Sinkholes: An Introduction

I don’t know how many of you have heard this news, but a massive sinkhole in Florida took the life of a man while he was sleeping in his bed. The area is very unstable, and the house is being demolished. The neighbouring home was also compromised, and both families had only a short amount of time to retrieve precious items within the homes.

In such a tragic event as this - and because this deals with geologic topics I often focus on - I felt very compelled to talk about the importance of knowing your area, as well as signs of how to contact officials if you find you may be in danger of sinkholes. I’ve personally dealt with sinkholes on too many (planned & unplanned) occasions, have fallen in them, have rescued animals from them, and had my past home demolished because of them. I feel for this family greatly.

The photos above are screencaps from the video on nbcnews.com that accompanies the story. There are examples of past sinkholes, as well as the diagrams giving you a cross section with the general way they work.

I’ve studied sinkholes from the small to the massive. They can range in all sorts of sizes: from length, to width, to depth. Just goole “sinkhole” and you will find a whole bunch of photos. Here’s some from National Geographic that show the world’s most well known pits.

Sinkholes can occur anywhere on Earth, at any time, and the process that manifests before they collapse can be sudden or many, many years in the making. These events are all due to erosion. Much of the time, underground caverns/voids form under the karst process when water erodes the vulnerable soluble bedrock (like limestone), making the ground above unstable over a period of time until it collapses. Here are a few diagrams other than the ones above: state.fl.us, esi.utexas.edu.

Sinkholes also are not always isolated, as underground drainage (natural and artificial) can lead to networks of caverns and underground streams which contribute to the general weakening of a certain area. One may form today, but another could form within minutes, days, or years from the other. In the second photo above, the states highlighted are ones that have been found to be more vulnerable to sinkholes in the US.

I explained the geological term for “sinkhole” above, but the word is more widely used in media to discuss any depression that forms on the Earth’s surface. Many sinkholes can occur due to piping, mines, or anything artificially made that has compromised the stability of the surrounding rock too. There are “sinkholes” (technically: piping pseudokarst) that have occurred like the ones in Guatemala, where the city lies on hundreds of feet of volcanic deposits, and ageing piping was part of the area’s demise.

When it comes to sinkholes in your area, it’s best to do research and read about past incidents in your town, study what your house/area sits on, and read about your climate. If you find yourself surrounded by small sinkholes, there’s a good chance something bigger is below. Speaking from experience, when you’re in a foot of water, and the surface is being covered quickly with developing bubbles all around you, get out.

Usually, with the thousands of sinkholes that happen each year, most of the time no one is severely hurt. Though, this story is a sad reminder of why we must continue to study Earth Sciences, learn from these events, and figure out what we can do to prevent anyone else from being injured or killed.