Great Lakes of North America

Topic: World Physical Features and Natural Regions · NCERT: Beyond NCERT

Meaning

The Great Lakes are five connected freshwater lakes in east-central North America: Superior, Michigan, Huron, Erie and Ontario. Four of them lie on the USA–Canada border, and Lake Michigan lies wholly inside the USA. Together they form the largest surface of fresh water in the world [2]. They drain into the Atlantic Ocean through the St Lawrence River.

They supply water, shipping routes and jobs to millions of people in two countries. They are also a well-known example of two countries managing shared waters together.

Explanation

How the lakes formed

• Cause: during the Ice Age, huge ice sheets (thick layers of ice covering a large area of land) moved south over North America.
• Process: the moving ice scraped and deepened old river valleys and low ground into large hollows.
• Result: when the ice melted, its meltwater filled these hollows and made the lakes. Because of this, the Great Lakes are called glacial lakes.

The five lakes and how water flows

• Mnemonic HOMES: Huron, Ontario, Michigan, Erie, Superior.
• Order from west to east, in the direction the water flows: Superior → Michigan / Huron → Erie → Ontario.
• Water starts in Superior, the highest and largest lake.
• Michigan and Huron come next and are joined to each other.
• Water moves on into Erie.
• From Erie it flows down the Niagara River into Ontario. Niagara Falls is on this river.

• From Ontario the water leaves through the St Lawrence River and reaches the Atlantic Ocean.

• Key facts about single lakes:

• Lake Superior is the largest freshwater lake in the world by area, about 82,100 sq km [2].
• Lake Michigan is the only one of the five that lies wholly in the USA. The other four are shared by the USA and Canada.

Size and value

• Area: the five lakes together cover about 244,106 sq km, which is the largest surface of fresh water in the world [2].
• Share of fresh water:
• The Great Lakes basin (all the land that drains into the lakes) holds about 95% of North America's fresh surface water [3].

• It holds about 18% of the world's fresh surface water [3].

• People: the basin is shared by 2 countries, 8 US states and 1 Canadian province (Ontario). More than 40 million people depend on it for water at home and in industry [3].

Shipping and shared management

• St Lawrence Seaway (opened 1959): a system of locks (closed sections of a canal that raise or lower ships between different water levels) and canals.
• It lets ocean-going ships sail from the Atlantic deep into the middle of the continent.

• This made the lakes a major inland shipping route.

• International Joint Commission: a body set up by the USA and Canada. It manages the boundary waters (lakes and rivers along the border) jointly.

Where it occurs

• Region: east-central North America, along the USA–Canada border.
• Countries and units: the USA (8 states) and Canada (province of Ontario) [3].
• Lake Michigan: wholly inside the USA.
• Niagara River and Niagara Falls: between Lake Erie and Lake Ontario.
• Outlet: the St Lawrence River, which carries the water to the Atlantic Ocean. The St Lawrence Seaway runs along it.
• Other large North American lakes that are NOT part of the Great Lakes:
• Great Bear Lake (Northwest Territories, Canada): the largest lake wholly inside Canada. The Arctic Circle crosses it.
• Great Slave Lake (Northwest Territories, Canada): the deepest lake in North America (about 614 m). The Mackenzie River flows out of it.
• Great Salt Lake (Utah, USA): a salty lake in a closed basin, left over from the Ice Age Lake Bonneville.

Don't confuse with

• Caspian Sea: the world's largest inland water body (about 371,000 sq km), but it is salt water in a closed basin. Lake Superior is the largest freshwater lake by area.
• Lake Baikal: the deepest and oldest lake, holding about 20% of the world's unfrozen fresh water [1]. The Great Lakes are the largest by surface area of fresh water [2]. Baikal wins on depth and volume. The Great Lakes win on area.
• Great Bear Lake and Great Slave Lake: they have "Great" in their names but are not among the five Great Lakes. Both lie wholly in Canada's Northwest Territories.
• Lake Victoria: the second-largest freshwater lake by area, in Africa. Lake Superior is first.

Prelims Hooks

• HOMES = Huron, Ontario, Michigan, Erie, Superior. Michigan is the only one wholly in the USA.
• Flow order, west to east: Superior → Michigan / Huron → Erie → Ontario → St Lawrence River → Atlantic.
• Niagara Falls is on the Niagara River, between Erie and Ontario, not between Huron and Erie.
• Largest freshwater lake by area: Superior (about 82,100 sq km) [2]. Largest inland water body: Caspian (salt water).
• St Lawrence Seaway opened in 1959. Boundary waters are managed by the USA–Canada International Joint Commission.
• Trap: Great Bear Lake and Great Slave Lake are in Canada but are not among the five Great Lakes.

Mains Points

• Shared lakes need shared rules (GS-I/II):
• The USA and Canada manage the Great Lakes jointly through the International Joint Commission.
• Other examples are the Caspian (Aktau Convention 2018) and the Lake Chad Basin Commission.

• Lesson for India: joint bodies with clear rules can help manage river waters shared between states and with neighbouring countries.

• A resource that supports a whole region (GS-III):

• The basin holds about 95% of North America's fresh surface water and supports more than 40 million people [3].

• The St Lawrence Seaway (1959) links the interior of the continent to the Atlantic. This shows how inland waterways can cut transport costs and support industry. It is useful when discussing India's inland waterways.

• Fresh water is scarce and must be protected (GS-III):

• The lakes hold about 18% of the world's fresh surface water [3]. Heavy use by homes and industry means their water needs careful management.
• Compare the Aral Sea and Lake Chad, which each shrank by about 90% because of overuse and drought.

Related concepts

• Caspian Sea
• Lake Baikal
• Aral Sea
• Lake Victoria
• Lake Tanganyika
• Lake Chad

Read more

• Lakes and inland seas