Shadow Falls EarthCache
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The spot where you are standing used to be covered by the ancient Glacial River Warren. It carved out the river's path through the area sending the water from Lake Agassiz some 10,000 or so years ago. Since that time sand, silt, and clay have been filling the valley forming the colorful landforms across the flood plain.
The rock formations were originally formed during the Cambrian and Ordovician periods (some 550-450 million years ago). At that time shallow seas covered much of southeastern Minnesota and the surrounding regions. Sand accumulated around the shorelines of these seas creating beaches and sandbars throughout the area. Sand and silt formed in the mud flats or offshore in these same seas. The remains of organisms also settled at the bottom as large layers on the sea floor. These various sediments eventually compacted and cemented to create sandstone, shale, limestone, and dolomite.
Along the Mississippi River there are bluffs ranging from 100 to 400 feet in height. The limestone and dolomite have resisted much of the weathering and erosion where the sandstone and shale has weathered heavily. The limestone and dolomite are more heavily packed than the poorly cemented sandstone and shale. Stream erosion has played a great part in this process. As the glacier and Lake Agassiz retreated the water cut the valleys wider and deeper.
The Shadow Falls are hidden within a deep ravine near Summit Avenue in Minneapolis/St. Paul. The Shadow Falls Creek flows over different layers of bedrock and over the past 11,000 years have worked to shape and expose layers of the Mississippi River Gorge.
The falls were created when ground water springs in the area worked their way through the sandstone and eroded the underbelly of the Limestone above. Numerous fossils can be seen throughout the Limestone layers over the falls which date back over 400 million years.
In the late 1800's investors wanted to use the area as a summer resort but concerned citizens were able to convince the two cities to preserve the area as a forested bluff for public use.
Now the falls area, in the summer months, is frequented by hikers and geocachers as a means of exercise and exploration. In the winter the falls freeze and you can often find ice climbers scaling the frozen waterfall.
Requirement 1: At the posted coordinates: what are the 6 sections of earth that you are standing on right now?(hint: its on the board) From this information what layer or layers do you think took the shortest amount of time to erode through and why?
Head to Trailhead and walk down the trail until getting close to Stage 2. (there are faster routes but this one is the safest and most scenic)
Requirement 2: Take an elevation reading at the top of the falls at Stage 1 and at Stage 2. Between the two points how much rock has been eroded by the water?
Requirement 3: Underneath the falling water, what types of broken rocks are on the ground?
There will be times of the year where getting to Stage 2 is dangerous. Please use your common sense and do not try if you are not able to safely get to it. If it has rained recently, everything will be very very slippery.
This cache is registered with The City of Saint Paul Department of Parks and Recreation.
As always please do not post any answers in your log. Thanks for visiting!
Additional Hints
(Decrypt)
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