BOULDER, COLORADO—Shards of volcanic glass and large amounts of sulfur in polar ice cores from the Arctic and Antarctic suggest that the cause of the Little Ice Age could be attributed to the powerful eruption of a volcano. (The sulfur in the atmosphere would have reflected solar energy back into space, cooling the planet.) Scientists now think that Indonesia’s Samalas Volcano, located on Lombok Island, could be the culprit for the cold summers, rains, floods, and poor harvests of the medieval period, beginning between 1275 and 1300 A.D. Historic records indicate that Samalas erupted before the end of the thirteenth century, and an examination of the volcano’s caldera confirmed that a large explosion had occurred. “An equatorial eruption is more consistent with the apparent climate impacts,” added Gifford Miller of the University of Colorado, Boulder. And, the chemical composition of the glass from the ice cores is a much closer match to Samalas glass than obsidian from other contenders.