Volcanos Volcanos are among the most awesome and destructive forces in nature. A single volcano can inject massive amounts of fine ash and gas high into the atmosphere producing global climactic effects. High speed, sometimes explosive flows of hot, poisonous gas with entrained ash and rocky debris, called pyroclastic flows, blast down volcanic slopes destroying everything in their path. Powerful, rapidly flowing muddy mixtures of rock and debris, called lahars, are mobilized by water high on volcanic flanks and sent careening down to valleys below with often disastrous effects. Slower, steadier flows of hot lava and cement-like mud made up of volcanic ash mixed with rainwater can inundate vast areas of land surrounding a volcano.
Volcanic eruptions pose numerous hazards and can have substantial environmental effects.
In the immediate vicinity of an eruption the primary hazards are debris falls, pyroclastic flows and lahars. Ash plumes can cover a wide region down-wind and can be hazardous to aircraft. Mud flows can cover fertile regions far from the volcano, destroying crops and villages in their path. Large eruptions inject massive amounts of water vapor, carbon dioxide, sulfur dioxide and other gasses into the stratosphere. Most of the sulfur dioxide is converted into sulfuric acid aerosol particles which can remain aloft for a very long time.