Volcanos Cradle of life, Hazards to life
Volcanos – Cradle of Life We have already discussed the probable connection between volcanos and the origin of life Now we will examine the opposite situation – volcanos as hazards to life and property
Volcanos – fluid eruptions Fluid eruptions are characterized by lava flows There is little ash produced in comparison to the lava Major threat is to property rather than life
Hawaiian lava flow and power lines
Truck – burned by lava, then encased in igneous rock
Lava flow crosses road
Hawaiian lava flow and house fire
Lava flow and church fire
Trying to stop the lava
Volcanos – explosive eruptions Explosive eruptions are characterized by violent eruptions of gasses and ash
Explosive or “Plinian” Eruptions
Volcanos – explosive eruptions Explosive eruptions are characterized by violent eruptions of gasses and ash These eruptions produce “glowing clouds”
Explosive eruption and “glowing clouds”
“Glowing Clouds” Columns of ash, drops of lava and gasses are shot into the air Column reaches a certain height and the upward force is balanced by gravity Gravity brings the ash and gasses back to the surface where they flow along the ground
Glowing Cloud on Mt. St. Helens
“Glowing Clouds” Glowing clouds range in temperature from about 500 degrees (C) to nearly 1000 degrees Because they are more dense than air, they hug the ground and move at speeds from 100 to 200 mph
Vesuvius
Vesuvius – 79 A.D. The “type” example of a Plinian eruption Pliny the Younger’s account of the eruption
Pompeii – 79 A.D.
Herculaneum – 79 A.D.
Casts from Herculaneum
Citizens of Herculaneum
Vesuvius Today – Naples and vicinity
Vesuvius Today Approximately 1 million people live in the shadow of Vesuvius Nearly 3 million people are nearby A glowing cloud from Vesuvius would reach the Bay of Naples in about 5 minutes Prediction of eruption is difficult A catastrophe waiting to happen?
Other areas of Plinian risk Long Valley Caldera, California Valles, New Mexico Yellowstone National Park
Additional Volcanic Hazards Associated earthquakes Mudflows Acid precipitation – major source of SO x Particulate matter – blocks sunlight Short-term changes in climate