Stoked on Science: Rocks of Revelstoke

How the beginnings of mountains started

Jade Harvey. (File)

Jade Harvey. (File)

Part 1 – Flat and Wet

It’s September — and summer is slipping away.

As I relinquish days spent on sweltering hot climbs, ascending baked rock, finishing with cool dips in our lakes and rivers, the next few episodes of Stoked on Science will pay homage to the rocks of Revelstoke and the incredible geological history of our locality.

So complex and unique is this history it will take several episodes in order to do it justice.

I am inspired to this right now as a result of our local climbing community.

They work so hard to connect people with the rocks of Revelstoke and highlight its specialness.

From Reudi Beglinger, author of ‘Revelstoke Rocks’ climbing guide, to Douglas Sproul (and friends), who work tirelessly to improve climbing outdoors here, and the Revelstoke Multiplex Society, working hard on bringing a world class facility with indoor climbing to the city.

Part of their fundraising is the exceptionally cool sounding SENDtember STOKEtacular, Named for the word used to describe completing a climb — a ‘send.’

We all love things with ‘stoke’ in the title here. Happening Sept. 20 to 22 at the the Lamplighter Campground, it’s the first of what is hoped will be an annual festival.

It will be fascinating for those who already love climbing or those yet to discover it.

Climbing wouldn’t be a thing if there were not rock formations to scale.

To think about how the rocks we know today came about, we have to slide back in time to around a billion years before present, to a very different landscape, devoid of complex life.

Where now we see the Coast Mountains, our Columbia Mountains and spreading all the way east our Rocky Mountains, once existed a very flat area running all the way from the Arctic to Mexico. This flat land was only just above sea level.

Due to the earth’s crust being stretched and moved by plate tectonics, the earth’s surface sunk down creating a basin which was eventually flooded and filled in by sediments from the adjacent shallow sea.

Into this vast shallow sea, covering hundreds of thousands of square kilometres, the rivers from the surrounding regions poured their loads of silt and mud and the waves of the sea spread them far and wide depositing them into the huge basin.

Over millions of years, the accumulation of sediments filled the basin — mud, silt, sand and precipitates. But simultaneously, the the basin deepened through the weight of the load and the continuing tectonic activity.

We know this as scientists have calculated the age of the rocks by looking at the stratigraphy (layers), and at an even rate of filling there has been thousands and thousands of feet of material accumulated. But all of them show features of shallow water origins.

Thus despite the infilling, the basin must’ve been sinking or the materials would have extended above the shallow sea and deposits would no longer be of a shallow water nature. How do we know that our mountains are really of these oceanic origins?

Well, rocks in the Selkirks and Purcells are made distinctly of rocks from a sedimentary origin — rocks made from layers of ancient gravels, sands, muds and other sediments that over time and pressure are solidified into rocks.

These are solely created by the layering underwater of these sediments. Also around 600 million years ago, living things began to propagate through these shallow seas.

Many of these animals had hard skeletons, which when they died fell to the bottom of the sea to be deposited as well.

Many remained intact buried beneath more layers of fine sediments, which now when rocks are split open can be seen in their entirety.

Some of these fossils can often be compared to modern animals (which have evolved from these ancient creatures) and they still live underwater. So underwater our mountains once must’ve been.

Okay, so how do we get a sea floor becoming high mountains? How did the jagged peaks of the Selkirks and the more rounded and smoother sloped Purcells arise from this soft, flat, wet landscape?

The next stage of Columbia Mountains development began around 200 million years ago when this peaceful basin environment would be thrust into instability by violent forces from within the earth.

Tune in next week for the next installment of the history of Revelstoke rocks.

Jade Harvey has a degree in physical geography and likes to share her passion for science through writing and telling stories.