Littoral cone

A littoral cone lies on the right, on top of the cliffs

Littoral cones are a form of volcanic cone. They form from the interaction between lava flows and water. Steam explosions fragment the lava and the fragments can pile up and form a cone. Such cones usually form on aa lava flows, and typically require large lava flows to form. They have been found on Hawaii and elsewhere.

Littoral cones are semicircular cones which are breached in the direction of the lava flow that created them. They are formed by mounds of clasts that appear like cones without a crater.[1] Littoral cones are constructed by ash, lava bombs and lapilli.[2] Their component material is usually poorly sorted and can feature agglutinated structures and layering.[3] Sometimes spatter-fed lava flows occur on such cones.[4] They are formed by degassed hyaloclastite.[5][1] The most common form found on Hawaii involves two semicircles on both sides of the lava flow that generated them;[6] some such cones on Hawaii form a complete rim with diametres of 200–400 metres (660–1,310 ft).[7] Puu Ki on Hawaii has nested craters on top of a lava tube.[8] Typically such cones are not larger than 800 metres (2,600 ft) wide and 75 metres (246 ft) high.[3] Other smaller cones on Hawaii have diametres of 40 metres (130 ft) and heights reaching 15 metres (49 ft).[9]

Littoral cones not primary volcanic vents and distinguishing between a littoral cone and a primary vent can be difficult.[3] A littoral cone forms when lava flows from land into water. Interaction between the water and the lava leads to steam explosions. These explosions throw lava fragments into the air; under favourable circumstances these fragments pile up on land and form a cone.[10] This activity may resemble that of fire fountaining.[9] Repeated phases of magma-water mixing lead to the formation of bedded deposits.[2] The steam explosions can lead to the formation of Pele's hair.[11] The forming lava flows need to be sufficiently large;[12] the minimum size of lava flows that have formed such cones in Hawaii is 38,000,000 cubic metres (50,000,000 cu yd).[13] Of these, about 5-6% of their volume is converted to fragments.[3] Usually littoral cones are formed by aa lava as their fragmented nature allows ideal water-lava interactions, but pahoehoe and intermediary lavas can also form littoral cones.[14] Other properties such as the speed of the lava flow and the structure of the flow front also influence the formation of littoral cones.[13] Larger lava flow rates generate larger cones.[15] In some littoral cones on Hawaii that were formed by pahoehoe lava flows, the collapse of a lava bench and subsequent steam explosions formed the cones instead.[7] Pyroclastic flows can also form littoral cones, one such cone has been found on Lombok and formed during the 1257 Samalas eruption.[16]

Pseudocraters and littoral cones have been found on Iceland, Hawaii, Cerro Azul in the Gálapagos Islands,[7] Deception Island, Antarctica,[17] and Medicine Lake Volcano, California.[18] Sometimes the words "pseudocrater" and "littoral cone" are used as synonyms.[19] Littoral cones are usually quickly removed by sea erosion; thus littoral cones are rare.[10]

Prehistorical littoral cones have been found on the coast of Hawaii, where the volcanoes Mauna Loa and Kilauea face the sea. They were named "littoral cones" by Wentworth in 1938.[20] About 50 large cones are found on these two volcanoes and only three of them were formed during historical times; no such cones have been found on the other Hawaiian volcanoes.[10] The Puu Oo and Mauna Ulu eruptions of Kilauea have also formed small littoral cones.[7]

Examples of littoral cones include Sand Hills (1840 eruption) on Kilauea in Hawaii,[21] 'Au'au, Nā Pu'u a Pele, Pu'u Hou (1868 eruption) and Pu'u Kī (eruption 1300 years ago) at Mauna Loa on Hawaii,[6] a cone close to Villamil at Sierra Negra, Galapagos,[22] Eldborg (1800 years ago) at Hengill on Iceland,[23] a cone in the Winter Water unit of the Columbia Plateau Basalts, Oregon,[24] a cone at Becharof Lake, Alaska,[25] Burilan and Devil Rock on Gaua,[26] and Ponta de Ferraria (eruption 840 ± 60 years ago) on São Miguel Island, Azores.[27] The Speedwell Vent in Derbyshire, United Kingdom may also be a littoral cone of Carboniferous age.[28] Pleistocene littoral cones may also exist in Lake Tahoe, California.[29]

References

  1. 1 2 Fisher 1968, p. 839.
  2. 1 2 Richard V. Fisher; Hans-Ulrich Schmincke (6 December 2012). Pyroclastic Rocks. Springer Science & Business Media. pp. 263–264. ISBN 978-3-642-74864-6.
  3. 1 2 3 4 Green, Jack (1982-01-01). Beaches and Coastal Geology. Encyclopedia of Earth Science. Springer US. pp. 519–520. doi:10.1007/0-387-30843-1_260. ISBN 9780879332136.
  4. ↑ Greeley, Ronald; Fagents, Sarah A. (25 September 2001). "Icelandic pseudocraters as analogs to some volcanic cones on Mars". Journal of Geophysical Research: Planets. 106 (E9): 20533. doi:10.1029/2000JE001378.
  5. ↑ Jurado-Chichay, Rowland & Walker 1996, p. 477.
  6. 1 2 Jurado-Chichay, Rowland & Walker 1996, p. 472.
  7. 1 2 3 4 Jurado-Chichay, Rowland & Walker 1996, p. 471.
  8. ↑ Walker, George P. L. (1993). "Basaltic-volcano systems". Geological Society, London, Special Publications. 76 (1): 25. doi:10.1144/GSL.SP.1993.076.01.01.
  9. 1 2 Jurado-Chichay, Rowland & Walker 1996, p. 478.
  10. 1 2 3 Moore & Ault 1965, p. 3.
  11. ↑ Mattox, Tari N; Mangan, Margaret T (January 1997). "Littoral hydrovolcanic explosions: a case study of lava–seawater interaction at Kilauea Volcano". Journal of Volcanology and Geothermal Research. 75 (1-2): 6–8. doi:10.1016/S0377-0273(96)00048-0.
  12. ↑ Moore & Ault 1965, p. 9.
  13. 1 2 Moore & Ault 1965, p. 10.
  14. ↑ Fisher 1968, p. 861.
  15. ↑ Jurado-Chichay, Rowland & Walker 1996, p. 481.
  16. ↑ Vidal, Céline M.; Komorowski, Jean-Christophe; Métrich, Nicole; Pratomo, Indyo; Kartadinata, Nugraha; Prambada, Oktory; Michel, Agnès; Carazzo, Guillaume; Lavigne, Franck; Rodysill, Jessica; Fontijn, Karen; Surono (8 August 2015). "Dynamics of the major plinian eruption of Samalas in 1257 A.D. (Lombok, Indonesia)". Bulletin of Volcanology. 77 (9): 7. doi:10.1007/s00445-015-0960-9.
  17. ↑ Smellie, J.L. (27 April 2004). "Lithostratigraphy and volcanic evolution of Deception Island, South Shetland Islands". Antarctic Science. 13 (02): 201. doi:10.1017/S0954102001000281.
  18. ↑ "DIGITAL GEOLOGIC MAP DATABASE OF MEDICINE LAKE VOLCANO, CALIFORNIA". gsa.confex.com. Retrieved 2016-11-24.
  19. ↑ EINARSSON, ARNI (February 1982). "The palaeolimnology of Lake Myvatn, northern Iceland: plant and animal microfossils in the sediment". Freshwater Biology. 12 (1): 65. doi:10.1111/j.1365-2427.1982.tb00603.x.
  20. ↑ Fisher 1968, p. 842.
  21. ↑ Fisher 1968, p. 841.
  22. ↑ Reynolds, Robert W.; Geist, Dennis; Kurz, Mark D. (December 1995). "Physical volcanology and structural development of Sierra Negra volcano, Isabela Island, Gal´apagos archipelago". Geological Society of America Bulletin. 107 (12): 1401–1402. doi:10.1130/0016-7606(1995)107<1398:PVASDO>2.3.CO;2.
  23. ↑ Stevenson, J. A.; Mitchell, N.; Mochrie, F.; Cassidy, M.; Pinkerton, H. (2009-12-01). "Lava entering water: the different behaviour of aa and pahoehoe at the Nesjahraun, Thingvellir, Iceland". AGU Fall Meeting Abstracts. 51.
  24. ↑ "COLUMBIA RIVER BASALT AQUIFER CHARACTERISTICS REVEALED BY STATEMAP MAPPING IN OREGON�S UMATILLA BASIN". gsa.confex.com. Retrieved 2016-11-24. replacement character in |title= at position 85 (help)
  25. ↑ Lu, Zhong; Wicks, Charles; Dzurisin, Daniel; Power, John A.; Moran, Seth C.; Thatcher, Wayne (July 2002). "Magmatic inflation at a dormant stratovolcano: 1996-1998 activity at Mount Peulik volcano, Alaska, revealed by satellite radar interferometry". Journal of Geophysical Research: Solid Earth. 107 (B7): 4. doi:10.1029/2001JB000471.
  26. ↑ Métrich, N.; Bertagnini, A.; Garaebiti, E.; Vergniolle, S.; Bani, P.; Beaumais, A.; Neuville, D.R. (August 2016). "Magma transfer and degassing budget: Application to the 2009–2010 eruptive crisis of Mt Garet (Vanuatu arc)". Journal of Volcanology and Geothermal Research. 322: 49. doi:10.1016/j.jvolgeores.2015.06.003.
  27. ↑ Lima, Ana; Nunes, João Carlos; Brilha, José (9 November 2016). "Monitoring of the Visitors Impact at "Ponta da Ferraria e Pico das Camarinhas" Geosite (São Miguel Island, Azores UNESCO Global Geopark, Portugal)". Geoheritage: 3. doi:10.1007/s12371-016-0203-2.
  28. ↑ Cheshire, S. G.; Bell, J.D. (1 December 1976). "THE SPEEDWELL VENT, CASTLETON, DERBYSHIRE: A CARBONIFEROUS LITTORAL CONE". Proceedings of the Yorkshire Geological Society. 41 (2). doi:10.1144/pygs.41.2.173.
  29. ↑ "PLIOCENE/PLEISTOCENE BASALTIC PILLOW LAVA AND TUFF ALONG NW SHORE OF LAKE TAHOE, CA: NEARSHORE VENT OR LITTORAL CONE?". gsa.confex.com. Retrieved 2016-11-24.

Sources

  • Fisher, Richard V. (October 1968). "Puu Hou littoral cones, Hawaii". Geologische Rundschau. 57 (3): 837–864. doi:10.1007/BF01845368. 
  • Jurado-Chichay, Zinzuni; Rowland, Scott K.; Walker, George P. L. (April 1996). "The formation of circular littoral cones from tube-fed p?hoehoe: Mauna Loa, Hawai'i". Bulletin of Volcanology. 57 (7): 471–482. doi:10.1007/BF00304433. 
  • Moore, James G; Ault, Wayne U (1965-01-01). "Historic Littoral Cones in Hawaii". ResearchGate. 19(1) (1). 
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