Shifting tectonic plates gave Alaska’s Aleutian Islands a later-life lift
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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.
view moreCredit: Anahi Carrera
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.”
The first hints that an uplift event had occurred across the Aleutians came in the 1970s when oceanographers took sediment cores from the ocean floor surrounding the islands. The cores contained an anomalous layer of land-derived clay minerals and other sediment deposited during a relatively short period several million years ago. One scenario to explain that sediment is that the islands were suddenly deformed and lifted upward, where stronger winds and heavier rains could carry sediment into the ocean.
But outside the sediment layer, there was no direct evidence for an uplift event, or the timing of this event, in the Aleutians — that is, until this research.
For the study, Cooperdock and Carrera, who is now a postdoctoral researcher at Pacific Northwest National Laboratory, used a technique called apatite thermochronometry to analyze rock samples taken from across the Aleutian archipelago, a span of nearly 1,000 miles. The technique measures the amount of helium gas found within crystals of the mineral apatite.
Apatite contains trace amounts of the radioactive elements uranium and thorium. The decay of those elements produces helium, which escapes the apatite when the crystals are buried deep underground at high temperatures. But when the rocks move from deep underground to near the surface, they cool dramatically, and the helium can no longer escape. By measuring how much helium is trapped in the apatite, and comparing it to how much uranium and thorium remain, the researchers can estimate when the rock cooled, which reveals roughly when it made its way to the surface.
The researchers found that 77% of the rocks they analyzed had cooled down at roughly the same time — a span between around 5 million to 7 million years ago. The cooling ages were consistent regardless of the formation age of the rocks and despite having come from far-separated islands across the arc. The consistent cooling age suggests the rocks came to the surface around the same time, providing the first direct evidence for a massive uplift event that spanned the entire island arc.
The timing of the uplift coincides with a previously known event during which the Pacific plate rotated, causing widespread deformation and uplift along the Ring of Fire. It’s now clear, the researchers say, that this plate rotation, driven by the slow churning of Earth’s mantle, caused this dramatic uplift of the Aleutians.
“It’s really exciting to be able to show that these processes deep within the Earth — many kilometers in depth — are actually driving what we see on the surface,” Carrera said. “It’s great to have this amazing dataset that’s able to demonstrate that link.”
The research was supported by the U.S. National Science Foundation (EAR-1949148).
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.
Credit
Anahi Carrera
Journal
Geology
Article Title
Synchronous arc exhumation of the central and western Aleutian Islands at 7–5 Ma, Alaska, USA
Article Publication Date
17-Jun-2026
