Community Chat

[Noel7]

What Causes Sinkholes from National Geographic

"...explained that Florida has a landscape uniquely susceptible to sinkholes. The state sits over carbonate rock made of mostly limestone and dolostone.

Sinkholes usually form gradually. When finer, sandlike sediment sits over bedrock it can fill the cracks and holes. As the sandier sediment creeps downward, the land sitting atop it subsides. As the void grows, or if top sediment is suddenly washed away by water, sinkholes can form (and are often filled with water).

Occasionally, underground cavities can form under surface rock. When the cavity expands so much that the surface can no longer support its weight, it suddenly collapses.

Florida's 2015 study found that, in addition to the natural geological events that create sinkholes, certain human activities—such as water pumping and ground loading—may make the Earth's surface more vulnerable."

https://news.nationalgeographic.com/2017/07/florida-sinkhole-swallows-homes-video-spd/

[KingstonsMom]

@Carmie

I never knew that PA has them too!

That has to be so scary, feeling like your home is falling under your feet!

At least in my area we have warnings for severe tropical storms and hurricanes and can get out of the way.

[151949]

The underground fire in Centralia, Pa is a smoldering coal seam in a mine , not a sinkhole. It has been going on for decades - it was caused by someone starting a fire to burn trash in the mine and it lit the coal. Almost everyone has left that town but there are still 63 people living there. I imagine it does not smell very good there since the fire never goes out.

I've never heard of all the other sinkholes mentioned, but I lived in West Pa where , generally, sinkholes occur because an underground mine collapses. Almost all of the property in western Pa is undermined with old coal mines.

[Zhills]

---

@Noel7wrote:

What Causes Sinkholes from National Geographic

"...explained that Florida has a landscape uniquely susceptible to sinkholes. The state sits over carbonate rock made of mostly limestone and dolostone.

Sinkholes usually form gradually. When finer, sandlike sediment sits over bedrock it can fill the cracks and holes. As the sandier sediment creeps downward, the land sitting atop it subsides. As the void grows, or if top sediment is suddenly washed away by water, sinkholes can form (and are often filled with water).

Occasionally, underground cavities can form under surface rock. When the cavity expands so much that the surface can no longer support its weight, it suddenly collapses.

Florida's 2015 study found that, in addition to the natural geological events that create sinkholes, certain human activities—such as water pumping and ground loading—may make the Earth's surface more vulnerable."

https://news.nationalgeographic.com/2017/07/florida-sinkhole-swallows-homes-video-spd/

---

Sinkholes are caused by underground erosion. They may be a result of a manmade issue, such as a leaky water pipe, or a natural issue, such as an underground stream. As water wears away at soil, soft stone like limestone, and other residue, a large cavern that is either empty or filled very loosely with sediment forms. Eventually, whatever is sitting on top of that cavern becomes too much for the earth to bear and the entire thing falls in.

Areas of the country with “soft foundations,” like Florida, which is built entirely on limestone, for example, are prime targets for sinkholes. However, any area where water or water runoff is slightly acidic is also at risk since this type of water can wear away not only limestone, but other types of rock as well.

This is called the karst process and often results in the loss of entire buildings or other structures when the enormous sinkholes it causes collapse in on themselves.

According to this new geological survey, far more people are at risk from sinkholes than scientists have traditionally thought. In fact, according to the survey, “if you live in Pennsylvania, Missouri, Kentucky, Texas, Tennessee, or anywhere in the northern plains, you’re at risk from sinkholes too.”

[Noel7]

@Zhills

Usually I don't put up an entire article because that's illegal.

It's better to put up a section and then a link for others to access.

[Zhills]

It is only a small portion of the article.  Just  info about the different types of rocks underneath us.

[Noel7]

---

@Zhillswrote:

It is only a small portion of the article.  Just  info about the different types of rocks underneath us.

---

Right, but we now have the article in its entirety.

[Zhills]

I believe we have parts of 2 completely different articles.  I did not see anything like the one I quoted.  They are the same subject but not the same article.  Mine is less than 2 paragraphs, I spread them out to make it easier to read.  Sorry I upset you.  Just trying to help with info.

[cherry]

Can they just fill in the holes ,or is the entire area unstable?

[Zhills]

Just depends on the type of soil and the reason for the sinkhole.  They do fill some in and they have a way of stablizing the ground around it.  They do soil bores where they test for the type of layers of soil.  They go very deep.

The first one I saw was 80' deep.  They dumped 3 truck loads of broken concrete in it and it all disappeared.  Possible the bottom was an underground stream.  Finally got the rocks to lodge enough to fill in to the top.  This was 40 years ago and they have rebuilt on the site today.  The hole was straight down just like a well.  Could stand on the driveway and look 80 feet down!

Most of them are not as deep as this one was.