Wednesday, April 15, 2015

Living on the edge: A geological primer of Hocking Hills

Rock bridge Hocking Hills Wes Supper
Rock Bridge, Hocking Hills
The Hocking Hills region is a stunning anomaly.  Chockablock full of magnificent gorges and waterfalls, outlandish cliff sides, rock formations, and rare plants and animals that would require a hundred miles of travel just to find another one like it.  You see, the Hocking Hills region is unique because it always seems to find itself perched right on the edge.

The actual rock itself, is a type of sandstone, made up of different particles that were once floating along in rivers and streams.  As those rivers and streams entered a shallow sea, they slowed down, and the particles began to settle to the bottom.   Back then the Hocking Hills area had more of a coastal feel to it, right on the edge of a large body of water.  To be fair, this was a while back.  In fact we’re talking before dinosaurs!  Over time, that sediment compressed and developed in layers of rock several hundred feet thick. 

Over time the fickle earth changed its mind and the area was no longer near any kind of sea whatsoever.  The only water, fell from the sky and began to traverse across the surface, slowly eating into and eroding the very sandstone it had helped put there in the first place! 

Now imagine making a concrete sandwich, with the buns having plenty of mortar, AKA glue to hold everything together, while you skimped on the mortar with the burger, so it kind of falls apart easier than the buns when it gets wet.  Well that’s similar to the making of this sandstone rock, which is why recessed caves are a prominent feature of the Hocking Hills.  (Think concrete sandwich with only half the meat gone.)     

Glaciers in Hocking Hills

Fast forward geologic time and the once flat coastal area of the Hocking Hills had developed nooks, crannies, peaks, and valleys, though we wouldn’t recognize the place… yet.  Long after the dinosaurs had come and gone, Canada got such enormous amounts of snow dumped on it that it began to squish out from the sheer weight and volume, and glaciers started to ooze to the south.  In fact the last one almost reached Hocking Hills State Park, but not quite. Once again, right on the edge, as a finger of it slid past Laurelville and made it about halfway to South Bloomingville, before giving up and returning home where it was colder.

As that glacier slowly retreated, it did something very important.  It melted. As it melted it left behind souvenirs of its journey.  Stuff got caught up in it or pushed along by it as it traveled south.  Stuff like sand, clay, seeds, and the like.   Additionally, with the glaciers big thaw, came lots of water and the erosion of the sandstone went on a serious bender!   

The gorges got deeper.  The waterfalls got bigger.  Water percolated through the porous sandstone and just like it does on our roads during the winter, popped out pebbles and created “potholes” in the roofs and walls of canyons, and continues to do so even today.  

 In some places, it did the opposite, perhaps nostalgic for its coastal days, the stuff once caught up in the glacier began to settle to the bottom and accumulate.  Imagine filling in the Grand Canyon with silt and sand. Today the Hocking River actually flows across the surface of something just like that as it makes its way through the Hocking Hills.  You can get up close and personal with these outwash terraces on the right banks of the wide sweeping left hand turn about halfway between our Trip A and our Livery.  Proof positive that the locals here in the Hocking Hills are living on the edge!


Geology of Hocking Hills State Park region, Hansen 
Ice Age in Ohio, Hansen  
Glacial Map of Ohio, ODNR 
Another Blog on Hocking Hills Geology 

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