Lake Michigan dune grass

 

Great Lakes Dunes

The Great Lakes system consists of five lakes, Click for full size picturetheir 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

Dunes_Jan_26_2000The 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 northernLake_Michigan_Oct_31_99 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.Click for larger view 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.