Download Volcanoes

Volcanoes
The Volcanic Setting
Subduction zones
Rift valleys
Hot spots
Type of Eruption
Effusive
• gentle flows
• lots of lava
Explosive
• viscous lava
• trapped gases
Landforms
shield volcanoes
cinder cones
plateau basalts
composite volcanoes
calderas
Cinder cone
Big Cinder Butte,
Craters of the Moon, Idaho
- forms small hills, less than 450 m high
- black scoria rock with air bubbles
Shield volcano
Mauna Loa, Hawaii
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Low viscosity magma
Gases readily escape
from this magma
Effusive eruptions
Kilauea, Hawaii
Seamounts
Hot spot
Plateau basalts
CONTINENTAL
RIFT VALLEY
Photo of Rift Valley
In East Africa
Composite volcano
Mount Pinatubo
June, 1991
Shield/Composite Comparison
Mount St. Helens: the day before
Four years later
Live Photo of Mt. St. Helens
http://www.fs.fed.us/gpnf/volcanocams/msh/
Flooding (from steam-melted ice and snow)
Carbon dioxide
(CO2 : 250,000 ppm !)
Hydrogen sulphide (H2S)
Sulphur dioxide (SO2)
Hydrofluoric acid (HF)
Chlorine (Cl) compounds
Four years later
Caldera
Crater Lake, Oregon
6600 years ago
windblown ash landed
in Calgary
Volcanic hazards and effects
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hot ash (pyroclastics)
steam and gas explosions
lava flows
poisonous gases
(sulfuric acid; even CO2 if
at extreme concentrations)
landslides
tree blowdowns
lahars (steam-melted ice and
snow cause flooding and
large mudflows)
increase in atmospheric dust
(decreased global
temperatures in short term –
increase in long term?)
Volcanic Benefits
New fertile soils
- Hawaii, Philippines
Geothermal energy
- Iceland, Italy, New Zealand
New real estate
- Iceland, Japan, Hawaii
Diamond-bearing Kimberlite Pipe