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Drone study reveals how water shapes mountains over time

A recent study led by Penn State scientists and published in Science Advances reveals new insights into how water shapes mountainous terrain over geological time. 

Using drone technology, the team’s research in central Taiwan has identified a critical link between the size of river boulders and river steepness, shedding light on the relationship between underground tectonic processes and surface landscape changes.

Focus of the research

“Over the course of a mountain belt developing, we’re seeing differences in how rivers incise, or cut down into the bedrock, in the younger and older sections. It means that as a mountain belt evolves, erosion is changing at the surface,” explained lead author Julia Carr, a 2022 Ph.D. graduate in Geosciences from Penn State.

The study focuses on the process of uplift, where tectonic plate collisions push previously buried rocks to the surface, leading to variations in rock properties. These properties, including rock hardness and the orientation of fractures, impact how these rocks erode when exposed to surface elements.

Critical new insights 

In Taiwan, the researchers observed that the main indicator of rock strength in the mountains was the size of boulders in rivers, with larger and stronger boulders found where rocks had been buried deeper in the Earth’s crust. 

“When the boulders in the channels are larger, the river needs to steepen to be able to erode at the same rate,” said co-author Roman DiBiase, an associate professor of Geosciences at Penn State.

This study also sheds light on the challenges of accounting for rock strength in erosion models. 

“Determining the controls on river incision into rock is important for understanding how mountain ranges evolve over geologic time,” DiBiase added.

Comprehensive survey

The researchers utilized drones to navigate the challenging terrain and collect extensive data on river channel morphology and boulder measurements. 

Carr notes the uniqueness of this approach, emphasizing that such a comprehensive survey reveals patterns that would be missed by conventional field surveys.

Ideal study setting

The central mountain range of Taiwan, one of the steepest and most erosion-prone landscapes on Earth, provided an ideal setting for this study. 

The systematic burial depth patterns in this region, resulting from millions of years of tectonic activity, offer valuable insights into the connection between a rock’s subsurface history and its surface properties.

Study implications 

“If we apply this, it implies this primary rock strength signal controlling boulder size is setting river incision in the landscape. And that matches with the local steepness of the rivers,” Carr explained.

This study not only advances our understanding of how mountains evolve but also has broader applications in developing erosion models for other mountain ranges, enhancing our comprehension of Earth’s dynamic landscape.

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