Effusive eruption

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Video of lava agitating and bubbling in the volcano eruption of
Litli-Hrútur
, 2023

An effusive eruption is a type of volcanic eruption in which lava steadily flows out of a volcano onto the ground.

Overview

Effusive eruption of basaltic ʻaʻā lava at Mauna Loa in 1984

There are two major groupings of eruptions: effusive and explosive.

lava flows is governed by the type of lava (i.e. composition), rate and duration of eruption, and topography of the surrounding landscape.[3]

For an effusive eruption to occur, magma must be permeable enough to allow the expulsion of gas bubbles contained within it. If the magma is not above a certain permeability threshold, it cannot degas and will erupt explosively. Additionally, at a certain threshold, fragmentation within the magma can cause an explosive eruption. This threshold is governed by the Reynolds number, a dimensionless number in fluid dynamics that is directly proportional to fluid velocity. Eruptions will be effusive if the magma has a low ascent velocity. At higher magma ascent rates, the fragmentation within the magma passes a threshold and results in explosive eruptions.[4] Silicic magma also exhibits this transition between effusive and explosive eruptions,[5] but the fragmentation mechanism differs.[4] The 1912 Novarupta eruption and the 2003 Stromboli eruption both exhibited a transition between explosive and effusive eruption patterns.[5][6]

Basaltic eruptions

pāhoehoe.[8] This type of lava flow builds shield volcanoes, which are, for example, numerous in Hawaii,[9]
and is how the island was and currently is being formed.

Silicic eruptions

Alaskan volcano Novarupta with an effused lava dome at the summit.

lava domes, because their high viscosity[15] does not allow it to flow like that of basaltic magmas. When felsic domes form, they are emplaced within and on top of the conduit.[16] If a dome forms and crystallizes enough early in an eruption, it acts as a plug on the system,[16] denying the main mechanism of degassing. If this happens, it is common that the eruption will change from effusive to explosive, due to pressure build up below the lava dome.[10]

References

  1. ^ a b "Eruption Styles". volcano.oregonstate.edu. Retrieved 2018-04-25.
  2. ^ Program, Volcano Hazards. "USGS: Volcano Hazards Program Glossary - Effusive eruption". volcanoes.usgs.gov. Retrieved 2018-04-25.
  3. ^ Marshak, Stephen. Essentials of geology. New York: W.W. Norton, 2013.
  4. ^ .
  5. ^ .
  6. .
  7. ^ "Effusive Volcanoes". gwentprepared.org.uk. Archived from the original on 2016-08-18. Retrieved 2018-04-25.
  8. ^ Camp, Vic. "How Volcanoes Work - Basaltic Lava". Department of Geological Sciences, San Diego State University. Retrieved 28 October 2014.
  9. ^ "Effusive & Explosive Eruptions". The Geological Society.
  10. ^
    ISSN 0377-0273
    .
  11. .
  12. .
  13. .
  14. ^ "How Volcanoes Work - Andesitic to Rhyolitic Lava".
  15. ^ "USGS: Volcano Hazards Program Glossary".
  16. ^ a b Nelson, Stephen (26 August 2017). "Volcanoes and Volcanic Eruptions". www.Tulane.edu. Retrieved 25 April 2018.