A fascinating geological phenomenon is currently unfolding beneath the Sierra Nevada mountains, where the lithosphere is peeling away from the crust. This process mirrors the ancient mechanisms believed to have formed continents. Researchers have discovered that this peeling is ongoing in the central Sierra region, while the southern section has already experienced significant loss, sinking into the deeper mantle.
The study, led by geoscientist Vera Schulte-Pelkum from the University of Colorado Boulder and seismologist Deborah Kilb from the University of California San Diego, reveals that the lithosphere, lying between 25 and 43 miles (40 to 70 kilometers) below the earth's surface, is actively detaching from the crust above. The team analyzed earthquake records from 1985 to 2023, noting bizarrely deep earthquakes occurring over 25 miles (40 kilometers) down, with tremors ranging from magnitudes 1.9 to 3.2.
The researchers' findings indicate that while the southern Sierra has already lost its lithosphere, leading to a downward shift, the northern end remains untouched by this peeling process. This raises questions about how this geological event might affect the overall stability of the region in the future.
Schulte-Pelkum emphasized the ongoing nature of this process, stating, "Now, we're saying, 'I think it's still going on.'" Her insights suggest that residents and visitors in the Sierra region may be unaware of the significant geological activity occurring beneath their feet. "You could be standing in the Sierras fishing, and there could be this huge layer peeling off beneath you and you don’t even know," she added.
The implications of this study extend beyond California. The researchers propose that similar processes may be occurring elsewhere in the world, including regions like New Zealand, the Anatolian plateau in Turkey, and the Carpathian Mountains in Eastern Europe. This research contributes to a broader understanding of how continental crust forms and evolves over time.
The study suggests that the lithosphere may have peeled away from below the southern Sierra roughly 3 million to 4 million years ago. This peeling process plays a crucial role in creating continental crust, which is less dense than oceanic crust, allowing it to sit higher and persist longer over geological time scales.
The results of this groundbreaking study were published in December in the journal Geophysical Research Letters. The findings not only shed light on the complex geology of the Sierra Nevada but also open new avenues for further exploration of similar occurrences around the globe.
Schulte-Pelkum's remarks point towards exciting possibilities for future research: "We could go and look for this in a number of other places where people have proposed that maybe the lithosphere used to be thicker and has peeled off now."
