How climate change is making N.W.T.'s Smoking Hills more acidic, toxic

Calgary researchers discovered in the Northwest Territories what they believe is some of the most acidic natural water in the world.

Climate change is causing thawing of the permafrost and slumping — a process of land erosion — from the Smoking Hills Formation. That’s leading to toxic metals and a highly acidic solution to leak into rivers, bays and potentially the Arctic Ocean.

Geological Survey of Canada research scientist Stephen Grasby visited the site on the territory's north shore in 2017 as well as 2023, and was fascinated by the sheer scale of the toxicity and acidity in the ponds around the Smoking Hills.

“It’s humbling to see the powers of nature for good and bad,” Grasby says. “Nature is producing some of the most toxic acidic waters you would find anywhere — far worse than humans can ever make at an industrial site.”

The toxic metals causing this natural phenomenon were trapped in iron sulfide minerals buried underground known as pyrite, or “fool’s gold,” 85 million years ago when Arctic Canada was ravaged by active volcanism. Pyrite is known to absorb these metals and only releases them when exposed to oxygen.

Previously, most of it was covered by a rock layer and permafrost.

However, Grasby says slumping has led to a steady increase in the exposure of pyrite to oxygen, releasing extreme heat and large quantities of metals into the bodies of water around the Smoking Hills. 

Between his two visits, Grasby noted a “dramatic change in the landscape” in terms of the number of slumps occurring.

The ponds had also turned black and looked closer to oil than water, with such high acidity that the team’s equipment struggled to precisely measure its pH level.

“It's the first time in my career I've ever seen this," said Grasby. "Our pH meters were reading negative pH values, and they only go down to about negative two, and if it's more acidic than that, the meter just can't read it anymore.”

The temperature of the ground surrounding the water was also too hot to measure, as their equipment could only read up to 350 C. Grasby found evidence that suggested the temperature was more than three times that.

“There's places where we found rocks that look just like lava you would see in Hawaii — this solidified lava,” Grasby said. “That tells you that the rocks got hot enough that they melted, they flowed out of the old crop and then hardened in the air again. You need [temperatures] over 1,200 C to melt those rocks.” 

Known as paralava, the hot rocks lie just under the surface, creating a crème brûlée effect where simply walking on the ground exposes the hot layer underneath.

“We, just out of curiosity, took a picture of the ground with the thermal camera, and it says it's 25 C. We took a step and moved a foot back and took a photo of the same area now with the footprint, and the footprint is reading 350 C just inches down into the ground.”