Sinkholes are terrifying. People, homes, hotels, entire parts of Louisiana bayous — all of them keep getting swallowed up by giant ground vacuums. You don’t know when it’s going to happen. You don’t know where it’s going to happen. The earth just gives way without warning and sucks people in, like a golem opening his mouth. It’s like when a sleeping Johnny Depp is sucked into his bed in Nightmare on Elm Street, except these sinkholes happen when you’re awake (unless you’re that one guy from Florida whose bedroom plummeted 100 feet into the earth while he was asleep — WTF, they couldn’t even find his body). So why am I the only person I know freaking out about sinkholes?
I didn’t know sinkholes existed until this year when that guy got swallowed (I’m an idiot), but apparently they’ve been around for awhile. (Two giant sinkholes in Venezuela — Sima Humboldt and Sima Martel — are around 1.8 billion years old and are both big enough to have developed their own tiny ecosystems inside them.) And I figured sinkholes were probably caused by people taking long showers and not recycling their Greek yogurt containers. But humans aren’t the only reason sinkholes exist; it’s nature’s fault, too.
A sinkhole is exactly what it sounds like: a collapsed void of earth that is formed when a cavernous space under the ground sucks everything into it and makes a hole. The ground is made up of three basic parts (from top to bottom): topsoil, something called overburden and then bedrock. Most sinkholes are formed when water erodes the bedrock, which is already naturally filled with a bunch of little cracks, and then layers of overburden fall in, followed by the topsoil. And sinkholes frequently happen in areas where the bedrock consists of soft minerals and rock, which is more susceptible to erosion.
As far as naturally occurring sinkholes go, there are several kinds. The first and less dramatic is a “cover-subsidence” sinkhole. This happens gradually when water seeps into the ground and dissolves the rock underneath it. Stuff from the surface starts falling into the void, making a sinkhole. These are typically shallow.
The second kind is a “cover-collapse” sinkhole, the kind that happens suddenly and sucks stuff like humans into its gaping maw. This horrifying geographic phenomenon happens when caverns form under the layers of topsoil and overburden because of erosion, and sediment falls into the caverns over and over again to fill them until there’s nothing left to keep filling in the hole. Eventually, there’s a hollow space just underneath the topsoil that we can’t see and when the ground becomes thin enough, it either collapses under its own weight or collapses when a bus, cat, etc. puts their weight on it.
In 2010, an entire factory(!) fell into a sinkhole in Guatemala City — which is built on soft volcanic ash and limestone — after heavy rains (and sewer runoff, but we’ll get to the part where humans are ruining the earth in a second).
Lastly, there’s a “dissolution” sinkhole. These are boring.
But then there’s the kind of sinkholes that happen because we, as humans, keep messing with nature. We drill into the ground to build sewer pipes and mines and subway stations and parking lots, which mess with the flow of water and irrigation and subsequently increase the rate of erosion causing sinkholes.
In 1986, a human-made mine flooded in Russia, causing a sinkhole that is about 656 feet deep today — and growing.
In 1994, a huge stack of phosphogypsum, a radioactive waste formed during phosphate processing, collapsed in Florida. The phosphate people kept making stacks of the waste, each weighing millions of tons, because they didn’t know what else to do with it. Florida’s soil is prone to sinkholes and one of the radioactive stacks put too much weight on the ground and collapsed into a 150-foot sinkhole. The phosphogypsum then leaked into the water supply.
Then there’s the giant sinkhole that swallowed a grove of trees on the Louisiana bayou a couple weeks ago. You’ve probably seen the YouTube video. It was likely the result of a collapsed salt dome, but the state of Louisiana is arguing that the sinkhole disaster — which has expanded to cover 24 acres since 2012 — doesn’t have natural origins. In fact, they’re suing the Texas Brine company for drilling too close to the edge of the natural salt dome, which they say prompted the collapse, the sinkhole and the evacuation of 350 area residents.
Just start Googling sinkholes and you can bring up any number of images of the beasts in action. And while they may be more common in regions with soluble rock terrain, heavy rains, etc., sinkholes can happen anywhere. Anywhere! Without warning. That’s fucked up, right?
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