I heard that on the radio news lying in bed this morning. It's terrible  Rescue services couldn't get to him because they didn't know what the safe distance is 

When I heard it I though how can you fall down a sink hole

Good grief indeed Baz  

Oops! I've just caught on to what you meant 

A sinkhole, also known as a sink, snake hole, swallow hole, swallet, doline, or cenote, is a natural depression or hole in the Earth's surface caused by karst processes — for example, the chemical dissolution of carbonate rocks^[1] or suffosion processes^[2] in sandstone. Sinkholes may vary in size from 1 to 600 metres (3.3 to 2,000 ft) both in diameter and depth, and vary in form from soil-lined bowls to bedrock-edged chasms. Sinkholes may be formed gradually or suddenly, and are found worldwide. The different terms for sinkholes are often used interchangeably.

 Formation mechanisms

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Sinkholes near the Dead Sea, formed by dissolution of underground salt by incoming freshwater, as a result of a continuing sea level drop.

A special type of sinkhole, formed by rainwater leaking through the pavement and carrying soil into a ruptured sewer pipe.

Sinkholes may capture surface drainage from running or standing water, but may also form in high and dry places in a certain location.

The mechanisms of formation involve natural processes of erosion^[4] or gradual removal of slightly soluble bedrock (such as limestone) by percolating water, the collapse of a cave roof, or a lowering of the water table. Sinkholes often form through the process of suffosion. Thus, for example, groundwater may dissolve the carbonate cement holding the sandstone particles together and then carry away the lax particles, gradually forming a void.

Occasionally a sinkhole may exhibit a visible opening into a cave below. In the case of exceptionally large sinkholes, such as the Minyé sinkhole in Papua New Guinea or Cedar Sink at Mammoth Cave National Park in Kentucky, a stream or river may be visible across its bottom flowing from one side to the other.

Sinkholes are common where the rock below the land surface is limestone or other carbonate rock, salt beds, or rocks that can naturally be dissolved by circulating ground water. As the rock dissolves, spaces and caverns develop underground. These sinkholes can be dramatic, because the surface land usually stays intact until there is not enough support. Then, a sudden collapse of the land surface can occur.

Sinkholes also form from human activity, such as the rare but still occasional collapse of abandoned mines in places like Louisiana. More commonly, sinkholes occur in urban areas due to water main breaks or sewer collapses when old pipes give way. They can also occur from the overpumping and extraction of groundwater and subsurface fluids. They can also form when natural water-drainage patterns are changed and new water-diversion systems are developed. Some sinkholes form when the land surface is changed, such as when industrial and runoff-storage ponds are created; the substantial weight of the new material can trigger an underground collapse of supporting material, thus causing a sinkhole.

I've just been talking about this with my son. It's a terrifying way to go. The stuff of horror movies.  Poor poor man. 

I was stunned when I saw the pictures of sinkholes.It is a terrible way to die and as you say it's like somthing out of the movies.The ground just disappears

I've some online friends in the US so was aware of sinkholes as it's been discussed before and I've seen other pics of sinkholes in the US. It's frightening that they happen so suddenly and no one knows when or where they may happen next.