A kettle lake is formed during glaciation when the ice starts to melt and a huge block of ice breaks off and melts more slowly. Sediments and gravels flow around the large block and settle in place while the ice continues to melt. When the block finally melts all the way, a large depression in the landscape is left that can be kept filled by rainwater or by ground water if the water table is high enough. This lake, the lake to the east, and the depression to the north were all formed this way.
At the posted coordinates, you will be standing on the forward edge of the terminal moraine that was left at the end of the last ice age. Ice sheets covered the area north of here from 25,000 years ago to 12,000 years ago to a depth of about 400 feet. Debris, rocks, gravels, and sands were picked up by the moving ice sheet as it scoured its way across the landscape. Where the ice sheet stopped, melt waters dropped the debris at the edges of the ice flow. The receding ice left hills of sediments and a pockmarked terrain that can be hundreds of feet thick. The landscape is now dotted with many hills, depressions and isolated ponds that are reminders of the last ice age.
This event also changed the courses of the Missouri and Yellowstone Rivers. which both flowed north into Canada before being pushed south. Following US 85 south back to Williston, the Little Muddy Creek follows the valley that the Yellowstone River created before being pushed south to its present course. The Missouri River flowed north near Culbertson, MT and created the valley that now contains Medicine Lake in NE Montana.
To log this Earth Cache, send me the answers to the following questions - DO NOT POST THESE ANSWERS IN YOU LOG OR IT WILL BE DELETED:
1. Look at the debris that is exposed at the posted coordinates. Describe the gravels and rocks located here by color, size, shape and are the rocks/gravels of a consistent size shape.
2. Look at the debris that is exposed at the second set of coordinates (N 48 degrees 36.459 W 103 degrees 37.538). Describe the gravels and rocks located here by color, size, shape and are the rocks/gravels of a consistent size shape.
3. Compare the debris encountered at position 1 to that encountered at position 2. Are they similar or different. If different, please give your own explanation as to why this might have occurred.
4. Bonus: Although not a requirement, posting a picture of you and your party with the lake and dock in the background or the informational sign will prove that you were at the location.
Some of the information described above came from the following website: http://ndstudies.gov/gr8/content/unit-i-paleocene-1200-ad/lesson/1/changing-landscapes/topic-2-geology/section-4-ice-age