Volcanology: State of the Science Eruption Analogues for Yucca Mountain

Stephen Sparks, University of Bristol, UK

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Talk OutlinePart 1: Advances in volcanology and prediction

• Case studies (Soufrière Hills example)

• Monitoring

• Modeling and prediction

Part 2: Volcanic analogues for Yucca Mountain

• 1973 Eldfell eruption, Iceland

• Etna lava rheology

• 1989 Lonquimay eruption, Chile

• Pyroclastic flows on Montserrat

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Case studies: Soufrière Hills

volcano, Montserrat

Lesser Antilles Arc

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Soufrière Hills Volcano

1995 to now

Hornblende Andesite

Lava Dome

• 0.7 km3 erupted so far

~3 m3/s

• extrusion viscosity

~ 1010 to 1012 Pa s

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Deformation and Extrusion 5

Numerical models of

conduit flow with degassing

and crystallization

Cyclic Volcanism

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Basic set of parameters

1 and 10 km3 chambers at 5 km depth

Input 2 m3/s

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Overpressure upper conduit: explanation for shallow

earthquakes, ground deformation, and explosions?

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Eruption of Eldfell, Iceland, 1973

Volcanic blast of Soufrière Hills

Analogues for

Yucca Mountain?

Lonquimay lava, Chile, 1989

Etna lava rheology

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Eldfell eruption, 1973

Heimaey Island, Iceland

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Chronology of 1973 Eldfell Eruption

22 January Earthquakes (~ 20 km depth?) 1.6 km fissure

opens at 0140

23 January Active fissure starts to focus

24 January Eruption at most intense; eruption

columns 8-9 km (500-800 m3/s); lava observed

26 January Fissure lengthens to 3 km; but activity focused

31 January Cone builds to 180 m high; intense

fire fountains; eruption rate 50-150 m3/s

4 February Lava flows into harbour; explosivity reduced

9 February Lava covers 2 km2 and eruption largely

extrusive; persistent Strombolian activity

25 February Temporary halt of lava

2-30 March Lava flows into NW of town; water cooling

starts on 8 March

April Lava flows to east

26 May Eruption north of Heimaey in ocean

July Eruption officially declared over

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23 January: Early fissure

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24 January: focusing of activity

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Gas Segregation

Mechanisms

Extrusion of degassed

lava and explosive activity

are simultaneous

Yuri Slezin

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31 January: cone largely built and extensive lava

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Tephra volume 0.02 km3

Lava volume 0.23 km3

Eruption Facts18

Destruction and

Protection of Houses

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Data on Eruption Jet Speeds

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Etna 1975 Trachybasalt lavas

• 50% phenocrysts + microlites

• Temperature 1070oC

• Extrusion viscosity ~ 105 Pa s

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Lonquimay, Chile, 1989

Mafic andesite ~1000oC

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Volcanic Blast at Soufrière Hills Volcano

26 December 1997

20 m/s

40 m/s

90 m/s

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20 m/s 40 m/s

Structures impacted by multiphase flows at ~50-150 m/s

Pyroclastic Flow Analogue

60-90 m/s

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Lessons for Yucca Mountain

• Intense explosive eruptions dominate

for ~ 1 week, but with lava effusion

• Discharge of explosive jet at hundreds

of m3/s and up to 200 m/s speed

• Wet magma starts < 1000oC, erupts

1030-1055oC: latent heat of crystallization

• Wet trachybasalt lava extrude with

viscosity ~104-105 Pa s

• Flow front evolves to aa (µ < 107 Pa s)

and blocky lava (µ = 107 to 1010 Pa s)

• Buildings destroyed by aa

• High speed gas-particle flows can be

highly destructive

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DisclaimerThis presentation was prepared to document work performed by the Center for Nuclear Waste Regulatory Analyses (CNWRA) for the Nuclear Regulatory Commission (NRC) under Contract No. NRC–02–02–012. The activities reported here were performed on behalf of the NRC Office of Nuclear Material Safety and Safeguards, Division of Waste Management. This presentation is an independent product of the CNWRA and does not necessarily reflect the view or regulatory position of the NRC.

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