Rocks Lifted by Pyroclastic Flows (image) University at Buffalo Share Print E-Mail Caption Photographs scanned from Kodachrome slides show dark rocks embedded in layers of ash. The rocks were picked up and moved across the landscape by pyroclastic flows when the Silver Creek caldera, a supervolcano, erupted 18.8 million years ago. Credit Credit: Greg A. Valentine Usage Restrictions This image may only be used with news reports discussing the research in the associated press release. Share Print E-Mail 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.