Great Lakes – Lake Superior EarthCache

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. Molten magma below the highlands of what is now Lake Superior spewed out to its sides, causing the highlands to sink and form a mammoth rock basin that would one day hold Lake Superior. 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, their leading edges left behind high ridges, some of which can be seen today in the cliffs of Door County, Wisconsin, and the Bruce Peninsula in Ontario. Huge lakes formed between these ridges from the retreating ice fronts, and continually changed over time as the ice sheet moved northward.

Without the immense weight of the glaciers-thousands of feet thick in places- the land began to rebound. Even today, virtually all of the land in the Great Lakes basin continues to rise. Southern parts of the basin are rising slightly, less than 3 inches per century. The northeastern corner of the Lake Superior basin, however, is rebounding in excess of 21 inches per century.

Lake Superior is the largest of the Great Lakes in surface area and volume. In fact, Superior has the largest surface area of any freshwater lake in the world. The lake stretches 350 miles from west to east and 160 miles north to south. Its shoreline is nearly 2,800 miles long. Superior is also the coldest and deepest of the five Great Lakes. Average depths are close to 500 feet; the deepest point in the lake reaches 1,332 feet. Lake Superior is also the headwaters to all the Great Lakes. These headwaters drop 20 feet plus through the St. Marys river to feed Lake Huron. Lake Huron is hydraulically with Lake Michigan through the Straits of Mackinac.

Because of the development of millions of years the entire area is very mineral rich. The Lake Superior basin region most prevalent minerals are iron ore and copper deposits. We are going to look at this some of these minerals that are here in this lake. The question is which one or is that which ones?

The area we have brought you to is the beach at Whitefish Point. This is also the home to the Great Lakes Shipwreck Museum, Whitefish Point Bird Obsevatory and a wonderful historical Lighthouse.

1. To log this cache you will need 2 clear jars with lids. We will be taking you to 2 areas on the lake for samples of the water. The locations are N46 46.070 W084 57.200 and N46 46.320 W084 57.400. One of these locations the water breaks onto the shore and has a lot of movement. The second location the water is somewhat calmer on a normal basis. We will be looking at the mineral sediment from each location. You will want to make each jar and record what the water samples look like when first drawn. Take these hame and let them settle for a couple of day and e-mail me with the results of each of these tests.
2. Next you will need to inspect the rocks that are all along the beach. There will be mineral deposits on many of these rocks please e-mail me with what kind of mineral deposits that you see here. These test will show you a sample of the amount of minerals in this lake.
3. Please post a picture of you and the one thing you found most interesting during your visit.

Thank you to Beenhere for your help with the development of this cache.