Great River Road
In Minnesota, United States
Size:  (not chosen)
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At this location you will find several interpretive signs describing the geology, flora and fauna of this region. Review these signs to answer the questions below. Note that due to the number of signs and amount of text to read through, that I have upped the difficulty on this Earthcache a little bit.
From Winona to La Crosse, the Mississippi River valley displays its greatest depth as it extends vertically through the sedimentary rock plateau. Here, Highway 61 follows the narrow strip between the river and the steep bluffs that mark the valley's western wall. The valley walls are composed of two different types of rock, which formed about 500 million years ago in a warm, shallow sea that covered much of what is now North America. The lower, more sloping parts of the valley walls are composed mostly of weakly cemented sedimentary rock which erodes easily. On the upper parts of the walls, steep cliffs shape the bluffs. The cliffs are composed of dolostone, a chemically altered sedimentary rock that is resistant to erosion.
Bluffs are formed as the Mississippi River or a tributary cuts into the soft sedimentary rock, initiating rockfalls that undercut the dolostone. The dolostone then breaks along vertical joints, leaving steep cliffs. Two of the most prominent bluffs in the area, are visible from this site on the west side of the valley. Both are designated Scientific and Natural Areas by the MN DNR for their unusual geology and rare biological communities.
These bluffs are within and area of deeply eroded stream valleys primarily east of the Mississippi River and covering southwestern Wisconsin. During the Ice Age of the last two million years, glacial ice never passed over and leveled this area, and no drift, or glacially carried sediment (clay, silt, sand, gravel and boulders), was deposited here. However, the landscape before you was blanketed with a layer of loess - a wind-blown, tan-colored rock dust. This dust was carried by winds from floodplains still bare of vegetation, which were repeatedly loaded with very fine sediment by streams that drained melting glaciers. Today, a distinctive and fertile soil has developed in the top of the loess, which helps to give rise to the diverse and sometimes unique plant communities found on these bluffs.
To log a find on this Earthcache email me the answers to the following questions:
1) Approximately how many feet deep is the Missippi River Valley along this stretch of Hwy 61.
2) What two types of rock predominately make up the bluffs and valley walls in this area.
3) This area of MN and WI were not directly affected by the last Ice Age. What name is used to describe such a region and how large is this region?
4) Give a brief description of a "Goat" prairie, including a specific measurement found on the interpretive signs.
5) What indirect glacial impacts did this region experience during the last ice age?
6) What specific scenic landforms are visible from this point and in which direction do they lie from GZ? Answers of "bluffs", "Mississippi River", etc. will not be accepted.
7) (optional) Post a photo taken from GZ with your log, so everyone can see how the area looks during different seasons. Feel free to include members of your group if you wish, but avoid including close-ups of the informational signs in your photo.
I apologize if the questions above seem overly specific or difficult, but the intent is to prevent people from logging a find who have not physically visited this site. If you visit the site and read the available interpretive signs, you should have no problems. If you are concerned about your answers, be sure to take a photo of your group/GPSr as concrete evidence of your visit.
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Last Updated: on 04/26/2016 17:59:33 Pacific Daylight Time (00:59 GMT)
Coordinates are in the WGS84 datum