geos 470r

1. GEOS 470R/570R Volcanology L24, 20 April 2010 Handing out PowerPoint slides for today No lab this Friday Combining last two labs on 30 Apr 2010 PowerPoint presentations on mafic eruptions Exercise on kimberlites and related rocks Volcano movie night: Supervolcano Saturday 24 Apr 2010, 6 pm, Seedorff house, 9275 N. Shannon Rd. “I have found that most people are about as happy as they make their minds up to be.” --Abraham Lincoln

3. Assigned reading For today, 20 April 2010 Voight, B., 1990, The 1985 Nevado del Ruiz volcano catastrophe: Anatomy and retrospection: Journal of Volcanology and Geothermal Research, v. 44, p. 349-386. For future None

4. Last time: Petrologic synthesis; Volcanic hazards, I. Petrologic synthesis Review of rock suites Silicic Intermediate Mafic Ultramafic and non-silicate Hazard, vulnerability, and risk Risk identification, analysis, reduction, transfer, and education Volcanic hazards Lava flows Ballistic ejecta and tephra falls Pyroclastic flows and surges and rock/debris avalanches Catastrophic failure of caldera lakes Lahars, mudflows, and jökulhlaups Earthquakes, ground deformation, air shocks, tsunamis, lightning Volcanic gases and aerosols Next time: Volcanic hazards, II.

5. Multi-dimensional continuum of magma compositions Earth’s petrologic universe Arbitrary subdivisions Given multiplicity of factors, might not expect there to be a perfect correlation of magma composition to tectonic setting

6. Silicic I Biotite high-silica rhyolite/granite (Ia) Bishop Tuff, Glass Mtn, Mono-Inyo, Pine Grove, Henderson Biotite high-silica rhyolite/granite zoned to intermediate compositions (IIa) Fraction, Ammonia Tanks, and Rainier Mesa Tuffs of the southern Nevada volcanic field Topaz rhyolite/granite Thomas Range, Wah Wah Mtns Calcic silicic rocks Whakamaru (Taupo) Peraluminous silicic rocks Macusani “S-type magmas”

7. Silicic II Fayalite-chevkinite high-silica rhyolite/granite (Ib) Lava Creek Tuff (LCT) and Huckleberry Ridge Tuff (HRT) of the Yellowstone volcanic field “A-type magmas” Fayalite-chevkinite high-silica rhyolite/granite zoned to intermediate compositions (IIb) Tshirege Member of the Bandelier Tuff from Valles caldera, Jemez Mtns “A-type magmas” Peralkaline, silica-oversaturated silicic rocks, zoned from comendite to subalkaline rhyodacite Spearhead Member of the Thirsty Canyon Tuff, Tala Tuff of Sierra La Primavera, Mexico, Tuff of Devine Canyon Peralkaline, silica-oversaturated silicic rocks, zoned from comendite to trachyte Grouse Canyon Member of the Belted Range Tuff, Kane Wash Tuff Strongly peralkaline, silicic to intermediate rocks, with low-silica comendite, pantellerite, and trachyte Pantelleria, Menengai, Fantale, Socorro, Gran Canaria, Terceira

8. Intermediate I Rhyolite / gap / zoned intermediate VTTS Tuff at Katmai-Novarupta “I-type magmas” Zoned intermediate Shikotsu, Mazama, Aso-4, Aniakchak, Krakatau, Quizapu “I-type magmas” Monotonous intermediate Monotony, Fish Canyon, Snowshoe Mountain, Mt. Jefferson, Loma Seca “I-type magmas” High-K calc-alkalic to shoshonitic El Chichón, Egan Range, Absaroka

9. Intermediate II Boninites (high-Mg andesites) Chichi-jima, Cape Vogel Adakites (sodic andesites and dacites of trondhjemite-tonalite-granodiorite suite) Adak, Vizcaino Peninsula, Mindanao, Cayambe Igneous charnockites (pigeonite-bearing silicic rocks) Magic Reservoir, Bruneau-Jarbidge, Yardea dacite “C-type magmas” Alkalic, silica-undersaturated intermediate rocks (phonolite-trachyte)

10. Mafic I Tholeiitic basalts of mid-ocean ridge basalts (MORBs) Mid-Atlantic Ridge, East Pacific Rise Olivine tholeiites and Fe-rich derivatives: ferrobasalt, ferroandesite Iceland (volcanic island straddling spreading center) Continental flood basalts (quartz tholeiites and Fe-rich differentiates) Columbia River (~16 Ma), Ethiopia (~25 Ma), North Atlantic (~59 Ma), Deccan (~66 Ma), Paraná-Etendeka ( ~132 Ma), Karoo (~183 Ma), Central Atlantic (~200 Ma), Siberia (~248 Ma), Keweenawan (~1095 Ma), Coppermine River and MacKenzie (~1267 Ma) Plateau basalts (high-Al basalts) Snake River Plain Tholeiitic arcs (low-K series) Tonga-Kermadec

11. Mafic II Oceanic Islands Entirely tholeiitic (Galapagos) Mostly tholeiitic with lesser alkaline capping (Hawaii) Pre-shield stage (alkaline basalt) Shield-forming (tholeiitic basalt) Post-shield alkaline suite (alkaline basalt, hawaiite, mugearite, benmoreite) Post-erosion stage (alkaline basalt, basanite, nephelinite, melilitite) Mostly to entirely alkaline (Gran Canaria, Terceira, Tahiti, Tristan da Cunha) Mildly alkaline olivine basalts (OIBs) and sodic differentiates (hawaiite, mugearite, benmoreite, trachyte)—Terceira (Azores) Highly alkaline, silica-undersaturated basanite and differentiaties (phono-tephrite, tephriphonolite, phonolite)—Tristan da Cunha

12. Ultramafic Carbonatite-nephelinite complexes Ol Doinyo Lengai, Shombole Primitive, silica-undersaturated, mafic to ultramafic Lamprophyres Lamproites Orangeites and kimberlites Limburgite Komatiites

13. Definition of Risk Hazard Annualized probability of the specific hazard, e.g., tephra fall, lahar Vulnerability Average degree of loss on scale of 0.0 to 1.0 to elements exposed to hazard (e.g., humans, agriculture, buildings) Risk Hazard X Vulnerability = Risk

14. Stages of risk management Risk identification Risk analysis Risk reduction Risk transfer

15. Risk identification: Hazards Lava flows Ballistic ejecta Tephra falls Pyroclastic flows Pyroclastic surges Lahars Jökulhlaups Rock/debris avalanches Earthquakes Ground deformation Tsunamis Air shocks Lightning Gases and aerosols

16. Lava flows Temperatures above ignition points of many materials Velocities from a few tens of m / hr to 60 km / hr Bury or crush objects in their path Follow topographic depressions Can be tens of km long Noxious haze from sustained eruptions

17. Ballistic ejecta >10 km radius of vent High impact energies Densities <3 t / m3 Fresh bombs above ignition temperatures of many materials

18. Tephra falls Downwind transport velocity >10 to <100 km / hr Exponential decrease in thickness downwind Can extend >1000 km downwind Lapilli and ash (<64 mm diameter) are at thermal equilibrium Can produce impenetrable darkness Compacts to half initial thickness in a few days Surface crusting encourages runoff Abrasive, conductive, and magnetic Airborne ash is a special hazard to aviation Ash accumulations on slopes of volcanoes can create debris-flow hazards that may extend for several decades to centuries after eruptions

19. Hazards to jet engines Particles and acid aerosols are concentrated by engine compressor Metal surfaces quickly abraded Fuel nozzles clog Operating temperatures of engines (1400°C) can melt volcanic glass particles Melted ash coats and sticks to turbine blades, causing engine to shut down automatically Pilot should decrease power to engines to lower temperature Not gun engines to escape cloud, which raises engine T

20. Pyroclastic flows Concentrated gas-solid dispersion Flow velocities up to 160 m / s Emplacement temperatures <100 to >900°C Small flows travel 5 - 10 km down topographic lows Large flows travel 50 - 100 km Large flows climb topographic obstructions At obstructions or bends in channels, lighter weight, intensely hot, upper part of density current can separate from lower part and move up hill

21. Pyroclastic surges Low concentration but high kinetic energy Radius of deposition 10 – 15 km Climb topographic obstructions Emplacement velocities >10’s of m / s

22. Failure of caldera lakes Calderas are natural reservoirs These reservoirs commonly sit at high elevation Great hazards Some contain volumes that are comparable to that in large natural reservoirs Crater Lake, OR 1.9 x 1010 m3 Atitlán, Guatemala 4.0 x 1010 m3 Katmai 3.3 x 109 m3 Rims may be prone to failure

23. Lahars Generated with rainfalls <10 mm / hr Bulk fluid densities 2 – 2.4 t / m3; sediment content 75-90 wt% Peak flow rates >10,000 m3 / s Velocities >10 m / s not uncommon Increase turbidity and chemical contamination in water bodies Rapid aggradation, incision, or lateral migration Travel distances up to 10’s of km Hazard may continue for months or years after eruption

24. Mudflows Aerial view of the Acaban River channel As it passes through Angeles City near Clark Air Base On 12 August Mudflows caused collapse of main bridges Note makeshift bridges for pedestrians at lower left

25. Jökulhlaups Can occur with little or no warning Discharges may be >100,000 m3 / s

26. Rock/debris avalanches Sector collapse, minimum volume of 10 – 20 m3 Travel distances to >30 km Deposits cover >100 km2 Emplacement velocities up to 100 m / s Create topography, pond lakes Can produce tsunamis in coastal areas

27. Earthquakes Maximum Modified Mercalli intensity of 8 or less Damage limited to small areas Damage dependent on subgrade conditions Much stronger for caldera-related eruptions Even small calderas or craters, as for Pinatubo Exacerbates other issues, like collapse of buildings due to ash/water accumulations, as at Pinatubo

28. Volcano-related earthquake damage Destruction of older brick structures in Pozzuoli, Bay of Naples, Italy Caused by earthquakes related to volcanic unrest at Campi Flegrei, 1982-1984 Involved increased seismicity and 1.8 m of ground uplift but no eruption

29. Ground deformation Damage limited to 10 - 20 km radius Subsidence may affect 100’s of km2

30. Bay of Naples, Italy Pozzuoli, Italy, at or near the center of the Campanian caldera that erupted the Campanian ignimbrite 37 ka Area is site of repeated inflation and subsidence; some structures historically have bobbed several meters above and below sea level

31. Ground deformation at Pozzuoli, Italy Buttressed buildings in Pozzuoli, April 1984 Many buildings cracked Buildings pushed out of line so that doors and windows would not open Many inhabitants forced to evacuate to tent and trailer camps

32. Tsunamis Tsunami: Japanese for “harbor wave” or “seismic sea wave” (public’s “tidal wave,” though unrelated to tides) Open ocean travel rate >800 km / hr Exceptionally, waves to >30 m Inundation velocities 1 – 8 m / s Triggered by variety of volcanic events

33. Augustine volcano, Cook Inlet, AK West Island debris avalanche, 500 yr old, viewed from summit of Augustine volcano Buried former coastline, traveled 5 km farther into Cook Inlet Generate tsunami waves that run 5 – 30 m above sea level at distances of 80 – 100 km

34. Tsunami at Krakatau, Sunda Straits, Indonesia Caldera collapse at Krakatau on 26 August 1883 Tsunami killed 36,000 people Travel times (hr) and maximum wave heights (m) as tsunami propagated along coastlines Maximum wave heights varied greatly depending on coastal aspect and morphology

35. Volcanic triggers of tsunamis Santorini Caldera collapse and pyroclastic flows into sea Wave height 10 - 50 m Travel distance 150 – 500 km Mount St. Helens, 18 May 1980 Debris avalanche into Spirit Lake caused tsunami Wave height 260 m Travel distance 4 km Lake Nyos, Cameroon Exhalative emission of CO2 Wave height 25 - 75 m Travel distance 5 km

36. Air shocks Up to 15-fold amplification of atmospheric pressure

37. Lightning Cloud-to-ground lightning from ash cloud Strikes related to quantity of tephra Electrostatic charge builds up from volcanic particles scraping against each other

38. Lightning at Mount St. Helens 30,000 acres of forest fires were ignited by lightning strikes from the eruption cloud on 18 May 1980

39. Volcanic gases and aerosols Water vapor a major component SO2 next most important Corrosive or reactive: SO2, H2S, HF, HCl CO2 in areas of low ground or poor drainage pH of associated rainwater may be 4.0-4.5

40. Gases and volcanic lakes Cold springs degas below thermally stratified lakes, allowing accumulation of gas Lake Monoun, 15 August 1984 Killed 39 people Lake Nyos, 21 August 1986 Killed ~1700 people Landslides may have triggered releases Gas denser than air Hugs ground, asphyxiating life in its path

41. Lecture 24: Volcanic hazards, II: Eruption response and mitigation Cultural theories: People as risk takers Individualist Egalitarian Hierarchist Fatalist Hermit Volcanic crisis management Risk identification Risk analysis Risk reduction Risk transfer Risk education The danger of living inside a paradigm Inquiry into breakthroughs Volcanic hazards: “What you don’t know you don’t know”

42. Cultural theories: Categories of people as risk takers Individualist Optimistic view—building codes have been improved, so risk is decreased Egalitarian Invokes precautionary principle, presses for urgent action Buildings are better but exposure is increasing (e.g., more people), so better land-use planning needed Hierarchist Everyone knows her/his place Things are about right as they are, but more research needed and more regulation required Fatalist Hopes for best, fears worst Whatever risk reduction is done, volcano will get you anyway Hermit What volcano?

43. Questions What type of risk taker are you? What type of risk takers are the volcanologists who work on active volcanoes? Possibility for a disconnect Individualist Optimistic view—building codes have been improved, so risk is decreased Egalitarian Invokes precautionary principle, presses for urgent action Buildings are better but exposure is increasing (e.g., more people), so better land-use planning needed Hierarchist Everyone knows her/his place Things are about right as they are, but more research needed and more regulation required Fatalist Hopes for best, fears worst Whatever risk reduction is done, volcano will get you anyway Hermit What volcano?

44. Stages of risk management Risk identification Risk analysis Risk reduction Risk transfer Risk education

45. Risk analysis Relative risk indices for volcanoes in Papua New Guineas for Volcanic Explosivity Index (VEI) = 4

46. Risk reduction Lahars Concrete levee designed to retain lahars from Mayon volcano, Philippines

47. Risk reduction Lahars Settling basins made of steel and concrete on slopes of Usu volcano, Hokkaido, Japan Retention ponds designed to impede the passage downstream of successively smaller boulders and trees Principle Reduce energy of flow Trap the larger material Reduce the volume

48. Risk reduction Ballistic ejecta Reinforced concrete shelter designed to resist impact of ballistic ejecta, Sakurajima, Kyushu, Japan

49. Risk education Lack of knowledge of hazards was an issue even with USGS scientists and managers Kraffts’ “disaster movies” helped Education of the decision makers and the public during the monitoring phase was a key issue at the Nevado del Ruiz disaster “Flujos de lodo (mudflow) just didn’t mean a thing to the people of Armero” --C. Newhall Confronting the issue for Pinatubo saved lives Kraffts’ “disaster movies” helped again

50. Response and mitigation of lava flows

51. Mount Etna, Sicily, Italy

52. Mount Etna, Sicily, Italy Slow-moving mafic lava flows Earthen barriers slowed lava flows but generally have not been successful Most effective control: diverting lava flows near the source, high on mountain, by breaching natural lava levees by excavation and blasting Began with eruption of 1991-1992 Saved village of Zafferana Etnea

53. Mount Etna diversion

54. Adjustments to risk Modify the hazard Not likely for volcanoes Modify vulnerability to hazards Land use planning Build diversions for lahars Risk transfer--distribute loss to wider community Insurance Disaster relief Most common form of adjustment made: Do nothing

55. “What you don’t know you don’t know” The danger of living inside a paradigm False sense of familiarity Decisions seriously affected by “What you don’t know you don’t know” Corollary: the Law of Unintended Consequences

56. Mount Unzen, 3 June 1991 French volcanologists Maurice and Katia Krafft, American volcanologist Harry Glicken, and 40 Japanese journalists were killed during emplacement of a pyroclastic flow What they knew Unzen produces small, though remarkably numerous (>5000), pyroclastic flows from Plinian column collapse Steep valleys on the volcano’s flanks channelize the pyroclastic flows Adjacent ridges provide tempting perches to view small pyroclastic flows

57. Pyroclastic flow from dome collapse at Mount Unzen What they didn’t know The flow could be larger in volume than earlier ones

58. Pyroclastic flow from dome collapse at Mount Unzen What killed them The flow was large enough to permit separation of glowing cloud from underlying glowing avalanche The cloud climbed the ridge, engulfing their viewpoint

59. The volcanologist and the public The balancing act Sounding the alarm to save lives The cost of false alarms False alarms Considerable monetary costs of evacuation, work loss, etc. May cause people not to act the next time an alarm is sounded

60. Lessons from the Armero catastrophe, Nevado del Ruiz, Columbia On the whole, the government acted responsibly But was not willing to bear the economic or political costs of early evacuation or a false alarm Science accurately foresaw the hazards But was insufficiently precise to render reliable warning of the crucial event at the last possible minute Crucial event occurred two days before the Armero emergency-management plan was to be critically examined and improved Thus bureaucratic delays to progress of emergency management over previous year also contributed to outcome

61. Special problem: Large eruptions Managing risks from low probability – high impact events Great difficulty in predicting Notoriously difficult for people to deal with rationally—before and after the latest (rare) event Analogies with fatalities at industrial accidents Compare the public and the government dealing with the 9/11 terrorist attack Before and after

62. A lesson from Mount St. Helens Great maps of distribution of eruptive products of last 4500 yr, and good knowledge of its 40,000 yr history Experts correctly predicted the ash distribution, the mudflows, the floods, and the pyroclastic flows But the experts couldn’t imagine a debris avalanche collapsing the mountain or the lateral blasts

63. Mount St. Helens lesson, cont’d The eruption involved a debris avalanche, followed about a minute later by a directed blast Neither previously was widely recognized volcanic processes The avalanche and directed blasts of the 18 May 1980 eruption were far more destructive than the pyroclastic flows and lahars, which had been most feared Scientists expected a clear warning of impending eruption, from leveling data, seismic monitoring, etc. None was recognized at the time Only 2 of the 57 fatalities occurred within the “red zone” of hazard maps

64. Question What about the next voluminous silicic, caldera-forming pyroclastic eruption? Something akin to an eruption that led to deposition of the Bishop tuff and collapse of the Long Valley caldera (or Yellowstone, etc.) There is no historical precedent for an eruption as voluminous and explosive—nothing even close to it

65. Magnitude of the problem Comparison of tephra volumes Note logarithmic scale

66. Mount St. Helens vs. Yellowstone

67. Question What is it that we “don’t know we don’t know” about silicic, caldera-forming pyroclastic eruptions?

68. Question What do you do—if anything—if you are concerned about what you don’t know you don’t know?

69. Breaking the cycle “What you don’t know you don’t know” could be something regarding volcanic hazards or It could be that you are looking for a scientific breakthrough in another area (even something personal, rather than technical)

70. Consider engaging in an inquiry Act as if, or pretending that, you really don’t know anything Purposefully approach the problem from an entirely different point of view Like an outsider would, like—or perhaps not like—a technically trained person from another field would approach it (a botanist, an astrophysicist) Work from first principles to see what might be possible Be creative Brainstorm about what might be possible, i.e., possible scenarios Effectively engage others creatively--in groups

71. Possible benefits Geologists have an easier time seeing what they’re looking for, rather than something they don’t expect Create hypotheses, then test them against evidence that you never thought to look for before Intentional breakthrough discovery vs. serendipitous discovery

72. Summary Cultural theories: People as risk takers Individualist Egalitarian Hierarchist Fatalist Hermit Volcanic crisis management Risk identification Risk analysis Risk reduction Risk transfer Risk education The danger of living inside a paradigm Volcanic hazards: “What you don’t know you don’t know” Inquiry into breakthroughs Next time: Volcanism and mineral deposits, I.