A layover on a trip to India began a research odyssey that has led scientists to verify the existence of a "lost continent" below the East African island nation of Mauritius in the Indian Ocean.
A paper published in the journal Nature Communications this week outlined the presence of ancient continental crust — broken off from a larger "super-continent" — under the volcanic island best known for its beach resorts.
Lead author Lewis Ashwal, a geologist at the University of the Witwatersrand in Johannesburg, South Africa, wasn't looking for a day at the beach when he and some colleagues had a one-night layover in Mauritius en route to India.
"We're not the kind of people who are going to waste a day reading a book and getting a sunburn," says Ashwal, who is part of a group of scientists who study the age of rocks in places like India, Madagascar and the Seychelles, with the aim of learning more about how the continents broke apart.
"Swimming — who cares? I've done enough of that."
So he and his colleagues rented a car and headed inland from the tiny nation's gorgeous coral beaches, through sugar plantations and to volcanic craters, where they collected rocks containing the mineral zircon.
Zircon is found mainly in the granites that form continents.
Although it would take years and many more trips to Mauritius to prove, the group has now shown that the rocks under the island date back as far as three billion years.
The breakup of a super-continent
That's ancient compared to the oldest volcanic rocks that make up the island, which are just nine million years old at most.
The lost continent is part of a super-continent known to scientists as Gondwana, which broke apart into Africa, India, Australia and Antarctica when the Indian Ocean was formed.
The researchers are calling the newly found continent Mauritia.
On that first foray away from Mauritius's gated resorts, a colleague from Norway found rocks containing zircon crystals. But problems with sample contamination caused by the crushing equipment in his Oslo lab rendered the results useless.
"He was very depressed and he sort of dropped [the research]," says Ashwal.
Sampling with sand toys
But four years later another group returned to Mauritius to get samples of zircon that didn't need to be crushed — those found in beach sand.
The scientists used ordinary beach toys meant for building sandcastles. "Clean stuff, because if you bring tools from the lab, they could be contaminated," Ashwal says.
He and colleagues published their findings about those beachfront zircon samples in 2013.
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But other scientists were skeptical, he says.
Critics postulated that the beach zircon could have been transported to Mauritius by wind, waves, vehicle tires, people's shoes — even bird poop.
"It began to get ridiculous," says Ashwal.
But the group pressed on another two years, sampling and analyzing a wide variety of rocks and getting isotope data showing "spectacular ages," he says.
At 2.5 to three billion years old, these samples — brought to the surface through volcanic eruptions — show what has to be a continent, says Ashwal. "There's no other place that rocks these old are found."
How the world works
Finding a "new-to-us" continent is about much more than this discovery alone.
"Our work is addressing the question of how continents break apart from each other and how new oceans are formed," says Ashwal.
"If we are able to reconstruct their positions in the past, where they were and at what time in the past, then we can understand better how the earth works."