The Quick 'n' Dirty Self-Help Karst Tour

I have no problem admitting that whatever the opposite of a geologist is, I'm that. Before I moved down to Kentucky I had the luxury of being able to, for the most part, ignore the ground beneath my feet; but those days are in the past. Now I work at a park and the third commonest question I get from people (after "Are there any poisonous snakes?" and "Where are the restrooms?") is, "What's karst?"

The geologic phenomenon known as karst is a big deal in Kentucky. The word itself derives from a Slavic word indicating barren, stony ground. It refers to a terrain formed from the slow dissolving of soluble bedrock such as dolostone or limestone, resulting in caves, sinkholes, sinking springs, subterranean drainage, and general all-around instability. Because of its predominately limestone bedrock, Kentucky is one of the most well-known karst landscapes in the world; this results in some amazing places— like Mammoth Cave National Park—and also some accidents, like the 40-foot sinkhole in the National Corvette Museum in Bowling Green. Now I find myself smacked down in the middle of some of the karstiest karst you’ll see anywhere and I've resigned myself to the fact that I better learn something about it; so I've put together (mostly for my own edification) a self-help guide to some elements of karst topography.

And if you want you can follow along with a picture from our beautiful signage.

For the sake of demonstration and a visual tour, let’s start at the beginning with the karst system at the park where I work. The headwaters (so to speak) of our little spring system is the Blue Hole. Essentially a sinkhole filled by water leaking through an underground fissure, prismatic effects work together with the Blue Hole's depth--an abrupt 15 feet--to create its unique appearance. 

or MAGIC

Insulated by the bedrock, the water coming up from the Blue Hole stays a balmy 55 degrees Fahrenheit all year around (similar to many cave systems). You can see a little snow on the bank, but otherwise there's no clue that this photo of an American Robin stopping for a drink was taken on subzero January morning. Aquatic plants, like the water purslane in the background, stay green all year round in the spring water.
 A few yards past the Blue Hole, the water disappears underground again into a handful of crevices. Following the trail for another 1/8 of a mile or so, and you'd never know there's water running under your feet until you come around the corner and stumble upon the second spring in the karst window, known as the Boils. Much shallower--about calf-deep--than the Blue Hole, the underground water filling the Boils comes to the surface under enough pressure to create a bubbling, roiling effect. After a solid rain the Boils sometimes rises up a foot or two like a tiny Old Faithful.

The Boils, after several weeks without rain. Most of the water comes up through cracks and crevices hidden under the limestone outcropping.

And then the old H20 is above ground again for another quarter mile or so. If you deviate from the path of the water a little and go up the hill into the woods you'll find something of both historical and geological interest (if you're a massive nerd). Way back in the day before the land was a park, it served as a farm (and also an old settlement site, and a gunpowder mill, and an illegal dump, and lots of other things, but that's a long story). One of the remnants of the earlier usage are long stretches of ye olde famous Kentucky drystone fences, so called because they're held together by artful stacking and gravity versus mortar. Usually dating back to the 19th century, the drystone fences have weathered the years shockingly well. Coming from Ohio--a land of short-lived split rail and barbwire fences--I was surprised coming into the Bluegrass region, where hundred-year-old property lines are still clearly visible in many places. Most of the fences on the park, and some of the other historical structures, were built from limestone from a little limestone quarry situated up the hill from the springs.

Limestone quarry, a couple different views and a closeup (right) of the stacking

This rocky outcropping gives you a nice little cross section of what's going on under your feet. It's stacked very loosely, more like paper piled up than the stratification that you sometimes see in bedrock where highways were cut through and that sort of thing.If you wanted to you could walk up and pull out big slats of rock just like it's a giant game of limestone Jenga. (But don't. Because it's on the National Register of Historic Places and you aren't supposed to destroy it. Actually it's a good idea not to destroy things in general.) Limestone (in case you didn't know) is basically made of sediment and remains of smashed sea creatures from the millions-year-old sea that once covered Kentucky. This means that some of the best fossil hunting I've ever come across has been in the Commonwealth. Most of what I've found in areas like this has been branch coral and brachiopods, but just about anywhere where you find some good exposed limestone has the possibility to be fossiliferous. That's a real word.

Whoa, so fossiliferous!
(from a creek bed in Madison Co., KY)

If you're interested in the fossiliferous properties of local limestone, get more a more educated and in-depth look at it here.

Anyway, back to the water. After the Boils, it continues as an above-ground stream for maybe another 1/8 of a mile or so, and then it abruptly disappears at the back side of the park, into a little cave entrance called the Final Sink. Unlike the cracks that allow the water to come up from the Boils, the Final Sink is large enough and cave-y enough that an adventurous skinny person would be able to crawl down it, but it certainly doesn't look tempting. (This is the spot where, on a school field trip I was leading, one of the kids yelled "I SEE EYES! I SEE GLOWING EYES DOWN THERE!")

If you look at the upper righthand corner, you can sort of see another element of karst topography, a small sinkhole on the far side of the Final Sink.

In an interesting twist, the park was owned by a development company back in the day and slated to be filled in and become part of an industrial park. This backfired when the plan was derailed by a city ordinance prohibiting people from filling in sinkholes and springs. (Why anyone would think it was a good idea to build on sinkholes I have no idea.)

So there you have it, some karst topography. At the very least I've come to appreciate the effect geology can have on a landscape. I've vastly oversimplified the whole idea here, because that's where I am in my learning curve, but if you're all about the karst and want to see some awesome examples, be sure to hit up the Bluegrass region. And if you aren't all about the karst, at least you learned not to build a house on a sinkhole.

And everyone likes nice fences.
(Bryan Station Rd., Lexington, KY)

Words from Aldo

"A man may not care for golf and still be human, but the man who does not like to see, hunt, photograph, or otherwise outwit birds or animals is hardly normal. He is supercivilized, and I for one do not know how to deal with him. Babes do not tremble when they are shown a golf ball, but I should not like to own the boy whose hair does not lift his hat when he sees his first deer. We are dealing, therefore, with something that lies pretty deep." 

--Aldo Leopold, "Goose Music"