http://www.blastr.com/2015-1-13/nasa-deploys-special-robot-designed-explore-deep-inside-active-volcanoes
Volcanoes I
What determines whether a volcano
extrudes magma violently or gently?
• Composition
• Temperature
• Dissolved gasses (amount)
Composition
• Shield volcano- basalt lava flows
• Stratovolcano- Highly variable; alternating
basaltic to rhyolitic lavas and tephra with an
overall andesite composition
Temperature
• It can reach up to 700-1,200 °C (1,292 to
2,192 °F).
Dissolved gasses
• H2O- Water vapor
• CO2- Carbon dioxide
• SO2- Sulfur dioxide
Which factors affect viscosity?
• Higher temperature, less viscous; lower temperature,
more viscous
• Greater silica content, greater viscosity; lower silica,
lower viscosity
• Higher amount of volatiles (dissolved gases), lower
viscosity; Lower amount of volatiles, greater viscosity
How does a magma chamber form?
• rocks closer to the surface become less dense
• the magma stops rising
• minerals with high melting temperatures
• magma enriched with silica
How is a Hawaiian-type of eruption
triggered?
• A Hawaiian-type of eruption is quiet or gentle
• eruptions are triggered by the arrival of a new batch
of magma
• The magma chamber swells
• The basaltic magma becomes more mobile
What are lava fountains and how
are they produced?
• Fluid basaltic magmas
• These pressurized gases are easily released
• These gases may propel lava hundreds of
meters
What is the role of dissolved gases
in explosive or violent eruptions?
• Because of its high viscosity, dissolved gases in silicarich magmas
• These dissolved gases begin forming tiny bubbles
• These tiny bubbles build up over a long period of
time
• When the pressure overcomes the strength of the
overlying rock
• The sudden release of pressure may generate an
explosive event
What materials are extruded
during an eruption?
• Lava flows
• Gases
• Pyroclastic materials
Lava Flows
• AA lava flow- Basalt characteristically
form flows known by the Hawaiian names
pahoehoe and aa.
• Pahoehoe lava flow- Are characterized by
smooth, gently undulating, or broadly
hummocky surfaces.
Pyroclastic materials
•
•
•
•
•
ash and dust
welded tuff
Cinders
Block and bombs
Scoria and pumice
References
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•
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http://www.blastr.com/2015-1-13/nasa-deploys-special-robot-designed-explore-deep-inside-active-volcanoes
https://hedcenscience.wordpress.com/environmental-science-9/
www.geology.sdsu.edu/how_volcanoes_work/Volcano_types.html