Lecture 1 Understanding and forecasting unrest at fast

Lecture 1 Understanding and forecasting unrest at fast and slow volcanoes

Fast volcanoes These commonly re-activate, erupt, and quieten in a short period of time. Their magmas are commonly mobile (hot, crystal-poor, volatile-rich, and bubbly). Examples include Krakatau 1883, Mt. St Helens 1980, and Pinatubo 1991.

Slow volcanoes These systems are restless for years to decades. Their magmas tend to be sluggish (crystalrich and degassed). Examples include Nevado de Ruiz in Colombia and Popocatépetl in Mexico.

Fast vs slow Both types of systems accelerate and decelerate. But their rates are vastly different, posing particular problems in each case.

Triggers Inputs of deep (mafic) magma Tectonic earthquakes

Chaitén Soufrière Hills Turrialba Merapi Chaitén

Eruptive sequence A series of plinian eruptions in early May 2008, with rapid rise of mobile magma Explosive-effusive activity later in May 2008 Then emplacement of a lava dome until late 2009 or earliest 2010

Chaitén erupting explosively and effusively on 26 May 2008 photo courtesy U. S. Geological Survey

Chaitén lava dome photographed on 24 Jan 2010 Pallister et al. 2013, Andean Geology 40: 227 -294

Precursory activity at Chaitén Published reports suggest that felt earthquakes began on 30 April, one day before the eruption. However, local accounts may indicate that earthquakes were felt in Chaitén town as early as January 2008. Earthquakes were recorded in 2004 -2005.

Lava dome growth as a function of time at Chaitén Pallister et al. 2013, Andean Geology 40: 227 -294

Magma plumbing beneath Chaitén Michimahuida volcano Liquiñe-Ofqui fault zone Wicks et al. , 2011, Nature 478: 374 -378

Merapi Soufrière Hills Turrialba Merapi Chaitén

Merapi erupting in early November 2010, with before and after images Images courtesy BRGM

Summit deformation in September-October 2010 Surono et al. , 2012, J. Volcanol. Geotherm. Res. 241 -242: 121 -135

Types of volcanic earthquakes (long-period earthquake) Courtesy USGS

Seismicity at Merapi, late 2010 Lava dome growing Surono et al. , 2012, J. Volcanol. Geotherm. Res. 241 -242: 121 -135

SO 2 fluxes lava dome Surono et al. , 2012, J. Volcanol. Geotherm. Res. 241 -242: 121 -135

Tectonic triggering of eruptions Volcano station Distant station Surono et al. , 2012, J. Volcanol. Geotherm. Res. 241 -242: 121 -135

Soufrière Hills Turrialba Merapi Chaitén

5 km Courtesy NASA

Courtesy NASA

Escalating activity at Soufrière Hills, 19951997 Aug-Oct explosions 18 Sept explosion May-June pf activity July-Aug activity Collapse and blast 1996 1997 Sparks et al. 1998, Geophys. Res. Lett. 25: 3421 -3424

July-August 1996 activity – precursors to the first explosive eruption

19 August 1997 vulcanian eruption Courtesy The Atlantic

Deformation, seismicity, and vulcanian eruptions, August 1997 C = large dome collapse P = weak explosion E = vulcanian eruption Druitt et al. , 2002, Geol. Soc. London Mem. 21: 281 -306

Turrialba Soufrière Hills Turrialba Merapi Chaitén

Summit region of Turrialba prior to 1996 Courtesy Smithsonian Institution

p. H of fumarole condensates, 1992 -2009 Martini et al. , 2010, J. Volcanol. Geotherm. Res. 198: 416 -432

SO 2 fluxes from Turrialba, 2008 -2012 Conde et al. , 2014, Int. J. Earth Sci. 103: 1983 -1998

Carbon/sulfur ratios and SO 2 fluxes, 2014 -2015 De Moor et al. , 2016, J. Geophys. Res. 121: 5761 -5775

Carbon isotopes of gas at Turrialba, April 2014 Soil gases High-T vents plume atmosphere Malowany et al. , 2017, G-cubed

May 2016

In summary…

Fast volcanoes - Long repose periods - High magmatic water contents (~7 wt. %) - Fast magma ascent - Large eruptions - Rapidly decaying activity afterward - Mobile magmas Are there signs of re-activation well in advance (i. e. , years) of eruption ?

Climactic eruption pre-climactic post-climactic ? Chaitén 2008 1 year Merapi 2010 Mt. St. Helens 1980 Mt. Pinatubo 1991 Krakatau 1883 Cordón Caulle 2011 ~2 years 0. 5 El Chichón 1982 0. 1 1 Years 5

Slow volcanoes - Lower magmatic water (~3 wt. % ? ) - Slow ramping up - Slow magma ascent - progressive structural opening

Popocatépetl, Mexico, volcanotectonic seismicity, 1990 -1994 De la Cruz-Reyna et al. , 2008, Bull. Volcanol. 70: 753 -767

Popocatépetl, Mexico, SO 2 fluxes, 1994 -1997 First lava dome First eruption Delgado-Granados et al. , 2001, J. Volcanol. Geotherm. Res. 108: 107 -120

FAST SLOW PINATUBO ’ 91 shallow dacitic reservoir shallow reservoir plexus mid-crustal reservoirs ascent of mafic magma MOHO deep (28 -35 km) long-period earthquakes

Some summary thoughts For fast volcanoes, their short precursory period is problematic forecasting For slow volcanoes, their initiation and termination can be difficult to identify

Seismic forecasting

White and Mc. Causland, 2016, J. Volcanol. Geotherm. Res. 309: 139 -155

Cumulative VT energy (a) energy FAST large eruption Time (weeks to months) (b) SLOW energy small eruptions Time (years)

Gas forecasting

Mt. St. Helens, 10 April 1980 courtesy USGS

Turrialba 2014 -2015 De Moor et al. , 2016, J. Geophys. Res. 121: 5761 -5775

Cumulative VT energy (a) FAST energy H 2 S/SO 2 large eruption Time (weeks) (b) CO 2/SO 2 energy SLOW small eruptions Time (years)

Turrialba, May 2016

Masaya volcano, Nicaragua courtesy

5 May 2017 at Masaya volcano, Nicaragua

CO 2/SO 2 = 4. 02, R 2 = 0. 91