Classification of Volcano: Eruption Style Pt 1

The eruptive style of a volcano is based on:

• Physical nature of the magma
• Character of explosive activity
• Nature of effusive activity
• Nature of dominant ejecta
• Structures built around vent

The five eruptive style are

• Hawaiian Eruptions
• Strombolian Eruptions
• Peléean Eruptions
• Plinian Eruptions
• Vulcanian Eruptions

Hawaiian Eruption

1984 eruption of Mauna Loa
Source: http://hvo.wr.usgs.gov/maunaloa/history/4305078_L.jpg

Hawaiin eruptions are the calmest of the eruption styles. They are characterized by the effusive emission of highly fluid and basaltic lavas with low gas contents. The volume of the ejected pyroclastic material is less than that of all the other eruption types. The characteristic of Hawaiian eruptions is the steady lava fountaining and the production of thin lava flows which eventually builds up to form large, broad shield volcanoes. Most of the eruption starts from fissures which come together to one or more central vents. The lava flows down away from the source vents in lava channels and lava tubes.

Strombolian Eruption

Strombolian activity on Mt. Etna in October 2002
Source: http://www.geology.sdsu.edu/how_volcanoes_work/Images/Pfeiffer/etna_strom02.jpg

Strombolian eruptions are named from the small volcanic-island of Stromboli, located between Sicily and Italy. The term “strombolian” has been used to describe a variety of volcanic eruptions that varies from small volcanic blasts, to kilometer-high eruptive columns. Strombolian activity is characterized by short-lived, explosive outbursts of pasty lava ejected a few tens or hundreds of meters into the air.

Strombolian eruptions never develop a sustained eruption column, unlike Hawaiian eruptions. The basaltic lava flows are relatively viscous. The gas pressure is also high as it is required to fragment the pasty lava, therefore resulting in periodic explosions with booming blasts. Although they are noisier as compared to Hawaiian eruptions, they are not more dangerous that it. Strombolian eruptions eject bomb sized and lapilli sized fragments that travels in a parabolic manner before it accumulates around the vent to construct the volcanic structure.