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A journey through Earth’s history by canoe part 2: Rivers keep flowing and life goes on

 

The Coppermine River cuts its way through a volcanic landscape.

From the beginning of life, rivers experiment, trying new directions and invariably taking the easiest path. Everything follows the line of least resistance, a river, a vein cutting through rock, animals crossing a hillside, people on their way to work.

As we go in search of some of the earliest life, passing through layers of time, we follow the Coppermine River winding its way through the Arctic landscape, cutting the easiest path through a remote part of the world that those brave enough to travel it are lucky to see.

Braving some of the many rapids on the Coppermine River.

Our journey increases in length everyday – the shortest path is not always the easiest. Our navigation through the water avoids rocks and shallows and is more haphazard than can accurately be measured on a map. We are reminded by our wise river guides: ‘follow the water and it will show you the way.’

‘Where are we now? On the river for sure…’

We are using human muscle and the power of water to get where we want to go. As we get more proficient at reading the river we start to see that at times it requires no effort, just an awareness to see how the water will move us. Always limited by where the river takes us, it brings an understanding of the lives of early explorers restricted by the winds and currents in their efforts to cross seas or explore landscapes via river.

The Coppermine River landscape from above.

About half way down the 200 km section of the Coppermine River the landscape drastically changes. Green mountains made up of endless layers of dark lava, with a gentle, wide river flowing between them, give way to steeper-walled canyons of red sandstone overlying the lavas.

A lone muskox watched us paddle past.

Here the river is much more unforgiving. The rapids along the Coppermine have apt names – Muskox Rapids where we see a big herd of muskoxen grazing the landscape; Sandstone Rapids surrounded by layered cliffs of red sandstone; and Escape Rapids, where the escape is through a narrow gorge, which makes a spectacular camping spot on the edge of a rocky cliff.

A muskox bull, leader of the herd, comes in close to determine whether we are a threat.

The sandstones here are fluvial deposits, laid down by another river, more than a billion years ago. There is something awesome about travelling along a river cutting its way through rocks that are remnants of ancient rivers gone by. As geologists examine layers of sedimentary rocks, their minds are always on these questions: what kind of environment were these sediments deposited in? When were they laid down? How and under what climatic conditions; was it a river, an ocean, a glacier?

Modern ripples in sand deposited by the river overly ancient ripples preserved in sandstone.

Structures and minerals in the rocks reveal clues to how they were deposited. You can even tell the direction an ancient river flowed, all from looking at structures formed by the currents and imprinted in the rock. Ripples and mud cracks are preserved to tell the story of the path of an ancient fossilized river.

An important part of this trip is finding out the exact age of these rocks. We know that they are just over a billion years old, but more precise timings would allow us to pinpoint exactly how things such as the huge volcanic eruptions affected life and the climate.

Scouring the riverbank to understand how these rocks were deposited.

Fortunately a very hardy mineral, zircon, is found within some of these rocks. Zircon is like a time capsule and can be used to figure out the age of rocks through radioactive elements held within the mineral.

As the river winds its way through spectacular canyons and gorges, we reach yet another set of sedimentary rocks on top of the red fluvial sandstones. They are lightly coloured sandstones and dark shales deposited in a marine environment suggesting a higher sea level at this time.

Pointing out evidence of microbial life in some old and confusing rocks!

The fossils we are looking for are broadly named as Acritarchs. The word comes from the greek words akritos (meaning confusing) and arch (meaning old). As you can surmise, we are looking at some old and confusing rocks! And what is most confusing is that in the field all we can do is sample them, we won’t see the fossils until we get back to a lab and can use powerful microscopes to examine them. This makes it even more exciting, will we sample the right rocks!?

The shales contain small black flakes, evidence of organic material suggesting that there are microfossils preserved after the volcanic event ultimately pointing to life going on. By comparing the fossils found before and after the volcanic events, we can get an idea of how this huge eruption affected life – was it a help or hindrance to the diversification of life on this planet?

some of the gorges are so narrow that they create impassable rapids, like those at Bloody Falls a day from the mouth of the river.

Four golden eagles are flying overhead, guiding us as we paddle down the last section of river. Entering Kugluktuk, the Inuit settlement at the mouth of the Coppermine River on the Arctic Ocean’s coast, we are warmly greeted by children’s smiling faces and many questions about our adventure on this legendary river. We go home with barrels full of rocks that we have paddled down the river and hold evidence of how life diversified on the planet and how it survived huge volcanic eruptions.

Locals in Kugluktuk taking advantage of the midnight sun with a swim in the Arctic Ocean.

Rob Rainbird the leader of the expedition reflects on this amazing journey: ‘This was a dream come true, to mount a research expedition that accomplished all of its goals at the same time as providing our own low impact transportation and having maybe just a little bit of fun along the way. Thanks to great weather, an excellent research team and expert guiding, we did it!’

The 12-member expedition was led by Geological Survey of Canada scientist, Dr Rob Rainbird with a team of Canadian and international scientists. National Geographic and BBC photographer, writer, and geologist Dr Vivien Cumming documented the expedition north of the Arctic Circle.

You can follow Dr Vivien Cumming’s adventures on viviencumming.com and on instagram and twitter: @drvivcumming

Vivien Cumming will be posting a series of blogs on National Geographic Voices starting here: https://voices.nationalgeographic.org/2017/08/24/exploring-earths-wildest-places-to-journey-back-in-time/

You can read more about the expedition here: http://science.gc.ca/eic/site/063.nsf/eng/h_97409.html