Lake Superior 
The greatest of the Great Lakes is Lake
Superior, the northernmost and westernmost Great Lake and
the biggest, the deepest, the coldest and the most pristine.
Its name comes from early French explorers who labeled it
"le lac superieur," meaning "the uppermost lake." According
to Native American Objibway lore, it is protected by
Nanabijou, Spirit of the Deep Sea Water.Roughly the same
shape and slightly larger than South Carolina, Lake Superior
has a surface area of more than 31,000 square miles -- the
largest of any freshwater lake in the world. Only Siberia's
Lake Baykal, because it is deeper, holds more water.
Bordered on the north by Ontario, on the west by Minnesota
and on the south by Wisconsin and Michigan, Superior at its
greatest measures 350 miles long and 160 miles across.The
lake's surface is about 600 feet above sea level, with an
average depth of 490 feet and a maximum depth of 1,333 feet.
Its clear, frigid waters are bordered by 2,980 miles of
shoreline, 90 percent of which is forested, much of it still
wilderness.
Superior's flushing time -- the time it
takes for all the water now in the lake to be replaced by
new water -- is 191 years, the longest of any of the Great
Lakes. This also makes Superior the most vulnerable to
long-term water pollution: if the lake were to become
polluted today, and all pollution stopped tomorrow, it would
take almost 200 years before its water would again be as
pure as it was yesterday.At Superior's southeastern corner,
its sparkling waters flow into the
St. Marys River, a crooked 61-mile channel of
water separating Michigan's
Upper Peninsula from Ontario. Just 16 miles from the
mouth of the river and Lake Huron are the St. Marys Rapids,
where the river drops about 20 feet in half a mile. For
centuries, these rapids were a barrier to water travel
between Lake Superior and the other lakes. It wasn't until
1855 that the first locks and canal for moving ships around
these rapids was built at the international twin cities of
Sault Ste. Marie.
Today there are five locks -- four operated
by the U.S. and one by Canada -- including the giant Poe
Lock, the largest on the Great Lakes, which can hold ships
up to 1,100 feet long and 105 feet wide. In peak years, more
tons of cargo passes through these locks than any other on
Earth. |
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