Startlingly Big Sinkhole Opens in New Zealand

A sinkhole that opened up in Rotorua, New Zealand
Scientists consider this new sinkhole in New Zealand to be 'pretty spectacular.'. euronews/YouTube

A sinkhole is the last thing you want to discover, let alone one the length of two football fields and six stories deep.

Colin Tremain, a farm manager in the North Island town of Rotorua in New Zealand, found such a sinkhole April 30, following heavy rains in the area over the weekend.

"It wasn't until I came down in daylight that I actually saw just how big it was," he told the Australian Broadcasting Corporation (ABC).

Decades in the making

Tremain is used to these sinkholes, however. It's the ninth one to form on the property in recent years.

It's also the largest so far, and one of the largest that vulcanologist Brad Scott has seen.

"The largest I've seen prior to this would be about a third of the size of this, so this is really big," Scott told ABC.

The sinkhole is actually located in the crater of a dormant 60,000-year-old volcano.

"Then there's a stack of about 10 to 12 meters of sediment sitting on top of it from lakes that have formed in this crater the top three meters is volcanic ash," Scott told TVNZ.

What causes sinkholes?

Sinkholes form when water collects underground without any external drainage. Over time, the water erodes the bedrock, forming a cavern. Eventually, the top layer — the ground we walk and build on — collapses, or sinks, into the cavern. Heavy rainfalls, like the one Scott mentions, can be the straw that breaks the sinkhole's back, as it were.

"The cavity would have been present from all the rainfall events over the last 40, 50, 100 years. The high-intensity rainfall that we experienced on the weekend just accelerates the process."

The sinkhole has already earned the nickname of "Grand Canyon of Rotorua," according to The sinkhole isn't expected to grow much more larger, however.

Luckily, no one, including the farm's animals, were harmed when the sinkhole appeared.

"We'll keep it fenced off as it is to keep stock out — although stock aren't stupid, they're not going to walk into a hole. They can spot danger," Tremain told Newshub.