During low tide one day in March 1986, paleogeologist Brian Atwater dug along Neah Bay with a "nejiri gama", a small hand hoe. Under a top layer of sand, he uncovered a distinct plant—arrowgrass—that had grown in a layer of marsh soil. This finding was evidence that the ground had suddenly sunk under sea level, causing saltwater to kill the vegetation. The event had happened so quickly that the top layer of sand sealed away the air, thus preserving centuries-old plants.