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 flowand power lines

Truck – burned by lava, then encased in igneous rock

Lava flow crosses road

Hawaiian lava flowand 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 eruptionand “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 SOx

• Particulate matter – blocks sunlight

• Short-term changes in climate