Shell Midden (image) University of Washington Caption A large shell midden from the Inca period at a study site in Peru's Ica valley is shown. The climate is so dry that even wooden structures are preserved. Credit M. Carré / Univ. of Montpellier Usage Restrictions With credit 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.