Wednesday, October 7, 2015

A Pair Of Waterfalls

The ridge and valley section of Pennsylvania is geologically quite old and was, with minor exceptions, not covered with ice during either of the last two glacial epochs (the Wisconsinan and the Illinoian). The ridges are composed of folded layers of sedimentary rock, often compared to the ridges formed when a carpet is pushed up from one side.
From Bing Maps

The result is that most stream valleys are quite mature, the streams having eroded their way through the underlying strata during the last several million years. In addition, there are very few places where the strata are anywhere near horizontal. 

Therefore, waterfalls are very, very uncommon in the ridge and valley section unlike in areas to the north that have been relatively recently glaciated and the underlying sedimentary rock is in more horizontal layers.

McElhattan Run is one of the streams in the ridge and valley section. The stream originates in a wetland known as Rosecrans Bog and flows for almost two miles across a fairly level high valley, losing but 65 feet of elevation. The stream, there called Jamison Run, is the major tributary to the reservoir that supplies drinking water to the City of Lock Haven and other communities.

After exiting the reservoir the stream’s name changes to McElhattan Run and it begins its descent of over 1,100 feet in seven and three-quarter miles until it enters the Susquehanna River near the town of McElhattan. For the first three-fourths of that distance the stream flows through either state forest or watershed land, through a deep, narrow gap in the long ridge that is Bald Eagle Mountain.

Only twice have I hiked along McElhattan Run, the first time in 1986 and the second two weeks ago. In that deep gap there are large boulder fields, what in German would be called Felsenmeer (sea of rocks), relics of the last glacial epoch when the area was impacted by low temperatures and resembled regions currently above the Arctic Circle.  

However, the more aesthetically pleasing features of McElhattan Run are the large rock ledges and outcrops in the upper reaches –

Which are surpassed in visual beauty by the pair of waterfalls not far below the reservoir, one on the main stream –

And another, on an unnamed tributary, almost directly across from the first –

The waterfalls aren't very high, but they're still well worth the hike up through the deep gap.


Molly said...

What a beautiful place.


The Furry Gnome said...

I love it when you can relate the waterfalls to the underlying geology. Very interesting stuff!

Unknown said...

Wow, the waterfalls are gorgeous!