According to a team led by Penn State scientists, drones flying along kilometers of rivers in the rugged, hilly terrain of central Taiwan and analyzing the rock qualities have offered fresh hints about how water helps build mountains over geological time. The researchers discovered a relationship between the size of pebbles in rivers and their steepness. The link demonstrates how rock qualities can influence the relationship between deep subsurface tectonic processes and how mountainous landscapes change shape. They published their findings in the journal Science Advances. "Over the course of a mountain belt developing, we're seeing differences in how rivers