Firefighters in Greece narrowly saved the ruins of Olympia from the wildfires that spread across the nation * over the weekend. The blaze torched the edges of the stadium, but officials say the archaeological treasure survived. Can ancient ruins catch on fire?
No, but they can crumble from the heat. Greek ruins made of limestone or marble aren't going to burst into flames, but they can undergo physical and chemical changes when subjected to the heat of burning vegetation nearby. The outside layers of an ancient building heat up faster than the inside, causing the surface to crack and fall off in dinner plate-sized chunks. At about 1,000 degrees Fahrenheit, the rocks begin to release carbon dioxide. (Trees ignite at about 660 degrees, and wildfires can reach 1,800 degrees.) Since CO2 helps hold limestone and marble together, sustained heat can weaken the material until it's reduced to powder.
Olympia sits in the middle of a dense pine forest, which provides plenty of kindling for a fire. (Some ruins have wooden scaffolding to support ancient walls; these can also be set ablaze.) To protect the site from fire during the dry Greek summers, engineers had installed 50-foot metal fire towers in the hills to the north.
Earlier buildings from the archaic period—those constructed in the 7th and 6th century B.C.—were made with wooden columns and roofs. These frequently burned down and had to be rebuilt; none survive today. For instance, an arsonist destroyed the Temple of Artemis at Ephesus, which was called one of the seven ancient wonders of the world and took more than 100 years to erect.
Greece isn't the only place where flames threaten ancient structures. Peru's Machu Picchu regularly endures fires set by small farmers clearing land; in 1997, a fire reached the lowest terraces of the site. And in 2000, a 12,000-acre fire endangered the archaeological sites of the Pueblo Indians at Colorado's Mesa Verde. But that fire turned out to be a blessing; the blaze stripped away enough vegetation to reveal 1,400 new structures.
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Explainer thanks George Davis of the University of Arizona, David Gilman Romano of the University of Pennsylvania Museum of Archaeology and Anthropology, Curtis Runnels of Boston University, Christopher Witmore of the Joukowsky Institute for Archaeology and the Ancient World, and Linda Towle of Mesa Verde National Park.