EMAIL YOUR ANSWERS THE SAME DAY YOU LOG THIS CACHE! NO GROUP ANSWERS ALLOWED!
1. How tall is Big Manitou Falls ___?___ Feet. It is the __?__ highest east of the Rocky Mountains.
2. Lake Superior sandstone is exposed at the gorge about __?__ feet from here.
3. What other great force 10,000 – 12,000 years ago occurred here to shape the landscape?
4. What effect, in your observation, does the upstream dam have on the waterfalls?
5. READ THE CACHE PAGE, WHAT IS THE FORCE that likely created Big Manitou Falls?
Pictures are welcomed, but not a requirement to claim this earthcache. Thanks for visiting this unique area.
Welcome to Pattison State Park. The Park is named for Martin Pattison, an early lumber man and miner. In 1917, Pattison learned of a plan to build a power dam on the Black River which would have destroyed Big Manitou Falls. To block the development, he secretly purchased 660 acres along the river from a number of landowners including James Barden. With the donation of the land, in 1918, Pattison saved the waterfall and property surrounding it. With this donation of land, Wisconsin dedicated its sixth state park on January 20, 1920.
THE DOUGLAS FAULT – BIG MANITOU FALLS
The following information is taken from the Pattison State Park, Big Manitou Geology Walk publication, available in print at the state park office. PUB-PR-521 2000 The cache coordinates bring you to the cantilevered overlook at Big Manitou Falls. Your answers to claim this earthcache will be at the overlook, from the nearby interpretive sign, and your observations on your hike to the overlook.
This picture shows the location of the earthcache coordinates with the “You Are Here” symbol on the map.
Big Manitou Falls. This falls is the highest in Wisconsin and among the 4th highest east of the Rocky Mountains. The dark brown rock it plunges over is called basalt or trap rock. Basalt is an igneous rock and represents solidified remnants of ancient lava flows which extended across the entire regional about a billion years ago. The flows originated from deep fissures in the area now covered by Lake Superior and extended 100 miles south of the park. The extensive distribution of the flows and fine texture tell us the lava was very fluid and cooled rapidly enough to prevent the formation of crystals.
Note that the basalt is massive and lacks bedding, or stratification, so common in sedimentary rock. But, you can see places where the bedrock character changes. These are areas where flowing lava covered rock that had been deposited by previous flows. The top of an older flow is usually different in color than the bottom of a younger flow above it. Hundreds or thousands of years between lava flows allowed weathering and oxidation to change rock color and to produce broken rock and even soil-like material, depending on the time involved. Finally, the texture of the top of a flow is usually finer than the mid-portion due to more rapid cooling at the surface. With these facts in mind, try to locate flow contacts in the surrounding rock walls.
If you could look closely, you would see that the upper surface of a lava flow is marked by small pits left when bubbles of gas escaped during the cooling process. The majority of pits are but a fraction of an inch in diameter, but some of the larger ones were the original “homes” of agates which weathered loose and eventually washed up onto the shore of Lake Superior.
The following picture shows the location of the Douglas Fault and its effect on the bedrock of northern Douglas County.
The Douglas Fault. As you look downstream, you can see, on the right (through summer leaves not as visible), an outcropping of light colored sedimentary rock known as Lake Superior sandstone. It was formed millions of years ago when great oceans covered this area. Streams carrying runoff into the ocean also carried grains of sand that settled to the bottom as great pressure over long periods of time cemented the grains into sandstone. (Take the trail to the bottom of the gorge to see the beautifully layered sandstone up close! Find the nearby cache there: GC4NKEY Pattison: WGA State Park Series)
Downstream on the left, almost across the gorge from the sandstone is basalt. The area between the two types of rock is the well-known Douglas Fault. The fault is the location of a huge crack in the basalt bedrock which extends from an area east of Ashland, Wisconsin, to the vicinity of the Twin Cities, Minnesota.
About a half billion years ago, the rock mass on which you are standing (south of the crack) was pushed upward by great forces within the earth. This movement, called a “thrust fault” is far less common than faulting when the rock mass moves downward. The high ridge to the north (located in Minnesota) is a similar fault resulting in the basin now occupied by Lake Superior. The rock beneath you moved slowly and at a 50-60 angle.
At Amnicon Falls State Park, and elsewhere, the location of the Douglas Fault is exposed, but here at Pattison State Park it is covered with debris from the steep banks and is less visible.
Where the rock mass moved, great pressure and heat were created. These forces ground the basalt into sharp-angled fragments which were later cemented together. This material is called breccia. In addition, the great forces caused fractures to radiate deep into the bedrock. These fractures were filled with a variety of materials and became veins of quartz, calcite and other minerals.
These two images show how the bedrock at Pattison Park was formed.
EMAIL YOUR ANSWERS THE SAME DAY YOU LOG THIS CACHE! NO GROUP ANSWERS ALLOWED!
1. How tall is Big Manitou Falls ___?___ Feet. It is the __?__ highest east of the Rocky Mountains.
2. Lake Superior sandstone is exposed at the gorge about __?__ feet from here.
3. What other great force 10,000 – 12,000 years ago occurred here to shape the landscape?
4. What effect, in your observation, does the upstream dam have on the waterfalls?
5. READ THE CACHE PAGE, WHAT IS THE FORCE that likely created Big Manitou Falls?
Pictures are welcomed, but not a requirement to claim this earthcache. Thanks for visiting this unique area.
This cache placed by a member of:
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Thanks for the assistance and permission for this earthcache which was granted by the Wisconsin Department of Natural Resources, Kevin Fiend, Superintendent, to highlight the geological features of Pattison State Park.
PARK