A globe-circling eruption
On June 4, 2011, after a half-century of quiet, the Puyehue-Cordón Caulle Volcanic Complex awoke with a powerful Plinian eruption. A fissure in the Cordón Caulle rift zone opened, sending a column of ash and gas soaring to an altitude of 10 to 12 kilometers. The initial explosion was intense, releasing energy equivalent to 70 Hiroshima atomic bombs and ejecting an estimated 100 million tons of ash, sand, and pumice. This ranked as a 5 on the Volcanic Explosivity Index (VEI), making it one of the largest eruptions of the 21st century.
The fine, glassy ash, primarily rhyolitic in composition, entered high-altitude jet streams. These powerful winds transported the plume eastward across Argentina and out over the Atlantic Ocean. In a matter of days, the ash cloud reached Australia and New Zealand, thousands of kilometers away. The plume completed its first circumnavigation of the Southern Hemisphere in about two weeks. The global spread of the ash created significant disruption. Hundreds of flights were canceled in Australia and New Zealand, stranding tens of thousands of passengers. Volcanic ash is a serious threat to aviation; its fine particles can melt in the heat of a jet engine, solidifying into glass and causing engine failure. The disruption continued for weeks as the main cloud circled the globe a second time and winds stirred up previously deposited ash in Patagonia.