5. Lake Superior has its origins in the North American Mid-Continent Rift of 1.1 to 1.2 billion years ago, which produced a huge plume of hot mantle where the present lake sits. The crust tore apart, leaving an arc-shaped scar stretching form Kansas through Minnesota, then down to Michigan.
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About a billion years ago, a fracture in the earth running from what is now Oklahoma to Lake Superior generated volcanic activity that almost split North America. Over a period of 20 million years, lava intermittently flowed from the fracture.
Lightfoot sings that Superior, they said, never gives up her dead. This is because of the unusually cold water, under 36 °F (2 °C) on average around 1970. Normally, bacteria decaying a sunken body will bloat it with gas, causing it to float to the surface after a few days.
Lake Superior's beaches are open and safe for swimming over 90% of the time, and the water is extremely clear, with an average underwater visibility of 8.3 m (27 ft).
Although the exact number of shipwrecks on Lake Superior is difficult to track, most historians mark it at about 6,000, although some say it could be upwards of 25,000. Just to the east of Pictured Rocks National Lakeshore, sits Whitefish Point, the site of the most famous shipwreck of Lake Superior.
Lake Superior is generally calm and easily paddled between early June and mid-August. Mornings tend to be best for paddling, but it is not unusual to have a glassy calm for days on end.
Spanning nearly 32,000 square miles, Lake Superior is not only the largest freshwater lake in the world (by surface area) but it is also one of the largest lakes in the world, second only to the Caspian Sea.
It is the deepest (1,335 feet) of the Great Lakes. If you go swimming there in the hottest part of the summer, you'll soon learn that Lake Superior is also the coldest of the Great Lakes - brrr, icy cold at an average temperature of 40° F (4°C).
Drinking Water - State of the Great Lakes. The 2012 Great Lakes Water Quality Agreement states that “the Waters of the Great Lakes should be a source of safe, high quality drinking water”. Approximately 8.5 million Canadians and 19.5 million Americans get their drinking water from the surface waters of the Great Lakes.
Lake Superior freezes at least in part every year and less frequently in its entirety. The last year that it froze completely was in February 1994. It almost froze completely in March 2003 and this photograph was taken by the GOES satellite on March 7, 2003.
Except for shallow bays and beaches, the water temperature in the lake seldom reaches 55 degrees F., even during the hottest summer weather. Survival time in the lake, without a life jacket is, on average, less than two hours.
Lake Superior is the Cleanest and Clearest Great LakeBecause of its somewhat isolated location and long cold winters, not much farming is done along Superior's shores. This means lower amounts of nutrients, sediments, and organic material are floating around the lake.
AP'S ASSESSMENT: False. Bull shark sightings have been confirmed in the Mississippi River as far north as Alton, Illinois, but reports of the sharks being found in the Great Lakes are either hearsay or hoaxes, multiple experts told The Associated Press.
Lake Superior is the largest freshwater lake in the world by surface area and the third-largest by volume, holding 10% of the world's surface fresh water.