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From here, you get an excellent view of just how large Lake Pepin is. You also get a great view of how high the bluffs are on the each side of the lake.
Lake Pepin is a wide stretch of the Mississippi River, surprizingly, the widest natural part of the Mississippi River. The purpose of your visit here is to discover why Lake Pepin is here, why there are high bluffs on either side of the lake, and learn about the origins of Lake Pepin.
You will notice that the landscape of the shoreline is varied, given its great length, but in general it consists of 400 foot high fairly flat-topped bluffs cut down by the Mississippi and its tributaries.
The area around Lake Pepin is part of the "driftless" area, an area caused by glacial meltwaters, but not itself visited by glaciers. The rock within approximately 20 miles south of the Mississippi is dolomite and, to a lesser extent, sandstone (Oneota and Shakopee Formations) deposited in the early Ordovician period. Near the river this has been cut away to expose upper Cambrian sandstone and shale.
As Minnesota's last glaciation ended and the ice sheet retreated, a huge amount of meltwater came off the glaciers and produced proglacial lakes and rivers. The largest of these lakes was Lake Agassiz, the result of the melt of the St. Louis glacier to the northwest. Beginning about 11,700 years ago, Lake Agassiz emptied into the River Warren roughly where Minnesota, North Dakota and South Dakota intersect. River Warren followed a path which approximates the course of the Minnesota River today. There were also smaller lakes, to the west of modern Lake Superior, which flowed southward into the Kettle and Glacial St. Croix rivers, the latter of which approximates today's upper Mississippi. These three converged in the Twin Cities area to become Glacial River Mississippi. This river carried an enormous amount of water in a short period of time from the melting of the glacier, as evidenced by its broad valley. Its stream frequently split into multiple channels, isolating islands of bedrock from the banks of the river.
These rapid flowing, high volume, glacial meltwaters dug the deep ravine that you see today, and caused the high bluffs on either side of Lake Pepin, that are still present today.
About the same time, glacial meltwaters in Wisconsin followed along near the course of the modern day Chippewa River. Since the Chippewa River has a higher gradient, more silt, sand and gravel was brought down to the Chippewa River delta as it entered into the Mississippi River, than even the mighty Mississippi could wash away and a natural dam formed. Even today, the delta of the Chippewa River continues to bring down sediment due to the high gradient of the Chippewa River valley, which has formed a natural dam of the Mississipi where the Chippewa flows into the Mississippi. The confluence of the two rivers has resulted in a natural dam, located at the downstream end of Lake Pepin.
The lake originally extended upstream all the way to St. Paul, that is, to more than twice its current length. Since the lake's inception, however, sediment has filled in the channel and raised the lakebottom, so that its deepest point today is the approximate elevation of the top of the lake in its early days. This filling, along with the drop in water volume, has helped create the landscape of the river's edge: many subordinate channels have been abandoned, the water being diverted to the more deeply-cut main channel, leaving flat strips on which are built railroads and highways. Examples of the bluff areas and uplands which were originally islands in the torrential glacial stream (but which are now separated only by areas of low, flat ground) are Barn Bluff in Redwing and the area of land which includes the Minnesota Memorial Hardwood State Forest.
Although the Lake Pepin area has never been directly glaciated, glacial processes are responsible for its appearance. Postglacial streams and the filling of the lake with sediment have altered the landscape as well, but the most striking features are the direct effect of the repeated Pleistocene glaciations of Minnesota.
To log this cache, you need do three things:
1. Physically visit the shores of Lake Pepin at the above coordinates and include in your log a description of what Lake Pepin looks like to you.
2. Send me a brief email that tells me how long Lake Pepin is, in miles, at the current time.
3. Include in your email to me, your speculation on whether Lake Pepin will grow larger or shrink over time, and explain why.
(Due to Earthcache Rules, I need to delete logs that do not meet the above very easy requirements.)
Additional Hints
(Decrypt)
Ernq gur fvta, ybbx ng gur ynxr, rawbl.