Volcanoes
View From Space - Klyuchevskaya, Russia
Shiveluch, Russia
Cleveland Volcano, Alaska
Mount Etna From Space
Mount Etna From Space
Mount Etna From Space
Mount Etna
Magma – molten rock beneath
the surface
Lava – molten rock on the
surface
Where Does Magma Come From?
• Earth’s interior is hot (25 C/km near surface
= 1000 C at 40 km)
• Pressure inhibits melting
– Mantle is solid
– Never far below melting point
• Volcanoes fed by small pockets 0-100 km
deep
– Rising hot material may melt
– Water can lower melting point
Why Igneous Rock Classification Matters
• Silica Content = Viscosity
• Silica Content Governs Violence of
Eruptions
– Silica Poor (Basalt): Fluid lavas, generally little
explosive activity
– Intermediate Lavas (Andesite): Pasty lavas,
explosive eruptions common
– Silica-Rich Lavas (Rhyolite): Extremely viscous
lava and explosive eruptions
Types of Volcanoes
Bowen's Series and Volcanoes
Volcanic Rocks
(Rare) Basalt Andesite
Rhyolite
Plutonic Rocks
Dunite Gabbro Diorite
Granite
Fluid
Lava Is...
Viscous
Mild
Eruptions
Violent
Type of Volcano
Shield Volcano Stratovolcano Plug Dome
A Cinder
Cone:
Wizard
Island, Crater
Lake, Oregon
Anatomy of a Cinder Cone, Hawaii
Shield Volcano: Haleakala, Hawaii
Eyjafjallajokull, Iceland
Stratovolcano: Mount Shasta,
California
Lava Dome, California
Products of Eruptions
Lava Flows
Pyroclastic Debris
• Bombs
• Lapilli
• Ash
Mudflows
Landslides
Gases
• Steam
• Carbon Dioxide
• H2S
• SO2
• HCl
• HF
Environmental Hazards of Volcanoes
Pollution
• SO2, HCl in Water
Lava Flows
Falling Ejecta
Ash Falls
• Building Collapse
• Crop Destruction
Mudflows
• Direct Damage
(Colombia, 1985)
• Floods (Several Types)
Blast (Mt. St. Helens, 1980)
Pyroclastic Flow (St. Pierre,
1902)
Gas (Lake Nyos, Cameroon,
1986)
Pyroclastic Flow or Nuee Ardente
(French: Fiery Cloud)
How Calderas Form
Crater Lake, Oregon
The Stump of Mount Mazama
Supervolcanoes?
• Magma Chamber Collapse (Yellowstone?)
– Destruction of crops
– Destruction of high technology
– Economic Disruption
– Climatic Effects
• Flood Basalts
– Climatic Effects
– Toxicity
Jemez Caldera, New Mexico
Jemez Caldera, New Mexico
Collapsing Volcanoes – Mount Rainier
Collapsing Volcanoes - Hawaii
Landslide, Mount Saint Helens
Shastina and Landslide Deposit
Mount Shasta and Landslide Deposit
Evolution of Volcanoes
An active volcanic landscape
Evolution of Volcanoes
A volcanic landscape after a million years or so