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http://www.miamiherald.com/2013/03/01/3260805/florida-man-vanishes-after-being.html

Posted: 02-03-2013 01:26 Post subject:

My mistake, it was Lo!, not Wild Talents:

Posted: 02-03-2013 01:56 Post subject:

Incidentally, and slightly oddly, I hit 'refresh' on the browser that I used to search for the Cumpston story, and the second result is now my last post (above) -- but dated 13 January.

I'm slightly at a loss to explain this, but then I'm not very IT savvy.

Anyone?

Posted: 02-03-2013 03:44 Post subject:

I have often marvelled at the speed Google indexes this site - maybe that explains FT's sensitivity over legal matters.

Indexing posts before they are made, suggests we are all redundant! Shocked

Posted: 02-03-2013 14:48 Post subject:

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'?)

Posted: 02-03-2013 15:10 Post subject:

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

Posted: 05-03-2013 08:36 Post subject:

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

Posted: 05-03-2013 09:00 Post subject:

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

Posted: 05-03-2013 14:39 Post subject:

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.

Posted: 14-03-2013 00:31 Post subject:

Posted: 10-04-2013 08:26 Post subject:

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

Posted: 10-04-2013 13:22 Post subject:

Posted: 10-04-2013 15:41 Post subject:

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.

Posted: 10-04-2013 19:46 Post subject:

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.

Posted: 10-04-2013 20:36 Post subject: