Arrowhead Park 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. Describe the formation of the quartzite you see in the park.
2. Estimate the height of the quartzite outcropping at ground zero. Describe the changes in height around the pond. What would account for the change?
3. Describe the quartzite in terms of redness with 1 being a very light pink and 10 being red.
4. The striations on the quartzite indicate the direction of the glacial flow. Examine the quartzite. What is the direction of the glacial flow?
This Earthcache is located at Arrowhead Park in what used to be known as East Sioux Falls. Settlers began arriving in the area in the 1860s. Soon after, they began to quarry the Sioux quartzite in the area, and East Sioux Falls became known as a quarry-man’s town. East Sioux Falls was officially established in 1887 and flourished for several years. The financial panic of 1893 and technological change lead to the town’s downfall and the demise of the local quarrying operations. Today, the quarry has been converted to a nature preserve. The open-pit mine where quartzite was once excavated has since been filled with water and serves as a pond for waterfowl and fish. Despite the area’s transformation, quartzite outcroppings can still be seen today. Please observe park hours and only search for this during the daylight. Enjoy!
The area near Sioux Falls and extending north toward Garretson is known for its ancient rock formations. These outcrops of finely textured Sioux quartzite dot the landscape. Sioux quartzite is an extremely hard rock that is resistant to erosion. 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. Looking at the exposed quartzite, one can see the documentation of the water that covered much of the earth on at least two dozen occasions.
The origins of the Sioux quartzite begin when prehistoric seas receded and left behind sandstone composed of rounded quartz sand grains. The mountain building forces of the earth placed incredible stress on this sandstone. Eventually, all of the stress caused the sand particles to become cemented together with the quartz. Over time, a solid, interlocking mass of crystals formed and the sandstone metamorphosed into quartzite. Because the sand grains had been cemented together with the quartz, there are no tiny openings in the quartzite as there are in sandstone. This feature gives the Sioux quartzite its unusually resistant quality. The resulting rock also contained a small amount of an iron-containing mineral called hematite, which give the rock its pinkish color.
Over one billion years ago, geologists believe that a large mountain range of quartzite once dominated this area. The quartzite stretched from just west of the Missouri River in central South Dakota to the bend in the Minnesota River in Minnesota. Throughout the course of millions of years, inland sees added deposits of chalk, limestone, and sandstone over large sections of this massive quartzite formation and mostly buried the quartzite. As the glaciers of recent ice ages passed over Arrowhead Park, they warped and tilted the rocks until the quartzite was exposed. As time passed, wind and weather gave the quartzite its glossy sheen.
The Sioux quartzite is exposed mainly along river valleys, but also in many other places throughout southeastern South Dakota, southwestern Minnesota, and the northwestern tip of Iowa. The ancient formation that is still largely buried underground is said to cover an area of about 6000 square miles in these three states. Exposed bits of quartzite can be seen here at Arrowhead Park, at Falls Park in downtown Sioux Falls, at Gitchie Manitou Park in Iowa, at Palisades State Park near Garretson, along the Big Sioux River in Dell Rapids, along the Split Rock Creek in Garretson, and in Blue Mounds State Park and Split Rock Creek State Park, both in Minnesota.
Careful examination of the quartzite at Arrowhead Park will reveal the ripple marks left by the ancient oceans. Circular and crescent-shaped marks can also be seen. These marks were more than likely created by a large river of glacial melt water which once flowed down the Big Sioux Valley. The rocks that were carried by the swift current struck up against the quartzite, producing the circular cracks. There is also evidence of smoothed and scratched surfaces, which were made by glaciers that passed over the region during the Ice Age.
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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