Lake Superior:
A Great Inland Sea
By Heather Kemp
Information from the MN Sea Grant, MN Historical Society and MN DNR
How was Lake Superior formed?
Lake Superior was formed from both fire and ice. Fire, in the form of volcanoes and ice, in the form of glaciers .
One million years ago, volcanoes erupted covering the area with molten basalt . The land sunk under the weight of the basalt forming a broad,shallow basin .
Two million years ago, glaciers carved out the basin. Then, ten thousand years ago, as the glaciers started to retreat, an ice mass got blocked and melted. The melted water filled the basin creating Lake Superior.
What makes Lake Superior so special?
Lake Superior is special for many reasons. First, it is the largest freshwater lake in the world by surface area . It also contains 10% of the world's surface fresh water and it is the third largest lake in the world by volume .
It is so large it contains 3-quadrillion gallons of water. That is a large number. What does that mean? That amount of water is the same as all the water in all the other North American Great Lakes (Michigan, Erie, Ontario, and Huron) plus with three more Lake Erie's. Another way to look at it is lie this, that it is also enough water to submerge North and South America under 1 foot of fresh water. That is a lot of water!
Lake Superior is also the deepest of the Great Lakes. The deepest spot in Lake Superior is 1,332 feet. One of the world's tallest buildings, Chicago's Sears Tower, would fit in that hole with only a few floors sticking above the water. That is deep!
Location
Lake Superior's shoreline is in two countries, the United States and Canada. In the United States, the shoreline is in two states, Minnesota and Wisconsin.
Shipping
Many ships travel on Lake Superior on their way to and from the Atlantic Ocean. It takes seven days to travel that distance. The Duluth, Minnesota/Superior, Wisconsin port is the busiest inland port in the United States with more than 1,000 ships visiting every year. These ships carry grain, taconite and coal.
Tourism
Lake Superior attracts many visitors every year bringing money to the many communities that are along it's shore. People come to sightsee, fish and boat. Not many people swim in Lake Superior though. The average water temperature of Lake Superior is 45 degrees Fahrenheit. That is cold!
Shipwrecks
There have been around 350 shipwrecks on Lake Superior. Most of these occurred during the fall when "northeasters" are common. These are gales with strong wind and rain. One of the most famous shipwrecks in Lake Superior was of the SS Edmund Fitzgerald which happened on November 10, 1975 and 29 people died.
Agates
Lake Superior agates are different from other agates around the world because of their color. The color of Lake Superior agates are rich red, orange and yellows. This color scheme is caused by the oxidation of iron . One can find these agates anywhere there is exposed gravel and rocks. This would include practically all the beaches on Lake Superior.