The largest sinkhole in New Zealand opened up on its North Island, measuring 656 feet in length and 66 feet in depth — for people trying to visualize the measurements — that’s almost two football fields long and a six-storey building deep.

The sinkhole opened up overnight last week, about 15 kilometers south-east of the city of Rotorua in a region called Earthquake Flat.

"This is pretty spectacular, it's a lot bigger than the ones I'd normally see. The largest I've seen prior to this would be about a third of the size of this, so this is really big," volcanologist Brad Scott from Kiwi geoscience firm GNS Science said, Science Alert reported. 

The depth and expanse of the sinkhole was not the only reason that had scientists flocking to the site to examine it more closely.

"What I see in the bottom of this hole is the original 60,000-year-old volcanic deposit that came out of this crater," Scott said. "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."

But, there is no reason to worry, as the volcano in question is a dormant one.

The sinkhole might have revealed itself recently, but it was over 100 years in making. According to scientists, heavy rainfall for centuries slowly eroded away the underground limestone reserve in the area. Finally, a period of intense rainfall in the region at the end of April — almost 170 millimeters of rain in 38 hours — that lasted for about a week, caused the surface to give way and collapse, forming a canyon.

The scientists are still studying the sinkhole to understand the gradual build-up and layering of rock, sediment, and soil over decades and even centuries.

The sinkhole was first discovered by a New Zealand farm assistant, who failed to realize its stature due to the lack of light during dawn. Gabriel Lafalla, was rounding up the cows to milk them early in the morning, when he narrowly missed riding his bike into the deep chasm.

"I could have died," he said, Science Alert reported. "I touched myself [the sign of the cross] and said to myself, 'I'm alive.'"

Colin Tremain, a farm manager near where the sizeable crack appeared, said: "It wasn't until I came down in daylight that I actually saw just how big it was. 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 added that while sinkholes were pretty common in the area, a sinkhole of that proportion was unheard of. Also, he did not think he could do much to prevent it from eating away at the land. “(I'll) put a fence around it and forget about it, waste of time filling it in," he said, Phys.org reported.

Posted Date : May 9, 2018
Ref : IBT

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