A Brief History of
Fallingbrook
or
How Fallingbrook Got its Mud
by David Villeneuve (1991)
Your memories of seeing your new house being built in Fallingbrook probably also include the memory of that incredibly sticky clay which never came off your boots. But why is it that Fallingbrook has clay beneath, but other places like Kanata have rock? And what is underneath the clay?
We start our history one billion years ago, when the most advanced life forms on earth were single-celled creatures living in the water, when the air held little oxygen. In a series of violent upheavals, the mountains which today are the Gatineau hills were thrust up as high as the Andes. Over the next 400 million years, they were slowly eroded till they resembled the rolling hills of today.
Meanwhile the lower lands, which included most of eastern Ontario, were submerged under a sea which came and went over the millenia. The seas were filled with strange shelled creatures whose shells make up the limestone deep under us today. This limestone can be almost a kilometer deep in places, and can be seen along the escarpment north of Princess Louise Drive. If you're taking notes, it's of the Bobcaygeon formation, formed during the Middle Ordovician Period (480 million years ago).
Nothing much happened over the next 400 million years, except minor things like the continents splitting apart, the coming and going of dinosaurs, and the arrival of mammals. Then, about one million years ago, the glaciers came and covered northern Canada as far south as here. The land was buried under kilometers of ice. Only about 15,000 years ago did the ice begin to melt. The land which had been compressed under the ice found itself under water once again, the Champlain Sea. The Great Lakes drained through the Ottawa River from Petawawa. The Ottawa River's path was different then, flowing through Mer Bleu and joining the present-day Ottawa River near Alfred. Aerial photos of Mer Bleu show clearly the remains of a 7000 year old river bed, and it is still damp.
As the meltwater flowed toward the St Lawrence River, erosion cut into the underlying rocks and formed the Ottawa River valley. The runoff contained sand and silt which deposited on the bottom of the river. When the Ottawa River finally shrunk to its present size, the surrounding land was covered with a deep layer of mud, which makes up the clay which our houses are built on. Sand from ancient river banks can be found just this side of Navan.
When the trunk sewer was put alongside Tenth Line Road in 1989, surveys showed that the clay was over 100 feet thick in places. About 50 feet down, it is largely Leda clay, a type of marine clay named after a type of clam often found in such clay deposits. Leda clay is particularly treacherous, since it can suddenly slide. The contractors who excavated for the sewer were particulary concerned that Tenth Line Road might slide into their hole. The remnants of such landslides can still be seen along the escarpment in Beacon Hill North.
The depth of the clay depends on the underlying rocks: sometimes the rocks come right to the surface, such as at the escarpment or by the Town Hall. The rock nearer the Ottawa River comes from older formations than that in Fallingbrook. The depth of the clay makes it difficult to erect tall buildings in the area. The Brewers Retail store at Fallingbrook Centre had to have a special floating basement built in order to support the weight of the beer stored upstairs.
So when you remember the clay that stuck to your boots as you watched the construction of your new home in Fallingbrook, remember how long it took for the clay to get here.
Sources of Information