Shallow Grooves - Earth.com

During these trips, Heinrich noticed grooves carved in the granite, basalt, and sandstone rock that made up the tunnels. After getting a closer look, he realized they were claw marks. “Most consist of long, shallow grooves parallel to each other,” he and his team wrote in their group research paper about this project. Photo Credit: watchJojo / YouTube

News coming your way
The biggest news about our planet delivered to you each day