It's the Pits! EarthCache
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In order to count this Earthcache as a find, you must complete the following tasks and email the answers to me.
1. What is the elevation at ground zero?
2. Estimate the height of the moraine to the east (St. Ann’s Hill).
3. Describe the size and shape of the gravel pit.
4. Estimate the depth of the pit.
5. Take a small sample of the water from the gravel pit and describe its appearance.
This Earthcache is located at a local park near the banks of the Big Sioux River. Kiddie Ponds for fishing are located in this park along with a disc golf course. The bike path and zoo are also located in the area. Bring a pole for fishing, a disc for golfing, or a bike for riding! Enjoy!
The numerous gravel channels in the area owe their origin to the last of the four ice sheets which are known to have invaded the central part of the continent some 20,000 years ago. The Watertown area lies in a region between the western edge of the Des Moines ice lobe and the eastern edge of the Dakota lobe of the Wisconsin ice sheet. These two lobes join about fifty miles north of Watertown forming a sharp depression in the ice down which both lobes drained. The Big Sioux River valley carried the main streams of water and was sent by many outwashes and channels from both ice fronts. These drainage channels were cut in an older drift sheet, the remnants of which are still exposed on the highlands between the channels. Two distinct sets of glacial phenomena, therefore, are involved in the origin of the area: the older drift sheet, whose surface characters determine the details of the drainage lines, and the younger drift sheet with its lake basins and attendant outwash deposits. Outwash refers to the material carried away from a glacier by meltwater and deposited beyond the moraine or ridge of glacial debris.
The older drift is characterized by long, gently rolling slopes. The surface area composed of the older drifts is well drained largely because the valley is so wide and shallow. Underneath, the older drift is comprised of pebbles and boulders. The surface appears to only have been lightly covered with glacial debris.
The surface over which the last ice sheet (Wisconsin) moved has been largely destroyed by the deposits of that glacier. The Wisconsin ice sheet left piles of debris that are recognized now in the long, gentle slopes that are scattered throughout the area. The Dakota lobe of the Wisconsin ice sheet, which moved down the James Valley, spread eastward until its front halted near Lake Kampeska. When the glacier stopped, all of the sediment and debris it had been pushing also stopped and formed a moraine. Hills in the area mark the edges of the glacier. The southern extent can be seen in a ridge of hills located about five miles south of Lake Pelican which extend slightly west and north along the western edge of the lake. At this point, the moraine bends to the northeast for three miles, ending at Stony Point on Lake Kampeska. The moraine picks up again on the opposite side of Kampeska and follows a northwestward trend to Medicine Lake. At Medicine Lake, the moraine makes another bend to the northwest and continues on the west side of the Big Sioux Valley. Derby Downs and St. Ann’s Hill are examples of moraine created by the Wisconsin ice sheet. These two areas also show the extent of the glacier.
The Wisconsin ice front produced a lot of outwash--especially in the Watertown area. Some of the sediments washed over the slopes of the older drifts, but most of it collected in definite channels and on outwash plains. The ice in the vicinity of Punished Woman’s Lake discharged a large quantity of water down the channel in which Gravel Creek lies. Flowing south, the water in this channel carried gravel that was eventually discharged into the Big Sioux Valley northeast of Lake Kampeska. Water also poured off the lobe, carrying enormous amounts of debris, which were dumped as sand and gravels in areas along the Big Sioux River.
Kame-like gravel hills (eskers) were also left behind by the ice lobe. These gravels were deposited on clay banks and later covered with silt. These hills can be traced along the eastern shore of Lake Kampeska from City Park to the water filtration plant. From here, the eskers slope to the east and the south for about a mile before merging with the general level of the gravel flats of the Big Sioux Valley in Watertown. A sample of bedrock along the Big Sioux River in Watertown showed about five feet of silt on the top layer, followed by sixteen feet of gravel, and then twenty feet of bounder clay (glacial till) at the deepest layer.
Gravel channels run parallel to the Big Sioux River as it makes its way through Watertown. The disc golf course, located along the Big Sioux River, sits on a gravel channel. The Kiddie Ponds in the park are actually old gravel pits that have been filled in with water. The McLaughlin Wildlife Sanctuary in southern Watertown is also an old gravel pit that has been transformed into a pond for waterfowl. Active gravel pits can be found just north of Lake Kampeska.
Resources:
Rothrock, E. Paul. Water Supplies and Geology of Lake Kampeska. Publication. Vermillion, SD: University of South Dakota, 1933. Print.
NOT A LOGGING REQUIREMENT: Feel free to post pictures of your group at the area or the area itself - I love looking at the pictures.
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