01-24-2003 - Earth

sagar: Author=’Eleanor Imster’ program=’3672′ video=”_JB:_ This is Earth and Sky. Around North America’s Great Lakes, glacial ice advanced and retreated between 13 and 18 thousand years ago.

_DB:_ The ice ripped up rocks and ground them into sand. Waves eroded the sand and washed it to the shore of the Great Lakes. Wind blew the sand inland, forming vast dune fields.

_JB:_ There’s still a lot of sand in the Great Lakes – so the dunes are still growing. And the winds keep the dunes undulating inland. For example, Michigan’s Green Mountain Dune has moved 30 meters – about 100 feet – in the past 200 years.

_DB:_ The dunes also undergo change because of plants that grow on them. Marram grass catches blowing sand and forms small mounds that can build into large dunes with time. Grassy dunes support bird life – eagles, cranes, wrens and plovers. But the sand dune ecosystem is fragile. Dune buggies and even walking on the dunes tear out grass roots and leave bare piles of sand.

_JB:_ Plus the car industry mines dunes for sand used in engine block castings. Even after passage of the Sand Dune Protection and Management Act in 1976, hundreds of acres of dunes have disappeared due to mining. Special thanks today to the “U.S. Forest Service”:http://www.fs.fed.us/ and to the “National Fish and Wildlife Foundation”:http://www.nfwf.org/ – supporting the conservation of native fish, wildlife, plants and their habitats. We’re Block and Byrd for Earth and Sky.

Written by EarthSky