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 silica-rich 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 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