Dinosaurs had such an immense impact on Earth that their sudden extinction led to wide-scale changes in landscapes—including the shape of rivers—and these changes are reflected in the geologic record, according to a University of Michigan study.

Scientists have long recognized the stark difference in rock formations from just before dinosaurs went extinct to just after, but chalked it up to sea level rise, coincidence, or other abiotic reasons. But U-M paleontologist Luke Weaver shows that once dinosaurs were extinguished, forests were allowed to flourish, which had a strong impact on rivers.

Weaver and colleagues examined locations throughout the western United States that depicted sudden geologic changes that occurred at the boundary between the age of dinosaurs and the age of mammals.