Rock Doc

By DR. E. KIRSTEN PETERS

I was living in eastern Washington State in May of 1980 when Mount St. Helens erupted after a massive landslide triggered by a magnitude 5.1 quake. Vast amounts of molten rock were violently released to the surface of the earth, erupting not only as sizeable rocks but as fine-grained volcanic ash that floated on the breeze. Us "down-winders" were enveloped in conditions that were dark as night until the ash finally fell to the ground.

Volcanic ash isn't the same material as the ash in your fireplace -- it's fine-grained volcanic rock. The St. Helens' ash was a mess all...