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Swallowed up by the ground... Sinkholes!
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krakentenOffline
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PostPosted: 02-03-2013 13:48    Post subject: Reply with quote

Low probability? Just takes once, like the recent asteroid strike.

Population density makes such events more likely to affect humans, of course, just as surveillance cameras have shown us how frequent large fireballs actually are.

In legend and lore, the phrase, "the Earth swallowed them up" occurs frequently, once it was thought to refer to earthquakes, but now we see another possibility.

Our planet is full of surprises, our memories short. If it happens infrequently, many humans are inclined to think it won't happen again. I have heard people say,"that was back in history times", as though we have stepped out of history.

The recent discovery of King Richard III's grave is an example, a large church and its graveyard, lost for centuries in the press of events.

I'm currently living in the town where I grew up, and often returned to for extended stays. Like much of America, the old 'down town' is moribund and vacant, buildings crumbling from neglect.

I'm also in the house where I grew up, and I walk my dog through that now sad old business district, and I cannot remember what was in most of the vacant store fronts. Now they're full of spiders and dust, then they were businesses where I often shopped. But I can't recall what half of them once were.

History is fragile and fleeting, remember, once the civilization of Egypt was a mystery, and there are still lost cities undiscovered.

(why is it all old ruins are 'built by devils'?)
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Pietro_Mercurios
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PostPosted: 02-03-2013 14:10    Post subject: Reply with quote

There were two previous dedicated sinkhole threads, 've merged them under the catch-all title, Sinkholes!.

+ added today's Florida sinkhole story and related posts moved from, Underground. All moved to, Earth Mysteries - The Land.

P_M
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rynner2Offline
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PostPosted: 05-03-2013 07:36    Post subject: Reply with quote

Who, What, Why: How are sinkholes formed?

A Florida man whose bedroom was engulfed by a sinkhole as he slept is presumed dead. How - and where - do sinkholes open up?

Sinkholes, or dolines, often take thousands of years to form and vary hugely in size.
The deepest is China's Xiaozhai Tienkeng at 2172ft (662m). The Qattara Depression in Egypt is roughly 50 miles (80km) by 75 miles (121km) in surface size.

But often sinkholes can be only a few metres in diameter.
They are usually the result of what are known as Karst processes. They happen when a layer of rock underneath the ground is dissolved by acidic water.
Usually this layer is a soluble carbonate rock, such as limestone or its purer form, chalk. Florida is particularly prone to sinkholes as the entire state has limestone underneath it.

Typically rainfall seeps through the soil, absorbing carbon dioxide and reacting with decaying vegetation. As a result, the water that reaches the soluble rock is acidic.
The acidic water causes the erosion of the soluble rock layers beneath the surface - eventually creating cavernous spaces.

The soil or sand over the limestone collapses into a sinkhole when it is no longer supported because of the cavity below. This final collapse of the surface might take anything from a few minutes to several hours.

There are warning signs in urban areas. These include doors and windows failing to close properly, or cracks appearing in the foundations of houses. In some cases ground movement can be detected.

Heavy rainfall or poor drainage systems can trigger a collapse.
But predictions are not easy.
"It can be very difficult to predict collapse because there is very little surface evidence of the features," says Dr Vanessa Banks, an expert in shallow geohazards and risk at the British Geological Survey.
Different rock types behave in different ways, she adds.

The timing of a collapse also depends on the nature of the soil or rock at the surface which forms a "bridge" over the growing cavern below.
"Consolidated deposits such as sandstone will bridge voids until their tensional strength is exceeded, when the rock will fail and collapse into the underlying cavity," says Banks.

Certain types of ground - such as gravel and sand - are not fixed in place and so more prone to being washed away.
The erosion may take many years but the collapse may be sudden as it depends on a tipping point determined by the material at the surface, Banks says.

Moreover, acidic water varies in its strength - and therefore the rate of erosion - depending on the soil and rock it filters through.
"Water acidity can typically have a pH level of about 6.5 - still drinkable to all intents and purposes - but also be as low as four," explains Banks. Iron and sand can increase the acidity. So too can sandstone and shale.

Human development can also affect these natural processes.
When people are building a basement, they may need to drain water, explains Banks. This drainage of water can destabilise the soil by washing away smaller particles - like sand - that are necessary to keep larger particles together, increasing the chances of collapse.
In January, a sinkhole that swallowed an entire building complex in Guangzhou, China, may have been triggered by the construction of an underground metro line nearby.

Burst water mains or sewage systems also cause many urban sinkholes to happen, regardless of the rock type below.
These cause instability in the surrounding area, often giving the impression of a natural sinkhole, says Banks.
Urban development also adds more weight to the surface layer, potentially speeding up the collapse of a sinkhole.

It is crucial to undertake extensive site investigations prior to building work, says Banks.
There are rules and guidelines for the construction industry in the UK that prevent the discharge of water within a minimum of five metres from a house.
But Banks says that concrete urban development on the whole could in fact be "slowing [sinkholes' natural] formation by restricting this drainage water from seeping through".

There are more sinkholes in rural environments, she says, primarily because risky areas are typically avoided by urban developers.

http://www.bbc.co.uk/news/magazine-21600410
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rynner2Offline
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PostPosted: 05-03-2013 08:00    Post subject: Reply with quote

In pictures: sinkholes, craters and collapsed roads around the world
[Picture Gallery]
http://www.telegraph.co.uk/news/picturegalleries/worldnews/9908055/In-pictures-sinkholes-craters-and-collapsed-roads-around-the-world.html
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krakentenOffline
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PostPosted: 05-03-2013 13:39    Post subject: Reply with quote

Sinkholes often become death traps for animals, we have discovered many good specimens of extinct creatures in old sinkholes.

Caves are the last truly mysterious places left. One cavern system in the American Southwest has a hole near the entrance from which issues a fifty mile per hour wind, and nobody knows where it comes from.

Sorry, saw it on TV, got no references to cite, but I'm going to use it in a horror story soon.
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ramonmercadoOnline
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PostPosted: 13-03-2013 23:31    Post subject: Reply with quote

Quote:
Illinois golfer plunges down sinkhole on the 14th
http://www.bbc.co.uk/news/world-us-canada-21773499

Mark Mihal's golf partners rescue him from the 18ft-deep sinkhole with a rope

Family told sinkhole house was 'stable' Watch
An Illinois man has survived an 18ft (5.4m) fall inside a sinkhole while he was golfing, two weeks after another sinkhole swallowed a person in Florida.

Mark Mihal, 43, was investigating an unusual depression when the earth gave way on the 14th hole of the fairway in Waterloo, Illinois.

Friends managed to bring the mortgage broker to safety with a rope, and he escaped with only a sore shoulder.

Mr Mihal said he felt lucky to survive the "absolutely crazy" accident.

"It didn't look unstable,'' Mr Mihal said of the slump in the ground, which exposed a 10ft-wide sinkhole once he stood on it. "And then I was gone.

"I was just freefalling. It felt like forever, but it was just a second or two, and I didn't know what I was going to hit. And all I saw was darkness.''

Such holes are common in south-western Illinois, where old underground mines frequently cause the earth to cave in.

According to Sam Panno, a senior geochemist with the Illinois State Geological Survey, there are as many as 15,000 sinkholes in the region.

Florida man Jeffrey Bush, 36, is presumed dead after a sinkhole swallowed his bedroom near Tampa this month.


Aerial footage showing the 18ft (5.4m) deep and 10ft (3.1m) wide pit
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rynner2Offline
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PostPosted: 10-04-2013 07:26    Post subject: Reply with quote

In pictures: the Russian city of Samara being 'eaten alive' by sinkholes

[Picture gallery - 16 pics]

Residents of Samara, in south Russia, have seen cars and buses vanish beneath their streets as an epidemic of sinkholes spreads through the city. Words by Paul Wright

http://www.telegraph.co.uk/news/picturegalleries/worldnews/9981444/In-pictures-the-Russian-city-of-Samara-being-eaten-alive-by-sinkholes.html
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ramonmercadoOnline
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PostPosted: 10-04-2013 12:22    Post subject: Reply with quote

rynner2 wrote:
In pictures: the Russian city of Samara being 'eaten alive' by sinkholes

[Picture gallery - 16 pics]

Residents of Samara, in south Russia, have seen cars and buses vanish beneath their streets as an epidemic of sinkholes spreads through the city. Words by Paul Wright

http://www.telegraph.co.uk/news/picturegalleries/worldnews/9981444/In-pictures-the-Russian-city-of-Samara-being-eaten-alive-by-sinkholes.html


Wow! Appointment in Samara indeed.
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krakentenOffline
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PostPosted: 10-04-2013 14:41    Post subject: Reply with quote

There seems to be rather a lot of sinkholes, just now.

This could be because, with the web, stories that might once have only been of local note now spread world wide, or....

Acid rain accellerates the dissolution of limestone, thus, if the local geology has many limestone caverns, and acid rain is pronounced (Soviet era recklessness spawned many ecological problems) sinkholes are to be expected.

Might be this is causing a cluster of sinkholes?

Could be worse, think of Chernobyl?

And this might be a spelunker's version of Paradise.
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MythopoeikaOffline
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PostPosted: 10-04-2013 18:46    Post subject: Reply with quote

The number of sinkholes in that area may be mostly down to cost-cutting and poor road construction. Clearly those roads don't have appropriate steel reinforcement.
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rynner2Offline
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PostPosted: 10-04-2013 19:36    Post subject: Reply with quote

Mythopoeika wrote:
The number of sinkholes in that area may be mostly down to cost-cutting and poor road construction. Clearly those roads don't have appropriate steel reinforcement.

How many roads in this country have "steel reinforcement"? I've been watching a few construction and road building projects recently, and most roads have various foundation materials (rock, rubble, specially selected soil, etc), all compacted nicely by various machines such as rollers, and then overlaid with a few coats of asphalt.

I have seen sections of road (and bridges, of course) built of steel-reinforced concrete, but only where they were expected to bear abnormally high loads, such as a heavy crane and a big lift, for example.
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krakentenOffline
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PostPosted: 10-04-2013 21:53    Post subject: Reply with quote

Even rebar is going to fail with a big hole below.

A sinkhole is a cavern, the top of which has eroded away, Some are large, some small, the sacred cenotes of Central America are sikkholes

Fact is, any limestone cavern close to the surface will become a sinkhole, sooner or later.

However, a cluster of such is suspicious, but perhaps it's best to get them located all at once. If they want a subway system, well, it's a thought?
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rynner2Offline
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PostPosted: 20-04-2013 08:28    Post subject: Reply with quote

A new one:

Car swallowed by sinkhole on suburban Chicago street
The vehicle was one of three cars which toppled into a sinkhole after a water main burst in the South Deering area of the city.
[video]
5:36PM BST 19 Apr 2013

A rainstorm pummeling the Chicago area ripped open a sinkhole that swallowed three cars, injuring one driver badly enough that he had to be taken to hospital.

The gaping sinkhole opened up a residential street in the South Deering area of the city in the early hours of Thursday morning after a cast iron water main dating back to 1915 broke during the massive storm.

The hole spanned the entire width of the road. Only the bonnet of one of the vehicles could be seen peeking from the chasm.

http://www.telegraph.co.uk/news/worldnews/northamerica/usa/10006519/Car-swallowed-by-sinkhole-on-suburban-Chicago-street.html
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kamalktkOffline
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PostPosted: 24-04-2013 14:23    Post subject: Reply with quote

I didn't find a whirlpool thread, but I guess this is probably a sinkhole that opened under the water.
https://www.youtube.com/watch?v=eqROBTVgL6A
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rynner2Offline
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PostPosted: 24-04-2013 15:19    Post subject: Reply with quote

kamalktk wrote:
I didn't find a whirlpool thread, but I guess this is probably a sinkhole that opened under the water.
https://www.youtube.com/watch?v=eqROBTVgL6A

You may be right.

There isn't a whirlpool thread, but there's a post about Scotland's Corryvrecken here:
http://www.forteantimes.com/forum/viewtopic.php?p=546967#546967

and a reply by me at the bottom of that page about one in Strangford Lough, NI, but both these two are caused by strong tides, not sinkholes.

The Norwegian Maelstrom is also an effect of the tide:
http://en.wikipedia.org/wiki/Maelstrom
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