Volcanic Hazards and Their Mitigation: Progress and Problems

VOLCANIC HAZARDS AND THEIR MITIGATION- PROGRESS AN D PROBLEMS RobertI. Tilling U.S. GeologicalSurvey Menlo Park, California "Natural calamitystrikes at aboutthe timewhen one forgets its terror." Japaneseproverb [see Shimozuru, 1981 ] Abstract. At the beginningof the twentiethcentury, disastersof the 1980s (Mount St. Helens, U.S.A. (1980), volcanologybegan to emerge as a modem scienceas a E1 Chich6n, Mexico (1982); Galunggung, Indonesia result of increasedinterest in eruptivephenomena follow- (1982); and Nevado del Rufz, Colombia (1985)) illustrates ing some of the worst volcanic disastersin recorded the importanceof predisastergeoscience studies, volcanic history: Krakatau (Indonesia) in 1883 and Mont Pe16e hazards assessments,volcano monitoring, contingency (Martinique), Soufri•re (St. Vincent), and Santa Maria planning,and effectivecommunications between scientists (Guatemala)in 1902. Volcanologyis againexperiencing a and authorities. The death toll (>22,000) from the Rufz period of heightened public awarenessand scientific catastropheprobably could have been greatly reduced;the growthin the 1980s, the worst periodsince 1902 in terms reasonsfor the tragically ineffective implementationof of volcanic disasters and crises. A review of hazards evacuationmeasures are still unclearand puzzlingin view mitigation approaches and techniques indicates that of the fact that sufficientwarnings were given. The most significantadvances have been made in hazardsassess- pressing problem in the mitigation of volcanic and ment, volcanomonitoring, and eruptionforecasting. For associatedhazards on a global scale is that most of the example, the remarkable accuracyof the predictionsof world's dangerousvolcanoes are in densely populated dome-buildingevents at Mount St. Helenssince June 1980 countries that lack the economic and scientific resources or is unprecedented. Yet a predictive capability for more the political will to adequatelystudy and monitor them. voluminousand explosive eruptions still has not been This problem afflicts both developed and developing achieved. Studies of magma-inducedseismicity and countries,but it is especially acute for the latter. The ground deformation continue to provide the most sys- greatestadvances in volcanic hazards mitigation in the tematicand reliable data for early detectionof precursors near future are most likely to be achieved by wider to eruptionsand shallow intrusions. In addition, some applicationof existing technologyto poorly understood othergeophysical monitoring techniques and geochemical and studiedvolcanoes, rather than by refinementsor new methodshave been refined and are being more widely discoveriesin technologyalone. appliedand tested. Comparisonof the four major volcanic INTRODUCTION AND HISTORICAL PERSPECTIVE in volcanology,the studyof the transportand eruptionof magma [Sigurdsson,1987], with emphasison active or Most of the Earth's crustis of magmaticorigin, attesting potentiallyactive volcanoes [Tilling, 1987a]. to the enormousrole that volcanic and related magmatic Of themore than 1300 volcanoesknown to haveerupted processeshave played in formingthe outermostsolid rind in Holocenetime, about half are classifiedas active (i.e., of our planet. In addition,the distributionof volcanoes, thosethat have eruptedin recordedhistory). On average, pastand present,can be closelylinked to the dynamicsof about 50 of thesevolcanoes erupt each year, an eruption the crust and mantle within a plate tectonics context. frequencythat appearsto be obtainedfor all historicaltime Some foreign rock fragments (called "xenoliths") [Sirekinet al., 1981]. Individualvolcanoes, however, may contained in eruptive products represent the deepest remain in reposefor many centuriesor even millennia and samplesof the Earth's interiorthat havebeen recovered to thus may be classified as dormant (i.e., could become datefrom any drill hole. Thus it is hardlysurprising that activeagain) or extinct(i.e., not expectedto eruptagain). many geoscientistswork in terranesor on researchtopics The shortcomingsof pigeonholeclassification are evident; directly or indirectlyassociated with volcanicrocks. Yet in a generalway, the longer the period of intereruption within the geosciencecommunity, relatively few specialize repose,the more energeticthe next eruption. Some of the Thispaper is notsubject to U.S. copyright. Reviewsof Geophysics,27, 2 / May 1989 pages23 7-269 Publishedin 1989 by the AmericanGeophysical Union. Papernumber 89RG00436 '237' 238'Tilling: VOLCANICHAZARDS AND THEIRMITIGATION 27,2/REVIEWSOFGEOPHYSICS worst volcanic catastrophesin history have occurred at Guatemala)killed more than 36,000 people. T. A. Jaggar, volcanoesbelieved to be "extinct," for example,the A.D. Jr., a 31-year-oldassistant professor in geologyat Harvard 79 eruption of Vesuvius that destroyedPompeii and Universityat the time, was one of the geologistssent to Herculaneum [Sigurdssonet al., 1985] and the 1951 study the effects of the Mont Pe16eand Soufribreerup- eruptionof Mount Lamington,Papua New Guinea[Taylor, tions. Thisexperience and that gained later from studiesof 1958]. volcanoesand earthquakesin Alaska, Italy, Japan,and Costa Rica convinced Jaggar that the expeditionary VolcanicDisasters and the Emergenceof Volcanology methodof studywas inadequateand that to fully under- HistoriCally,thestudy of eruP•ve phenomena hasbeen standvolcanoes, it is necessaryto observeand measure spurred by volcanic catastrophes. Indeed, the earliest theireruptive and associated seismic activity on a continu- accuratedescription of an eruptionis containedin letters ousbasis before, during, and after eruptions. The devasta- from Pliny the Youngerto the Romanhistorian Tacitus, tion Jaggarwitnessed at Martinquealso convinced him that describingthe asphyxiationof his uncle, the famous a better understandingof the processesthat could kill scholarPliny the Elder, who was observingthe A.D. 79 "thousandsof personsby subterraneanmachinery totally eruptionof Vesuviusas it destroyedPompeii. The 1815 unknownto geologistsand thenunexplainable was worthy eruption of Tambora (Sumbawa Island, Indonesia), of a life work" [Jaggar,1956, p. 62]. consideredthe largesteruption in recordedhistory, caused Jaggarwas a scientificvisionary who recognizedthat a morethan 90,000 humandeaths and global climatic impact true understandingof eruptivephenomena would require [Self et al., 1984; Stothers,1984; Storereeland Storereel, the establishmentof permanent observatoriesto study 1983]. Yet becauseof the volcano's remoteness,poor active volcanoes [Macdonald, 1953]. His vision and global communications,and the immature statusof the researchgoals were sharedenthusiastically by the noted natural sciencesat the time, this huge eruptionattracted Japanese seismologist, F. Omori, of the Imperial little attentionbeyond the affectedpart of the Indonesian EarthquakeInvestigation Committee. In 1910, Omori archipelago. The first scientificexpedition to study this designedand deployeda seismometer("tromometer") to cataclysmicevent was not sent until 1847 [Zollinger, detect earthquakesbeneath Usu Volcano (Hokkaido), 1855]. That same year, a small primitive volcano ob- marking the first instrumentalmonitoring of a volcano servatorywas established on the flank of Vesuvius. [Shimozuru, 1981]. In 1911, Omori founded an ob- In contrastto the feeble, belated scientificresponse to servatoryat AsamaVolcano (I-Ionshu). Meanwhile, Jaggar the Tambora eruption, the 1883 eruption of Krakatau obtainedseveral Omori-type seismometersand designed (Sunda Strait, between Java and Sumatra, Indonesia) equipmentto measurethe temperatureof an active lava promptedthe first well-organizedscientific investigation lake in Halemaumau Crater within Kilauea Volcano's of a volcaniccatastrophe and its aftermath[Verbeek, 1885; summitcaldera [Jaggar, 1956]. A "technologystation" Symons, 1888] (see also Sirekin and Fiske [1983]). was set up at the edge of Halemaumaulava lake in July Scientific expeditions were quickly dispatched,and 1911, and, after many difficulties, F. A. Perret and E. S. comprehensivestudies were made and published by Shepherd (Geophysical Laboratory of the Carnegie scientists from the Netherlands and other countries within Institution,Washington, D.C.) succeededin obtainingthe a few yearsof the eruption. As emphasizedby Sirekinand first thermocouplemeasurement of the temperature(1000 Fiske [1984], who aptly termedKrakatau 1883 "a classic + 25øC)of liquidbasaltic lava (see Shepherd [1912], cited geophysicalevent," these studiesgreatly advancednot in the work of Bevenset al., [1988], andApple [1987]). only volcanology,but also meteorology,oceanography, The Hawaiian Volcano Observatory (HVO) was andbiology. From the 1883 Krakataueruption "the world founded "officially" in January 1912, upon Jaggar's quickly learned that the impacts of large geophysical arrivalto assumethe directorship.Following the founding events are global, and that they demonstratethe inter- of the observatoriesin Japanand Hawaii the youngscience dependenceof land,sea, and air" [Simkinand Fiske, 1984, of volcanologyhas continuedto mature through the p. 48]. establishment of, and studies conducted at, additional The study of the effects of the 1883 Krakatau volcanoobservatories elsewhere in the world. Jaggar's catastropheprovided new insightsinto the processesand visionaryobjective of a global network of observatories hazardsassociated with a violentlyexplosive eruption, but has only been partially achieved,because many of the little was learned about how

Load more