Sinkholes Revealed

Sinkholes are considered a type of land subsidence.

Land subsidence occurs when large amounts of ground water have been withdrawn from certain types of rocks, such as fine-grained sediments.


Sinkholes are common where the rock below the land surface is limestone, carbonate rock, salt beds, or rocks that can naturally be dissolved by ground water circulating through them. As the rock dissolves, spaces and caverns develop underground. Sinkholes are dramatic because the land usually stays intact for a while until the underground spaces just get too big. If there is not enough support for the land above the spaces then a sudden collapse of the land surface can occur.

What is a Sinkhole

A sinkhole is an area of ground that has no natural external surface drainage--when it rains, all of the water stays inside the sinkhole and typically drains into the subsurface. Sinkholes can vary from a few feet to hundreds of acres and from less than 1 to more than 100 feet deep. Some are shaped like shallow bowls or saucers whereas others have vertical walls; some hold water and form natural ponds. Typically, sinkholes form so slowly that little change is seen in one's life- time, but they can form suddenly when a collapse occurs. Such a collapse can have a dramatic effect if it occurs in an urban setting.

"but they can form suddenly when a collapse occurs"

this quote from above is a bit misleading as sinkholes do not form suddenly they sink suddenly after forming over time.
it would be better described as "they are noticed suddenly when a collapse occurs"





There are three types of sinkholes, each of which forms through a different process.



1. SOLUTION SINKHOLES

Solution sinkholes form where soluble bedrock (i.e., limestone, dolomite, marble, and rock salt) is exposed at the land surface and thus subjected to weathering by dissolution. Surface water collects in natural depressions and slowly dissolves a sinkhole.

[atsimg]http://files.abovetopsecret.com/images/member/fb4703c96e88.jpg[/atsimg]
A solution sinkhole forms at the land surface as bedrock dissolves to create a somewhat
circular depression. The photo below shows solution sinkholes in Florida.
[atsimg]http://files.abovetopsecret.com/images/member/2b59dd800bec.jpg[/atsimg]

2. SUBSIDENCE SINKHOLES

Subsidence sinkholes are similar to solution sinkholes, except
that the soluble bedrock is covered by a thin layer of soil and/or
sediment. Surface water infiltration dissolves cavities where the
bedrock is most intensely fractured, and the overlying sediment
gradually moves downward into the expanding cavity.

The formation of a subsidence sinkhole is illustrated below. Note that the geologic conditions include soluble bedrock (such as limestone) covered by relatively thin deposits of sediments. This type of sinkhole tends to form naturally and is not greatly affected by human activities.


(1) Initially the bedrock contains fractures and small cavities that have formed by dissolution, but no land subsidence has occurred.
[atsimg]http://files.abovetopsecret.com/images/member/f77ec395b360.jpg[/atsimg]

(2) Small cavities and cracks grow larger through time, and sediments from above are slowly carried down by infiltrating rainwater to fill the voids forming in the bedrock.
[atsimg]http://files.abovetopsecret.com/images/member/f90c827e6ca7.jpg[/atsimg]

(3) Sediments from the upper layers continue to fill in the openings in the bedrock, gradually causing a depression to form at the land surface. If water collects in the depression, a new lake also forms.
[atsimg]http://files.abovetopsecret.com/images/member/cf6b769d369d.jpg[/atsimg]



3. COLLAPSE SINKHOLES

Collapse sinkholes form when surface materials suddenly sink
into a subsurface cavity or cave. The cavities form slowly over
time, as groundwater moves along fractures in soluble bedrock
and enlarges them through dissolution, and the actual collapse
can occur in two different ways:

a. When a cavity gets sufficiently large, the "roof" becomes too
thin to support the weight of any overlying rock or sediment,
so it collapses into the cavity.



b. Caves are sometimes able to support the weight of overlying
sediments because they are filled groundwater. However, if
groundwater levels are lowered, then the overlying sediment
will first erode and then collapse into the dewatered cavity.

Lake Jackson drains into the Porter Hole Sink

On September 16, 1999, much of the central portion of Lake Jackson, a large lake on Tallahassee's northern side, drained down an eight-foot-diameter sinkhole known as Porter Hole. Sinkholes in Lake Jackson open and drain portions of the lake approximately every 25 years. Following the September 1999 event, the FGS, in cooperation with the Northwest Florida Water Management District, Leon County, and the Florida State University Department of Geological Sciences began investigating this phenomenon. This investigation will improve our understanding of the connection between Lake Jackson and the Floridan aquifer system, which provides most of the areas drinking water.

The Porter Sink area prior to the sudden drainage through a collapse sinkhole.
[atsimg]http://files.abovetopsecret.com/images/member/e2669c83951a.jpg[/atsimg]

Lake levels begin to drop at a rate that exceeds normal conditions.
[atsimg]http://files.abovetopsecret.com/images/member/c5def1e06c6d.jpg[/atsimg]

Drainage of the lake reveals sinkholes at the bottom.
[atsimg]http://files.abovetopsecret.com/images/member/945026367ad2.jpg[/atsimg]

Drainage into one the sinkholes.
[atsimg]http://files.abovetopsecret.com/images/member/0923d3dc6ec5.jpg[/atsimg]

Close up view of drainage into a sinkhole.
[atsimg]http://files.abovetopsecret.com/images/member/1dfe243b5d98.jpg[/atsimg]

The lake bottom after water has drained.
[atsimg]http://files.abovetopsecret.com/images/member/e653e6f8a4b0.jpg[/atsimg]

The Porter Sink area after the lake has drained.
[atsimg]http://files.abovetopsecret.com/images/member/d863ad53dd18.jpg[/atsimg]

Down the sink!
[atsimg]http://files.abovetopsecret.com/images/member/14d8fff2fa75.jpg[/atsimg]


There you have it Sinkholes Explained I hope you enjoy this thread and geology as much I do!

Excellent thread, as always W1ll, S+F.

But how to explain this ?

news.nationalgeographic.com...


Described as approx. 330 feet deep and EMPTY

Which surely means there must have existed a circular hole at least 660 feet deep, in order for it to swallow 330 feet of earth and buildings and still leave an empty gaping hole another 330 feet deep ?

Didnt a lake, somewhere down in South America, suddenly disappear about a year ago?
I wonder if thats what happened to it, a large sink hole or collapsed lava tube?

reply to post by -W1LL


really good thread I used to live in tallahassee and I saw this happen before it happened we used to bass fish there I understand it has returned now as my son who still lives there fished it recently never thought to much about as it was expected every 25 years or so but now being older and i wonder if wiser i wonder if here are other lakes similar to this and of course where does the water go the other sinks in the area as far as i remember were not really affected when jackson left

Originally posted by Dock9
But how to explain this ?

news.nationalgeographic.com...


Described as approx. 330 feet deep and EMPTY

Which surely means there must have existed a circular hole at least 660 feet deep, in order for it to swallow 330 feet of earth and buildings and still leave an empty gaping hole another 330 feet deep ?

beats me :p

But somehow, most of them will be natural...

Originally posted by Dock9
But how to explain this ?

news.nationalgeographic.com...


Described as approx. 330 feet deep and EMPTY

Which surely means there must have existed a circular hole at least 660 feet deep, in order for it to swallow 330 feet of earth and buildings and still leave an empty gaping hole another 330 feet deep ?

I remember seeing this. sinkhole~!

Rainstorms and a ruptured sewer main may have caused the sinkhole, officials in Guatemala told the Associated Press. After the collapse, the seemingly bottomless depths gave off tremors, sounds of flowing water, and the scent of sewage.

that is most likely the cause.. water runoff or from the sewer eroding soil into the sewer system slowly...

reply to post by -W1LL


They claim it was caused by leaky drains -- but does that sound feasible to you ?

In the close-up photos online, a broken drainage pipe is visible. But to suggest that leakage from that pipe (of a few inches diameter ) could be responsible for the sudden and almost perfectly circular, gaping hole of 330 feet and more deep, is stretching things, don't you feel ?

And again, for the underground hole to have swallowed in minutes millions of tons of earth (plus buildings) requires the hole to be at least twice the size of the hole we see today

That's pretty phenomenal - an unsuspected, almost perfectly circular hole of a minimum of 660 feet deep ( and how wide across -- 150 feet ? ) all allegedly caused by a leaking pipe of a few inches diameter combined with substrata consisting perhaps of caves

Even so, why the almost perfect circle ? I mean, let's say there existed a large cave 660 feet below the surface. Is it likely that possible cave was perfectly circular and 660 feet deep ?

S&F Great thread. Informative, well laid out, even though our beloved ATS has been inundated with garbage and doom, it is threads like these that keep me coming back. I can't help but post a video for contribution sake.

reply to post by -W1LL


Great thread and very informative.

I live in Florida and got to witness a large sinkhole (150 ft.in diameter) in the making a few years ago.

I was on a job site, when all of a sudden the animals and birds started to vacate the near bye area.
Upon further inspection I got to witness a sinkhole opening up, it was surreal to say the least.

The ground just disappeared, there were 70 ft tall pine trees just sinking in front of me, into the hole which opened very quickly and expanded out from the center. I watched it swallow the back half of a near bye TV repair shop as well.

In the end the sinkhole measured approx 150 ft in diameter and about 80 ft deep.

Originally posted by Dock9
reply to post by -W1LL

 

They claim it was caused by leaky drains -- but does that sound feasible to you ?

In the close-up photos online, a broken drainage pipe is visible. But to suggest that leakage from that pipe (of a few inches diameter ) could be responsible for the sudden and almost perfectly circular, gaping hole of 330 feet and more deep, is stretching things, don't you feel ?

And again, for the underground hole to have swallowed in minutes millions of tons of earth (plus buildings) requires the hole to be at least twice the size of the hole we see today

That's pretty phenomenal - an unsuspected, almost perfectly circular hole of a minimum of 660 feet deep ( and how wide across -- 150 feet ? ) all allegedly caused by a leaking pipe of a few inches diameter combined with substrata consisting perhaps of caves

Even so, why the almost perfect circle ? I mean, let's say there existed a large cave 660 feet below the surface. Is it likely that possible cave was perfectly circular and 660 feet deep ?

yes, over time it is possible that a large area like this was eroding away. the top was covered by a street essentially creating a bridge over the Void so all of that soil did not get washed away all at once...

the perfect circle can be attributed to many things, Gravity comes to mind... if you take a flat level table or floor and pour a tablespoon of water on it the water will gather in a circle.. it is essentially the same with erosion.

there are underground tunnels formed by water all over South America and most of them look like tunnels drilled by a machine...I have swam in natural springs that went down or hundreds of feet in a perfect circle connecting to the underground tunnels.

I can't believe I didn't think of this pic for my OP its a perfect example.

Blue Hole of Belize
[atsimg]http://files.abovetopsecret.com/images/member/69605a78391c.jpg[/atsimg]

[atsimg]http://files.abovetopsecret.com/images/member/52ac39517de7.jpg[/atsimg]

I hope to dive there one day!! 300m in diameter and 120m in depth!


the main thing to remember is the sinkhole in Guatemala must have been eroding for quite some time little by little until the surface of the road could not hold itself up anymore...

what surprises me is a car or truck did not trigger the cave in.

Sink holes are totally interesting. In developed areas I think they result from dammed waterways and draining the aquifers. My theory is the earth is trying to repair itself.

The holes in the ocean are really cool too. Meteors perhaps?

Good thread.

reply to post by gatewaywithin


you have reminded me of a great story!!

I was at a jobsite Observing heavy equpment excavating down to bedrock with scrapers.
sitting in my truck on top of a 400' cut looking down on the operators. when I feel this huge Jolt. and my truck shakes. it was a windy area and slightly windy tht day but I just figured it was a gust of wind I got out had a look around at the cliff and saw nothing abnormal.

I did have a bad feeling though. So I got in my truck and drove around the Pit to the other side so I would be Facing the slope I was just sitting on top of.
I also should mention as I was leaving the area I drove over a small crack about 4" wide and 10' long crossing the road this was a construction site so I did not think anything of it until I was on the other side and A flood of water started pouring from the bottom of the slope I mean this was like a storm drain realeasing floodwater!

then all at once the hilltop I was just sitting on DROPPED a section 600' long by 400' tall and 150-200' wide at the top.
If i had stayed there 5 min longer I would have needed a crane to get my truck out it was an amazing thing to witness, Geologist' from all over came to check it out and I got to walk the top of it taking measurements and observing what happened. it was a vertical layer of clay not more than a couple inches think that ran the whole length and height of the landslide. the scrapers and gone down low enough to release the water from the bottom and that is what made this landslide which could be explained as a typical sinkhole = the loss of water in soil creating a void..

I wish I could find the pics I am searching around on the Net for it now. but it was a private construction site. so there was not much coverage.. this is the same job site we unearthed what i think was labeled as one of the oldest mastodon' ever uncovered a mother and her baby!!

Pics from the Jobsite Dig.

S NF for ye , but then i star and flag all of my friends threads .....


nice explination tho and sadly very logical...... i was hopeing that the earth her self created these sink holes to suck in evil people , ect ect ....

www.earthcurrent.com...

Florida Woman swallowed by sinkhole in her backyard . . . Again

The woman, Carla Chapman of Plant City, Florida was working in her backyard when she fell through the surface and into a sinkhole. She had her cell phone on her, but the sinkhole created terrible reception and she kept getting disconnected when she tried calling for help. Finally she got the idea to dial 911 and then throw her phone up out of the hole back into her yard where there would be a cleaner signal.

proof of my theory

reply to post by -W1LL


Great Story, it's always invigorating watching these events unfold, especially when noone get's hurt!

Originally posted by Dock9
But how to explain this ?

news.nationalgeographic.com...


Described as approx. 330 feet deep and EMPTY

Which surely means there must have existed a circular hole at least 660 feet deep, in order for it to swallow 330 feet of earth and buildings and still leave an empty gaping hole another 330 feet deep ?

Gophers.

reply to post by -W1LL


Gday again W1LL.

Thanks for posting,
It was a very interesting read and explained many things to me.
As i said to you in the other thread, that its people like yourself that makes ATS a great site.
Thanks and take care.

S&F
Ps. the photo of The Blue Hole of Belize is awesome.
I hope you get to swim there one day, it would be truely magical

Nice job op. I lived near Tatamy, Pa. for 10yrs, a big problem there. They had to replace a state highway brigdea few years back do to a sinkhole.
Just recently saw an article if I recall on extinction protocol about that area.

Originally posted by -W1LL

the perfect circle can be attributed to many things, Gravity comes to mind... if you take a flat level table or floor and pour a tablespoon of water on it the water will gather in a circle.. it is essentially the same with erosion.

Don't mean to nit pick but hat example is actually surface tension, which is also responsible for many circles in nature.

The Guatemala "sink hole" has been called a piping feature by geologists like Sam Bonis.
The "Piping Feature" at Guatemala City: Don't Call it a Sinkhole

Geologist Sam Bonis told the Web site that sinkholes occur on land that sits atop solid bedrock; piping features, however, refer to holes that form above less solid ground

Discovery News reports that Guatemala City “is built on pumice fill—ash flows made up of loose, gravel-like particles deposited during ancient volcanic eruptions. In places, the debris is piled over 600 feet thick, filling up what would otherwise be a v-shaped valley of faulted bedrock.”

When I moved to Florida we had to have a guy come out and inspect for sink holes.
It's a major problem here probably because of all the under ground water ways and 100's if not 1,000 of man made canals here in Cape Coral.

Freaky stuff, makes you think twice about where you step next.

The huge ones are really mind blowing thanks for sharing everyone.