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Quest for potholes sends Back Roads Bill and friends bushwacking (4 photos)

This week Bill tells us a story about finding a glacial pothole that has eluded him for quite some time. He is asking readers to send along their pothole locations for a Northern Ontario treasure hunt

Potholes, not the spring kind that affect the alignment of your vehicle but the glacial ones; Village Media readers may know the entire Great Lakes and beyond once drained eastward that’s a lot of water and there is geological evidence to prove it.

Recently, it seemed to be an anticlimactic Back Roads Bill expression, “Found it! But it’s not the one in the photo?” It would take yet one more day to find the elusive and mother lode of potholes.

Along with erratic boulders and striations, potholes represent present-day evidence of mega geologic events like the most recent ice age.

Dr. Eric Mattson, a Professor of Geography at Nipissing University in North Bay says, these potholes are the result of massive volumes of glacial melt-water draining through a spillway that is now referred to as the North Bay Outlet. In terms of process, potholes are formed by stationary rotary currents carrying pebbles and stones (called “grinders”) which abrade depressions in the softer bedrock along the bed of the stream.

These grinders ever so gradually wear the holes deeper and deeper into the bedrock.

“It is a whirlpool effect of water and gyrating stones of varied sizes. As a result of the constant whirling of the stones, the potholes take on a remarkably symmetrical, round shape,” Mattson says. 

Some of them can be found in Potholes Provincial Park near Wawa and the Rockwood Conservation Area potholes near Guelph. Potholes are natural anomalies and are found in many places, access is a matter of available information.

After sixteen years, including many site visits with willing volunteers, searching by bushwhacking an irregular area of 1 km x 400 m, three significant potholes cited in a 1972 report have been re-located. These potholes are within one of the four significant glacial-fluvial spillways that drained all of the Great Lakes and beyond. It was a matter of misinformation; it became a puzzle of interpreting references and more.

In the beginning, it was a Geological Survey of Canada, report with a black and white photo, a field researcher is seen, legs dangling over the edge of a deep pothole somewhere west of Mattawa, along what was the main CPR railway line. It was titled: ‘Quaternary Geology of the North Bay-Mattawa Region’ by J. E. Harrison.

“The photo shows the larger of two potholes on a granite gneiss ridge in a channel 200 yards east of Morel siding. Harrison’s paper stated, “…deglaciation, permitted waters from the upper Great Lakes to spill eastward through the area.”

We’re talking approximately eight thousand years ago and several outlets drained into the Ottawa drainage system.

“East of where?” This became the mantra as there was no additional information. Many friends and colleagues and interested people have walked the pipeline to the tracks and searched both sides of the railway corridor, off and on throughout the years, besides it is my avocation.

Two years ago new spatial information was found. A 2004 academic paper by Professor Paul Karrow from the University of Waterloo, included a table of information identifying the Morel potholes but these coordinates were incorrect when using the GPS and the author had not visited the site. The anecdotal field notes were vague and the latitude-longitude was not accurately identified. It is difficult to estimate decimal seconds on a topographic map – as they did not have GPS back in the day.

Local Bonfield resident and Professor Emeritus, Queen’s University, Dr. Larry Dyke became involved. He is a geologist and undertook a number of searches with me and designed a new search area off of the railway line which represents the bottom of the once fluvial spillway.

Larry says, “It seemed the potholes could be lower. I think there could have already been under-ice flow that could have started the pothole forming. In any event, such a feature indicates a strong flow of water, strong enough to keep cobbles in the pothole swirling, continuing the boring, and for quite some time." 

Again no luck and Larry moved this summer to North Vancouver.

Along came Dr. Jeff Scott from Nipissing University, who wanted to be the “research assistant,” his title. He helped meander through the saplings and alders and low-wet areas on a number of trips with his sidekick, dog Juno.

“We tried to train Juno to find potholes but that was more wasted time,“ said Jeff.

A story appeared in a local newspaper but there was no community response as to the location, no one seemed to know. Facebook responses included sending me photos of other potholes I have highlighted in stories and posts. 

It was time to give up. After too many attempts, it was time to move on.

One more review of the literature revealed other researchers who may have been there. What “sealed the deal,” was a new field note reference, within a radiocarbon dating paper of 1969 by W.Blake, “…90 m south of the east end of the CPR shunting track at Morel…,” he had actually been there in 1969.

Railway buffs will know a shunting track is a third track, not the siding, it exists but is derelict and overgrown along the 1 km corridor, towards the west end, the opposite end of where most of the reconnaissance had been focused.

Friday the 13th afternoon was a lucky one, after 16 years of combing both sides of the railway, more than 100 hours of fieldwork and research, and more than a dozen trips to the area, one of the elusive Morel glacial pothole/kettle was located. It wasn’t the largest one though depicted in the 1972 photo.

It took Saturday with Jeff to find the larger pothole close enough to the other.  

"No adventure is complete without an adventure! And in the search for the Morel pothole, this was certainly the case. Attempting to discern what the authors meant with their limited directions became key as did looking through other print material that had been cited by the authors. As information emerged, the adventure certainly took on new twists, new meaning and new opportunities. For me, the third attempt at finding the potholes certainly proved valuable with two circular and deep holes carved in the granite ridge. Good sleuthing, enjoyable time in the outdoors, reiteration of details and perseverance all paid off. Perhaps you will choose to visit the potholes for an adventure of your own," he said.

There are three potholes on top of the low lying ridge of exposed bedrock. The larger pothole is 23 m away in a northerly direction from the smaller. It measures more than 12' or 3.6 m in-depth and is dry. The smaller one measures 4' 6" or 1.37 m across and about the same depth. The interesting aspect here is that if has no fissures or crack for the water to escape. We bailed it out and this took a while for the bucket brigade. There is also an enormous broken pothole between the two worth looking at for its cylindrical appearance and depth.

For some reason, I could not give up on finding these glacial souvenirs and I will use my fingers and toes to count back the number of times I have searched. Each time I go back and stare down into the larger pothole, I know why. What on earth could be better than to go back in time? Go and have a look, here’s the map.

Tell me about your favourite pothole, erratic or striation for a treasure hunt.


Bill Steer

About the Author: Bill Steer

Back Roads Bill Steer is an avid outdoorsman and is founder of the Canadian Ecology Centre
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