk and the highly endangered Canada lynx.
More than 33
million people inhabit this drainage basin, that is over one-tenth of the
population of the United States and a quarter of the population of
Canada. Strenuous efforts are being made to clean up the effects of their
waste, as well as that of pollution from industries around the lakes, in
order to prevent any further damage to this beautiful wilderness.
