The Nature of Volcanicity

Hazards

Types of Lava

• Basaltic

• Andesitic

• Rhyolitic

Basaltic Characteristics

• Low viscosity

• Low silica content

• High temperature (1100-1200)

Andesitic Characteristics

• Moderate viscosity

• Moderate silica content

• Medium temperature (850-1100)

Rhyolitic Characteristics

• High viscosity

• High silica content

• Low temperature (650-900)

Volcanic Explosivity Index

• Logarithmic scale to measure the relative explosivity, magnitude and intensity of eruptions

• Based on the volume of ejecta (tephra) and column height

• 0-8 (non-explosive to ‘super volcanic’)

Primary Impacts

• Tephra and ash clouds

• Pyroclastic flows

• Volcanic gases

• Lava flows

• Lahars

Secondary Impacts

• Lahars

• Flooding / tsunamis

• Acid rain

• Climate change