- What is Tephra fall?
- Tephra, a volcanology term for ash, is small rock fragments ejected from a volcano into the atmosphere, which is then deposited around and downwind of the volcano. The size and thickness of the deposits decreases with increased distance from its source.
- Tephra can be a nuisance to people in many ways. Even small amounts can cause or aggravate respiratory problems in humans. It kills crops, damages machinery, and is a hazard to aviators. Tephra is heavy - a significant accumulation (4 inches) on a roof top could collapse a building (Hoblitt and other, 1995:2). In addition, it often blocks out the sun creating darkness and unnecessary panic.
- Tephra fall at Mount Rainier?
- The winds around Mount Rainier generally flow from southwest to northeast (U.S. Geodynamics Committee, 1994:34); therefore, the tephra deposits would probably only affect the towns around the volcano - not the Seattle-Tacoma metropolitan area unless the winds happen to be blowing in the opposite direction. (U.S. Geodynamics Committee, 1994:34). The hazard map above shows the probability for tephra fall deposits of 1/3 of an inch and 4 inches during one year.