Swallowed Up By The Ground: Sinkholes!

EnolaGaia

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Here's a big one recently emerging in New Zealand ...

6-Story Deep Sinkhole Opens Up in New Zealand After Heavy Rains
A spectacular sinkhole the length of two football fields and the depth of a six-story building has opened up on a New Zealand farm. ..

A New Zealand farm worker says he was in for the surprise of a lifetime this week when he went to round up cows for milking and instead discovered a massive sinkhole that had opened up overnight in a field.

The sinkhole located near the North Island town of Rotorua is at least six stories deep and two football fields in length. It reportedly opened up after several days of heavy rain, the Associated Press reports.

Farm manager Colin Tremain said he didn't realize just how massive the hole was until he went out at daybreak to survey the sinkhole.
Volcanologist Brad Scott told Newshub television that it is the largest sinkhole he has ever seen. ...

Scott noted that nine other sinkholes have opened up in the area in the past two years. ...
SOURCE (with video): https://weather.com/news/news/2018-05-05-new-zealand-sinkhole-6-stories
 

EnolaGaia

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I didn't find a whirlpool thread, but I guess this is probably a sinkhole that opened under the water.
Yes - that's what I think it is / was ...

Here's a new whirlpool caused by a sinkhole opening beneath an Arkansas river, which caused the death of a kayaker.

Rare river sinkhole created whirlpool, led to man's death

A kayaker bypassed a part of an Arkansas scenic river known as Dead Man's Curve during a weekend trip, but a rare sinkhole created a whirlpool along his alternate channel and dragged him to his death.

Donald Wright, 64, from Searcy, Arkansas, died Saturday at Saddler Falls along the Spring River ... At least one other person was injured.

Sinkholes are common in the northern half of Arkansas, where subterranean limestone erodes away easily. Small whirlpools are common where bits of land extend into waterways, but having a sinkhole open a whirlpool in the middle of a stream is uncommon.

"I've been here for 40 years. This is the first one I've ever heard forming in a river like this," said Bill Prior, a geologist supervisor at the Arkansas Geological Survey. ...

The Spring River was flowing normally Saturday — fed by Mammoth Spring, the second-largest spring in the Ozark Mountains. Its steady flow, at about 356 cubic feet per second (enough to fill an Olympic-sized swimming pool every four minutes), makes it desirable for basic training on kayaks and canoes.

"Classes are often held on the Spring River because Mammoth Spring has such a reliable flow," said Jonathan Gillip, field operations chief for surface water at the U.S. Geological Survey office in Little Rock.

Dead Man's Curve has the occasional switchback, falls and pools, but isn't terribly turbulent, said Rocky McCollum, owner of Spring River Camp and Canoe. Boaters avoid it mainly to take a short cut around the switchbacks — but doing so Saturday put them on a portion of the stream where the river bed gave way.

"There are thousands of sinkholes across the northern part of the state," Gillip said. "This is an active one that people happened to see collapse, and it had a traumatic impact." ...

Saturday's whirlpool was both instantaneous and thousands of years in the making. The Spring River eroded harder rock above an underground cavity, and when the river bed gave way, it created a vacuum that sucked the water in a "pretty strong vortex," Prior said.

Rachel Ratliff, Rocky McCollum's daughter, rented canoes to Wright's group and said Wright was wearing a life jacket and was an experienced kayaker. "But the river is stronger than any life jacket there is," she said.

If the sinkhole system were closed, the water would drain into the cavity and eventually refill enough to kill the whirlpool. But because there's no change at the river gauge at Hardy, about 20 miles (32 kilometers) downstream, the whirlpool is likely diverting water back into the river, Gillip said. ...

... The Arkansas Game and Fish Commission warned prospective boaters to stay away from the whirlpool, which is marked off by buoys and ropes.
SOURCE: https://www.newstimes.com/news/us/article/Fatal-boating-accident-occurs-in-whirlpool-on-12984064.php
 

EnolaGaia

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Here's a photo of the deadly Arkansas whirlpool. Like the one in kamalktk's cited post, it doesn't look like all that big a threat at face value. The downward suction must be very strong ...

ArkansasWhirlpool.jpg
 

EnolaGaia

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Here's a 2-for-1 item ... There's the basic vehicle-eating sinkhole story, then there's the coincidence of the incident being responded to by the last guy to fall into the 'same' sinkhole 3 years earlier ...

Sinkhole swallows SUV amid heavy rains in Colorado
... A sinkhole opened up amid heavy rains on a Colorado road and swallowed an entire SUV in an incident caught on camera by a witness.

Sheridan Police tweeted a photo showing the Toyota RAV4 almost completely submerged in water at the bottom of the 15-foot-deep sinkhole Tuesday evening on Oxford Avenue in Sheridan.

Police said the driver was able to get out of the vehicle before it fell into the hole. She was not injured. ...

A sinkhole previously opened up at the same intersection in 2015. On that occasion, a police SUV fell 15-20 feet down the hole. Sgt. Greg Miller, the driver of the SUV in 2015, was among the officers who responded to Tuesday's incident.
SOURCE: https://www.upi.com/Odd_News/2018/0...V-amid-heavy-rains-in-Colorado/7681532530678/
 

Sharon Hill

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Here's a photo of the deadly Arkansas whirlpool. Like the one in kamalktk's cited post, it doesn't look like all that big a threat at face value. The downward suction must be very strong ...

You can see the creek bottom in this picture meaning that there is not much water above the hole and so the drawdown is strong and focused. Imagine you are walking along the creek bottom (though they were boating in this case) and you step into this soft ground and the hole opens, it's a treacherous situation. I've heard of some pretty large trout sucked into holes in Pennsylvania streams due to swallets like this. It signifies that the water table is below the stream bed - not a good situation to have.
 
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