This news release is available in Japanese.
Detailed tabletop experiments are helping researchers understand how Earth's landscapes erode to form networks of hills and valleys. The findings, which highlight a balance between processes that send sediments down hills and those that wash them out of valleys, might also help researchers predict how climate change could transform landscapes in the future. Kristin Sweeney and colleagues developed a laboratory device that mimicked the processes that smooth or disturb soil to make hillslopes, and those that cut it away to make valleys. To achieve the former effect, they bombarded their artificial landscape with large, energetic water droplets, and to achieve the latter effect, the landscape was misted. Results reveal that the hillslope processes that involve transport of sand down a hill, such as when dirt is knocked loose by an animal, play a key role in the transformation of landscapes. In a series of experiments, the researchers show that larger drops of simulated rainfall are associated with smoother, wider valleys and that mist tends to form denser networks with hills that are located closer together. Taken together, their findings lend support to a popular theory of landscape evolution, suggesting that the scale of erosion depends on the balance between tumbling sediments and runoff processes that carve out rivers and valleys. Since this balance is altered by changes in climate and land use, the researchers' methods might offer a new way to study landscape evolution in the face of such changes. A Perspective article by Scott McCoy discusses the experiments in greater detail.
Article #10: "Experimental evidence for hillslope control of landscape scale," by K.E. Sweeney; J.J. Roering at University of Oregon in Eugene, OR; C. Ellis at University of Minnesota in Minneapolis, MN.