Field work in Japan (IMAGE) Northwestern University Caption Researchers hike up the side of Mount Ashibetsu in Japan to examine fossilized volanic ash that dates back to the Early Cretaceous. Credit Luca Podrecca/Northwestern University Usage Restrictions add credit License Original content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.