Many of the Aleutian Islands rose at the same time, 5-7 million years ago. It was part of a geological event that showed up across the Pacific Rim, according to a study published on June 17.
Two researchers with Brown University measured the helium in 43 rocks, from Unalaska to Attu. They found 33 of the samples reached the surface in the same window.
“It's rare to see such a pattern across such large distances that you're seeing,” said Anahi Carrera, who led the study. “It's telling you, hey, something happened at this time.”
Carrera kept running into that same time period in other people’s work — the San Andreas Fault in California, the Alpine Fault in New Zealand, the Cascades and the Coast Mountains in British Columbia.
“I was like, ‘OK, so this is a very important geologic time period,’” she said. “Not just for the Aleutians, but across like the Pacific Rim or Ring of Fire.”
So she connected the dots.
Around 6 million years ago, the Pacific plate rotated about 10 degrees clockwise. That shift changed the pressure along the plate boundary, and according to Carrera’s paper, it helped pop up the Aleutian Islands.
What that would have been like to live through is unclear.
“If there were any people living there, they wouldn't necessarily realize that they were living in that period,” said Emily Cooperdock, co-author of the study. “But it has long-term impacts on how the islands' landforms evolve.”
What is clear is that the Aleutians are one-of-a-kind. Carrera said many volcanic island chains end up getting smashed into continents over millions of years.
“So it's very rare to have one as the Aleutian Islands that has been stable since its inception,” she said, “and that we're able to go on the ground and investigate what has happened, what processes have played, when when did volcanism happen, when were they uplifted, all of that.”
There’s more to come from Carrera on the Aleutians. She has a paper under review on Unalaska’s Shaler Mountains and why they’re so high.
