Split Rock Lake 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. Estimate the size of Split Rock Lake.
2. Estimate the amount of water and rate at which the water flows per minute at the dam.
3. What other evidence of quartzite do you see in the area?
This Earthcache is located in Split Rock Creek State Park near Ihlen, Minnesota. The park sits atop the Coteau des Prairies. The main feature in the park is the lake, which is the largest body of water in Pipestone County. A day pass or annual pass will be required to enter the park. This park is popular among campers, sightseers, fishers, hikers, and swimmers. The coordinates will take you to a bench just off the trail. Have a seat, read the informational sign, and enjoy the area!
Geologists believe the terrain in the Split Rock Creek area was formed by three major ice movements during the last glacial period. As these glaciers melted, they deposited a slightly irregular blanket of glacial till over the entire area. These deposits descend on a gentle slope from west to east across the south-western portion of the state.
The land in the Split Rock Creek area is part of a vast geographic formation known as the Coteau des Prairies. The Coteau is a high plateau of land that is shaped like a flat iron and consists of several hundred feet of glacial material underlain by sedimentary rock. The Coteau des Prairies stretches about 200 miles from north to south and 100 miles from east to west. It covers much of eastern South Dakota, southwestern Minnesota, and northwestern Iowa.
20,000 years ago, a massive glacier carved out the plateau. During the last ice age, two lobes (tongue-like extensions of the main ice sheet) of the glacier parted around the pre-existing plateau. These lobes, the James River Lobe and the Des Moines Lobe, moved south along pre-glacial stream valleys just to the east and west of the plateau. As the lobes moved south, they further deepened the low lying prairies on either side of the plateau, which then drained meltwater as the glaciers retreated to the north.
In some areas, particularly on the western edge of the Coteau, the change in elevation is quite dramatic. This change in elevation has resulted in different drainage patterns for the Coteau than for the rest of southwestern Minnesota. A major drainage divide, which runs roughly from Worthington to Lake benton, lies about fifteen miles east of the park. From the divide, the Mississippi River drainage flows to the northeast, while the Missouri River drainage flows to the south and southwest.
The most prominent features of Split Rock Creek State Park are its lake and quartzite dam. A dam is a barrier that confines water or underground streams. Dams generally serve the primary purpose of retaining water. They can also be used for a variety of other purposes:
- to generate hydroelectric power
- as a water supply for a community
- to control and stabilize water flow for agricultural and irrigation purposes
- to prevent floods, to prevent water from coming into an area that would be otherwise submerged, allowing its reclamation for human use
- to divert water to another drainage or reservoir to increase flow there and improve water use in that particular area
for recreation and aquatic beauty
Split Rock Lake is the largest lake in the county and was created in 1938. In order to provide water-based recreation for an area of the state that has few lakes, a large dam was constructed by the Works Progress Administration (WPA). This dam was built entirely out of Sioux quartzite.
Sioux quartzite is an extremely hard rock that is resistant to erosion and is often used as a building material. It is a pink colored rock that varies from very light pink to very dark pink based on the amount of iron oxide present. The quartzite outcroppings that you see in the area date back to the Precambrian Era. The Precambrian is a geological time period that begins with the formation of the earth and ends with the appearance of hard shell animals. The Sioux quartzite is estimated to be about 1.8 billion years old. These pink stones were one of the first water-deposited rocks to be laid down over the ancient, metamorphic rocks and granites that were created during Earth’s formation.
Before the creation of Split Rock Lake, Split Rock Creek flowed freely through the park. When the dam was constructed, a reservoir of water was created. This reservoir was filled by Split Rock Creek. Today, Split Rock Creek flows into Split Rock Lake and continues on its journey on the other side of the dam.
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.
Additional Hints
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