An Ontario Geological Survey map of documented forest rings in Northern Ontario. Note that the size of the rings on the map is to show the distribution of different-sized rings, they are not proportional to the map scale. (Courtesy Ontario Geological Survey)

The Cheecka Ring is a ring measuring about 1 kilometre in diameter, located 20 km east of Hearst, Ont. Scientists believe it was formed by a natural gas deposit. (Courtesy S. Hamilton, OGS)

It is a strange phenomenon: thousands of large, perfectly round "forest rings" dot the boreal landscape of northern Ontario.

From the air, these mysterious light-coloured rings of stunted tree growth are clearly visible, but on the ground, you could walk right through them without noticing them. They range in diameter from 30 metres to 2 kilometres, with the average ring measuring about 91 metres across. Over 2,000 of these forest rings have been documented, but scientists estimate the actual number is more than 8,000.

What causes these near-perfect circles in the forest?

Since they were discovered on aerial photos about 50 years ago, the rings have baffled biologists, geologists and foresters. Some explanations put a UFO or extraterrestrial spin on the phenomenon. Astronomers suggest the rings might be the result of meteor strikes. Prospectors wonder whether the formations signal diamond-bearing kimberlites, a type of igneous rock.

Stew Hamilton, a Sudbury-based geochemist with the Sedimentary Geoscience Section of the Ontario Geological Survey, says forest rings are caused by giant, natural electrochemical cells — big centres of negative charges called reduced chimneys — that are frequently situated over metal or mineral deposits, or methane. (Courtesy Ontario MNR)

"We have been working on the rings since 1998, and there have been many developments, but there are still many unanswered questions," says Stew Hamilton, a Sudbury-based geochemist with the Sedimentary Geoscience Section of the Ontario Geological Survey.

Hamilton first became interested in the rings in 1997 when Sudbury prospector and geologist Bob Komarechka asked him about the potential kimberlite link. Now he has some new theories about how the giant rings were created, and his paper discussing some of the strange electrical phenomena that occur over the rings has been accepted for publication in the journal Geophysics.

According to Hamilton, the forest rings are caused by giant, naturally occurring electrochemical cells — big centres of negative charges (called reduced chimneys) that are frequently situated over metal or mineral deposits or methane (a natural gas source).

Think of them as huge natural electrical batteries with a negative charge in carbonate soil and surrounded by oxygen that carries a positive charge. The current from the batteries — the negative charge — travels outward and where it meets the positive charge, acidic conditions are created that eat away at the carbonate soil, causing it to drop in a circular depression around the natural battery.

How it all started

The origin of Ontario's methane-based forest rings, according to Hamilton's theory, lies in the glaciers and glacial lakes that at one time covered the province. As the glaciers began receding from northern Ontario about 10,000 years ago, they left behind a mix of clay and other glacial sediment.

Bacteria began eating the dead plankton and other organic matter left in the clay, a process that can only last a few thousand years before the organic matter is consumed, a short time, geologically speaking. This produced methane, a chemical that is the principal component of natural gas. In the case of forest rings, the methane is released into the atmosphere partly through the depressions of the rings.

So why the perfectly formed circles?

"Because force goes out in a circle," Hamilton says. "For example, throw a stick in the water. At first it makes a stick shape when it hits the water, then perfect circles go out from that. Electricity is just the same."

Gordon Southam, a geo-microbiologist at the University of Western Ontario, has just begun working with Hamilton on the biogeochemical aspects of forest rings.

"We debate back and forth on the various theories on forest ring formation. I find it extremely interesting any time that water-rock interactions release materials that support the growth of the biosphere; we're very interested in litho-trophic [rock-eating] bacteria," Southam says.

Rings in farmer's fields in Southern Ontario's Essex County, a few kilometres from the Michigan border, formed by oil deposits. (Courtesy Ontario MNR)

"In the case of forest rings, they appear to create anoxic [oxygen-free] conditions that support methane-producing bacteria below ground and methane-oxidizing bacteria near the earth's surface."

A map of forest rings in northeastern Ontario devised by Hamilton also seems to indicate that the creation of these anoxic conditions appears to be coinciding with permafrost melting, which is causing new activity in the biosphere.

Why is northern Ontario lord of the rings?

Although northern Ontario has the highest concentration of forest rings, you can also find them in the Yukon, Quebec, Russia and Australia.

"For years, we have been puzzled as to why Ontario has so many, and we now think we have some of the answers," Hamilton says. "We have measured the isotopic signature of natural gas in a number of rings, and it suggests the gas is very geologically young and is likely still being produced today and constantly escaping into the atmosphere. Northern Ontario has the youngest and most extensive glacial clay deposits in the world, and therefore we also have the most rings."

He estimates 80 per cent to 85 per cent of the region's rings are methane-based, with the rest being a result of kimberlite; hydrogen sulfide (recognizable by its "rotten egg” smell); metal-based sources such as nickel, copper and zinc; or buried peat. These, too, are all sources of negative electrical charge and have a capacity to create similar electrical fields as methane.

"On the one hand, the rings are a large potential source of relatively clean natural gas. On the other hand, they are constantly venting methane into the atmosphere, which has a greenhouse gas equivalent that is more than 20 times that of carbon dioxide," said Hamilton.

He is keen to see companies develop technology to extract the gas and use it as energy.

"Extracting the gas would therefore be doubly beneficial and also fairly easy from a technical point of view."

Source of charge unclear

And what about those other exotic theories of forest rings?

"It is definitely not a UFO thing, crop circles, tree-killing fungus or meteors falling from the sky," Hamilton laughs.

He does admit, though, that forest rings have "a million mysteries." For example, the electrical field found inside the forest rings is a puzzle that needs to be solved.

"It shouldn't be there," Hamilton says. "Something is creating a huge electrical field, and we think it might be millions of chemical-eating micro-organisms in the soil."

Hamilton, University of Ottawa geochemist Kéiko H. Hattori (chair of the department of earth sciences) and graduate student Kerstin Brauneder are the only Canadian scientists currently studying forest rings. This summer, they will test their hypothesis by generating chemicals in test tubes and adding some forest ring micro-organisms (bacteria) to the chemicals.

"To see a perfectly round forest ring in the middle of the forest is really very strange," said Brauneder, whose master's thesis is titled Origin and Distribution of Forest Ring-Related Methane.

The R2 Ring is a 300-metre wide ring located about 40 kilometres south of Hearst, Ont. The geological source of the ring is unknown, but its shape can be clearly seen in this aerial photograph of the forest. (Courtesy S. Hamilton, OGS)

"This summer, Dr. Hamilton and I will be sampling soils over five forest rings near Timmins and Hearst. Together with Dr. Southam, we will try to recreate a small-scale forest ring phenomena in-vitro, in a test tube, to see where and how methane-producing microbial communities grow. Understanding the methane-cycle of the rings is important, because we are hoping the methane could eventually be used as a new energy source for isolated communities."

Calling the forest rings the "world's largest petri dish," Hamilton said the testing will be the first step to recreating, in the lab, the mysterious electrical field process.

"Our hypothesis is that with the forest rings, millions of micro-organisms are creating a massive, low-voltage electrical field that causes their food, the chemicals, to come forward to them. The bacteria don't have to move — the food keeps coming to them along the electrical field they have created," explained Hamilton.

This, he said, also poses an intriguing question: "Are micro-organisms changing and modifying geology?"

"It is a new paradigm for us. What science doesn't understand is the most interesting, and we're having a lot of fun working on the many pieces of the strange puzzle. This is beyond science fiction — it is unbelievable."

The author is a freelance writer based in Thunder Bay, Ont.