Being a flood control area, the depth varies a bit. The pics are from a day when the water was very high, yet I have seen it at least 6 feet higher. Is the pattern solely from erosion? I have never seen an animal, other than some huge spiders, on these rocks, yet the areas look inviting to animals.
I think the rock is limestone or sandstone, but I am no geologist, and this is just something I’ve heard. Extra credit: Find the bird!
From the picture titled “cliffs2” (these) link, the circular pockets look like places where volcanic ash and/or gas was trapped in the tuff while the rock was forming.
Before the board crashed, I was just about topost a picture of the tuff that is along the banks of the Colorado River in Arizona (Grand Cayon stuff). Where the water has eroded the tuff it does actually look a bit like slate.
While travelling to do rock climbing and caving, I’ve seen some gorgeous formations created with volcanic rock. Ash flows are cool.
The website (first link in the OP) says the cliffs are sandstone. It’s not unusual for sandstone to weather in layers, as it’s a sedimentary rock which deposits in layers of varying grain size and matrix composition. The bubbles might just be…bubbles; sandstone forms from mud, and can contain bubbles from air trapped in the mud. IANAG, though.
It looks like sandstone you see in Wisconsin. Often it’s recessed in an undercut, so the drip line is many feet beyond the wall. The outer layer can have a hard coating, and finding holes in it is possible.
I can’t find what I wanted to show. The sandstone erodes out faster than the veins of quartz and iron or lead and you get ribbon effects on the cliff face. It’s not unusual to find hollow pockets in the sandstone with quartz crystals lining or filling them.
There is some karst in south central PA, in the Appalachian Mountain Section, though not as much as in the Great Valley and Piedmont Lowlands. Loyalhanna Lake, however, is in southwestern PA, in the Pittsburg Lowland Section, which is wholly distinct from from the karst region.
“Loyalhanna,” BTW, is a hard name to research in PA geology, as Loyalhanna Creek and Loyalhanna Lake are a bit distant from Loyalhanna Gorge (where US Route 30 runs), and then there’s the “The Mississippian (Chesterian) Loyalhanna Member of the Mauch Chunk Formation,” which runs all the way into the friggin’ Alleghenies. All connected, of course, but when you’re trying to find out whether there’s limestone here, and the literature tells you there’s limestone in this other place by the same name…
hehe. Yep, a great blue heron. I followed him around all day.
Nametag thanks for the links. I never thought geology could be so interesting! Harmonious Discord, Edward The Head, panache45, Swallowed My Cellphone, Pygmy Rugger: Thanks to everyone for the info. Hope to see you on the water!!
Also, I spoke with a park ranger at Crooked Creek Lake yesterday evening and he confirmed with 100% certainty that the cliffs are sandstone. His cite was conversation with other rangers.
Vetbridge, have you ever visited Laurel Caverns? Their interior reminds me of your cliffs. It looks to be the right area, too.
Since the rangers were so confident that it’s sandstone, it might be Pottsville, which is full of caves (which to my mind would make it soft and prone to forming what you saw):
“Pottsville Sandstone. This sandstone is of Pennsylvanian age and occurs just above the Mauch Chunk formation. It has two sublayers: the Homewood Sandstone and Connoquenessing Sandstone. Both are massive cross-bedded layers containing plant fossils. Well-known outcrops of Pottsville Sandstone include Elk Rocks in Fayette County, Beam Rocks in Somerset County, and Wolf Rocks in Westmoreland County.” Cite
I’ve always had a soft spot for physical geography.
