Sinkholes around the world

Sinkholes are nature’s most extreme form of subsidence, but what causes them, how big can they be and most importantly, can we ever expect to experience one in our own back gardens? We look at some of the biggest sinkholes around the world, from ancient phenomenon, to very recent examples.

Italy

Naples sinkhole subsidence

To those of you thinking giant sinkholes don’t happen all that regularly… This hole opened in the middle of a residential district in Naples, Italy in 2015.

This sinkhole was caused by heavy rainfall and an underground water leak loosening the earth above a disused train tunnel. 380 people required emergency re-homing while the hole was filled in and inspected.

Where – Naples, Italy

When – February 2015

Size - 10 metres

Cause – Water logging around underground tunnel

USA

Florida Winter Park subsidence sink hole

Florida has many sinkholes. The porous limestone bedrock has many water filled caves and tunnels carved out over thousands of years. This network of water and soft rock was once a sea bed and has now created the perfect environment for large scale subsidence and sinkholes across the county.

The area’s most famous sink hole occurred in 1981 and was the largest of its kind witnessed by man. Amongst the 250,000 cubic yards of soil the hole devoured was 5 porches, half an Olympic swimming pool and a three bedroom house!

Where – Winter Park, Florida

When – May 1981

Size – 350ft across and 75ft deep

Cause – Water logging around underground tunnel

UK

UK Norwich subsidence sink hole

‘Cover-collapse’ sinkholes are the dramatic form of subsidence depicted so far. This is where the soil is slowly eroded underground until the point where the surface dramatically collapses in. Sometimes caused by something heavy moves across, like in 1988 on Earlham Road in Norwich.

A medieval chalk mine, long forgotten, and not noted in any land histories suddenly collapsed under the weight of a double decker bus. Although this incident happened in 1988, many sink holes appear every year in the UK. In fact chalk mines, chalky earth, salt deposits and of course, lots of rain makes many areas susceptible to sinkholes and subsidence such as this.

Where – Norwich, Uk

When – March 1981

Size – 20ft

Cause – Disused chalk mines

China

China subsidence sink hole

From a tiny hole in the sidewalk to the deepest sinkhole known. Nicked named ‘Heavenly Hole’, Xiaozhai Tiankeng is 662 metres at its deepest (that’s more than twice the height of the Eiffel Tower!).

Xiaozhai is a sinkhole formed over the top of a gigantic cavern formed by an underground river and creating a double depth hole which is thousands of years old. 50 of the 75 largest sink holes are in China and many of these are so big that they easily enclose their own micro climates and cultures and even have species unique to these areas.

Where – Chongqing, China

When – Ancient

Size – 626m long, 537m wide, 511m to 662m deep

Cause – Chalk rock on top of underground caverns

Turkmenistan

Turkmenistan subsidence sink hole

It’s not just water which can create cavities underground. Gas can also displace earth and create craters. In 1971 a gas field in Derweze collapsed an underground cavern which was quickly set a light to control the levels of methane it was subsequently leaking. This has created burning hole 69 metres wide and 30 deep, nick named the ‘Door to Hell’ which has been continuously aflame since it was created nearly 35 years ago.

Where – Derweze, Turkmenistan

When – 1971

Size – 70m wide, 30m deep

Cause – Natural gas over underground cavern

Belize

Belize subsidence sink hole

Sinkholes do not necessarily need to be on land. Although water can provide better support than nothing at all where cave roofs are concerned, it is still possible for underwater caves to collapse too. The Great Blue Hole in Belize is a beautiful example of what that looks like.

A when a 150,000 year old cave was flooded with rising sea levels at the end of the glacial period this 300 meter wide and 124 meter deep hole was uncovered and is now a UNESCO heritage and one of the best diving spots in the world, full of sea life, crystal waters and yes, before you ask, you can find sharks down there too!

Where – Lighthouse Reef, Belize

When – 120,000 years ago

Size – 300m wide, 124m deep

Cause – Rising sea levels flooded limestone cave

 

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