Florida holiday villa collapses into sinkhole.

A three story holiday villa at a resort in Lake County, Florida, has partially collapsed into a sinkhole described as between 12 and 15 meters wide. The 24 unit building at the Summer Bay Resort in Clermont, roughly 16 km to the west of Disney World, was evacuated at about 11.30 pm local time on Sunday 11 August 2013 (around 3.30 am GMT), after cracks appeared in the structure and the power failed. At about 3.00 am local time (6.00 am GMT) the about 30% of the building collapsed into the sinkhole. There are no reports of any injuries, but nearby villas have been evacuated as a precaution.

The partially collapsed building at the Summer Bay Resort in Lake County, Florida on Monday 12 August 2013. AP.

Sinkholes are generally caused by water eroding soft limestone or unconsolidated deposits from beneath, causing a hole that works its way upwards and eventually opening spectacularly at the surface. Where there are unconsolidated deposits at the surface they can infill from the sides, apparently swallowing objects at the surface, including people, without trace.

Southwest Florida is particularly prone to sinkholes, due to the porous limestone that underlies much of the area. This is eroded over time by acid in rainwater (most rainwater is slightly acidic, though pollution can make this worse), and can collapse suddenly, causing overlying sediments to collapse into the hole and a sinkhole to open up. This can be triggered by human activity, such as pumping water out (which causes the water to flow, facilitating acid dissolution of the limestone), but is essentially a natural process. 

The approximate location of the collapsed villa. Google Maps.

See also Massive sinkhole opens up in Wallace County, Kansas, Six year old boy swallowed by Indiana sinkhole, Car and driver swallowed by Ohio sinkhole, Iowa sinkhole linked to nineteenth century mines and Florida man swallowed by sinkhole in home.

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Car and driver swallowed by Ohio sinkhole.

An Ohio woman and her car were swallowed by a 3 m sinkhole that opened up before her on North Detroit Avenue in Toledo in the northwest of the state on Wednesday 3 July 2013. Pamela Knox, 60, saw the hole start to open up beneath the car in front of her, which was able to accelerate away, but was unable to prevent herself from from falling in. She was rescued unhurt by the Toledo Fire and Rescue Department, and taken to a local hospital as a precaution. The sinkhole was apparently caused by a burst water main that washed sediments from beneath the road.

Car trapped inside the Toledo sinkhole. Matthew Hertzfeld/AP.

A member of Toledo Fire and Rescue Department Rescuing Ms Knox from the hole. Toledo Police Department.

See also Iowa sinkhole linked to nineteenth century mines, Man swallowed by sinkhole in Shenzhen, South China, Florida man swallowed by sinkhole in home and Massive sinkhole opens up in Assumption Parish, Louisiana.

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Iowa sinkhole linked to nineteenth century mines.

A three meter wide, three meter deep sinkhole that opened up in Runnells, Polk County, Iowa, around the beginning of June has been linked to abandoned nineteenth century coal workings in the town by the Iowa Department of Agriculture’s Mines and Minerals Bureau. Engineers plan to begin excavation work at the site of the sinkhole, close to the home of local resident Bob Borg, on Friday 14 June 2013. The appearance of the hole necessitated the removal of a pole supporting power cables which was in danger of falling onto Mr Borg's house.

The Runnells sinkhole. Des Moines Register.

The State of Iowa required all mines to be documented and mapped from 1902 onwards, but mining began around Runnells in the 1880s, fueled by the demand for coal for paddle-steamers on the Des Moines River. A large number of mines popped up in the area at this time, many of them small, family-run operations with no effective record keeping. 

Sinkholes have been a longstanding problem in the eastern part of Runnells, though there have not been any major incidents leading to loss of life or property. Engineers from the Mines and Minerals Bureau will attempt to ascertain whether this sinkhole is the result of an abandoned mine, or another cause, such as an old well or septic tank. If an abandoned mine is found then the plan is to infill it with crushed limestone as far as possible.

The approximate location of the Runnells sinkhole.

See also Man swallowed by sinkhole in Shenzhen, South China, Florida man swallowed by sinkhole in home, Massive sinkhole opens up in Assumption Parish, Louisiana and Disaster at Gleision Colliery, Godre'r Graig, West Glamorgan. 15 September 2011.

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Florida man swallowed by sinkhole in home.

Around 11.00 pm local time on Thursday 27 February 2013, the family of Florida man Jeff Bush heard a loud crash followed by screaming from his bedroom, in Faithway Drive, Seffner near Tampa. His brother, Jeremy, rushed into the room to find the a mattress disappearing into a hole in the floor and nor sign of Mr Bush. Jeremy leapt into the hole, which was continuing to grow, but was unable to find his brother, who is now missing presumed dead. Several nearby houses have now been cordoned off, while Hillsborough County Fire Rescue attempt to locate Mr Bush and determine how far the hole will spread.

Deputies from the Hillsborough County Sheriff's Office setting up a cordon around homes affected by the sinkhole. Reuters/Brian Blanco.

Southwest Florida is particularly prone to sinkholes, thought the Seffner Sinkhole is considered exceptional, due to the porous limestone that underlies much of the area. This is eroded over time by acid in rainwater (most rainwater is slightly acidic, though pollution can make this worse), and can collapse suddenly, causing overlying sediments to collapse into the hole and a sinkhole to open up. This can be triggered by human activity, such as pumping water out (which causes the water to flow, facilitating acid dissolution of the limestone), but is essentially a natural process. 

Graphic showing the processes by which sinkholes can form in southern Florida. Southwest Florida Water Management District.

See also To cull or not to cull? The Goliath Grouper in Floridan waters, Massive sinkhole opens up in Assumption Parish, Louisiana.

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Earthquake under Maine shakes New England.

On Tuesday 16 October 2012, slightly after 7.10 pm local time (slightly after 11.10 pm, GMT) the United States Geological Survey recorded a Magnitude 4.0 Earthquake 5 km underground, roughly 30 km southwest of Portland, Maine. This is not an especially large quake, but it was quite shallow and is far larger than the area is used to, leading the USGS estimate that there was a 24% chance of the quake resulting in at least one fatality. There have not been any reports of damage or casualties, but the quake appears to have caused widespread alarm over much of New England.

The location of the 16 October 2012 Earthquake. Google Maps.

Earthquakes in Maine are an uncommon occurrence, but they do occur, with six Earthquakes of Magnitude 4.0 or greater being recorded in the twentieth century, the largest being the Magnitude 4.8 Bowmantown quake of 1973. The precise cause of these quakes is unclear, though they are thought to be associated with tectonic stresses in the Appalachian Mountains. The state is cross-cut from north-to-south by a number of ancient faults associated with the formation and breakup of the ancient supercontinent of Pangea, between 300 and 200 million years ago, though no sign of modern movement on these faults has been discovered.

Witness accounts of quakes can help geologists to understand these events and the rock structures that cause them. If you felt this quake you can report it to the USGS here.

See also Earthquake in Labrador, Canada, Quebec Earthquake, 27 August 2011, Virginia Earthquake shakes Washington, New York, Earthquake in South Dakota, 9 August 2011 and Earthquakes on Sciency Thoughts YouTube.

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Massive sinkhole opens up in Assumption Parish, Louisiana.

On 3 August 2012 an area of woodland 100 m across in Assumption Parish, Louisiana, unexpectedly sunk 130 m into the ground, the tops of the Cyprus trees just visible through the mire that filled the hole. Local authorities have issued a mandatory evacuation order on about 150 homes in the area; this is short of a full compulsory evacuation order, and does allow people the option of remaining in their homes for the time being. The nearby Highway 70 was briefly close, while damage to a natural gas pipeline was investigated, but has now reopened.

Areal photograph of the Assumption Parish sinkhole. The tops of trees can be sen in the water that has flooded the hole. ABC News.

When the sinkhole opened up bubbling was observed at the surface and an oily sheen observed, causing concern that the hole could be linked to previous oil and gas exploration in the area, with the possibility of radioactive contamination (crude oil in some areas contains radioactive material). But investigations by the Louisiana Department of Environmental Quality revealed the oily material to be mostly diesel oil and found no trace of radioactive material.

The hole is now being linked to a brine extraction operation run by the Texas Brine Company in the area until last year. Such operations extract salt from subterranean deposits by injecting water into the saltbeds then removing the water with the dissolved salt, which can then be recovered and sold. Such operations can cause subsidence by removing layers of salt from underneath overlying rock beds. The Texas Brine Company, which still retains responsibility for the site, is drilling an exploratory borehole to try to determine the state of the salt caverns beneath the area, and is said to have made a 'substantial contribution' to a fund to assist residents of the evacuation zone, though how this fund will be administered is still not clear.

See also United States Geological Survey releases new topographical maps of California, Louisiana and Mississippi, How the Deepwater Horizon oil spill effected wildlife on the Gulf of Mexico, BP hopes to have reached settlement with thousands of Gulf Oil Spill victims and BP takes legal action against Halliburton over Deepwater Horizon disaster.

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