15,000-year-old cavern found in St-Léonard
Glacier dislodged limestone to form St-Léonard park’s natural wonder
Daniel Caron’s eyes twinkle with excitement as he recounts how he and fellow spelunker Luc Le Blanc finally managed to dig their way into a massive, naturally occurring underground cavern beneath a city park in the borough of St-Léonard one day last October.
“In the life of a spelunker, something like this happens once,” Caron said. “It was so easy to open it up. We were happy and surprised, but it was a complete fluke.”
On Friday, Caron took reporters on a tour of what they found on Oct. 12: a 250-metre-long cavern that has existed for at least 15,000 years, according to caving experts. The cavern extends behind the much smaller cave that has long delighted visitors to Parc Pie-XII on Lavoisier Blvd. near Viau Blvd.
Caron and others had long suspected there was more to the StLéonard Cavern, which was discovered in 1812.
As a teenager growing up in St-Michel in the 1960s, Caron remembers digging into and exploring the cave at night with friends, despite attempts by local authorities to keep them out.
In the early 1980s, the city of St-Léonard decided to make the small cave accessible to the public in a controlled way. Stairs descending into the mouth of the cave were built, a door installed and a wrought-iron fence was erected to keep trespassers out.
Since 1982, about 70,000 people, mostly schoolchildren, have toured the original cave, through educational tours conducted by the Sociétê québécoise de spéléologie (SQS).
But in 2014, Caron and Le Blanc, both members of the SQS, decided to get serious about their hunch that there was more cavern to discover.
“It’s always the goal of a spelunker to find a new cavern, or find an extension to an existing cavern like this,” he said.
In 2014, Caron and Le Blanc examined the original cave using calibrated tools and a technique called radioesthesia, that can detect empty areas behind rock, “a bit like the way witches used divining rods to find water,” Caron said.
The next year, they discovered a fissure in a wall at the back of the cave, and were able to send a small camera through to confirm that there was empty space about a metre in.
“We couldn’t see how big, but we saw an empty space. In 2016 we tried to dig there but it was solid rock, solid limestone, so we couldn’t get through it.”
This fall they brought in industrial drills and other equipment, and on Oct. 12, they broke through to the larger cavern.
“After a few hours of digging, it was big enough to get the upper part of our bodies through, and we could see that on the other side, it was vast. We started yelling, ‘Yes! We did it! We did it!’ ”
The next day they came back and made the opening larger. They saw there was a drop, and brought in a ladder. When they climbed down, they found several large cavern branches, parts of which were underwater. They actually swam through parts of it to see how far the cavern went, and later explored it with an inflatable dinghy.
To get into the biggest gallery of the newly discovered cavern Friday, visitors had to squeeze through the small passageway that Caron and Le Blanc managed to dig out that first day, and then climb down a ladder.
Descending into the main gallery of the newly discovered cavern, which is about six metres high and about three metres wide, Caron showed off the remarkably regular and smooth limestone walls striped with calcite flowstones, and the many stalactites — calcium formations that look like icicles — hanging from the smooth, flat ceiling.
What makes this cavern special, he said, is the fact that it was formed by a glacier dislodging a massive slab of limestone, which may have measured 10 metres thick and a kilometre long. Caves that are formed by lava or underground streams are more meandering with irregular walls, he said.
Dominic Perri, city councillor for the district of St-Léonard Ouest, said he hopes that eventually the new cavern will also be made accessible to the public. But first, steps must be taken to protect it, he said.
“Before the borough took control of the cavern in 1982, it was open and people would get in and sometimes do damage, like breaking off the stalactites and that sort of thing,” he said.
The borough has ordered studies to be done over the next year to ensure the cavern is properly documented, through photos, measuring and mapping.
“The specialists tell us this type of cave is very unusual, if not unique in the world,” Perri said. “We want to maintain it because it is our heritage, but also because it has scientific value in terms of the way it is shaped and how it was made.”