For countless millennia, the cliffs of Padloping Island have stood watch before the frigid waters of Baffin Bay like sentinels guarding a desolate land.
But in recent years, scientists have come to realize these craggy formations are guarding something else – a secret so old it dates back to the earliest chapters in the Earth’s history and may preserve a unique record of how our planet was first put together.
Now this remote Arctic landscape, largely unknown even to geologists, has proved so alluring that researchers around the world are wondering how they might get there and come away with a trove of fresh samples for detailed study.
The obstacles are formidable. The stern grey cliffs tower hundreds of metres above the waves and can only be reached by a 90-kilometre boat ride through treacherous ice floes. Upon arrival, eager rock hunters face the prospect of being hunted themselves as they hammer away.
“You have to go well armed. There are a lot of polar bears,” said Don Francis, a retired McGill University geochemist who is one of the few scientists to have ever set foot on Padloping Island.
The rocks he gathered there on two separate visits, most recently in 2004, are what has sparked the growing interest in the site among colleagues who study the Earth’s remote past.
Their attention underscores an underappreciated fact about Canada. While the nation is young in geopolitical terms (149 years young to be exact), parts of its surface are as venerable as it gets.
Those parts include the Acasta Gneiss, a block of Canadian Shield found north of Yellowknife, that is thought to be the oldest intact fragment of the Earth’s crust, dating back just over four billion years. More controversial is the Nuvvuagittuq Greenstone Belt, located along the eastern shore of Hudson Bay, which one 2012 study pegged at 4.3 billion years old.
Padloping Island is something else again. It is a 25 kilometre-long layer cake of rock that is barely separated from the eastern edge of Baffin Island. Its grey cliffs are made from basalt – hardened lava – that is a mere 60 million years old. Yet, it contains a set of geochemical signatures that scientists say were written more than 4.5 billion years earlier, back when the Earth was still forming.
To understand why, one has to rewind the clock to the moment when Baffin Island, Greenland and Scotland were part of one big chunk of continental crust that was heated from below by molten material rising from deep within the Earth’s mantle. The surface rocks split apart and vast quantities of lava welled up to fill the gaps. Today, a lingering hot spot from that hellish period still smoulders under Iceland. But the initial eruption is what created the rocks of Padloping island.
They are not much to look at.
Recently, Lydia Hallis, a postdoctoral researcher at the University of Glasgow, showed me a small box of them that she keeps under her desk, drawn from Dr. Francis’s collection. Dr. Hallis, who cut her scientific teeth working on basalts gathered up by Apollo astronauts on the moon, has more recently turned her attention to related rock types found on Earth.
Her goal is to understand the early history of the Earth’s water. In the rocks of Padloping Island she found a clue. Glassy parts of the rock, which are thought to have cooled very quickly, contain trapped hydrogen from the Earth’s deep interior. The hydrogen comes from water, but not ocean water. Dr. Hallis showed it is much older and was incorporated into the mantle when the Earth coalesced out of the cloud of gas and dust that swirled around the infant sun. She now wants to compare hydrogen data from different layers of Padloping rock for a more thorough portrait of the Earth’s initial water supply – assuming she can get her hands on the samples she needs.
“I really want to go there and get up the cliff face,” said Dr. Hallis, who is a recreational rock climber but who says she knows getting an expedition mounted to such a remote site “is not a trivial thing.”
Equally enthusiastic is Hanika Rizo, a geochemist at the University of Quebec at Montreal and lead author of a study released in May that focuses on tungsten isotopes in the Padloping Island rocks. The tungsten is the byproduct of radioactive decay that dates back to the Earth’s formation. To their surprise, Dr. Rizo and her colleagues discovered the tungsten varies in a way that suggest the Earth’s mantle is a not a homogeneous blend. Instead, it may contain traces of its original building blocks, called planetesimals, that went into constructing Earth like lumps of different coloured Play-Doh.
It was long thought that such traces would have melted away when a Mars-sized object slammed into the young Earth just after it formed 4.5 billion years ago, throwing up enough debris to create the moon. Now Padloping Island is telling a different story and Dr. Rizo is keen to supplement the samples she has from Dr. Francis to find out more.
She has ruled out an attempt this year and is now looking to the summer of 2017 as the time when she may finally set foot on the island’s elusive shores. If she manages to get there, it’s unlikely she’ll be collecting only for herself.
“With all the results coming out of these rocks, other scientific groups will be interested in studying them for different purposes,“ Dr. Rizo said.
Meanwhile, one of Canada’s most curious geological formations keeps its lonely vigil, a domain of polar bears and puzzles.
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