1. 25 major crises 25 major crises Infrastructure in 12 countries Infrastructure in 12 countries (FY-03-11): 54 infrastructure missions, 12 crisis responses, 15 countries 2011: VDAP’s 25th Year

2. 25 major crises 25 major crises Infrastructure in 12 countries Infrastructure in 12 countries (FY-03-11): 54 infrastructure missions, 12 crisis responses, 15 countries 2011: VDAP’s 25th Year Distal VT’s H 2 O expulsion SO 2 drop EQ patterns (dVT-LF-hybrid-tremor) H 2 S to SO 2 CO 2 pulse Drumbeats Geodetic trends Magma type & texture Eruption rates RSAM trends Well levels Cl & F Distal VT’s EQ patterns (dVT-LF-hybrid-tremor) RSAM trends

3. The case for a process-oriented guide to forecasting explosive eruptions (at stratovolcanoes) Part 2. Frequently active volcanoes … “Difficult (or easier?) to predict eruptions. Fortunately most are <<VEI 4” John Pallister for the VDAP team (past and present): Randy White, Wendy McCausland, Andy Lockhart, Jeff Marso, John Ewert, Chris Newhall, C. Dan Miller, Rick Hoblitt, John Power, Tom Murray, Dave Harlow, Marvin Couchman, Julie Griswold, Gari Mayberry, Dave Schneider, Steve Schilling, Angie Diefenbach

4. Eruption possible (magma/fluids moving in crust) Magmatic eruption likely (magma & gas have reached shallow levels) High VEI (indicated by large volumes of gas-rich viscous magma and rapid ascent) Low VEI – (indicated by smaller volumes of gas-poor low-viscosity magma, and slow ascent No eruption (yet) … intrusion stalled…end of crisis ForecastSeismicDeforma -tion GasObserva- tions & history Petrology Tables of common indicators for likelihood and explosivity… based on VDAP experience Sudden changes (+/-) from background RSAM level (background may include: proximal VT’s, LF’s, tornillos, tremor, explosion signals)… Distal VT’s possible, but with cumulative M<4). Deformation localized near summit/vent areas. Little regional deformation unless unusually large batch of magma CO2 increase = deep degassing & early warning. SO2 increase if hot pathway, otherwise may be scrubbed and replaced by H2S or sudden decrease in emissions Steam emissions, phreatic eruptions, fractures opening. Water levels in nearby wells may change Rapid, steep increase in RSAM from background level (e.g., <1 week in some cases), LF/explosion signal followed by tremor typical. VT’s may/may not occur. Slower ramp-up in other cases (previous eruptions provide guides. Hybrid & drum-beat quakes may be detected and indicate magma rising Accelerating deformation of summit as eruption approaches SO2 & Cl emissions increase and SO2/H2S increases as magma rises and pathway dries out. Emissions may drop shortly before eruption if pathway obstructed More vigorous steam emissions & phreatic/ phreatomagmatic eruptions or sudden stoppage of observed emissions Initial tephra mainly composed of lithic debris, glass shards may or may not be present. Juvenile component minor but typically difficult to identify. (Petrology not diagnostic) Higher & more rapid increase in RSAM than past small eruptions, (including VT’s ), continued increase after initial vent clearing phreatic/ phreatomagmatic eruptions.. Escalating explosion signals and/or tremor precede biggest event(s) Deformation of greater magnitude and rate that past small eruptions Relatively large gas flux, especially following initial “vent clearing” events. Emissions may drop shortly before eruption if pathway obstructed. Early CO2 pulse may be 1 st warning of recharge and high VEI History includes larger multi-phase eruptions, and hydrous minerals. Initial phase of current activity explosive instead of extrusive. Unusually high extrusion rates (for initial phases) Tephra or lava from initial eruptions may contain gas-rich indicators (high volatiles in glass inclusions, bubble-wall shards, volatile-rich indicator minerals, e.g., hb). Silicic magma composition. These are only permissive indicators as gas-rich magma may not yet be shallow RSAM moderates & decreases after initial vent clearing events. Return to background levels, may take weeks Deformation ends or decreases, e.g., after initial explosions or lava (dome) erupted Gas emissions fall to background levels after initial vent clearing events and in parallel with seismic decrease History of small eruptions (no big PF sheets or thick tephra deposits). Eruptions may be “slow:” e.g., peak dome collapse weeks to months after onset of episode Early-erupted juvenile component degassed (microcrystalline, lacks volatile- rich indicator minerals or they have thick decompression rims = slow ascent). Magma is mafic (non-exclusive) Seismicity dies out after initial emissions Deformation ends, local deflation near vent Gas emissions drop to background levels Steam emissions or back to background No single indicator is conclusive! Synthesize! Don’t try to read this part, I will blow it up!

5. ForecastSeismicDeforma- tion GasObservations & history Petrology Magmatic eruption possible (magma/fluids moving in crust) Background level exceeded. Distal VT's as tectonic faults are pressurized and magma rises. VT number & energy increasing as magma rises. VT energy release often approaches or exceeds M4. (Spurr only M3). Also many intrusions stall without eruptions! Inflation detected = early warning; may be large. Broad (deep sourced) deformation CO2 increase = deep degassing, may provide early warning Hydrothermal system & fumaroles present but not necessarily elevated over background levels. Past history of explosive eruptions. (Montserrat no steaming). Water levels in wells may drop (e.g., due to dilatation) Products of past eruptions give range of most likely magma types and explosivity Magmatic eruption likely (magma & gas have reached shallow levels) Transitional from distal to proximal VT's as magma shallows. LF's and tremor appear and increase as hydrothermal system boils off & gas escapes. Hybrid earthquakes as magma continues to ascend. Tungurahua (1999) = exception… tremor & distal VT’s only… Localized deformation near summit/vent areas detected as magma rises into edifice. High and/or accelerating rate of deformation SO2 & Cl emissions increase and SO2/H2S increases as magma rises and system dries out. Gas emissions drop shortly before eruption if quenched- or silica- cap forms Steam emissions, phreatic and/or phreatomagmatic eruptions.. Water levels in wells may rise as magma/gas pressurizes aquifers or or fall as new fractures open. Geysering possible Initial tephra mainly composed of lithic debris; glass shards may or may not be present. Juvenile component minor but may be difficult to identify High VEI (favored by large volumes of gas- rich viscous magma and rapid ascent) High and rapidly increasing rate of seismic energy release (RSAM), usually includes large LF earthquakes. RSAM continues to increase after initial vent clearing emissions/phreatic /phreatomagmatic eruptions (may pause first). Swarms of deep LP’s or deep tremor indicate significant magmatic replenishment. Escalating explosion signals. Deformation may be broad, may include fracturing of summit, flank destabilization (e.g., “bulge”). Dike intrusion indicated Large gas flux following initial “vent clearing” events or emissions decrease abruptly while seismicity still high. Emissions from multiple /distributed vents… High VEI statistically more likely for “reawakening” volcanoes. History of large eruptions (e.g., big PF sheets, thick tephra, pumiceous deposits, fragmental pumices). Initial mingled magma eruption may indicate new intrusive trigger Tephra or lava from initial eruptive phase may contain gas-rich indicators (e.g., bubble-wall shards, high volatiles in glass inclusions, volatile-rich indicator minerals, e.g., hb). Silicic magma composition. Low VEI (favored by smaller volumes of gas-poor low- viscosity magma, and slow ascent RSAM moderates after initial vent clearing events or earlier large-RSAM crisis indicating earlier emplacement and degassing of shallow intrusion. (Beware: Pinatubo did the above in April, 1991, main eruption was in June). Slow growth and low M of LF or hybrid seismicity Deformation ends or decreases after initial vent-clearing events. Gas emissions fall or moderate after initial vent clearing events while seismicity decreasing or constant History of small eruptions, no extensive PF sheets or thick tephra deposits Early-erupted juvenile samples degassed (microcrystalline, lack volatile-rich indicator minerals or thick decompression rims = slow ascent). Mafic magma composition (non-exclusive) No eruption (yet) …or end (intrusion stalls) Seismicity returning to background levels gradually and stays there for ~ 2 months. Note that many intrusions stall without eruptions. Deformation ends, deflation may occur Gas emissions dropping to background levels Steam (H2O) emissions dominate Long-dormant (closed systems): No eruptions in many decades or centuries (e.g., MSH 1980, El Chichon 1982, Pinatubo 1991, Garbuna 2004, Huila 2007, Chaitén, 2008, Sinabung 2010, Vesuvius (0079, 0472,1631), Tambora (2011?)) See McCausland et al. poster for long-dormant systems matrix

6. 1. Controls on likelihood and explosivity of eruptions 2. Simplified conceptual model of magma ascent 3. Types of frequently-active stratovolcanoes 4. Multi-parameter forecasting guide for frequently- active volcanoes (matrices) 5. Event/probability trees & need for WOVOdat But first, some context.

7. Increasing explosivity Increasing probability of explosive eruption Gas content (saturation, separation of fluid phase, rate of bubble growth) Ascent rate (controlled by gas pressure, buoyancy, path effects*) Viscosity (controlled by composition, Complexly inter-dependent variables that control explosivity of eruptions Increasing gas content, ascent rate, & viscosity * Path effects include strength and permeability of wall rocks (gas loss), tectonic setting and state of stress, etc. Low viscosity & low to moderate gas content, moderate to high ascent rate = low explosivity (e.g., basalt shields) High gas content, high ascent rate & high viscosity = highly explosive (VEI >4) Most common at long-dormant volcanoes (moderate to large volume closed systems (e.g., Krakatoa 1883; Katmai 1912, Bezymianny 1956; MSH 1980, Pinatubo 1991; Hudson 1991; Chaitén, 2008; Kasatochi, 2008) Very high viscosity = uneruptable magma, intrusion stalls, gas escapes Garbuna 2005-06 Explosive fragmentation

8. Increasing explosivity Increasing probability of explosive eruption Gas content & Ascent rate Viscosity (controlled by composition, Complexly inter-dependent variables that control explosivity of eruptions at frequently active* (open-system) volcanoes Increasing gas content, ascent rate, & viscosity Typical: Low gas, high viscosity & slow ascent: typically andesite to dacite low-explosivity (VEI 1-3) domes & spines; & stalled intrusions (Domes: MSH 1981-86, Merapi 1967-2006, SHV 1995-present,, Huila 2008-present, Soputan 2000- 2007, Popocatepetl 1995-2005+, Unzen (1991-95), Usu (1910, 1944, 1977-80, 2000), Kelut, 2007; MSH 2004-2008. Stalled intrusions: Garbuna, 2003-04, Taal 1987-89, 92, 94, 2004, 06, 07, 11; Cotapaxi, 2001-03, Turrialba 2002-present) Spurr 2003-05, Three Sisters 1997-2007, Peulik 1996-98, Baker 1975, Fuji 2001, many others Exceptional: High gas, high viscosity, and rapid ascent or unloading: explosive (VEI 3-4+) basalt to andesite explosive eruptions (Merapi, 2010, 1872; Masaya, 1754; also Taal 1977, Villarrica 1810, Pichincha, Soputan, 2008, others) * One or more eruptions in past 1-3 decades

9. ~4 wt.% H 2 O (dissolved) > ~ 70 vol.% bubbles (gas fraction >0.7 = explosive fragmentation) ~4 wt.% H 2 O (dissolved) < ~ 70 vol.% bubbles (e.g., 0.1 wt% H 2 O) Volatile loss during ascent* vs. Eruption likelihood & explosivity: “It’s all about volatile loss during ascent” * Volatile loss = crystallization & increased viscosity. Requires permeable magma (fractures, foam), & permeable wall rocks, and/or convection w/in conduit

10. Frequently erupting “Open-Systems” (Hot pathways for gas & magma ascent. Most eruptions smaller than at long-dormant) Mostly basaltic to basaltic andesite, e.g., Stromboli, Etna, Soputan since 2007, Mayon, Fuego, Arenal, Villarrica, Pavlof, Shishaldin, etc. 1. Wide open Continuously open conduit; filled with low viscosity magma; gas escapes at shallow levels and through Strombolian eruptions; shallow crystallization may produce viscous magma & Vulcanian eruptions 2. Semi-steady state dome extrusions e.g., Merapi since 1968, Karangetang since 1970? Santiaguito since 1922, Popo since 1996, Bezymianny since 1956 Huila since 2008 Conduit mostly open; gas partly escapes during ascent; & magma viscosity increases, may occasionally solidify at shallow levels. Larger or more gas-rich magma batches produce Vulcanian eruptions 3. Degassed dome & spine extrusions e.g., MSH 2004-08, Kelut 2007 Conduit only open at depth; shallow levels solidify; most gas escapes during ascent, produces high- viscosity degassed magma

11. 1. HF Volcano-tectonic (dVT & VT’s); +/- DLPs 2. LF Low-frequency earthquakes, explosions, + hybrids 3. Volcanic tremor (+/- hybrids) Typical progression in earthquake types (long-dormant systems) Pinatubo examples Regional fault Long-dormant volcanoes provide context for evaluating frequently active systems 1. Deep: CO2, deformation, recharge? 2. Shallow: H 2 S, SO 2, Cl & deformation

12. RSAM - Real-time Seismic Amplitude Measurment Example from Volcan Huila, Colombia; courtesy of INGEOMINAS Real-time tools for analysis and forecasting Long dormant before 2007; frequently active dome extrusion since 2008 Belalcázar ■ 0 15 km Rio Simbola Rio Páez

13. Eruption possible (magma/fluids moving in crust) Magmatic eruption likely (magma & gas have reached shallow levels) High VEI (indicated by large volumes of gas-rich viscous magma and rapid ascent) Low VEI – (indicated by smaller volumes of gas-poor low-viscosity magma, and slow ascent No eruption (yet) … intrusion stalled…end of crisis ForecastSeismicDeforma -tion GasObserva- tions & history Petrology Tables of common indicators for likelihood and explosivity… based on VDAP experience Sudden changes (+/-) from background RSAM level (background may include: proximal VT’s, LF’s, tornillos, tremor, explosion signals)… Distal VT’s possible, but with cumulative M<4). Deformation localized near summit/vent areas. Little regional deformation unless unusually large batch of magma CO2 increase = deep degassing & early warning. SO2 increase if hot pathway, otherwise may be scrubbed and replaced by H2S or sudden decrease in emissions Steam emissions, phreatic eruptions, fractures opening. Water levels in nearby wells may change Rapid, steep increase in RSAM from background level (e.g., <1 week in some cases), LF/explosion signal followed by tremor typical. VT’s may/may not occur. Slower ramp-up in other cases (previous eruptions provide guides. Hybrid & drum-beat quakes may be detected and indicate magma rising Accelerating deformation of summit as eruption approaches SO2 & Cl emissions increase and SO2/H2S increases as magma rises and pathway dries out. Emissions may drop shortly before eruption if pathway obstructed More vigorous steam emissions & phreatic/ phreatomagmatic eruptions or sudden stoppage of observed emissions Initial tephra mainly composed of lithic debris, glass shards may or may not be present. Juvenile component minor but typically difficult to identify. (Petrology not diagnostic) Higher & more rapid increase in RSAM than past small eruptions, (including VT’s ), continued increase after initial vent clearing phreatic/ phreatomagmatic eruptions.. Escalating explosion signals and/or tremor precede biggest event(s) Deformation of greater magnitude and rate that past small eruptions Relatively large gas flux, especially following initial “vent clearing” events. Emissions may drop shortly before eruption if pathway obstructed. Early CO2 pulse may be 1 st warning of recharge and high VEI History includes larger multi-phase eruptions, and hydrous minerals. Initial phase of current activity explosive instead of extrusive. Unusually high extrusion rates (for initial phases) Tephra or lava from initial eruptions may contain gas-rich indicators (high volatiles in glass inclusions, bubble-wall shards, volatile-rich indicator minerals, e.g., hb). Silicic magma composition. These are only permissive indicators as gas-rich magma may not yet be shallow RSAM moderates & decreases after initial vent clearing events. Return to background levels, may take weeks Deformation ends or decreases, e.g., after initial explosions or lava (dome) erupted Gas emissions fall to background levels after initial vent clearing events and in parallel with seismic decrease History of small eruptions (no big PF sheets or thick tephra deposits). Eruptions may be “slow:” e.g., peak dome collapse weeks to months after onset of episode Early-erupted juvenile component degassed (microcrystalline, lacks volatile- rich indicator minerals or they have thick decompression rims = slow ascent). Magma is mafic (non-exclusive) Seismicity dies out after initial emissions Deformation ends, local deflation near vent Gas emissions drop to background levels Steam emissions or back to background No single indicator is conclusive! Synthesize! Don’t try to read this part, I will blow it up!

14. ForecastSeismicDeformationGasObservations & history Eruption possible (magma/ fluids moving in crust) Sudden changes from background RSAM level (background may include: proximal VT’s, LF’s, tornillos, tremor, explosion signals) Distal VT’s possible, but with cumulative M<4) If detected, localized near summit/vent areas. No regional deformation unless unusually large batch of magma Increase in fumarolic activity. Steam (H 2 O) emissions; S-species mainly scrubbed (H 2 S). May see sudden changes in emissions as pathways open & close. Increase in CO 2 = deep degassing (beware large pulse) Water levels in nearby wells change. Small increase in “background” monitoring data over periods of months Open (frequently active) systems: Repeated eruptions during the past 1-3 decades “Eruption Possible”

15. Open (frequently active) systems: Repeated eruptions during the past 1-3 decades “Magmatic eruption likely” ForecastSeismicDeforma- tion GasObserva- tions & history Petrology Magmatic eruption likely (magma & gas have reached shallow levels) Rapid & steep increase in RSAM from background level (e.g., <1 week in some cases), LF/explosion signal followed by tremor typical. VT’s may/may not occur. Slower ramp-up in some cases (previous eruptions provide guides). Hybrid & drum-beat quakes may be detected and indicate magma rising Accelerating deformation of summit as eruption approaches SO 2 & Cl and SO 2 /H 2 S increase as magma rises and pathway dries out. Emissions may drop shortly before eruption if pathway obstructed More vigorous steam emissions & phreatic/ phreato- magmatic eruptions or sudden stop of observed emissions (= capped & pressurizing) Initial tephra mainly lithic debris, glass shards may or may not be present. Juvenile component minor but typically difficult to identify. (Petrology not diagnostic) 10-minute RSAM Calendar date VEI 3 eruption of Soputan, 6 June 2008 Little time for warning

16. Open (frequently active) systems: Repeated eruptions during the past 1-3 decades “Low-moderate VEI” (e.g., VEI 2-3) ForecastSeismicDeforma- tion GasObservations & history Petrology (retrospective) Low VEI – (smaller volumes of gas-poor low- viscosity magma and slow ascent) RSAM moderates & decreases after initial vent clearing events. Return to background levels, may take weeks Deforma- tion ends or decreases, e.g., after initial explosions or lava (dome) erupted Gas emissions fall to near background levels after initial vent clearing events and in parallel with seismic decrease History of small eruptions (no big PF deposits or thick tephra deposits). Eruptions may be short duration or long, e.g., peak dome collapse weeks to months after onset of episode Early-erupted juvenile component degassed (microcrystalline, lacks volatile-rich indicator minerals or they have thick decompression rims = slow ascent. Magma mafic & xtal-poor ) 2008 microcrystalline basalt from VEI 2 eruption of Soputan (can be more explosive with higher gas)

17. Open (frequently active) systems: Repeated eruptions during the past 1-3 decades “High VEI” “High VEI” (e.g., VEI 4 “100-year” eruptions) ForecastSeismicDeforma- tion GasObserva- tions & history Petrology High VEI (favored by large volumes of gas-rich viscous magma and rapid ascent Higher & more rapid increase in RSAM than past small eruptions, (including VT’s ), continued increase after initial vent clearing phreatic/ phreatomagmatic eruptions.. Escalating explosion signals and/or tremor precede biggest event(s) Deformation of greater magnitude and rate that past small eruptions Relatively large gas flux, especially following initial “vent clearing” events. Emissions may drop shortly before eruption if pathway obstructed. Early CO 2 pulse & high CO 2 /SO 2 (early warning of recharge and high VEI) History includes larger multi-phase eruptions, and hydrous minerals. Initial phase of current activity explosive instead of extrusive. Unusually high extrusion rates (for initial phases) Tephra or lava from initial eruptions may contain gas-rich indicators (high volatiles in glass inclusions, bubble- wall shards, volatile- rich indicator minerals, e.g., hb). Evidence of separate gas phase at depth

18. Open (frequently active) systems: Repeated eruptions during the past 1-3 decades “High VEI” “High VEI” (e.g., VEI 4 “100-year” eruptions) ForecastSeismicDeforma- tion GasObserva- tions & history Petrology (mostly retrospective) High VEI (favored by large volumes of gas-rich viscous magma and rapid ascent Higher & more rapid increase in RSAM than past small eruptions, (including VT’s ), continued increase after initial vent clearing phreatic/ phreatomagmatic eruptions.. Escalating explosion signals and/or tremor precede biggest event(s) Deformation of greater magnitude and rate that past small eruptions Relatively large gas flux, especially following initial “vent clearing” events. Emissions may drop shortly before eruption if pathway obstructed. Early CO 2 pulse & high CO 2 /SO 2 (early warning of recharge and high VEI) History includes larger multi-phase eruptions, and hydrous minerals. Initial phase of current activity explosive instead of extrusive. Unusually high extrusion rates (for initial phases) Tephra or lava from initial eruptions may contain gas-rich indicators (high volatiles in glass inclusions, bubble- wall shards, volatile- rich indicator minerals, e.g., hb). Evidence of separate gas phase at depth. Silicic magma composition. 2010 Merapi basaltic andesite block

19. Open (frequently active) systems: Repeated eruptions during the past 1-3 decades ForecastSeismicDeformationGasObservations & history No eruption (yet) … end of crisis Seismicity dies out after initial emissions Deformation ends, local deflation near vent Gas emissions drop to background levels Steam emissions or back to background

20. Key differences in eruption & explosivity indicators at frequently- active vs. long-dormant volcanoes Frequently-active volcanoes have: “Leaky” hot pathways (conduits, fractures) for gas and magma ascent – this typically translates into: History of mainly small to moderate VEI eruptions (vs. large PF sheets) More rapid progression from heightened unrest to eruption Lower M seismicity (e.g., M4) & lower RSAM Missing seismic types (e.g., VT’s) possible compared to common long- dormant sequence (DVT & VT – LF – Hybrid – Tremor) Deformation mainly shallow & more localized Gas dominated by shallow- (Cl, F, SO 2 ) vs deep (CO 2 ) degassing species (unless “100-year” eruption) Quick progression from scrubbed (H 2 S) to dry (SO 2 ) species Generally more mafic magmas; many lack hydrous minerals (Thin- or un- rimmed hydrous minerals indicate rapid ascent & larger-than-normal eruption) Often “top driven,” e.g., small dome collapse unloads & triggers larger eruptive phase … ( vs. large summit/flank collapse trigger for long-dormant)

21. Integrating Event Tree & Monitoring Data “High VEI” Merapi Example ForecastSeismicDeforma- tion GasObserva- tions & history Petrology (mostly retrospective) High VEI (favored by large volumes of gas-rich viscous magma and rapid ascent Higher & more rapid increase in RSAM than past small eruptions, (including VT’s ), continued increase after initial vent clearing phreatic/ phreatomagmatic eruptions.. Escalating explosion signals and/or tremor precede biggest event(s) Deformation of greater magnitude and rate that past small eruptions Relatively large gas flux, especially following initial “vent clearing” events. Emissions may drop shortly before eruption if pathway obstructed. Early CO 2 pulse & high CO 2 /SO 2 (early warning of recharge and high VEI) History includes larger multi-phase eruptions, and hydrous minerals. Initial phase of current activity explosive instead of extrusive. Unusually high extrusion rates (for initial phases) Tephra or lava from initial eruptions may contain gas-rich indicators (high volatiles in glass inclusions, bubble- wall shards, volatile- rich indicator minerals, e.g., hb). Evidence of separate gas phase at depth. Silicic magma composition.

22. Basis for probability estimation, Merapi, v. 2, 06/26/2006 Conceptual background is in plain type; reasoning behind specific numbers on the tree is in italics. Node 1: Magma at the surface 1 (i.e., 100%). Merapi already woke up from a roughly 5 year sleep, so we can just use 1.0 (100%) as the probability in this tree. Node 2: Extrusion rate >100,000, 10-100,000, < 10,000 /d 100% for >100,000/day, based on estimates as of 5/14/06 (volume of the dome) and again on 5/20-5/23/06 (combination of dome growth and rate of rockfall and pyroclastic flow deposition in Kali Bedog). As of 6/20 and probably still as of 6/22, the extrusion rate is approximately 210,000 m3/d, of which 75,000 m3/d is growth of the lava dome and about 130,000 m3/d is in rockfalls and awan panas guguran (160,000 m3/d x 0.8 DRE correction, based on PLAZ seismic calibration). This has risen slightly from the 150,000- 175,000 m3/d estimated at the end of May. Extrusion rate is known to be a significant factor in the stability of lava domes, for four reasons:  high extrusion rate creates high shear strains in the carapace of the dome  it creates more weak, soft material in the core of the dome  any extrusion, especially at a high rate, causes loading of rocks beneath the dome and causes dome fronts to oversteepen  high extrusion rates favor incomplete degassing of the rising magma column, with the effect that internal gas pressures can build unless there is efficient degassing (pressure bleed). There is an implicit assumption here that original gas content of Merapi magmas is constant, so variability in gas content of magma reaching near the surface depends on magma ascent rate or its measurable proxy, magma extrusion rate. However, an apparent increase in SO2 emission beginning on June 13 (OMI data) without significant increase in extrusion rate suggests that there might also be an increase in concentration of gas in the magma. We don’t have a specific node for gas concentration in magma but it is indirectly included in Node 3 (gas pressures) if the supply rate of gas exceeds the magma’s capacity to bleed off that pressure. The basis for estimating extrusion rate = rate of growth of lava dome + rate of accumulation of pyroclastic deposits, e.g., endapan awan panas, guguran. The long term eruption rate for Merapi was estimated by Siswowidjoyo, Suryo, and Yokoyama (Bulletin of Volcanology, v. 57) as 1.2 million cubic meters per year, or approx 3300 m3/d. Their estimate does not include collapsed material (pyroclastics) – only volumes of lava domes – so it is probably underestimated by a factor of 2 or 3. So, we defined 3 branches here, 0-10,000; 10000-100000; and >100000 m3/d, equivalent in words to “normal,” “active (1990’s style), and “very active” Duration of the crisis (for annualization of risk, assume duration = 1 year) #1, #2 and #3 New dome + sm. Collapses 1 Near-surface gas pressure 60% #4=1930-scale collapse 2 14% 4% 20%30% #5 1872 expl eruption 3 Magma supply rate 10% Increased 70% #1, #2 and #3 70% 85% #4 1930-scale collapse 56% 80%10% #5 1872 expl eruption 5% #1, #2 and #3 New dome + sm. Collapses 87% Fluctuates slightly (2nd boiling, release) #4 1930-scale collapse 12%1% 60%10% This includes 2nd boiling, #5 1872 expl eruption Volcano restless constipation/breakthrough scenario small explosive events.3% ~Constant (self-sealing) 100%20% #1, #2 and #3 20%New dome + small collapses 8% 95% ~ Constant #4 1930-scale collapse 8%0% 40%5% 1% 8% 0% 6% 3% 10% Scenario 48% 1930 style collapse 10% 1872 style collapse 4% New dome + sm. collapses Increasing constant or decreasing 6% 1% 3% 4%

23. 2010 Merapi: Satellite radar = high initial extrusion rate & high probability of large eruption 31 Oct- 4 Nov: ~5 Mm 3 dome grows in crater at ≥25 m 3 s -1 ; constant MM2-3 tremor (25 km) 4 Nov.: CVGHM extends evacuations to 20 km – saves thousands of lives 5 Nov. 00:05: Largest eruption (VEI 4) – ash cloud to 55,000’, pyroclastic flows to 15 km International response- Indonesia, Europe, US, Japan North DLR, German Aerospace Center, 2010 2010 extrusion rate 10 X 2006 “The (2006) extrusion rate of ~210,000 m3/d as estimated on 6/20/06, or 2.4 m3/s, is high by Merapi standards and matched within the 20th century only in 1930 and 1961, and perhaps briefly in the first week of the 1992 eruption. Both times, the high rate seems to have contributed to large eruptions.” (VDAP-CVGHM Event Tree, 2006) Eruption Scenario Probabilities (with magma pressure: Increasing : Constant : Decreasing) Extrusion Rate (m3/s)1990’s type1930, 1961 type 1872 type >1.2 73:83:9315:10:5 10 : 5: 1 0.12 – 1.283:90:8710:5: 25: 2: 1 <0.12 m3/s85:80:705: 0: 00: 0: 0 VDAP-CVGHM Event Tree (2006)

24. Pallister et al. 2008 Iverson et al. 2006 The next frontier: relating individual event types to detailed processes

25. Long-dormant or frequently active? Frequency, size, and explosivity of past eruptions? (VEI range?) Size and character of deposits: Ash flow sheets vs. lava flow, domes & dome-collapse pf’s?, extensive lahars? Structure of the edifice? (e.g., stratovolcano? shield? caldera?) Stability of the edifice: steepness, structural weaknesses, evidence of past collapse, relation to regional tectonics? Nature of past eruptions Explosive vs. non-explosive vs. fumarolic? Previous “outsized” eruptions ? Composition and character of previous juvenile components? Vesicular or dense? Bulk rock and glass compositions (basalt-andesite-dacite-rhyolite)? Presence and condition of hydrous phases (e.g., amphibole & micas, reaction rims?). Other indicators of high P H 2 O or SO 2 (e.g., cummingtonite, anhydrite) Extent of fragmentation (e.g., “gray pumice”) Areas affected and population at risk? (Hazard assessment!) Checklist of questions to pose and attempt to answer before making a forecast (Part 1 – Geologic context) What does geology and petrology say about past eruptions & hazards?

26. Character of the current unrest? Seismic: RSAM (seismic energy trend)? Type, magnitude and frequency of events (VT, LF, VLF, DLF, hybrids, explosion signals, tremor)? Character and duration of events (e.g., distal-proximal VT’s, spasmodic bursts, continuous or banded tremor, LF’s or tornillos)? Comparison to background seismicity Nature of installations (how well-coupled, oriented, distance from vent) Comparison to previous episodes and/or to analogous unrest at other volcanoes? Deformation: Inflation, deflation, and/or lateral? Rate… and rate of change? Deep? Shallow? Large-volume? Small-volume?, Geometry? Comparison to previous episodes and/or to analogous unrest at other volcanoes? Checklist of questions to pose and attempt to answer before making a forecast (Part 2a – Monitoring data)

27. Gas: Emission levels, ratios and trends of: SO 2, CO 2, H 2 S, Cl, F, any other species? Likelihood of groundwater “scrubbing” (conversion of SO 2 to H 2 S)? Hot? dry? pathway to the surface? Conduit plugged by hydrothermal or solidified cap? Comparison to emissions during previous episodes? Observations (including remote sensing) Morphologic changes (e.g., fractures or other structures)? Character of Initial explosions/extrusions and any associated tephra? Groundwater changes? Vegetation changes? (e.g., tree-kills?) Comparison to previous episodes and/or to analogous unrest at other volcanoes? e.g., “ What proportion of previous volcanoes that exhibit the observed indicators continued to magmatic eruption and how big (VEI)? Event-probability tree? This is why we need WOVOdat ! -END- Checklist of questions to pose and attempt to answer before making a forecast (Part 2b – Monitoring data)

28. 1. HF Volcano- tectonic earthquakes (distal vs. proximal) 2. LF Low-frequency earthquakes 3. Volcanic tremor and Typical progression in earthquake types Plus Hybrids of HF & LF Original signal Low pass filtered Spectrogram Power Spectrum Real-time tools for analysis and forecasting – associating event types with processes Hybrid (VLF + HF) volcanic earthquake: represents rock breaking & magma or fluid transport

29. ForecastSeismicDeformationGasObservations & history Petrology Eruption possible (magma/fluids moving in crust) Sudden changes (+/-) from background RSAM level (background may include: proximal VT’s, LF’s, tornillos, tremor, explosion signals)… Distal VT’s possible, but with cumulative M<4). Deformation localized near summit/vent areas. Little regional deformation unless unusually large batch of magma CO2 increase = deep degassing & early warning. SO2 increase if hot pathway, otherwise may be scrubbed and replaced by H2S or sudden decrease in emissions Steam emissions, phreatic eruptions, fractures opening. Water levels in nearby wells may change Magmatic eruption likely (magma & gas have reached shallow levels) Rapid, steep increase in RSAM from background level (e.g., <1 week in some cases), LF/explosion signal followed by tremor typical. VT’s may/may not occur. Slower ramp- up in other cases (previous eruptions provide guides. Hybrid & drum-beat quakes may be detected and indicate magma rising Accelerating deformation of summit as eruption approaches SO2 & Cl emissions increase and SO2/H2S increases as magma rises and pathway dries out. Emissions may drop shortly before eruption if pathway obstructed More vigorous steam emissions & phreatic/ phreatomagmatic eruptions or sudden stoppage of observed emissions Initial tephra mainly composed of lithic debris, glass shards may or may not be present. Juvenile component minor but typically difficult to identify. (Petrology not diagnostic) High VEI (favored by large volumes of gas-rich viscous magma and rapid ascent Higher & more rapid increase in RSAM than past small eruptions, (including VT’s ), continued increase after initial vent clearing phreatic/ phreatomagmatic eruptions.. Escalating explosion signals and/or tremor precede biggest event(s) Deformation of greater magnitude and rate that past small eruptions Relatively large gas flux, especially following initial “vent clearing” events. Emissions may drop shortly before eruption if pathway obstructed. Early CO2 pulse may be 1 st warning of recharge and high VEI History includes larger multi-phase eruptions, and hydrous minerals. Initial phase of current activity explosive instead of extrusive. Unusually high extrusion rates (for initial phases) Tephra or lava from initial eruptions may contain gas-rich indicators (high volatiles in glass inclusions, bubble-wall shards, volatile-rich indicator minerals, e.g., hb). Silicic magma composition. These are only permissive indicators as gas-rich magma may not yet be shallow Low VEI – (favored by smaller volumes of gas-poor low- viscosity magma, and slow ascent RSAM moderates & decreases after initial vent clearing events. Return to background levels, may take weeks Deformation ends or decreases, e.g., after initial explosions or lava (dome) erupted Gas emissions fall to background levels after initial vent clearing events and in parallel with seismic decrease History of small eruptions (no big PF sheets or thick tephra deposits). Eruptions may be “slow:” e.g., peak dome collapse weeks to months after onset of episode Early-erupted juvenile component degassed (microcrystalline, lacks volatile- rich indicator minerals or they have thick decompression rims = slow ascent). Magma is mafic (non-exclusive) No eruption (yet) … end of crisis Seismicity dies out after initial emissions Deformation ends, local deflation near vent Gas emissions drop to background levels Steam emissions or back to background Open (frequently active) systems: Repeated eruptions during the past decade Conduit never freezes: e.g., basaltic & basaltic andesite systems like Stromboli, Etna, Soputan, Mayon, Fuego, Arenal, Villarrica, Telica, Llaima, Masaya 1970-1990, Mayon, Pavlof, Shishaldin and semi-steady state andesite to dacite dome extrusions like Santiaguito, Merapi, Karangetang, Huila since 2008, Popocatepetl since 1996, Colima since 1997, SHV since 2000 in which magma supply just enough to keep magma rising; occasional larger than normal influx or gas-rich influx drives more explosive eruption (e.g., Merapi 2010) may also be driven by “top down” processes (e.g., dome-collapse unloading as in Boxing Day 1997 eruption at SHV; summit dome collapse at Soputan in 2007-08)

30. ForecastSeismicDeforma- tion GasObservations & history Petrology Magmatic eruption possible (magma/fluids moving in crust) Background level exceeded. Distal VT's as tectonic faults are pressurized and magma rises. VT number & energy increasing as magma rises. VT energy release often approaches or exceeds M4. (Spurr only M3). Also many intrusions stall without eruptions! Inflation detected = early warning; may be large. Broad (deep sourced) deformation CO2 increase = deep degassing, may provide early warning Hydrothermal system & fumaroles present but not necessarily elevated over background levels. Past history of explosive eruptions. (Montserrat no steaming). Water levels in wells may drop (e.g., due to dilatation) Products of past eruptions give range of most likely magma types and explosivity Magmatic eruption likely (magma & gas have reached shallow levels) Transitional from distal to proximal VT's as magma shallows. LF's and tremor appear and increase as hydrothermal system boils off & gas escapes. Hybrid earthquakes as magma continues to ascend. Tungurahua (1999) = exception… tremor & distal VT’s only… Localized deformation near summit/vent areas detected as magma rises into edifice. High and/or accelerating rate of deformation SO2 & Cl emissions increase and SO2/H2S increases as magma rises and system dries out. Gas emissions drop shortly before eruption if quenched- or silica- cap forms Steam emissions, phreatic and/or phreatomagmatic eruptions.. Water levels in wells may rise as magma/gas pressurizes aquifers or or fall as new fractures open. Geysering possible Initial tephra mainly composed of lithic debris; glass shards may or may not be present. Juvenile component minor but may be difficult to identify High VEI (favored by large volumes of gas- rich viscous magma and rapid ascent) High and rapidly increasing rate of seismic energy release (RSAM), usually includes large LF earthquakes. RSAM continues to increase after initial vent clearing emissions/phreatic /phreatomagmatic eruptions (may pause first). Swarms of deep LP’s or deep tremor indicate significant magmatic replenishment. Escalating explosion signals. Deformation may be broad, may include fracturing of summit, flank destabilization (e.g., “bulge”). Dike intrusion indicated Large gas flux following initial “vent clearing” events or emissions decrease abruptly while seismicity still high. Emissions from multiple /distributed vents… High VEI statistically more likely for “reawakening” volcanoes. History of large eruptions (e.g., big PF sheets, thick tephra, pumiceous deposits, fragmental pumices). Initial mingled magma eruption may indicate new intrusive trigger Tephra or lava from initial eruptive phase may contain gas-rich indicators (e.g., bubble-wall shards, high volatiles in glass inclusions, volatile-rich indicator minerals, e.g., hb). Silicic magma composition. Low VEI (favored by smaller volumes of gas-poor low- viscosity magma, and slow ascent RSAM moderates after initial vent clearing events or earlier large-RSAM crisis indicating earlier emplacement and degassing of shallow intrusion. (Beware: Pinatubo did the above in April, 1991, main eruption was in June). Slow growth and low M of LF or hybrid seismicity Deformation ends or decreases after initial vent-clearing events. Gas emissions fall or moderate after initial vent clearing events while seismicity decreasing or constant History of small eruptions, no extensive PF sheets or thick tephra deposits Early-erupted juvenile samples degassed (microcrystalline, lack volatile-rich indicator minerals or thick decompression rims = slow ascent). Mafic magma composition (non-exclusive) No eruption (yet) …or end (intrusion stalls) Seismicity returning to background levels gradually and stays there for ~ 2 months. Note that many intrusions stall without eruptions. Deformation ends, deflation may occur Gas emissions dropping to background levels Steam (H2O) emissions dominate Long-dormant (closed systems): No eruptions in many decades or centuries (e.g., MSH 1980, El Chichon 1982, Pinatubo 1991, Garbuna 2004, Huila 2007, Chaitén, 2008, Sinabung 2010, Vesuvius (0079, 0472,1631), Tambora (2011?))

31. How big? Current Status What kind of eruption? What to expect next Quantifying forecasts: Use of Event & Probability Trees at Garbuna, PNG Tephra

32. Areas affected Vulnerability & Risk Probability Trees – Lessons from MSH, Garbuna, Merapi, Huila, Lunayyir Internal observatory use valuable Focuses scientists’ thinking Illuminates alternate viewpoints & uncertainties Aids in reaching consensus External: Use with care - requires user education Written explanations & scientific background essential (i.e., meta-data required!) For well-studied & well-monitored volcanoes nodes can be linked to measurable parameters ! Tephra cloud

33. Augustine, 2006