What Are Funnels and How Do They Work?
A crater formed in China this week that swallowed a bus, killing several people. A few months ago, in my hometown of Pittsburgh, another crater formed under a bus ; in this case, however, everyone escaped safely. In addition to buses, funnels can swallow cars , pedestrians and houses . Here’s a rundown of what funnels really are and how they arise.
What causes sinkhole?
A funnel is formed when the surface of the earth is no longer supported by what is beneath it.
You may think that when you are on the ground, there is nothing below you but the same. But there are different layers of dirt and stone. Sometimes a hole can form, but you don’t know it yet.
For example, water can slowly dissolve limestone over time. The spaces open up where limestone once was, and if large enough, they can turn into impressive caves . But if the spaces are too close to the surface, the ground above can suddenly give way, creating a sinkhole.
Can funnels form anywhere?
According to the US Geological Survey, sinkholes are most commonly found where there are underground rock deposits that can dissolve, such as limestone, carbonate, and salt formations. Risk areas include Florida, Texas, Alabama, Missouri, Kentucky, Tennessee, and Pennsylvania.
They can also occur where pits have been created in other ways, such as during construction or pumping out groundwater. Or the mines: in the area where I grew up, coal mines were dug up and abandoned decades ago . Several houses in our area had cracks in their foundations or masonry due to the slow, barely noticeable collapse of the earth. It was a famous phenomenon with a name (“mine sinking”) and insurance policies that could be bought from it. I remember walking with my family one summer evening to see a sinkhole that suddenly opened onto several streets.
How much should I worry?
First, sinkholes are rare. The likelihood that you will be personally consumed by failure is practically nil. And not all funnels open suddenly; many form slowly over the years.
Also there is nothing you can do with a funnel if you get caught on it – I’m not sure if that makes them more or less intimidating. Land subsidence may indicate that something is happening underground, but not all subsidence indicates failure, and not all subsidence is preceded by subsidence. If you think that a crater is forming in your yard, experts advise contacting an engineering or geological testing firm .
If you are facing failure in real life, stay away from the edge. As the sinkhole sinks, its edges may continue to collapse. (The Florida Department of Environmental Protection says this process can take several days, or longer if it rains.) Typically, a funnel in an urban area is filled with less dense material. will probably give way in the future, but some of the giant sinkholes found in nature could turn into beautiful natural ponds .