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The Science of Sinkholes: What You Should Know

by Dr. Anthony F. Randazzo

August 28, 2015

A Tampa man died when a sinkhole suddenly swallowed his entire bedroom and pulled it deep into the earth. But what exactly is a sinkhole and how do they happen?

WHAT CAUSES SINKHOLES?

Naturally occurring sinkholes, like the one that killed Jeremy Bush, are depressions in the earth caused by water erosion of the bedrock below a land surface. Acidic rainwater seeps through the ground and reaches soluble bedrock (usually salt, sandstone, or a carbonate rock such as limestone). It dissolves small amounts, and carries the particles away. Over time (even thousands of years), this process can enlarge natural pores and cracks in the bedrock. This can reach the point where large cavities or caves are formed. And with a gaping hole underground, there’s nothing to support the weight of layers of sediment above and finally that’s when the ground collapses.

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Non-naturally occurring sinkholes can form because of water main breaks, sewer collapses, or even abandoned mines. If there’s a substantial change in the weight of a land surface, such as when industrial or runoff-storage ponds are created, underground collapses may also be triggered.

WHERE ARE THEY LIKELY TO OCCUR?

Sinkholes are a worldwide phenomenon—geologists estimate that 10 percent of Earth’s surface (including the entirety of Florida) is shaped by dissolving bedrock prone to sinkholes. This type of landscape is called karst topography. Nearly every U.S. state is covered at least in part by karst topography and is therefore subject to damage. Sinkholes are considered most common in Florida, Texas, Alabama, Missouri, Kentucky, Tennessee, and Pennsylvania. Check out the U.S. Geological Survey’s map of the U.S.’s karst areas here.

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HOHOW BIG DO THESE THINGS GET?

Pretty massive, as it turns out. The Qattara Depression in Egypt extends to 440 feet below sea level, and a length of 186 miles (with a width of 95 miles). The 2007 and 2010 sinkholes in Guatemala City were 330 feet and 30 stories deep, respectively. In Sarisarinama, Venezuela, multiple sinkholes have reached about 1,000 feet wide and 1,150 feet deep. Of course, sinkholes aren’t always gargantuan. While some are catastrophic, others are no more than 2 or 3 feet in diameter and depth.

HOW CAN I TELL IF I’M LIVING ON A SINKHOLE & HOW CAN I FIX IT?

Consider sagging trees or fence posts, doors or windows that won’t close properly, and rainwater collecting in unusual spots as warning signs. Get the hell outta there and, if it’s on public property, you should then report it to local law enforcement. Small holes can be filled with natural materials like rock and clayey sand if it is on your own property. Larger sinkholes need professional work and will consequently require the help of experts. Geohazards can help by injecting grout into the area to fill up cracks and strengthen the foundation and ease your mind of worry.

Looking for more on Sinkholes? Check these out:

Why Do Sinkholes Form in Florida?


Sinkholes are a natural and common geologic feature in areas underlain with rock types that are soluble in natural water. In Florida, the most common of these soluble rock types are...

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Are There Different Types of Sinkholes?


There are three different types of sinkholes and their formation is dependent on the specific stratigraphy of a given region. In Florida...

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