#102 Volcanoes

Volcanoes blast more than 100 million tons of carbon dioxide into the atmosphere every year but the gas is usually [1] . When a volcano erupts, carbon dioxide spreads out into the atmosphere and isn't [2] in one spot. But sometimes the gas gets trapped [3] under enormous pressure. If it escapes to the surface in a dense [4] , it can push out oxygen-rich air and become deadly.