Great Lakes Dunes
The Great Lakes system consists of five lakes, 
their
connecting channels and the St. Lawrence River, which flows
into the Atlantic Ocean.
Ranked by surface area,
the lakes include Superior (31,700 square miles), Huron
(23,000 sq. mi.), Michigan (22,300 sq. mi.), Erie (9,910
sq. mi.) and Ontario (7,340 sq. mi.)..
Covering
more than 94,000 square miles and draining more
than twice
as much land, these freshwater seas hold an estimated
6 quadrillion gallons of water, about one-fifth of the
world's
fresh surface water supply and nine-tenths of the U.S.
supply. Spread evenly across the contiguous 48 states,
the lakes'
water would be about 9.5 feet deep
The world's largest freshwater dunes line the lakeshore. They are irreplaceable
because the glaciers and other forces that brought together stretches
of uninterrupted sand with freshwater beaches, grasses, mature forests
and wildlife will likely never return to recreate this unique environment.
No where else in the world are there quartz dunes, with it's silky
smooth sand, of the size and extent found around the Great Lakes.
The temperature of the sand can reach over 100 degrees in the sun
and plants that can survive in such heat must also be able to withstand
abrasive winds and the infamous Great Lakes winters
The
Dunes stretch along southern and eastern Lake Michigan
shoreline and up to the northern
lakeshore in Michigan's Upper Peninsula.
There are dunes on the eastern side of Lake Michigan, but they are
smaller in size than the larger, more well known dunes on the western
side of the state. There are also dunes along small areas
of Lake Huron, Erie, Superior and Ontario.
The relationship
between wind and water is important dune formation.
Water is moved by wind, and the
wind is swayed by the temperature of the water. This constant
interaction turns rocks containing quartz, granite
and sandstone, churned up and released by ancient glaciers,
into the sand. As waves approach the shore, they slow
and deposit sand along the beach. Fine sand (under 1/4 mm
diameter) will begin to roll in a breeze of eight to twelve
miles an hour, but it takes gale force winds of close to forty
miles an hour to lift up grains one millimeter into the air.
Wind loses velocity quickly as
it moves off the Great Lakes and, consequently, drops the sand.
This is why dune growth occurs only within about one-half mile of
the shoreline. The dunes support plant and animal life that can’t
be found elsewhere. In 1976 the Sand Dune Protection and Management
Act of 1976 was passed, which created designated sand dune areas
and requires mining permits. Subsequent amendments have created
the Critical Dunes Atlas which regulate "critical" dunes
that are adjacent to the shoreline and have unique value.
