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A sector collapse or lateral collapse is the structural failure and subsequent collapse of part of a volcano. Unlike a flank collapse, a sector collapse involves the central volcanic pipe. Sector collapses are one of the most hazardous volcanic events[2], often resulting in lateral blasts[1], landslides[3], and changes volcanic eruptive behavior. Sector collapse can be caused by earthquakes[3], volcanic eruptions[1], gradual volcanic deformation[1], and other processes. Sector collapse events can occur on volcanoes present at both convergent and divergent plate boundaries[1]. Sector collapses are generally very sudden, however some attempts have been made to predict collapse events.
Causes
editInternal
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Sector collapse can result from internal volcanic processes. Volcanic eruption can damage originally stable magma chambers, causing a portion of the volcano to collapse[1]. While eruption is one cause, sector collapse can occur without any eruption[3]. Magmatic intrusions can also lead to sector collapse. Dikes fracture and deform rock, leaving the volcano weaker and more susceptible to collapse[3]. Hydrothermal activity is another internal cause, likely due to reactions of acid-sulfates weakening volcanic rock[3]. Gravity-induced collapse occurs when the volcanic slope approaches the critical angle of repose[3]. The slope angle is a major factor in collapse events[2].
External
editSector collapse sometimes occurs because of external processes. Seismic activity is a prominent cause of collapse events. Earthquakes can weaken the structural stability of volcanoes, leading to sudden collapse or contributing to a later collapse[3]. Intense weather and heavy rainfall can cause damaging erosion, increasing likelihood of collapse[3]. Glacial melting is another external cause of sector collapse, with the majority of glacial melt induced collapses occuring during the pleistocene[4]. Glacial melting increases volcanic slope and decreases pore pressure, leading to sector collapse[4]. Sea level change has also been associated with sector collapse[3].
Predicting sector collapse
editBecause sector collapse events occur suddenly and over small time periods, they are difficult to predict[1]. More often, volcanoes are assessed for risk of sector collapse[4]. Collapse ultimately occurs due to structural instability[1], which can be determined by volcanic slope angle, composition of the volcano, deformation, and other factors[3].
Consequences
editChanges to volcanic systems
editSome volcanoes experience no changes in volcanic behavior while others experience altered rates of eruption and magma composition[1]. Collapse is typically followed by phreatic eruption[3] due to a reduction in magma chamber pressure after sector collapse[1]. Damage caused by collapse can create a new and different volcanic plumbing system, which could impact eruption rates[1]. Sector collapse often results in eruption of more mafic magma[1]. Large overlying surface mass and the denser nature of mafic magma often prevents its rise[1]. Collapse relieves some of the overlying surface mass thus allowing for more mafic magma composition[1].
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Human impacts
editSector collapses and landslides caused by them have directly resulted in 3,500+ fatalities since 1600 and caused extensive property damage[3]. A particularly deadly consequence of sector collapse is tsunami[3]. The Oshima-Oshima collapse led to a tsunami that killed 1,500 people[3]. Sector collapse events can also displace thousands and cause homelessness[3].
Identifying sector collapse
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Prehistoric sector collapses are stored in the geological record[1] in the form of debris avalanche deposits[2] and collapse scars[3]. Debris avalanche deposits can be found up to 20 km from the site of collapse[3]. Studying avalanche deposits informs on the time scale of the collapse and the volcano from which it originated[2]. Collapse scars are also an indicator of sector collapse and are often described as "amphitheatere" or "horse-shoe" shaped[3]. One such collapse scar is the Sciara del Fuoco formed on the Stromboli volcano due to a sector collapse[5].
Examples
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Prehistoric
editHistoric
edit- Mt St Helens, 1980[1]
- Bandai, 1888[1]
- Anak Krakatou, 2018[1]
- Ritter Island, 1888: largest historical collapse[1]
- Bezymianny, 1965[1]
- Oshima-Oshima, 1741[1]
See also
editReferences
edit- ^ a b c d e f g h i j k l m n o p q r s t u v w x Watt, Sebastian F. L. (2019-10-15). "The evolution of volcanic systems following sector collapse". Journal of Volcanology and Geothermal Research. 384: 280–303. doi:10.1016/j.jvolgeores.2019.05.012. ISSN 0377-0273.
- ^ a b c d Kervyn, M.; Ernst, G. G. J.; Klaudius, J.; Keller, J.; Mbede, E.; Jacobs, P. (2008-10-28). "Remote sensing study of sector collapses and debris avalanche deposits at Oldoinyo Lengai and Kerimasi volcanoes, Tanzania". International Journal of Remote Sensing. 29 (22): 6565–6595. Bibcode:2008IJRS...29.6565K. doi:10.1080/01431160802168137. ISSN 0143-1161. S2CID 128817424.
- ^ a b c d e f g h i j k l m n o p q r Romero, Jorge E.; Polacci, Margherita; Watt, Sebastian; Kitamura, Shigeru; Tormey, Daniel; Sielfeld, Gerd; Arzilli, Fabio; La Spina, Giuseppe; Franco, Luis; Burton, Mike; Polanco, Edmundo (2021). "Volcanic Lateral Collapse Processes in Mafic Arc Edifices: A Review of Their Driving Processes, Types and Consequences". Frontiers in Earth Science. 9. doi:10.3389/feart.2021.639825/full. ISSN 2296-6463.
{{cite journal}}: CS1 maint: unflagged free DOI (link) - ^ a b c Tormey, Daniel (2010-11-01). "Managing the effects of accelerated glacial melting on volcanic collapse and debris flows: Planchon–Peteroa Volcano, Southern Andes". Global and Planetary Change. 74 (2): 82–90. doi:10.1016/j.gloplacha.2010.08.003. ISSN 0921-8181.
- ^ a b Kokelaar, Peter; Romagnoli, Claudia (1995-08-01). "Sector collapse, sedimentation and clast population evolution at an active island-arc volcano: Stromboli, Italy". Bulletin of Volcanology. 57: 240–262. doi:10.1007/BF00265424. ISSN 0258-8900.