30: Alternative Canadian Rock

Episode 30: Alternative Canadian Rock

For the past two episodes, we explored the Faint Young Sun Paradox. Earth’s sun was much dimmer 4 billion years ago, and while Earth’s oceans should have been frozen solid, we clearly see evidence for liquid water in the oldest rocks. This paradox is solved using greenhouse gases like carbon dioxide, methane and water vapor, which provided a warm blanket under a weaker sun. Now let’s back up for a second. I said we have clear evidence for liquid water 4 billion years ago, and that’s true. However, that evidence is, well, not very exciting. We small changes in the chemistry of rocks, but nothing you can see with your eyes or feel with your hands.

Today, that changes as we return back to Earth in the Eoarchean Era. It’s time for a new set of rocks to examine, it’s time to move the story forward. Our previous field site, the oldest rocks on Earth, the Acasta Gneiss of Canada, told us stories about magma deep underground. In contrast, the second oldest rocks will tell us tales directly from Earth’s surface. We’ll finally see tangible evidence for water and volcanic eruptions. Today, we’ll set the stage- where these rocks are, how old they are, and how they were first discovered. It’s time to return to Canada.

Part 1: Land of Talk

Like the Acasta Gneiss, our new destination sits in northern Canada. Some folks just have all the fun. However, we must travel 1000 miles east, to a completely different province. 

Bienvenue a Quebec! Welcome to Quebec! Or more appropriately, Tungasugit, as we’ll visit the land of the Inuit today. 

Apologies for pronunciation throughout- it’s been a while since I’ve spoken French, and I’ve never spoken Inuktitut. 

Quebec is Canada’s largest province- twice the size of Texas or France. Most Quebecois live in the south, near Montreal and Quebec City. But our destination is much farther north. You can’t get there by car, even if you drove 14 hours straight north from Montreal to the end of the road. Instead, you must take a plane to the coastal village of Inukjuak, population 1,800. 

This northern tip of Quebec is solidly tundra, even though it’s farther south than the pine forests of the Acasta Gneiss. This tundra makes rock hunting a bit easier- you don’t have to worry about pesky trees. It’s also much colder- the average high in July is 55 degrees F, 13 C. You win some, you lose some.

The small port of Inukjuak sits on the eastern edge of Hudson Bay, a wide shallow sea in the Canadian Arctic. As we stroll along the shoreline, we pass through low rocky hills covered by splashes of orange lichen and pale green grass. A string of narrow islands sits just off the coast, while porpoises play in the calm coves. This landscape is the eastern arm of the great Canadian Shield, a horseshoe-shaped ring of rock that hugs Hudson Bay. If we wanted to, we could walk the long way around the bay back to the oldest rocks on Earth. If we did so, every stone on the way would be older than 2 billion years old. Canada is an extremely ancient place.

Fortunately, it’s only a 15 mile hike to our final destination, and there’s plenty of time to check out rocks along the way. Most are dull gray and speckled- boring at first, but as we look closer, we’ve met this rock before. This is our old friend tonalite, granite’s gray cousin, forged in magma chambers deep underground. We first met tonalites in the Acasta Gneiss- tonalites were the original rocks that were later contorted into zebra stripes of black and white. And as we walk farther along the Quebec shoreline, we once again see drab tonalites blending into striped gneisses. Once upon a time, this harsh landscape was a labyrinth of cooling subterranean magma. 

But don’t worry, we’re not doing another episode on tonalites today- these are not the rocks we’re looking for. The Quebec tonalites are much younger, only 2.7 billion years old, May on the Earth Calendar. We need to trek farther.

As we crest the last hill of tonalites, we finally see some different rocks on the tundra- pale green and rusty red, when suddenly we hear a noise over the horizon. A small speck hovering in the distance approaches and grows into a helicopter. As it touches down on the tundra shore, we see some geologists step out, wearing thick jackets, carrying bulky packs, and shouting to the pilot in Quebecois French as they part.

The year is 2001, and this expedition will place Quebec on the map of Earth’s oldest rocks. 

Part 2: The Tragically Hip

Let’s rewind a bit. In Episodes 24 and 25, we met the Geologic Survey of Canada, a national endeavor to catalog all the nation’s rocks. It was the Survey that discovered the Acasta Gneiss in the Northwest Territories, the oldest rocks on Earth. 

The Survey first explored northern Quebec in the 1960s- taking whistle-stop tours by helicopter around the frigid tundra. Most rocks they saw were tonalites, granites, and their cousins- just like we saw on our imaginary beach walk. Nothing wrong with these rocks, but when you spot something different in this sea of gray, you take notice.

Along the shoreline, researchers found a patch of darker stone along the seashore. The patch wasn’t huge- you could walk across it in 45 minutes, but what it lacked in size, it made up for in diversity. The most notable rocks had thin rusty red layers- the rust would rub off on your hands if you touched it. Even if you’re not a geologist, you’ve probably heard that rust means iron, and iron has very interesting stories to tell. In future decades, geologists would also describe ancient lava flows, ash beds, pebble beaches, and sandstones from this patch of tundra.

But in the 1960s, the discovery was simply marked as a few rusty iron-rich layers. And that was it for 40 years. The Survey wasn’t sleeping during this time- they made several returns to northern Quebec, but it’s a big place- remember, twice the size of Texas. Some corners were put on hold.

Eventually, the Quebecois took matters into their own hands. Quebec has its’ own geology survey, and they wanted new maps of the land, so they started Le Projet Grand-Nord, the Great North Project. Between 1998 and 2003, just five years, they mapped an area the size of Arizona or Finland, 300,000 km2.

Which brings us back to the tundra beach. In 2001, a large group of scientists and students surveyed the field site- special shout-outs to Pierre Nadeau, Martin Parent, Martin Simard, Laurent Godin, and Ross Stevenson. Don’t worry- all those names aren’t on the test, but there is one to remember, and it is a mouthful. Today’s word is the location’s name, the lonely rocky shoreline with the special rocks, our home for the next few episodes. 

The name for this place is Nuvvuagittuq (Noo-vooa-ghee-took). Once more: Nuvvuagittuq- again, apologies for any mispronunciation. You can find the spelling in the episode description. If you’re a long time listener, you know I love words and where they come from, but I could not for the life of me find the meaning of Nuvvuagittuq, even with an Inuktitut dictionary. My best guesses is something to do with a point or with clouds- if you know anyone who can translate this word, I would be very grateful.

So let’s return to Nuvvuagittuq in 2001. We’ll talk more about the rocks themselves next episode. The big question on everyone’s mind was: how old were these special rocks? That question is still a subject of great debate, twenty years later. 

Part 3: The Birthday Massacre

We’ve discussed how geologists date rocks several times on the show, so I invite the listener to check out Episodes 3 and 10 for a brush up. In one sentence: if you can find the mineral zircon in your sample, and you can measure the uranium and lead inside, you can estimate the age of a rock. 

This is exactly what the Quebec team did- researcher Jean David found some zircon, found uranium and lead, and came up with a date for Nuvvuagittuq: 3.83 billion years old, March 1st on the Earth Calendar. For reference, the oldest rocks on Earth, the Acasta Gneiss, are 4 billion years old, February 12th on the Calendar. That’s a decent chunk of time in between, but beggars can’t be choosers in the Eoarchean Era. 

In short, Nuvvuagittuq has the second oldest rocks on Earth. More accurately, tied for second place- there’s another spot on Earth that’s 3.8 billion years, and it was discovered far earlier. But we’ll meet that other contender in a few episodes. 

Even if they were tied for second, the Quebec team had a great discovery on their hands. Jean David gave several talks about how he dated Nuvvuagittuq, but this crucial research took a long time to reach the final stage- peer-reviewed publication. Here’s the thing- you can talk about a project as long as you want, but if it doesn’t get officially nitpicked by other scientists, it’s not going to be cited as much. And if you wait too long, someone else might step in to write your paper for you.

I’m not trying to badmouth anyone here. Perhaps the Quebec team tried to publish early and got torn apart by reviewers- I’ve been there. Perhaps other projects or life itself just got in the way- I’ve also been there. Science can be a hard and thankless job sometimes.

Whatever the case, by 2007, two researchers from the University of Colorado in Boulder visited Nuvvuagittuq, got their own data, and officially published their findings. These geologists- Nicole Cates and Stephen Mojzsis- start their paper by praising the “pioneering work” of the Quebec team, but also note a lack of detailed data. 

Fortunately, the Colorado team found very similar dates at Nuvvuagittuq, just slightly younger. And in a happy turn of events, Jean David and the Quebec team finally published a new set of dates a few years later. All the papers cheerfully agreed with each other- to prevent a complete numbers assault, we’ll just call Nuvvuagittuq 3.8 billion years old, the first week of March. 

But there’s one last chapter to the story, one that’s still being debated.

In 2012, a team led by Jonathan O’Neil at the Carnegie Institute of Washington, D.C. published a completely different set of dates from Nuvvuagittuq. Until now, all the dates in this show have come from the mineral zircon with the elements uranium and lead. It almost feels like mantra at this point. But while I’ve hyped up zircons, there are some big drawbacks. The biggest is that not all rocks have zircons in the first place. If you have granite or sandstone, you’re in business. If not, you have to look for alternatives, which is what O’Neil did.

Instead of zircon, O’Neil looked at garnet crystals, which contain the elements samarium and neodymium. There are a few other differences, but for today just imagine switching out one wrench with a slightly bigger wrench. You can still get the job done, but people might ask some questions. We’ll talk a more about these elements on a future episode.

After crunching the numbers, O’Neil found something incredible. According to his calculations, the Nuvvuagittuq rocks were older than previously thought. Much older- 4.4 billion years old. If you’re new to the show, 4.4 vs 3.8 might sound like nothing, but if you’ve been around, you might have given a little gasp, clutching your chest. Or maybe that’s just me. 

Let’s consult the Earth Calendar for context. The canon age of Nuvvuagituq is March 03, 3.8 billion. The Acasta Gneiss, the oldest accepted rocks on Earth, are February 12, 4 billion, half a month earlier. If O’Neil is right, then Nuvvuagituq is January 14th, another whole month back. This would completely blow the Acasta Gneiss out of the water, and would be tied with the Jack Hills Zircons from Episode 10, the oldest thing on Earth.

As I’ve mentioned, this date is not fully accepted. In short, most researchers think these really old chemicals were recycled and inherited from older rocks that have since been destroyed. The parent is gone, but the child remembers- for more on that idea, check out Episode 26. Every other study since 2012 places Nuvvuagittuq at 3.8 billion, so our show will as well. If these rocks are truly the oldest, then more data needs to be collected. If that happens, you’ll be the first to know. For now, it’s time to put our differences aside on dates, and get to the really importantstuff- the stories these rocks have to tell.

Summary:

In the world of ancient rocks, Nuvvuagittuq is the “new kid on the block”, one of the more recent discoveries. Who knows what else could be tucked away in the Canadian Arctic? If you look back at larger maps of Quebec, you will see many small pockets of ancient rock tucked away between the granite hills. The only difference between these unknown valleys and Nuvvuagittuq is a lack of research, a lack of dates. And even for a well-studied location, dates themselves can be a finnicky topic. On this show, Nuvvuagittuq will be 3.8 billion years old, but we’ll learn that time is not the only heated debate on the frigid tundra. In the next few episodes, we’ll swim through a sea of rust and meet some tiny tubes that might be the oldest fossils on Earth… or a red herring. Tune in next time to find out.