ISNS 4359 EARTHQUAKES and VOLCANOES Spring 2005 s1

ISNS 4359 EARTHQUAKES AND VOLCANOES Spring 2005 Steve Bergman, Instructor Lecture 20. Eruption Case Studies IV. Selected Hawaiian & Icelandic Eruptions Mauna Loa (ML) Hawai‘i The largest volcano on Earth (Hawaiian, mauna-‘mountain’, loa-‘big’) Kilauea (K) Hawai‘i The most continuously active volcano on Earth (Hawaiian, ‘much spreading’) 1. Locations: ML: 19.47N, 155.61W, elevation: 4170 m; K: 19.42N, 155.29W, elevation: 1247 m 2. Size & Type of volcanic features: Basaltic shield volcanoes (50-100 km diameter) mainly composed of thin (3-4 m thick) aa and pahoehoe lava flows <1 km wide and as long as >50 km; 3 x 5 km diameter caldera 180 m deep; rare tephra. 3. Relationship to Plate Boundaries/ Names of relevant plates: Intraplate hotspot/mantle plume in the middle of the Pacific Plate. 4. Date and duration of eruptions: The >5700 km long Hawaiian-Emperor seamount chain comprising 107 volcanoes (volume7x106 km3) is >80 million years old (Ma). The oldest Hawaiian island, Kauai is ~5 Ma. Hawaii emerged 700,000 yrs ago and is composed of five separate shield volcanoes (Kohala, Mauna Kea, Hualalai, ML, and K), and the subsea “pre-shield” Loihi Seamount. ML emerged ~500,000 yrs ago and has erupted 39 times between 1750 and 1984 (mean recurrence time of ~3 years). K emerged ~200,000 yrs ago; continuous eruption of lava (~1.5 m3/sec) has occurred since 1983 from the Pu’u O’o vent (VEI=1). 5. Type of Eruption/Deposits/Magma Composition: Basalt lavas and tuffs erupted from calderas and fissures. 6. Volume of all erupted products: Total ML volume ~40,000-80,000 km3; the 1984 ML flank eruption covered 50 km2 with 0.22 km3 lavas. Total K volume ~15,000-20,000 km3. 7. Area impacted by eruptions: [Subaerial] ML ~5000 km2; K ~1500 km2; [Submarine] ML ~4000 km2; K ~4700 km2. 8. Summary of volcanic events preceding eruption events: Two years of increased seismic activity and increased

CO2 emission preceded the last several eruptions at ML. 1790 K: last major caldera collapse, 1790-1960: mainly summit eruptions, since 1960: mainly flank eruptions. 9. Number of Deaths/Type of hazards: 1790 K eruption from the active caldera killed ~100 people (lava and pumice flows and base surge). ML & K lavas have destroyed 100s of houses, villages & ranches. 1868 ML eruption produced lahars killing ~36 and tsunami killing 46. 10. Subsequent activity: ML last erupted in 1984; the last three eruptions (1950, ‘75, ‘84) were separated by 9 & 25 years. Based on last 300 years of activity, ML will erupt prior to 2007 (95% probability). 11. Notable Items: The Hawaiian volcanic chain has been constructed at ~0.03 km3/yr for the last 25 million years. ML stands ~10 km above the adjacent seafloor (after accounting for the loading), making it Earth’s tallest volcano, higher than Mt. Everest rises above sea level. K stands ~6.8 km above the adjacent seafloor. Archibald Menzies made the first recorded ascent of ML Feb 1794. The Hawaiian hotspot is 80 km in diameter based on 60 km deep seismicity. Landslides totaling 1500-2000 km3 in volume traveled up to 100 km on the seafloor from ML. Selected References: Decker, R.W., Wright, & Stauffer, (editors) 1987. Volcanism in Hawaii. USGS Prof. Paper 1350. MacDonald,G.A., Abbott, A.T., & Cox, D.C., 1983. Volcanoes in the Sea (2nd edition). Univ. Hawaii Press, Honolulu. Rhodes, J.M., & Lockwood, J.P., (editors) 1995. Mauna Loa Revealed: structure, composition, history and hazards. Geophysical Monograph 92. AGU Washington (containing 20 papers). Stearns, H.T., 1985. Geology of the State of Hawaii (2nd edition). Pacific Books, Palo Alto, CA. Grimsvötn (1783 Lakagigar/Skaftar Fires), Iceland The longest single lava flow on Earth; the sixth deadliest eruption of 4 centuries; the most intense eruption & the greatest atmospheric pollution event of the last 2 centuries. 1. Location: 64.42N, 17.33W, elevation: 1724 m. 2. Size & Type of volcanic feature: Basaltic Central Volcano/Fissure eruption 3. Relationship to Plate Boundaries/ Names of relevant plates: Hotspot/mantle plume centered on a subaerial segment of spreading ridge between the diverging North American and Eurasian Plates (submarine ridge away from hotspot). 4. Date and duration of eruption: 8Jun1783-7Feb1784; 8 month mean and peak eruption rates of 1.4x106 and 2.4x107 kg/sec; 60% erupted in the first 45 days. 5. Type of Eruption/Deposits/Magma Composition: Basaltic fissure eruptions, Strombolian; and phreatomagmatic Plinian eruptions (injecting ash to elevations of 6-13 km) producing lavas, tuffs, and cinder and tuff cones. 6. Mass & Volume of erupted products: 3x1013 kg; 15.1 km3. Lava flows from the 27 km long Laki crater fissure extended ~70 km (total lava volume=14.7 km3; tephra volume~0.4 km3) VEI=4. 7. Area impacted by the eruption: lavas covered ~600 km2 8. Summary of volcanic events preceding the particular event: ~50 historical eruptions have occurred at Laki, the first in 1332. The 1783 event was preceded by one week of earthquake activity. 9. Number of Deaths/Type of hazards: 1706 eruption killed a third of Iceland’s population by smallpox. 1783 eruption destroyed summer crops, poisoned livestock, and caused widespread famine, killing 9350 (~24% of Iceland’s population), and destroying 14 farmsteads & 20 churches. 10. Subsequent activity: Grímsvötn is the most active Icelandic volcano; the 1938 eruption (volume 0.4 km3) was the third largest eruption in Iceland of the last century. Subglacial fissure eruptions occurred in 1982, 1996, & 1998. 10 11. Notable Items: 10 kg acid gases (250 Mtons SO2) were discharged. Ben Franklin (American Ambassador to the court of King Louis XVI in France) documented European effects of the dry blue fog and was first to record a link between volcanism and climate change. The eruption was followed by an unusually hot July (+3ºC, caused by greenhouse warming by CO2, which quickly dispersed) and three unusually cold Northern Hemisphere winters (-2-5ºC, caused by SO2 aerosol veils). Selected References: Franklin, B., 1784. Meteorological imaginations and conjectures. Lit. Phi. Soc. Manchester, Memoirs 2, 373-7. Jacoby, GC; Workman, KW; & D'Arrigo, RD 1999. Laki eruption of 1783, tree rings, and disaster for Northwest Alaska Inuit. Quaternary Science Reviews, 18, 12, 1365-71. Stothers, RB 1999. Volcanic dry fogs, climate cooling, and plague pandemics in Europe and the Middle East. Climatic Change, 42, 4, 713- 723. Thordarson, Th & Self, S, 1993. The Laki (Skaftar Fires) and Grimsvötn eruptons in 1783-5. Bull. Volcanology. 55, 233-63. Thordarson, Th & et al., 1996. Sulfur, chlorine, and fluorine degassing and atmospheric loading by the 1783-1784 AD Laki (Skaftar Fires) and eruptions in Iceland. Bulletin of Volcanology. 58, 205-25.