December GSA Today Cover Image (image) Geological Society of America Caption Hydraulic gold mining by Romans nearly 2,000 years ago left this dramatic example of human modification of the landscape at Las Médulas, Spain, a UNESCO World Heritage Site. Water obtained from surrounding mountainous watersheds was used to undermine the >100-m-thick Miocene alluvial fan sediments here until they collapsed -- a process called ruina montium, loosely translated as ruin the mountain -- and then washed to separate the gold. Tailings total ~90 Mm3. Photo by Justino Diez. Credit Photo by Justino Diez. Usage Restrictions Credit to author and mention of the article in the December GSA Today. 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.