Volcanic ash: Encyclopedia II - Volcanic ash - Dangers

Volcanic ash - Dangers

Volcanic ash is not poisonous, but inhaling it may cause problems for people whose respiratory system is already compromised by disorders such as asthma or emphysema. The abrasive texture can cause irritation and scratching of the surface of the eyes. People who wear contact lenses should wear glasses if they are experiencing an ash event. Furthermore, the combination of volcanic ash with the moisture in the lungs may create a substance akin to liquid cement. People should also take caution to filter the air they breathe with a damp cloth or a face mask when facing an ash event.

The most devastating effect of volcanic ash comes from pyroclastic flows. These occur when a volcanic eruption creates an "avalanche" of hot ash, gases, and rocks that flow at high speed down the flanks of the volcano. These flows can be impossible to outrun. In 1902, the city of St. Pierre in Martinique was destroyed by a pyroclastic flow which killed over 29,000 people.

Adapted from the Wikipedia article "Dangers", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki