How the Great Lakes were formed.
About a billion years ago, a fracture in the earth running from what is now Oklahoma to Lake Superior generated volcanic activity that almost split North America. Over a period of 20 million years, lava intermittently flowed from the fracture. This geomorphic age created mountains covering the regions now known as northern Wisconsin and Minnesota, and the Laurentian Mountains were formed in eastern Canada. Over time these mountains eroded, while occasional volcanic activity continued. Eventually the fracture stabilized and, over time, the rock tilted down from north to south.
The region went from fire to ice with the arrival of the glaciers, which advanced and retreated several times over the last 5 million years. During the periods of glaciation, giant sheets of ice flowed across the land, leveling mountains and carving out massive valleys. Where they encountered more resistant bedrock in the north, only the overlying layers were removed. To the south, the softer sandstones and shales were more affected. As the glaciers melted and began receding, some lakes were created. Though the original name of this glacial lake was Lake Algonquin. Over time Lake Algonquin became Lake Huron and Georgian Bay.
Since the retreat of the glaciers, water levels continued to undergo dramatic fluctuations, some in the magnitude of hundreds of feet. These extremes were caused by changing climates, crustal rebound and natural opening and closing of outlet channels. Within the last 1,000 years, evidence suggests that lake levels exceeded the range of levels recorded since 1865 by an additional five feet on lakes Michigan and Huron. Many dune formations-some hundreds of feet thick-were established during glacial periods. The tops of these dunes have been continuously sculpted by winds to form the majestic structures now visible.
Today, rebounding of the earth's crust, erosion, and changes in climate continue to alter the shapes and sizes of the Great Lakes. As one of the youngest natural features on the North American continent, the lakes remain a dynamic, evolving system.
Lake Huron water level is more than 20 feet below that of Lake Superior. There is an 8 foot difference between Lake Huron and Lake Erie, Huron being the higher of the two. Lakes Michigan and Huron are connected by the deep Straits of Mackinac and are considered to be one lake hydraulically with lake levels rising and falling together. Lake Huron is the third largest of the Great Lakes by volume, holding nearly 850 cubic miles of water. The shores of Huron extend more than 3,800 miles and are characterized by shallow, sandy beaches and the rocky coasts of Georgian Bay. Lake Huron is 206 miles wide and approximately 183 miles from north to south. Home to many ship wrecks, the lake averages a depth of 195 feet. This lake is also the third largest fresh water lake on earth.
This cache will take you to the beach in Port Sanilac. This will be a nice place to visit and learn a little more about this lake.
1. You will need a clear jar for a water sample. You will need to cap and allow the water to settle at home for 3 days undisturbed. Then e-mail a detailed description of has settled in the jar. You are doing this to better understand the water of this lake. The lake has a retention time of 22 years.
2. Being a deep glacial lake it will be interesting to see what the changes in the temparture of the water. We can then chart the change through out the year.
3. Very near the co-ordinance you will find a very large man made structure. E-mail me what is there. 4. Post a photo of yourself with this Great Lake in the back ground.
Thank you to Beenhere for your help with the development of this cache.
Be sure to e-mail me within 7 days of logging the cache to get credit for your work. If the rules of finding an Earthcache and e-mailing the owner is not followed your log will be deleted without notice!