Scientists uncover how Earth's continental crust begins to form in Alaska

A new study offers fresh insight into how continental crust forms. The research focuses on the Andreanof segment of the Aleutian Arc in Alaska, a rare site where the transition from volcanic arc to continent-like crust can be observed. The findings were published in the Journal of Geophysical Research: Solid Earth. Volcanic arcs, like the Aleutian Islands, are believed to play a key role in creating new continental crust. Yet the process remains poorly understood. Modern arc crust tends to be richer in iron and magnesium than typical continental crust, and the Andreanof segment still shows this difference.

Using seismic waves, Mark and colleagues imaged the crust beneath the Andreanof segment. They detected localized zones of slower seismic velocity under the Atka and Tanaga volcanoes. These areas may contain hotter or more silica-rich material in the lower crust, hinting at an early stage of continental crust formation.

The study captures a snapshot of this transformation in progress. The transition from mafic arc crust to more silica-rich, continent-like crust is complex and remains incomplete. Still, the findings provide direct evidence of how early continental crust may develop in place. The research highlights the Andreanof segment as a unique window into crustal evolution. It confirms that volcanic arcs contribute to continental crust formation. The study also underscores how much remains unknown about this fundamental Earth process.