Nevado del Ruiz, Columbia - 1985

•Erupts every 100+ years•130’ tall mudflows moving 30 mph•Buried Armero (45 miles away) at midnight•23,000 of the 28,700 citizens died

Volcanic ActivityNot Random- Plate Tectonics & Hot SpotsViolent

High viscosityContinental -AndesiteHigh gas content

MildLow viscosityOceanic - BasaltLow gas content

Volcanic Hazards

High ViscosityGlobal HazardsClimatic conditionsAir traffic

Low ViscosityLocal HazardsLava flows

Volcanic Hazards

Volcanic Ash

Dissolved Gases

Water Vapor - H2O

Carbon Dioxide - CO2

Sulfur Dioxide - SO2

Development of Pyroclastic Flows

Shield Volcanoes

Cinder Volcano

Composite VolcanoMount Shasta in California

Hot Spot Volcanoes

Caldera VolcanoesYellowstone & Toba

Profiles of Volcanoes

Mt. St. Helens Prior to the 1980 Eruption

Mt. St. Helens after the 1980 eruption

Mt. St. Helens

Plate Tectonics & Igneous Activity

Igneous activity is not randomMost volcanoes are in/near oceansBasaltic rocks = oceans & continentsGranitic rocks = continents

Volcanoes of the Cascade Range

World’s Major Volcanoes

Predicting Volcanic ActivityStudy the historyTopographic changesSeismic activityIncreased gasesGroundwater changes

End of Chapter 6