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Where the foothills of the Appalachian Mountains (allegheny plateaus fingerland) terminate into the glaciated allegheny plateau on the Mississippian exposure line lies the most central foot hills in Ohio and it’s classic temperate forests.
Sunrise over Pittsburgh, the confluence of the Monongahela and Allegheny Rivers
Enjoy these photos from my trips to Shenandoah in honor of NPS being ungovernable af on twitter pt 1
Fly poison, Allegheny stonecrop, a view of the Blue Ridge, American mountain ash, columnar jointing in metabasalt
Late autumn in Kempton, November 2nd 2015
Long Lakeshore
I saw this map and couldn’t help but wonder if this lake would hold the record for highest ratio of “shoreline length to lake area” in all of geologic history.
Sometime between 750,000 and 900,000 years ago, lobes of glaciers were beginning to extend southward from Canada into the Eastern United States. Prior to the formation of those glaciers, the rivers that drain the northwestern side of the Appalachian Mountains headed to the north, with the water exiting through what is today the St. Lawrence Seaway.
When the glaciers extended far enough south, the ice blocked the water flow and caused it to back up, creating a lake that reached depths of nearly 100 meters. The lake was extremely sinuous, filling the eroded and meandering river channels that formed during the long process of eroding the Appalachians.
Although there aren’t well-eroded shorelines as there are on other glacial lakes, remnants of this lake are found today in the form of sedimentary deposits created as streams carried dirt into the lake and deposited that dirt near the shoreline. Today abandoned terraces, small deltas, and hills can be found marking the elevation of these lakes. These sedimentary deposits are similar to the kind found at the edges of man-made lakes today (where rivers have been dammed but sediments still flow in).
The lake met its end when one of its edges ruptured. Near the southwestern edge of the lake, where the blue dashed line leaves its boundaries, the lake broke through a geologic divide and water began flowing the opposite way. As water flowed out, it carved a new channel and a new route west, where it eventually found its way to the Mississippi River. The rupture and draining of this glacial lake about 730,000 years ago led to the integration of the modern Ohio River system.
Small lakes formed later as various other ice sheets dammed river channels in this area, but none was nearly as expansive as Lake Monongahela.
-JBB
Image credit: https://wikimediafoundation.org/wiki/File:Lake_Monogahela.jpg
References: http://www.wvencyclopedia.org/articles/1273 http://bit.ly/1DvJdGs
