geos 470r/570r volcanology l24, 20 april 2015 handing out powerpoint slides for today volcano movie...

GEOS 470R/570R Volcanology

L24, 20 April 2015 Handing out

PowerPoint slides for today

Volcano movie night Pompeii, Wednesday, 29 Apr 2015, 6 pm

“I have found that most people are about as happy as they make their minds up to be.”

--Abraham Lincoln

Readings from textbook

For L24 from Lockwood and Hazlett (2010) Volcanoes—Global PerspectivesChapter 14

For L25 from Lockwood and Hazlett (2010) Volcanoes—Global PerspectivesChapter 15

Assigned reading

For L24, 20 April 2015Voight, B., 1990, The 1985 Nevado del Ruiz

volcano catastrophe: Anatomy and retrospection: Journal of Volcanology and Geothermal Research, v. 44, p. 349-386.

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.

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

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”

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

Intermediate I Rhyolite / gap / zoned intermediate

VTTS Tuff at Katmai-Novarupta “I-type magmas”

Zoned intermediateShikotsu, Mazama, Aso-4, Aniakchak, Krakatau,

Quizapu “I-type magmas”

Monotonous intermediateMonotony, Fish Canyon, Snowshoe Mountain, Mt.

Jefferson, Loma Seca “I-type magmas”

High-K calc-alkalic to shoshoniticEl Chichón, Egan Range, Absaroka

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)

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

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

Ultramafic

Carbonatite-nephelinite complexesOl Doinyo Lengai, Shombole

Primitive, silica-undersaturated, mafic to ultramaficLamprophyresLamproitesOrangeites and kimberlitesLimburgite

Komatiites

Definition of Risk

HazardAnnualized 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)

RiskHazard X Vulnerability = Risk

Blong, 2000, p. 1216

Stages of risk management

Risk identification Risk analysis Risk reduction Risk transfer

Blong, 2000

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

Blong, 2000, p. 1218

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

Blong, 2000, Table 1

P. Kresan

Ballistic ejecta

>10 km radius of vent High impact energies Densities <3 t / m3

Fresh bombs above ignition temperatures of many materials


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

Blong, 2000, Table 1; Pareschi et al., 2000

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

Fisher et al., 1997, Fig. 8-4

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

Blong, 2000, Table 1; Fisher, 1999, p. 98

Pyroclastic surges

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


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 reservoirsCrater 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

Waythomas et al., 1996

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


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

NOAA Mt Pinatubo-1991 Set, #16; photo by T.J. Casadevall, U. S. Geological

Survey

Jökulhlaups Can occur with little

or no warning Discharges may be

>100,000 m3 / s


Smellie, 2000, Fig. 3

Outburst flood (toe of glacier at top)

Rock and debris avalanches/ directed blast/sector collapse Sector collapse

Minimum volume of 10 – 20 m3

Transport Travel distances to >30 km

Deposits Cover an areas >100 km2

Emplacement velocities Up to 100 m / s

Create topography, pond lakes

Can produce tsunamis in coastal areas


Press and Siever, 2001, p. 111

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 PinatuboExacerbates other issues, like collapse of buildings

due to ash/water accumulations, as at Pinatubo

Modified from Blong, 2000, Table 1

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

Peterson and Tilling, 2000, Fig. 8

Ground deformation

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

From Table 1 of Blong, 2000

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

Fisher, 1999, Fig. 25

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

Fisher, 1999, Fig. 26

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

Modified from Blong, 2000, Table 1

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

Begét, 2000, Fig. 2

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 Begét, 2000, Fig. 3

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, CameroonExhalative emission of CO2

Wave height 25 - 75 m Travel distance 5 km

Air shocks

Up to 15-fold amplification of atmospheric pressure


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


Fisher et al., 1997, Fig. 8-1; photo by José Viramonte

Lightning, Volcán Cerro Negro 1971, Nicaragua

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


Gases and volcanic lakes

M. Barton

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

Crater lakes along Cameroon volcanic line: alkalic volcanoes parallel to Benue rift

Summary--Petrologic synthesis; Volcanic hazards, I.

Petrologic synthesis Broad spectrum of magma compositions on Earth are related to a

multidimensional continuum of Earth processes Unlikely that compositions map uniquely against single geologic settings

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, and lightning Volcanic gases and aerosols

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”

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?

Blong, 2000, p. 1216

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?

Stages of risk management

Risk identification Risk analysis Risk reduction Risk transfer Risk education

Blong, 2000

Risk analysis Relative risk indices for volcanoes in Papua New

Guineas for Volcanic Explosivity Index (VEI) = 4

Blong, 2000, Table II

Risk reduction

LaharsLateral dike made of

concrete designed to protect a town from lahars from Mayon volcano, Philippines

Blong, 2000, Fig. 2

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

Blong, 2000, Fig. 3

Risk reduction Ballistic ejecta

Reinforced concrete shelter designed to resist impact of ballistic ejecta, Sakurajima, Kyushu, Japan

Blong, 2000, Fig. 4

Risk education

Lack of knowledge of hazards was an issue even with USGS scientists and managersKraffts’ “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

Response and mitigation of lava flows

Fisher et al., 1997, Table 7-1

Mount Etna, Sicily, Italy

R. Decker

Mount Etna

National Geographic, Feb. 2002

Sampling lava at Mt. Etna

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 Fisher et al., 1997, Fig. 7-3; adapted from Barberi et al., 1993

Mount Etna diversion

Peterson and Tilling, 2000, Fig. 10

Adjustments to risk

Modify the hazardNot likely for volcanoes

Modify vulnerability to hazardsLand use planningBuild diversions for lahars

Risk transfer--distribute loss to wider community InsuranceDisaster relief

Most common form of adjustment made: Do nothing

Blong, 2000, p. 1216

“What you don’t know you don’t know”

The danger of living inside a paradigmFalse sense of familiarityDecisions seriously affected by “What you

don’t know you don’t know”Corollary: The Law of Unintended

Consequences

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


Pyroclastic flow from dome collapse at Mount Unzen What they didn’t know

The flow could be larger in volume than earlier ones

Fisher et al., 1997, Fig. 5-5B

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

Fisher et al., 1997, Fig. 5-5A

The volcanologist and the public

The balancing actSounding the alarm to save livesThe cost of false alarms

False alarmsConsiderable monetary costs of evacuation,

work loss, etc.May cause people not to act the next time an

alarm is sounded

Nevado del Ruiz, Columbia Prediction of possible types of emplacement modes

during imminent eruption

Schmincke, 2004, Fig. 13.14

Nevado del Ruiz, Columbia Actual results of eruption, 13 Nov 1985

Very minor tephra fallout fan Deadly lahars in lower reaches of Río Guali Río Lagunillas


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 the catastrophic outcome


Voight, 1990

Pinatubo

Maps, at similar scales, ofPrediction (made on 23 May 1991)Actual eruption (15 June 1991)


Special problem: Large eruptions

Managing risks from low probability – high impact eventsGreat difficulty in predictingNotoriously 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 attackBefore and after

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 historyExperts 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

Mount St. Helens lesson, cont’d The eruption involved a debris avalanche,

followed about a minute later by a directed blastNeither previously was a widely recognized volcanic

processThe 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

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

Magnitude of the problem

Comparison of tephra volumes Note logarithmic

scale

Simkin and Siebert, 2000, Fig. 6

Mount St. Helens vs. Yellowstone

Cas and Wright, 1987, Fig. 5.8; after Sarna-Wojcicki et al., 1981


Measurable ash fallout from three eruptions from Yellowstone since 2.2

Ma covered more than half of US

For comparison, dispersal of ash from 18 May 1980 eruption of

Mount St. Helens

Question

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

Question

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

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)

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 viewLike 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 creativeBrainstorm about what might be possible, i.e., possible

scenariosEffectively engage others creatively—in groups

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

Summary Cultural theories: People as risk takers

Individualists, egalitarians, hierarchists, fatalists, and hermits

Respond differently; require different strategies to engage Volcanic crisis management

Risk identification (volcanologists) Risk analysis (engineers and scientists) Risk reduction (government: building codes, land use

planning, physical diversions) Risk transfer (policy makers, insurers) Risk education (public servants and others)Most common form of risk adjustment made: Nothing

The danger of living inside a paradigm Volcanic hazards: “What you don’t know you don’t know” Inquiries may lead to breakthroughs

Next time: Volcanism and mineral deposits, I.

geos 470r/570r volcanology l24, 20 april 2015 handing out powerpoint slides for today volcano movie...

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