Overview of Volcanoes

Composition SiO2 Content

Viscosity Volatile Content

Eruptive Behavior

Type of Volcano

Mafic 50% Low Low Gentle

Shield Volcano

Intermediate 60% Medium Medium Both Gentle & Violent

Composite Cone

Felsic 70% HIgh HIgh Violent

Volcanic Dome

Gentle Eruption = Lava Flows

Violent Eruptions = Pyroclastic Flows

Types of Volcanoes

Compare the composition and size of a shield volcano

and a Composite Cone

Shield Volcano - Big Island of Hawaii

Lava Fountain

What is the viscosityof this lava?

It’s volatile content?

What’s its chemical composition?

Lava River

Is this behaviorgentle or violent?

Lava flow cause localized damage.

When this lava coolsIt forms basalt

Two typesof flows

Aa

Pahoehoe

Composite Cone - Philippines

Anatomy of a Composite Cone

Composite Cones Erupt Violently

Composite Cones Also Erupt Gently

What is the viscosityof this lava?

It’s volatile content?

What’s its chemical composition?

When this lava cools it formsAndesite

Volcanic Dome - Oregon

Volcanic Domes Fail Suddenly

SOME QUESTIONS

What is the viscosity of this lava?

It’s volatile content?

What’s its chemical composition?

When this lava cools it formsRhyolite

• Lava Flows• Volatiles• Pyroclastic Explosions• Lahars• Tephra

Volcanic Hazards

Volcanic Hazards - Lava Flows

Volcanic Hazards - Volatilities - VOG

Volcanic Hazards - Volatilities Carbon Dioxide Asphyxiation

Volcanic Hazards - Volatilities - Laze

Volcanic Hazards - Pyroclastic Explosion Nuee Ardente

Volcanic Hazards - Lahar

Lahars are caused by either:Intense rainfall around a volcanic summit

Suddenly melting snows and glaciers

Volcanic Hazards - Tephra

Tephra or Volcanic Ash is thickest closest to a volcanic eruption