It's official: A 3-billion-year-old
"lost continent" lurks beneath the Indian Ocean island of Mauritius, new research confirms.
Sparkly, iridescent flecks of rocks known as zircons from Mauritius date back billions of years, to
one of the earliest periods in Earth's history, the researchers found.
Other rocks on the island, by contrast, are no more than 9 million years old.
"The fact that we have found zircons of this age proves that there are much older crustal materials under Mauritius that could only have originated from a continent," Lewis Ashwal, lead author of the new
study and a geologist at the University of the Witwatersrand, Johannesburg in South Africa,
Earth's crust is made up of two parts: the planet's continents,
which rise high above the oceans because they are composed of
lighter rocks such as granite;
and the ocean basins, which sink lower because they are made up of denser rocks such as basalt, according to a video about
the new study. Whereas the continental crust may be 4 billion years old, oceanic crust is much younger, and is continually being formed as molten rock spews through fissures in the ocean floor, called midocean ridges.
The traditional thinking is that
the island of Mauritius was
formed by volcanic activity stemming from one of these midocean ridges, meaning older crust shouldn't be there.
But the new study suggests
that a tiny sliver of a primeval continent might have been left behind when the supercontinent Gondwana split up into Africa, India, Australia and Antarctica
more than 200 million years ago. Then, the fiery birth of the island blanketed the primeval rock
in layer after layer of cooling lava, building up the bulk of the island that is visible today, the
researchers said.
"According to the new results,
this breakup did not involve
a simple splitting of the ancient supercontinent of Gondwana, but rather a complex splintering took place, with fragments of continental crust of variable sizes left adrift within the evolving Indian Ocean basin," Ashwal said.
The new findings buttress results from a 2013 study that also found traces of ancient zircons
in beach sand on the relatively
young island. However, critics contended that this zircon could
have traveled there in trade
winds or been carried along on someone's shoes. In the new study, however, the zircons were found embedded in
6-million-year-old rock
known as trachyte, ruling
out the notion of wind-blown transfer, Ashwal said.
The findings were published
Tuesday Jan. 31 in the journal Nature Communications.
Originally published
on Live Science.