36: The Ghosts of Greenland

Part 1: The Choir and the Soloists

We have come a long way from Season 1, where the only rocks we could study were from outer space: asteroids, the Moon and beyond. This season, we finally have rocks on Earth we can visit and study. We’ve looked at two locations so far: Earth’s oldest rocks, the Acasta Gneiss, and Earth’s oldest surface rocks, from Nuvvuagittuq. But it’s still not a lot. For reference, Nuvvuagittuq is about the size of downtown Manhattan in New York City. The Acasta Gneiss covers a bit more ground, the size of an entire city like Hong Kong or Los Angeles.

Today, we will meet the last location of Season 2- the largest slice of rock yet. These stones cover 3000 km2, the size of a small country or state like Luxembourg or Rhode Island. More importantly, this new area has the most well-preserved rocks to date, the most pristine stories to tell.

But before we learn about this crown jewel of Season 2, I have a confession to make: I have skipped a few locations. I can already hear the scandalized gasps from the audience. How could I possibly look over these ancient treasures? What’s wrong with me?

That last question could take a whole other podcast to answer, but here’s what I’ve pruned and why. I’ve skipped two locations: one in Canada and the other in Antarctica. They’re called the Saglek and Napier locations respectively, if you’re interested.

Eoarchean locations are marked in red: We’ve covered 1: The Acasta Gneiss, 2: Nuvvuagittuq, and are starting 4: Greenland. We won’t cover 3: Saglek-Hebron Block and 4: Napier Complex, at least not in the main series.

In short, the Canadian site tells a similar story to our Nuvvuagittuq episodes. We would just be repeating what we’ve already learned. In contrast, the Antarctic location is very altered, cooked almost to oblivion. It is very hard to tell any original stories from these southern rocks, though I do give a brief overview in our continental mini-series.

OK, so maybe that’s a small confession, but there’s a larger point here. In Seasons 1 and 2, we could do deep dives on every single rock. But going forward, we’ll run into more rocks, more locations to study. On one hand, that’s great! We get to learn more about the ancient Earth. On the other hand, I can’t cover every single spot in this same level of detail.

Here’s how I like to think about ancient rocks, and how the show’s focus will pivot going forward.

I like to think of rocks around the world as a great choir, singing the planet’s history together. Most rocks are singing a similar tune, or at least they’re singing in harmony. In other words, a rock that’s 1 billion years old from China will probably resemble a rock that’s 1 billion years old from Sweden. This means it’s kind of pointless to nitpick over every single location on the planet, repeating the same old stories from China, then Mongolia, then Russia, then Finland, etc. Instead, I’ll focus on their shared stories, the harmonies they’re singing together. These will be larger themes like the evolution of life, the origins of the continents, the rise of oxygen, and many others.

But sometimes, one location sticks out from the crowd- a soloist breaking away from the background choir, singing its’ own tune. Perhaps these rocks are exceptionally well-preserved. Perhaps these rocks tell a different story than their neighbors, but these soloists are still critical to understanding the ancient world.

To boil that metaphor down: on this show we’ve covered broad global trends like the origins of life and plate tectonics- this is the background “choir” of the planet. We’ve also highlighted specific locations, “soloists” telling their own story: the oldest crystals in Australia, and the oldest rocks in Canada. I cannot cover every single rock on the Earth, but I promise you I will tell the Earth’s story to the best of my ability, in broad choruses and specific melodies.

With that caveat out of the way, let’s meet the final soloist, the last location of Season 2: Greenland.

Part 2: Northward Bound

Greenland is the largest island in the world that’s not a continent: it’s the size of Saudi Arabia, or Mexico, or Western Australia. Greenland sits around Arctic Circle between Europe and North America. Here, maps must stretch the island out to fit on a flat page, making it look even larger.

Greenland’s northernmost point is 84 N, the closest land to the North Pole. Greenland’s southernmost point, the only spot that actually has green forests is 60 N, the same latitude as Anchorage, Alaska, or St. Petersburg in Russia. That’s still pretty far north. Most of the land in between, 80%, is covered by a single giant ice sheet, up to 3 km, 2 miles thick. That’s half the height of Everest, 3x taller than the tallest building. After Antarctica, Greenland’s ice sheet is the largest on the planet. The surrounding land is either tundra or barren rock, a narrow strip hugging the shore.  

The irony of Greenland’s name is very apparent, and the story of that name is fairly well known, but here’s a brief history. The year is 982. It is the height of the Viking Age. People from Norway, Sweden, and Denmark have sailed across the seas and up rivers all around Europe. One far-flung corner of this Viking world is Iceland, a northern island we met in Episode 27. Here, an Icelandic man named Erik Thorvaldsson, or Erik the Red has just been convicted of killing his neighbors over property.

It's not the first time this has happened to Erik, and the council votes to banish him. For three years Erik cannot set foot on Iceland. So Erik packs his bags, gathers his mates, and sets sail for a land only told in stories and rumors- a land even farther to the northwest. When he returns three years later, he tells his own stories of green land that could settled, pitching it as Greenland, the hot new place to be, or at least lukewarm new place to be.

Greenland isn’t as hospitable as Iceland. It’s farther north, has far more ice and less land for crops. But Erik wasn’t completely lying. In 982, Greenland was slightly warmer, slightly more livable. The Norse settlements started by Erik and others would last for five hundred years, but would eventually fall apart as temperatures cooled.

As Europeans faded from Greenland, a new group filled the void- the Inuit people, arriving a few centuries after the Vikings. We first met the Inuit back in Episode 33, in northern Quebec. Thousands of years earlier, the Inuit’s ancestors crossed from Siberia into North America. Travelling east, they eventually reached Greenland as Europeans trickled away. As a side note, these Inuit ancestors were NOT the first folks to cross from North America. Several pre-Inuit peoples lived in Greenland long before the Vikings, but did not leave any descendants.

Today, there are three groups of Inuit around the island. The most populous are the Kalaallit (kah-lah-shitt) in the west, where our next few episodes will take place. These western folks gave Greenland it’s other official name: Kalaallit Nunaat, “the land of the Kalaallit”.

But while the Inuit explored Greenland, Europe never forgot their old colonies.

In the 1700s, centuries after the last Europeans left Greenland, Norway and Denmark gave it another shot, establishing a capital at modern-day Nuuk. To make a long story short, as of this episode, Greenland is an autonomous area of Denmark, part of the European Union. It’s not a sovereign nation yet but is growing more independent over time, so keep an eye open in the news. If Greenland were a nation, it would be the 12th largest in the world, but would have the 9th smallest population, just 55,000 people.  

To recap: Greenland is a land of extremes and edges- a huge island but not quite a continent, more than a territory but not yet a nation, not quite North American or European.

Greenland does not have the oldest rocks on Earth, but it does have the oldest well-preserved rocks. To finish this episode, let’s see how these rocks were discovered in the first place.

Part 3: The Logic Puzzle

In Episode 25, we met the Geological Survey of Canada, a government agency dedicated to geology research. The Canadian Survey discovered Earth’s oldest rocks, the Acasta Gneiss.

Today, we’ll meet the Geological Survey of Denmark and Greenland, or GEUS for short. Just like Canada’s survey, GEUS has been scouring their lands for decades: searching for resources, finding new rocks, and learning how old those rocks are. Denmark itself is a very young country, geologically speaking. Nearly all Danish rocks formed in the last week of the Earth Calendar, only the last 100 million years. That’s the end of the dinosaurs to today.

But Greenland is a very different story. Ignoring the ice caps, Greenland’s exposed rock is still ten times larger than the Danish homeland. Most of these rocks are over a billion years old, well before October on the Calendar. Just like Canada, Greenland is a very old place.

So how old are the oldest rocks in Greenland, where are they, and who found them?

Nuuk, the capital of Greenlnd

Our story starts in Nuuk, on Greenland’s southwest coast. Nuuk is Greenland’s capital and largest city, with a population of 20,000. It’s not a lot, but compared with the places we’ve been- the Australian Outback and the Canadian tundra, it’s a metropolis.

If you want to research Greenland’s rocks, Nuuk is a relatively cushy place to start. At the very least, you can come back to a roof over your head and a warm meal. But just outside the city limits, the wilderness is inescapable. Dramatic snow-capped mountains plunge into narrow fjords. The only vegetation are shrubs and lichen. The only way around this landscape is by boat, plane, or strenuous hiking- no roads leave Nuuk. In June, daylight lasts for 21 hours, but the average high is only 10 C, 50 F. In December, days last five hours.

Vic Mcgregor (3rd in line) and company in Antarctica, 1961. Copyright: antarcticanz.govt.nz

If you were hiking around this wilderness in the late 1960s, you would have met a tall young man wearing a parka, carrying a hammer, and probably a rifle strapped to his back in case of polar bears. This man is working with the Geologic Survey, but he is not Danish and he is not Inuit. If you introduce yourself, he responds in perfect English with a heavy Kiwi accent. This man is Vic McGregor, and he’s come a long way to put Greenland’s rocks on the map.

McGregor was born in New Zealand in 1940, earning a Master’s at the University of Auckland. His early work was in Antarctica, where he found a passion for polar research. Following his heart, McGregor moved all the way to Denmark to study rocks around Nuuk.

We’ll describe these rocks in future episodes, but they’re broadly lumped into two categories that we’ve already met. The most abundant rocks were grey, stiped gneisses, just like the Acasta Gneiss in Canada, forged in deep magma and twisted into new shapes. Sitting inside the grey gneisses were smaller pockets of darker stone. Sometimes these darker rocks would show tantalizing clues of the surface world, like volcanic flows or iron layers. These are “greenstones”, just like we saw in Nuvvuagittuq in Canada.

These two broad categories: gneisses and greenstones, are a vast oversimplification of Nuuk’s geology. Instead, McGregor saw many different generations of stone interrupting each other, like a rough manuscript with multiple authors. To make matters worse, the rocks were extremely altered- they had been buried, baked and squeezed by generations of mountain building. In other words, take that manuscript, tear out most of the pages, set it on fire, dunk it in water, and leave it out to dry for billions of years.

Now, try to figure out what the original story was, and what order it happened in- that was McGregor’s job.

McGregor took this hot mess of rock and slowly pieced the history together. For example, he would sometimes see one rock split in two by a different rock, just like an axe stuck in an old tree. Even this simple interaction tells a story: the tree came first, the axe second. In other words, a rock that cuts through another must be younger.

McGregor approached these rocks like a giant logic puzzle: if Rock A is cut by Rock B, then B must be younger, etc. Eventually, he developed a story, a series of events that happened a long time ago. But exactly how old was still a question.

In the 1960s, Greenland’s oldest rocks were “only” around 2.7 billion years old, May on the Earth Calendar. Pretty dang old, but we’re not there yet. According to McGregor’s logic puzzle, the rocks around Nuuk should be much older. All he needed were some dates of his own.

He reached out to Oxford University, where Lance Black, Noel Gale, Stephen Moorbath, and Robert Pankhurst would produce the first concrete dates for the Nuuk area in 1971. Over 50 years of research, those dates and locations would be expanded into a very wide window. The rocks around Nuuk fall between 3.9 and 3.6 billion years old, February 24th to March 15th on the Calendar. This window will be our home for the rest of the season.

In 1971, these ages were jaw-dropping. At the time, they were the oldest rocks known. So, what did McGregor do after this windfall? He stayed in Greenland, and I mean stayed.

McGregor built a house in a small village north of Nuuk, with only 200 neighbors. He still worked closely with the Geologic Survey, mapping western Greenland and serving as a guide. However, McGregor rarely left the area, only for international conferences. Another major passion was ping-pong, and McGregor would go on to coach Greenland’s top team. He seems like a very interesting character.

Sadly, McGregor would take his own life in 2000, in the small village that was his home for thirty years. Greenland has the highest rate of these cases in the world, compounded by isolation, extreme lengths of day and night, and harsh conditions. It is a beautiful land, but it can push people to their limits.

But McGregor’s story is not over yet- he is just one of many companions as we explore Greenland’s oldest rocks. Every scientist who researches these rocks owes a debt to Vic, which they readily acknowledge in their papers. It’s time to meet those scientists and the stories they’ve told over half a century.

Summary:

Greenland contains the largest slice of Eoarchean rocks, the timeframe of Season 2. These rocks are between 3.9 and 3.6 billion years old, late February to mid-March on the Earth Calendar. They were described by Vic McGregor in the 1960s and first dated at Oxford in the early 1970s. At the time, they were the oldest rocks known, and those early studies sparked a gold rush of scientific interest that continues today.  

Next time, we will visit the most pristine areas around Nuuk, and learn how some lucky rocks survived destruction for nearly four billion years.