Volcano or meteorite? During the last 100 years, two different theories have been put forward to explain the origin of Lake Mien. But in a new study, researchers from Lund University can finally establish that the Småland lake was formed by a giant celestial body.
For a long time, it was thought that the circular lake Mien in southern Småland was the remains of a volcano. But as early as 1910, geologist Arvid Högbom put forward a pioneering idea that the lake could instead be the result of a meteorite impact about 120 million years ago — a theory that has been prevalent in the research world since the 1960s. Despite a number of findings that support this, there has been stubborn opposition, mainly from the public.
But in a new study, published in the scientific journal Meteoritics and Planetary Science, a research team from Lund University has found decisive evidence for the meteorite theory. The researchers have discovered a mineral called reidite, which can only be created by the extreme pressures that occur during meteorite impacts. Josefin Martell, a doctoral student in geology at Lund University, said:
“We have examined hair-thin parts of the mineral zircon in rock samples from Mien. It is inside these shocked zircon grains that we have managed to find traces of the high-pressure polymorph reidite that acts as a kind of time capsule from the meteorite impact.”
Equivalent to the power of 1,000 atomic bombs
Reidite is formed at extremely high pressures, about 30 gigapascals. It can be compared with the pressure that prevails approximately 1,000 kilometers below the Earth’s surface. The only natural process that can give rise to this in a matter of seconds is precisely meteorite impact, Josefin Martell said:
“The celestial body caused the bedrock to melt. The crater that formed was originally around 9 kilometers in diameter. The force required to form one corresponds to about 1,000 atomic bombs.”
The research team at Lund University hopes that the discovery now puts an end to the discussion about the origin of the pike-rich lake Miens. Josefin Martell believes that once and for all, it is time to establish Mien as a so-called impact structure, saying:
“The residents of Tingsryd and the surrounding area should feel proud. Not many people have the opportunity to swim in an old impact structure.”
Provided by: Lund University [Note: Materials may be edited for content and length.]