Imagine this… a rocky shelf overhangs a shallow ocean floor somewhere near the equator, nestled in mud banks at the base of a tall cliff. Deep in the recesses of the dark space underneath lies a protected space, a sanctuary of sorts.
Strange looking creatures inhabit the waters around this place. Right out of science fiction, like the oddest characters out of a Star Wars Cantina Bar scene, predators & prey travel through its murky depths with bizarre tentacles flailing about. Some have mouths with jaws; most do not. Some have eyes; many do not. Some have eight legs; some have none. The occasional creature has a backbone, but jaws, vertebrae and eyes are all relatively new adaptations for the creatures in this prehistoric world.
A bizarre creature, called a trilobite, used this protected place to shed its exoskeletons as it grew. It was oval shaped and relatively flat, with a hardened, articulated armoured shell-like skin.
Much like snakes do today, shedding its exoskeleton was an essential part of its growth. Once its hard protective external armour was shed, its soft exposed skin made it exceptionally vulnerable. It needed a safe place to shed, rest & harden before venturing out into the ocean world once more.
Thousands of trilobites gathered here in this nursery & sanctuary… some young and small, no bigger than your baby fingernail, and some old and as large as an adult man’s hand… they all came here to seek safety & protection.
Then, the unexpected happened: a catastrophic, cataclysmic event occurred. Out of nowhere, a mud slide poured down from the escarpment cliffs above, completely burying the site, snuffing out life in a heartbeat. It happened so fast that no oxygen was buried under the mud. The trilobites, young & old, large and small, soft bodies and shed skins, were buried so deep that even scavengers could not locate them and disturb their burial.
Fast forward over 500 million years. The conditions of burial were perfect for preservation as the place became immortalized. Just the right amount of weight and pressure compressed the bodies and exoskeletons to turn them into rock. Minerals in the water travelled through on the backs of water droplets, leaching through the rock, turning the bodies into glossy black jewels, some with even their stomach contents and soft features, like their eyeballs, preserved!
Seas dried up. The land mass on which this site was situated drifted far from the equator where it once rested. The rock and its fossils were thrust and shoved skyward, to about 2200m above sea level as mountains were formed.
Then erosive elements acted on this rocky site, exposing it once more. Unearthing it, freeze-thaw cycles cracked the rocky shale blanket. Avalanches brought broken pieces down slope.
In 1886, railway workers, fulfilling our first Prime Minister, John A. Macdonald’s dream of connecting our vast country with a railway line, built the town of Field. The geological survey of Canada geologists came to the area to find resources to be mined. The railway workers and geologists found zinc and nickel… and stone bugs in the talus shards carried down the hillside! Our fossil fascination with this area began.
Fast forward to 1909. Charles Doolittle Walcott (what a name!), explored the mountains on horseback with his wife and two sons, searching for fossils for the Smithsonian collection. Palaeontologist and scientific administrator (head of the Smithsonian Institution), he found the famous Walcott Quarry site in 1909, 900m (3000 feet) above the town of Field and across the valley from the “stone bugs.” He returned year after year, until 1917, collecting fossils and documenting the fossil record, including the trilobite fossils of the Mount Stephen site that we visited.
What’s left today of the “stone bug” site is a strange, dark, triangular formation of rock known as Mount Stephen’s Quarry, almost 800m above the town of Field, B.C., just across the border from Alberta, near Lake Louise. Each year the freeze-thaw cycle and the powerful avalanches that rock this slope release more fossils onto the mountain side. Going on a guided interpretive hike there was a spectacular item to check off the ‘ol life bucket list!
“The animals of the Burgess Shale are holy objects — in the unconventional sense that this word conveys in some cultures. We do not place them on pedestals and worship from afar. We climb mountains and dynamite hillsides to find them. We quarry them, split them, carve them, draw them, and dissect them, struggling to wrest their secrets. We vilify and curse them for their damnable intransigence. They are grubby little creatures of a sea floor 530 million years old, but we greet them with awe because they are the Old Ones, and they are trying to tell us something.“
– Stephen Jay Gould, Wonderful Life: The Burgess Shale and the Nature of History.
Those words were written in 1989 and still hold true today. Come along and see for yourself, what we experienced… it was a place that left me with a deep-seated feeling of awe and reverence, for it was a spectacularly dramatic landscape and a place filled with a mind-blowing number of fossils. I felt like I was living in a dream!
On the way up the mountain side, our guide would stop at little teaching stations, letting us catch our breath & filling our minds with details that would set the stage for what we were to see and experience up top. At one point, we got to see 3D versions of the fossils… the trilobites and their predators… that we would later see, flattened into the rock shards. They are fun, bright colours, only because we have no idea what colour the creatures were.
She handed out identification cards (like the ones below) as we ate our lunch, and then we set off to explore to our hearts’ content for the next hour & a half.
We now know that the Burgess Shale has revealed countless species that have broken off the evolutionary tree and have no known descendants today. The Burgess Shale creatures do not have to be pigeon-holed into the “known” categories of life as we know it, today.
The shale of the Burgess quarries, including this one at Mount Stephen, is sedimentary rock that was put under greater pressure than the limestone in the surrounding mountain, and so its fossils are exceptionally well preserved. What makes the fossils of this formation so unique is the way that even their soft body parts are preserved… usually when you think of fossils, you think of (dinosaur) bones! Just bones.
It is also very special because it has captured a snapshot of time on our planet known as the Cambrian Explosion, when diversity amongst the animals on our planet was incredible!
The Cambrian Explosion was a time when eyes were developing in the animal kingdom. Think about what an incredible advantage that would be for species: if you can see prey, you can eat more; if you can see predators, you can avoid being eaten.
The Cambrian Explosion was a time, just after “snowball earth” when strange ferns and jellyfish that made up much of the plant and animal population went extinct, opening up huge areas of habitat to be exploited.
And the Cambrian Explosion was a time when the planet was warming up, with more oxygen in the oceans allowing for more phytoplankton, and so more food for the creatures that lived here.
It was an amazing world, so unlike the one we inhabit now. Its diversity was astounding. And its fossil records, preserved so well in the Burgess Shale, offer a glimpse into an alien environment so unlike our own!
I highly recommend signing up for a tour if you’re ever in Yoho National Park… walk on the trilo-bits! It’s like walking into a sci fi set. It’s such fun.
Three Burgess Shale Fossil quarries have been found in the Rocky Mountains so far. All lie in heavily protected, restricted access areas and are studied by Royal Ontario Museum scholars. The first two are the original Walcott Quarry (on the shoulder connecting Mount Field and Mount Wapta) and the Mt. Stephen one that we did, accessible by an interpretive guided hike through Parks Canada out of the Field Visitors’ Centre in Yoho National Park. For the latest creature found at the new quarry, see: Predatory Worm Emerges From The Burgess Shale.
The third is a relatively new acquisition, discovered unexpectedly during the Kootenay forest fire a few years ago, and a lot of very exciting research is coming out of there, including creatures that represent evolutionary leaps… with the oldest jaws and vertebrae on record! It is currently closed to the public and lies near Marble Canyon.
Tours to the sites must be reserved well in advance as they book up quickly. They are limited to 12 people at a time and run, rain or shine. We booked our end of July hike in March and there were limited spots available. Click here to book your tour and to find out more info (location, cost, dates available, etc.): Mount Stephen Quarry: Stone Bugs Galore.
All fossil bed hikes are exceptionally steep and strenuous. Parks Canada guides will not take you up unless you have 2L of water, rain gear, serious footwear and hiking poles. They have a volunteer “sweeper” who goes at the end of the group and returns anyone who cannot make it the whole way up, safely back to the visitors’ centre. I kid you not. We had one person in our group take advantage of this option. That being said, we had teens and fit people in their seventies on our tour, and they did fine.
Our guide told us that the Walcott Quarry hike was longer than our hikes up to the Mount Stephen fossil beds. As it was, ours was a 7-8 hour day; the Walcott day is 11 hours.
According to our guide, the Mt. Stephen Quarry has more fossils… those stone bugs are far more plentiful up there… but the Walcott Quarry has greater diversity of species represented. The Mt. Stephen exploration that we did was almost exclusively trilobites with the occasional predator.
This is a well organized excursion. Each break on the way up and on the way down was timely, and came with a “lesson.” In other words, you got a break when you need it to catch your breath or rest your knees, and you learned something while you were at it.
You get about an hour and a half up top, during which time you can eat lunch, explore to your hearts’ content and do an unlimited number of fossil rubbings (they provide you with pencils and paper).
Your group will have a maximum of 12 people in it and they will be from around the world. Our group had a family from Britain, a Dane, a German and some travellers from the United States.
A trip up to the Burgess Shale is something I highly recommend! It’s such a treasure! It’s such a fascinating glimpse into an alien world! In short, it is just so much fun!