Researchers at Brown have shown the first direct evidence for a massive geologic uplift of the entire Aleutian Island archipelago driven by a rotation of the Pacific tectonic plate.
PROVIDENCE, R.I. [Brown University] - New research by Brown University geologists confirms that the Aleutian Islands, the archipelago stretching from Alaska to Russia's Kamchatka Peninsula, experienced a massive geological uplift between 5 million and 7 million years ago.
The researchers conclude that the uplift - a rising of the Earth's crust that pushed the islands upwards and transformed their topography- was driven by an ancient rotation of the Pacific tectonic plate, which subducts beneath the North American plate near the Alaska Peninsula and the North Pacific.
"Our study presents the first evidence that the Aleutian Islands experienced this dramatic, chain-wide episode of uplift and erosion around 5 to 7 million years ago," said Anahi Carrera, the study's lead author who worked on the project as a doctoral student at Brown. "This was a time period when there was a major shift in the motion of the Pacific Plate, which we think is what caused these islands to be deformed and uplifted at the same time across this large distance."
The federally funded research, which Carrera co-authored with Emily Cooperdock, an assistant professor of Earth, environmental and planetary sciences and a faculty affiliate of the Institute at Brown for Environment and Society (IBES), is published in the journal Geology.
The Aleutian Islands form the northern boundary of the Ring of Fire, an arc of frequent volcanic and seismic activity that surrounds the Pacific Ocean. The islands themselves were formed by ancient volcanic activity beginning roughly 55 million years ago when the Pacific tectonic plate began subducting under the North American plate.
When one tectonic plate subducts beneath another, water and other volatiles trapped in the subducting plate cause melting in the mantle just below the crust. That leads to intense volcanic and earthquake activity along the plate boundaries. That much about subduction zones is well understood, Cooperdock said, but there are other dynamics at play that remain mysterious.
"Island arcs like the Aleutians are really dynamic places and some of the least understood places on our planet," she said. "Understanding what drives them in terms of things like uplift and erosion has been a really hard puzzle to crack."
