Reading Rocks - The Cape Breton Highlands
At the North end of Cape Breton is a place ‘where the mountains meet the sea’ - sudden cliffs rise up to stunning plateaus in Cape Breton Highlands National Park. We look into the origins of this landscape - why are there 500 metre cliffs here while the rest of the province is so relatively flat? And atop those cliffs we see how Cape Breton’s plateaus have sustained an isolated, lost world.
EPISODE NOTES
I went to the Cape Breton Highlands in search of moose, but made a pretty dumb error. I chose for home base a spot on the east side of the park, down by the shore. That meant getting to any of the plateau scrub favoured by the moose meant driving the winding road around the top of the park and down the other side to access them. Moose, meanwhile, are crepuscular, and it just was not realistic to get myself in place to be where they might be at sunrise or sunset. I kept my eyes peeled through every hike regardless, but the moose weren’t feeling generous.
TRANSCRIPT
At the North end of Cape Breton is a place described as ‘where the mountains meet the sea’.
A place where the Atlantic surf hits sheer rock walls that can rise hundreds of meters.
This is Cape Breton Highlands National Park. 951 square kilometres of deep river valleys, rocky gorges and soaring cliffs topped by expansive plateaus.
Most of the park is covered in boreal forest. But atop those plateaus, which can reach 518 meters above sea level, it’s a whole different world. Here you can find pockets of ecosystems more like an arctic tundra.
So, how did these Highlands get here in the first place? At this point it may sound like a familiar story if you’ve been following this whole geological exploration of the east coast.
They can be traced way back to the northwest coast of what would become South America. As the supercontinent Rodinia breaks up between 750 and 450 million years ago, the Bras D’or terrane forms here from a mix of metamorphic and igneous rocks.
The terrane is swept across the globe by hundreds of millions of years of tectonic activity, mashes together with the Aspy terrane and finds its way here during the orogenies that formed the precursor to the Appalachian mountain range.
Those mountains are another feature that keeps popping up. And no surprise - the Appalachians are one of the defining geological events of the east coast of North America. But now, from atop the Cape Breton Highlands, I think it’s high time to look back and really appreciate the extent of them.
Here is the range of what we currently call the Appalachians. But today they are relative foothills of their former glory. If we rewind the clock back 295 million years or so…
These are the Central Pangean mountains. Now we can see exactly how far this one geological feature really stretches and how connected it makes a lot of disparate landmasses today. If you know what you’re looking for, you can find rock formations linking this one great mountain chain from the Florida panhandle, to Western Africa, to the Scottish Highlands, to Norway, Greenland and, of course, Cape Breton.
We can see that the Central Pangean Mountains ran straight through Nova Scotia. Since then, erosion over the mesozoic era has seriously sanded down that once mighty mountain range. But the Cape Breton Highlands still stand as a bit of a surprising exception.
And a geological map of the area can tell us why. While much of the bedrock of the island is sedimentary, if you’ll recall, the terranes that make up the highlands are a defiant mix of igneous and metamorphic. And as we learned exploring Nova Scotia’s granite batholith last time, these types of rock are way more resistant to erosion.
So as the rest of the province was scoured down, the Cape Breton Highlands held firm, leaving us with their soaring cliffs, beautiful plateaus… and one more mystery.
I mentioned that the top of those plateaus are almost like an arctic tundra - a lean and hardy ecosystem and, with it, a conglomeration of rare animals and plants.
Over a third of species designated as rare in Nova Scotia are found on Cape Breton’s plateaus and in the deep rocky gorges between them. Included are 78 plant species cut off from the rest of their Canadian range. They exist in the high arctic tundra north of the tree line and… right here.
Why? There are competing theories. Example: these plants may have grown in an unbroken arc across similar Canadian environments but were separated by the last ice age. In this theory, the height of these resilient highlands made them a nunatak, just poking up above the ice, enough for those plants to cling onto life here.
But other theories point to local conditions - alkaline and calcium-rich soil, as surrounding environments changed. Or, as the climate warmed and plant species from further south invaded Canada, they pushed back these arctic species into the few remaining pockets where they still had an edge.
The debate’s raged since at least 1925. But whatever the reason, the geology of Cape Breton’s Highlands has given us this incredible place where the mountains meet the sea, topped with a veritable lost world to explore.