Types of volcanic activities Chapter 5, pages 113131 Online text http:pubs'usgs'govgipvolceruptions'

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Types of volcanic activitiesChapter 5, pages
113-131On-line text (http//pubs.usgs.gov/gip/vo
lc/eruptions.html)
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Hawaiian activity (pages 114-117)Example you
guessed it!

• High temperature and low viscosity basaltic lava
  flows
• Low proportion of dissolved gases
• Fire fountains and lava lakes are typical
• Mildest form of volcanic activity

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Strombolian activity (pages 117-129)Example
Stromboli, Etna

• Intermittent, discrete explosive bursts
• Pyroclasts and lava fragments are ejected with
  loud bangs
• Basaltic magma is involved, but with higher
  viscosity than Hawaiian magma
• NO eruption column develops
• Noisier than Hawaiian eruptions, but still
  relatively harmless

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Examples of Strombolian activity
Stromboli eruption, Oct. 1, 1998 (on-line link)
http//www.swisseduc.ch/stromboli/volcano/video/in
dex-en.html
Etna eruption, Nov. 1, 1999 (on-line link)
http//www.swisseduc.ch/stromboli/etna/etna99/etna
9911video-en.html
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Vulcanian activity (pages 120-123)Example
Vulcano, Italy

• Smaller magnitude of eruptions
• Eruption columns are MUCH higher than Strombolian
  eruptions (up to 10-20 km high)
• More violent and explosive than Strombolian
  eruptions
• High viscosity, usually andesitic magmas are
  involved
• Growing lava domes, ash fall and pyroclastic
  flows are common
• Volcanic effects are not widespread

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http//www.swisseduc.ch/stromboli/perm/vulcano/mov
s/rim1.mov
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Sub-plinian or Vesuvian activity(pages 123 -
124) Example Vesuvius

• Higher eruption columns than vulcanian eruptions
  (nearly 30 km high)
• Eruption columns are sustained for longer periods
• Extensive tephra and ash deposits
• More silicic magmas are usually involved
• Follows eruptive cycles of 25-30 years

http//www.swisseduc.ch/stromboli/perm/vesuv/icons
/aerial2.jpg
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Plinian activity (pages 124 - 125)Examples
Vesuvius, year 79, Pinatubo, 1991

• Eruptions that make history
• Powerful eruptions with exit velocities of
  several hundred meters per second.
• Eruption columns can reach up to 45 km (reach the
  stratosphere)
• Widespread tephra and ash deposits
• Involves mostly silicic magma

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Ultraplinian activity (page 125)Example Taupo
eruption, New Zealand, year 181None in the
recent historic past thank goodness

• The Taupo eruption created 10 cm thick Tephra
  deposits which covered more than 15,000 square
  kilometers
• Eruption columns must be higher than 45 km

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Peléean activity (pages 125-126)Example 1902
eruption of Mt. Pelée

• Characteristic feature nuées ardentes (also
  known as GLOWING CLOUDS or pyroclastic flows or
  Pyroclastic Density Clouds, AKA PDC)
• http//www.youtube.com/watch?v1zojFloLQaQ
• Can be associated with vulcanian or plinian
  eruptions

Note The same volcano can show several different
types of activities even during the same eruption
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Hydrovolcanic eruptions (pages 126-131)where
volcanoes meet water

• Movie clip Brimstone Pit eruption, 2004, Mariana
  volcanic chain, at a depth of 555 meters.
  http//oceanexplorer.noaa.gov/explorations/04fire/
  logs/april01/media/brimstone01_video.html
• Return to the Brimstone Pit, 2006
• http//oceanexplorer.noaa.gov/explorations/06fire/
  logs/april29/media/movies/nwrota_brimstone12_video
  .html
• Happens when volcanoes erupt on the ocean floor,
  under a lake, below glaciers etc.
• Or when volcanic vents on land encounter surface
  water (phreatic water) in an aquifer or wet
  sediments

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• When water comes in contact with hot volcanic
  ROCKS (NOT magma), violent steam explosions can
  happen.
• This is known as PHREATIC ERUPTION 9page 126)
• When large amounts of surface water interacts
  with magma, PHREATOMAGMATIC eruptions occur (page
  126)
• First, the magma becomes chilled and develops a
  solid skin, which then becomes fragmented
• These eruptions are violently explosive,
  comparable to nuclear reactor meltdowns

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Hydrovolcanic eruptions

• Surtseyan (page 127)
• Strombolian eruption water
• Powerful blasts of fragments with steam plumes
• May form volcanic islands (e.g. Surtsey, Iceland)

• Phreatoplinian (page 130)
• Sub-plinian or plinian eruption water
• None has been observed, but old deposits exist in
  New Zealand