Day Trip into the Brent Crater

A description, with photos, of a day's exploration of the Brent Crater in Algonquin Park by canoe. Our route took us from the Brent Road, down to Tecumseh Lake, through Gilmour Lake, Gilmour Creek and eventually to Brant Lake and return.

2009 May 12

panorama of brent crater in Algonquin Park

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From the historical plaque: First recognized in 1951 from aerial photographs, the crater is a circular depression about two miles in diameter formed in Precambrian crystalline rocks. Geophysical and diamond drilling investigations show that the crater has a present depth of about 1,400 feet but is partly filled with sedimentary rocks with a thickness of 900 feet. The rocks beneath the crater floor are thoroughly fragmented over a depth of 2,000 feet. Like the similar New Quebec (Chubb) crater, the Brent Crater is attributed to the high speed impact of a giant meteorite. It is calculated that the impact released energy equaling 250 megatons of TNT and occurred about 450 million years ago when this area was probably covered by a shallow sea.

We have previously visited the Brent Crater and Bob has done the walking trail (Brent Crater, Stairs, and Pitcher Plant). However, he wanted to see more than could reasonably be accomplished on foot. On 2009 May 12, Bob and our friend Ric portaged a canoe down to the crater floor and we went exploring.

portage from the Brent Road to Tecumseh Lake in the Brent Crater in Algonquin Park

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Along the portage from the Brent Road to Tecumseh Lake, which lies on the floor of the Brent Crater. The portage passes through an open, pleasant, mainly hardwood forest, following Muskwa Creek part of the way. However, once the blackflies are out, this section might be somewhat less pleasant.

Tecumseh Lake in the Brent Crater in Algonquin Park

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Access to Tecumseh Lake is not direct, but is achieved by a narrow and shallow channel (this is one of the wider sections) which is a hundred meters or more in length. Even with a small canoe and spring water levels, it was a nuisance to get through. It was impossible to paddle effectively and the bottom was too soft for poling. One technique that worked was grabbing the shoreline vegetation and pulling ourselves along. I suspect that later in the season, it would be necessary to drag the canoe through here (and end up with wet and mucky feet).

Tecumseh Lake in the Brent Crater in Algonquin Park

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Almost there! But Ric had to get out of the canoe to get us through this final gap into Tecumseh Lake.

White cedars on Tecumseh Lake in the Brent Crater in Algonquin Park

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White cedar along the shoreline on Tecumseh Lake.
The Brent Crater and the Brent Limestone Cliff are the only locations within Algonquin Park where limestone bedrock is present. (Limestone within the crater was protected from the erosional action of the glaciers. On top of the limestone, the crater is largely filled with glacial till, while the surrounding territory is scraped bare.) The presence of limestone results in Gilmour Lake and Tecumseh Lake being well buffered chemically against acidity. The presence of white cedar is a good indicator of the presence of lime in the water; they cannot tolerate high acidity. White cedars are quite prevalent, but do not dominate, the forests of the crater bottom.

Tecumseh Lake in the Brent Crater in Algonquin Park

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Another observation was that the water appeared very clear; it did not look to be significantly tannin stained. I would be interested to observe its clarity late in the season.

observation tower as seen from Tecumseh Lake in the Brent Crater in Algonquin Park

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Before descending into the crater, I had decided that I wanted to get a picture of the observation tower as seen from Tecumseh Lake. This turned out to be much more difficult that we had naively expected. We assumed that the tower would be prominently silhouetted on the skyline, but the land continues to rise behind the tower and the tower is hidden in the trees.

in Gilmour Creek looking towards Tecumseh Lake in the Brent Crater in Algonquin Park

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In Gilmour Creek looking out towards Tecumseh Lake.
When we entered here, we disturbed a bald eagle, probably hunting breeding suckers. Big schools of suckers were very evident in the two sections of Gilmour Creek that we explored. Some of the individual fish were quite large and showed up well against the sandy bottom.

Both Tecumseh Lake and Gilmour Lake gave the impression of being shallow lakes (consistent with being lakes in glacial till). However, according to my old (1978) copy of "Fishing in Algonquin Provincial Park", Gilmour Lake provides "good" lake trout fishing while both lakes provide "fair" brook trout fishing.

The beach on Gilmour Lake at the end of the portage from Tecumseh Lake in the Brent Crater in Algonquin Park

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The beach on Gilmour Lake at the end of the portage from Tecumseh Lake.

The clear water of Gilmour Lake in the Brent Crater in Algonquin Park

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The clear water of Gilmour Lake, the most buffered lake in the Park.

Gilmour Lake in the Brent Crater in Algonquin Park

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Making a whistle.
On many of our excursions, Ric takes a few minutes to make a whistle (you just never know when the O.P.P. is going to show up in one of their speedboats to check your safety equipment). On a previous trip, the whistle impressed Richard and Gregory sufficiently that they included the instructions on how to make one on their Grants Creek web page.

Gilmour Lake in the Brent Crater in Algonquin Park

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View from the campsite on Gilmour Lake, just south of the portage from Tecumseh Lake.
While this campsite is well used, it does not appear on the canoe routes map. I didn't notice whether it had an official sign or not, but I certainly didn't see any "closed" or "no camping" signs either(see notes).

Logging camp remains on Gilmour Lake in the Brent Crater in Algonquin Park

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Logging camp remains on Gilmour Lake.
These are up the beach, north of the portage from Tecumseh Lake.
According to "Names of Algonquin", Gilmour Lake is "named after the lumbering firm of Gilmour and Hughson ... out of Hull. Allan Gilmour of this company was an uncle of the Gilmour brothers of Trenton, Ontario. ... The two enterprises were unconnected commercially". It is therefore tempting to associate these remains with the Gilmour and Hughson Company, however, I know of no supporting evidence, and these remains are perhaps too recent.

Logging camp remains on Gilmour Lake in the Brent Crater in Algonquin Park

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Many logging camps were built with pine; this one was built with cedar.

Logging camp remains on Gilmour Lake in the Brent Crater in Algonquin Park

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We paced these logs off to be of the order of fifty feet.

Logging camp remains on Gilmour Lake in the Brent Crater in Algonquin Park

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This old oil drum stove had migrated over to near the campsite mentioned above.

Cedars and cedar roots along Gilmour Creek leading to Brant Lake

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Cedars and cedar roots along Gilmour Creek leading to Brant Lake.

Brant Lake in Algonquin Park

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Our lunch spot on Brant Lake.
We hadn't planned on going to Brant Lake. We just proceeded down Gilmour Creek, continually saying "Let's just see what's around the next bend".

Brant Lake in Algonquin Park

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The narrows in Brant Lake, leading eventually to Cedar Lake; exploration for another day.

After lunch, we retraced our route and returned to the car without incident. All in all, a pleasant spring day in the bush and the portage in and out of the crater was not nearly as bad as I had imagined it.

If you visit the crater with the expectation of seeing exciting and awe-inspiring evidence of an ancient cataclysm, you may well be disappointed. The lasting effects of the meteorite impact are there, but you have to search them out. To me, it was the knowledge of what had happened that most defined the location. Four hundred and fifty million years ago, you would have been paddling on a shallow tropical sea, close to the equator. Your paddling partners would have been trilobites. And then this peaceful scene would then instantly become the site of an explosion, many times more powerful than any man-made nuclear explosion. Your ashes would have been dispersed over hundreds of miles and perhaps around the globe.

Now, hundreds of millions of years later, the observable manifestations of the impact are the circular surrounding horizon -- although the view in any particular direction is not significantly different from what you might see elsewhere, and the view in the opposite direction may well be obscured by trees -- and the details of the flora, most notably the prevalence of white cedar. Another aspect of the environment is the absence of visible bedrock; the bottom of the crater is covered with glacial till. This gives rise to the beach on Gilmour Lake and to campsites akin to those found on the Petawawa sand plain. Under the thick layer of glacial till, an even thicker layer of sedimentary rock has buried the most direct evidence of the impact, the shattered bedrock.

The Brent Crater is a special place, but its charms are subtle, in stark contrast to its formation.

Notes

  1. Jeffrey McMurtrie (see Free Algonquin Provincial Park Map for Jeffrey's map of Algonquin Park) informs me that, according to his information, the campsite on Gilmour Lake, south of the portage from Tecumseh Lake, is in the MNR's database of campsites and thus appears to be an official campsite.

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