The dinosaurs, birds, and early mammals found in the fossil beds of northern China are famous—both for their exceptional preservation and for their incredible diversity. But no one knew how they died or why hundreds of creatures from different habitats were buried together on ancient lake floors.

Now researchers say they were likely killed by a series of volcanic eruptions more than 120 million years ago. The ash entombed and preserved them, much like the doomed victims of Pompeii. (See also "Pompeiians Flash-Heated to Death—No Time to Suffocate.")

After analyzing fossils and sediment, Baoyu Jiang of China's Nanjing University and his team concluded that lethal, sudden pyroclastic volcanic eruptions marked by air blasts, hot gas, and ground-hogging clouds of