Saturday, January 21, 2012

Drain the Great Lakes -- Post 2

Today I'll continue a review of some of the awesome facts presented in the National Geographic program Drain the Great Lakes.

The next segment in the show featured Lake Huron. 

Around 6,000 or 7,000 years ago when the levels of the lakes were still low, there was a land bridge that formed across what is now Lake Huron.

Underwater imaging has indicated that in the area of this one-time land bridge off the coast of Alpena, MI, there is a linear line of rocks that stretches for dozens of miles.  Scientists found what they believe are hunting pits, camps and rock structures called caribou "drive lines" on the bottom of Lake Huron.
Drive lines, also called drive lanes, are walls built of rocks that hunters used to lure caribou into ambush. A peculiarity of the deer species is that it readily follows linear cues, even though the rock walls are short enough to step over.

The next segment of the program moved south to Lake Erie, the shallowest of all the Great Lakes.  On the north shore there is this weird peninsula called Long Point that sticks out into Lake Erie around 25 miles.  This point is a remnant of the lower lake levels that still existed around 5,000 years ago.

When the lake levels were low, the Niagara Falls area certainly was much different.  Today, up to 36 million gallons of water flow over the falls per minute.

When the lake levels were low, there was but a trickle.

Another interesting anomaly found at the bottom of the Great Lakes are these pop up ridges that are scattered on the bottom of Lake Ontario.  Scientists have determined that they are compression fractures caused by tectonic pressure along fault lines.

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