Volcanic processes

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Volcanic processes
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Volcanic processes and types
 grey  volcanoes More explosive Andesitic Subduc
tions
 red  volcanoes Less explosive Basaltic Intra-pl
ate
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• Dynamic types related to magma/water interactions
• Dynamic types related to dissolved bubbles
• Dynamic types related to domes growth and
  collapse
• Dynamic types related to lava flows etc.
• Destruction of volcanic edifices
• Complex edifices

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Magma viscosity

• Figure 4-1. a. Calculated viscosities of
  anhydrous silicate liquids at one atmosphere
  pressure, calculated by the method of Bottinga
  and Weill (1972) by Hess (1989), Origin of
  Igneous Rocks. Harvard University Press. b.
  Variation in the viscosity of basalt as it
  crystallizes (after Murase and McBirney, 1973),
  Geol. Soc. Amer. Bull., 84, 3563-3592. c.
  Variation in the viscosity of rhyolite at 1000oC
  with increasing H2O content (after Shaw, 1965,
  Amer. J. Sci., 263, 120-153).

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Mount Saint-HelensThe post-18 May dome
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• Figure 4-7. Schematic cross section through a
  lava dome.

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Secondary ash fall (local surges)
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Dome growth and collapse

• Cortex of the dome  chills , interior still hot
• Steep slopes, local collapse
• Breccias
• Pyroclastic flows  block and ash flow 
• Dense flow, rich in blocks
• Smaller scale than plinian!!

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Montagne-Pelée, Martinique(lesser Antilles)
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Saint-Pierre, before
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Saint-Pierre, after
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Volcanic processes and types
 grey  volcanoes More explosive Andesitic Subduc
tions
 red  volcanoes Less explosive Basaltic Intra-pl
ate
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• Dynamic types related to magma/water interactions
• Dynamic types related to dissolved bubbles
• Dynamic types related to domes growth and
  collapse
• Dynamic types related to lava flows etc.
• Destruction of volcanic edifices
• Complex edifices

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Lava lakes
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Eruptive fissures
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Bubbles
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Scenic volcanoes!
Stromboli (Italy)
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Scoria cones
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Piton de la Fournaise (Réunion, Indian Ocean)
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• Cones groupe in Réunion

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• Puy de Pariou (France)
• (note also the pelean dome of Puy de Dome at the
  back)

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Scoria cones
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Disrupted cones
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Cones and lava flows
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Etna (Italy)
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Strange things lava flows do
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• No, there is nobody here it is just a weird but
  completely natural shape

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Multiple lava flows
Piton de la Fournaise (Réunion, Indian Ocean)
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Rift zone
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Aa and Pahoehoe
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Lava caves
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Prismation
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• Scoria base

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