Deep earth forces dominate mountain building, study finds

A recent study conducted by Colorado State University reveals that the explanations for how and why mountains are formed may be more complex than previously believed.

Lead author Sean Gallen, an assistant professor of geosciences at CSU, explains that mountain building is a fundamental process of Earth’s behavior. However, this study suggests that our understanding of it may not be as comprehensive as previously thought.

Gallen and his team employed innovative techniques and generated new datasets to reconstruct the long-term histories of mountain formation in southern Italy. Their unique approach yielded perplexing results.

In regions where tectonic plates converge, such as the Calabria region in southern Italy, one plate subducts beneath another. Mountains in such settings are traditionally thought to form through the folding and thickening of the Earth’s crust.

The team combined measurements from different timescales, ranging from thousands of years to tens of millions of years. By using the landscape as a sort of “geologic tape recorder” of tectonic history, they were able to uncover crucial information.

Surprisingly, the researchers observed that the flat, high-elevation patches of the landscape along the “toe” of the Italian peninsula indicated a period of slow mountain formation, while a steep transition below marked a rapid acceleration. This landscape provided valuable clues that enabled the team to create a comprehensive and continuous record of rock uplift, the most extensive of its kind.

Gallen explains that they anticipated a correlation between the rate at which one plate dives beneath the other over time and their record of rock uplift. However, this correlation was absent, suggesting that crustal deformation may not be the primary factor in the formation of the Calabrian mountains.

Instead, the data suggests that the primary factor controlling rock uplift in this region is the downward movement of the lower tectonic plate through Earth’s mantle and its influence on mantle flow patterns.

According to Gallen, this research challenges the conventional understanding of mountain building in southern Italy. The results indicate that deeper processes within the Earth’s system, rather than surface-level deformation, play a crucial role. While further data is needed to confirm these findings, existing numerical models support their interpretation.

Previously, scientists connected mountain height to interactions between tectonic plates in Earth’s flowing mantle. However, this study provides the first evidence that this mechanism is the dominant force in mountain formation in subduction zones.

Gallen emphasizes that these findings have significantly altered his perspective on subduction zones, a subject he has been studying in the Mediterranean for over 15 years. The records produced by this study suggest that signals from deep within the Earth have a profound influence on surface processes.

Transformative, transparent research

The study introduces groundbreaking techniques that revolutionize the reconstruction of long-term rock uplift histories.

The researchers developed an integrated framework that utilizes various standard measurements in geomorphology. These include thermochronology, cosmogenic nuclides, bedrock river profiles, and the analysis of past sea levels in marine terraces. By combining these different data sets in a unique way, the team was able to extend the timeline further back in history compared to existing methods.

The strength of this approach lies in its application to active systems, where the present-day landscape provides valuable insights into its past. However, as we go further back in geologic time, the reconstruction of history becomes increasingly challenging and uncertain.

The software developed for this study has been published in Nature Geoscience and is freely accessible to other researchers. Lead author Sean Gallen hopes that these innovative techniques will inspire further investigations and lead to exciting discoveries in other geographical areas.

Source: Colorado State University

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