In a big geological discovery, scientists have found signs of portions of the Earth’s crust peeling away and sinking into the mantle. This geological churning is happening beneath California’s Sierra Nevada mountains. The phenomenon has been happening for millions of years and could shed a new light on how the continents are formed.
Geologists used nearly four decades of seismic data from stations encompassing the northern, central and southern Sierra Nevada along California’s eastern border to uncover signs of a critical separation between the cool continental crust and mantle below.
The findings – made by researchers Vera Schulte-Pelkum from the University of Colorado Boulder and Deborah Kilb from the University of California San Diego – help resolve a mystery on how our planet generates lighter portions of its crust from the dense mix of minerals churning beneath.
In a study published in the journal Geophysical Research Letters, researchers stated that this process, called differentiation, happens when the dense layers of the Earth’s crust sink and get absorbed into the mantle, leaving the lighter layers behind.
“Our observations provide progressive snapshots of a lithospheric foundering process spanning several million years and hundreds of kilometres, illuminating a fundamental differentiation process by which continents are built,” the researchers noted in the paper.
Scientists have traced this peeling process beneath the Sierra Nevada using advanced imaging techniques. The southern section of the mountain range shows evidence of dense material that sank into the mantle millions of years ago. In the central region, the process is still ongoing, as indicated by small, deep earthquakes occurring beneath the surface.
The northern part of Sierra Nevada still retains its dense layer, making it a snapshot of an earlier stage in this geological cycle. This discovery provides a rare glimpse into the mechanisms behind continental evolution.