GSA Today
Volume 22, Number 12 (December 2012)

About the cover:
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. See related article, p. 4–10.

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