73
This and Lake Huron have few large cities on
their shores and their catchments are too cool and
rocky for intensive agriculture. As such, their
waters are very unproductive. The two lowest
lakes, Ontario and Erie, are smaller and more
responsive to environmental effects, whether
natural or not. They and Lake Michigan have
some of America’s largest industrial cities on
their shores which have discharged their wastes
into the lakes for many years.
Further, the basins of these fi ve lakes are
gouged by the successive advances and retreats
of enormous ice sheet formed during the
Wisconsin Glacial Period. This glacier is reached
as far south as St. Louis, at its greatest extent,
about 18,000 years ago. Later, it retreated and
the lakes gradually assumed their present shapes
and formed about 10,000 years ago. Hence, they
are contemporary with other glacial lakes with
similar latitudes like those of the English Lake
District and the Alpine Lakes of Europe.
Concomitant to above, some of the largest
industrial cities in North America are situated on
the shores of the Great Lakes, e.g . Chicago on
Lake Michigan and Detroit on the infl ow to Lake
Erie. The Great Lakes receive water from total
area of nearly 750,000 km
2 . The area is really not
very mountainous. But it collects enough water
to keep about 7,000 m
3 fl owing out of Lake
Ontario every second into the St. Lawrence River.
However, the land from which it drains is very
varied. It is covered with moraines left by the
retreating glacier to the south of the lakes and on
the tongue between Lakes Ontario, Erie and
Huron. This results in softly undulating country
with deep soils and rounded hills to the north.
Further, along the northern shore of Lake
Superior lies the southern edge of the Canadian
Lakes. This is very ancient and consists of hard
rocks which are often exposed on the surface.
The northern hardwood forests give way to the
great boreal coniferous forest on this land. It may
be noted here that true tides caused by the combined infl uence of the sun and moon cause
changes in water level of only about 3 cm at the
most. Much larger changes in level are caused by
winds and changes in barometric pressure. These
lead to regular slopping of the lake in its basin.
This phenomenon is known as ‘seiche’. Storms
may cause larger, often catastrophic changes in
level and even tidal waves. These lakes offer
good conditions for the formation of waves. The
region has strong winds, to which huge uninterrupted areas of deep water are exposed.
Landscape to the north and south of the Great
Lakes is covered with myriad of smaller lakes
gouged out by the force of the ice. Many of these,
e.g. Lake Winnipeg, the Great Slave Lake and the
Great Bear, are amongst the world’s largest. But
most of these are very much smaller particularly
in Wisconsin and Minnesota.
All the lakes have suffered from indiscriminate
disposal of human and industrial wastes. However,
the effects are localised and, perhaps, more evident in Lakes Superior and Huron. Lake Erie has
suffered much because it is relatively shallow.
Lake Erie was declared ‘dead’. Its epitaph was
written in the World’s Conservation Literature.
The main culprit was phosphorus particularly
from detergents. The Great Lakes have a profound
infl uence on the climate of the land around them
because of their huge volume of water.
A rich diversity of about 103 species of fi shes
have been recorded from the Great Lakes. These
include paddle fi sh ( Polyodon ), lake sturgeon
( Acipenser ) and bowfi n ( Amia ). As in Great
Lakes of Africa, there are no fl ocks of endemic
species although it supports a successful fi shery.
Salmonids form the major commercial fi shery.
The construction of Welland Canals allowed
ocean-going vessels to bypass Niagara Falls.
6.2.2 Lake Washington
This lake (located 47° 38′ N; 122° 14′ W; altitude,
about 6 m (regulated), lake area 87.6 km
2 , lake
volume 2.88 km
3 , maximum depth 62.5 m, mean
depth 32.9 m, catchment area 1,588 km
2 , principal infl ow Cedar River, outfl ow via Lake Union
and Ship Canal to Puget Sound) occupies a glacially formed trough just inland from the NW
coast of the USA. It was a relatively unproductive
lake in its natural state. The lake is now mainly
used for water-based recreation like sailing,
swimming and fi shing.
6.2 Lakes of Temperate Region
This and Lake Huron have few large cities on
their shores and their catchments are too cool and
rocky for intensive agriculture. As such, their
waters are very unproductive. The two lowest
lakes, Ontario and Erie, are smaller and more
responsive to environmental effects, whether
natural or not. They and Lake Michigan have
some of America’s largest industrial cities on
their shores which have discharged their wastes
into the lakes for many years.
Further, the basins of these fi ve lakes are
gouged by the successive advances and retreats
of enormous ice sheet formed during the
Wisconsin Glacial Period. This glacier is reached
as far south as St. Louis, at its greatest extent,
about 18,000 years ago. Later, it retreated and
the lakes gradually assumed their present shapes
and formed about 10,000 years ago. Hence, they
are contemporary with other glacial lakes with
similar latitudes like those of the English Lake
District and the Alpine Lakes of Europe.
Concomitant to above, some of the largest
industrial cities in North America are situated on
the shores of the Great Lakes, e.g . Chicago on
Lake Michigan and Detroit on the infl ow to Lake
Erie. The Great Lakes receive water from total
area of nearly 750,000 km
2 . The area is really not
very mountainous. But it collects enough water
to keep about 7,000 m
3 fl owing out of Lake
Ontario every second into the St. Lawrence River.
However, the land from which it drains is very
varied. It is covered with moraines left by the
retreating glacier to the south of the lakes and on
the tongue between Lakes Ontario, Erie and
Huron. This results in softly undulating country
with deep soils and rounded hills to the north.
Further, along the northern shore of Lake
Superior lies the southern edge of the Canadian
Lakes. This is very ancient and consists of hard
rocks which are often exposed on the surface.
The northern hardwood forests give way to the
great boreal coniferous forest on this land. It may
be noted here that true tides caused by the combined infl uence of the sun and moon cause
changes in water level of only about 3 cm at the
most. Much larger changes in level are caused by
winds and changes in barometric pressure. These
lead to regular slopping of the lake in its basin.
This phenomenon is known as ‘seiche’. Storms
may cause larger, often catastrophic changes in
level and even tidal waves. These lakes offer
good conditions for the formation of waves. The
region has strong winds, to which huge uninterrupted areas of deep water are exposed.
Landscape to the north and south of the Great
Lakes is covered with myriad of smaller lakes
gouged out by the force of the ice. Many of these,
e.g. Lake Winnipeg, the Great Slave Lake and the
Great Bear, are amongst the world’s largest. But
most of these are very much smaller particularly
in Wisconsin and Minnesota.
All the lakes have suffered from indiscriminate
disposal of human and industrial wastes. However,
the effects are localised and, perhaps, more evident in Lakes Superior and Huron. Lake Erie has
suffered much because it is relatively shallow.
Lake Erie was declared ‘dead’. Its epitaph was
written in the World’s Conservation Literature.
The main culprit was phosphorus particularly
from detergents. The Great Lakes have a profound
infl uence on the climate of the land around them
because of their huge volume of water.
A rich diversity of about 103 species of fi shes
have been recorded from the Great Lakes. These
include paddle fi sh ( Polyodon ), lake sturgeon
( Acipenser ) and bowfi n ( Amia ). As in Great
Lakes of Africa, there are no fl ocks of endemic
species although it supports a successful fi shery.
Salmonids form the major commercial fi shery.
The construction of Welland Canals allowed
ocean-going vessels to bypass Niagara Falls.
6.2.2 Lake Washington
This lake (located 47° 38′ N; 122° 14′ W; altitude,
about 6 m (regulated), lake area 87.6 km
2 , lake
volume 2.88 km
3 , maximum depth 62.5 m, mean
depth 32.9 m, catchment area 1,588 km
2 , principal infl ow Cedar River, outfl ow via Lake Union
and Ship Canal to Puget Sound) occupies a glacially formed trough just inland from the NW
coast of the USA. It was a relatively unproductive
lake in its natural state. The lake is now mainly
used for water-based recreation like sailing,
swimming and fi shing.
6.2 Lakes of Temperate Region