Bulletin of Volcanology

, Volume 54, Issue 2, pp 126–146 | Cite as

Mount St. Helens a decade after the 1980 eruptions: magmatic models, chemical cycles, and a revised hazards assessment

  • John S Pallister
  • Richard P Hoblitt
  • Dwight R Crandell
  • Donal R Mullineaux


Available geophysical and geologic data provide a simplified model of the current magmatic plumbing system of Mount St. Helens (MSH). This model and new geochemical data are the basis for the revised hazards assessment presented here. The assessment is weighted by the style of eruptions and the chemistry of magmas erupted during the past 500 years, the interval for which the most detailed stratigraphic and geochemical data are available. This interval includes the Kalama (A. D. 1480–1770s?), Goat Rocks (A.D. 1800–1857), and current eruptive periods. In each of these periods, silica content decreased, then increased. The Kalama is a large amplitude chemical cycle (SiO2: 57%–67%), produced by mixing of arc dacite, which is depleted in high field-strength and incompatible elements, with enriched (OIB-like) basalt. The Goat Rocks and current cycles are of small amplitude (SiO2: 61%–64% and 62%–65%) and are related to the fluid dynamics of magma withdrawal from a zoned reservoir. The cyclic behavior is used to forecast future activity. The 1980–1986 chemical cycle, and consequently the current eruptive period, appears to be virtually complete. This inference is supported by the progressively decreasing volumes and volatile contents of magma erupted since 1980, both changes that suggest a decreasing potential for a major explosive eruption in the near future. However, recent changes in seismicity and a series of small gas-release explosions (beginning in late 1989 and accompanied by eruption of a minor fraction of relatively low-silica tephra on 6 January and 5 November 1990) suggest that the current eruptive period may continue to produce small explosions and that a small amount of magma may still be present within the conduit. The gas-release explosions occur without warning and pose a continuing hazard, especially in the crater area. An eruption as large or larger than that of 18 May 1980 (≈0.5 km3 dense-rock equivalent) probably will occur only if magma rises from an inferred deep (≥7 km), relative large (5–7 km3) reservoir. A conservative approach to hazard assessment is to assume that this deep magma is rich in volatiles and capable of erupting explosively to produce voluminous fall deposits and pyroclastic flows. Warning of such an eruption is expectable, however, because magma ascent would probably be accompanied by shallow seismicity that could be detected by the existing seismic-monitoring system. A future large-volume eruption (≥0.1 km3) is virtually certain; the eruptive history of the past 500 years indicates the probability of a large explosive eruption is at least 1% annually. Intervals between large eruptions at Mount St. Helens have varied widely; consequently, we cannot confidently forecast whether the next large eruption will be years decades, or farther in the future. However, we can forecast the types of hazards, and the areas that will be most affected by future large-volume eruptions, as well as hazards associated with the approaching end of the current eruptive period.


Tephra Pyroclastic Flow Explosive Eruption Fall Deposit Magma Ascent 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Baedecker PA, McKown DM (1987) Instrumental neutron activation analysis of geochemical samples. In: Baedecker PA (ed) Methods for geochemical analysis. US Geol Surv Bull 1770. H1–H14Google Scholar
  2. Bard JP (1983) Metamorphism of an obducted island arc: example of the Kohistan sequence (Pakistan) in the Himalayan collided range. Earth Planet Sci Lett 45: 133–144Google Scholar
  3. Barker SE, Malone SD (in press) Magmatic system geometry at Mount St Helens modeled from the stress field associated with post-eruptive earthquakes. J Geophys ResGoogle Scholar
  4. Bennett JT, Krishnswami S, Turekian KK, Melson WG, Hopson CA (1982) The uranium and thorium decay series nuclides in Mt St Helens effusives. Earth Planet Sci Lett 60:61–69Google Scholar
  5. Blake S, Ivey GN (1986a) Magma-mixing and the dynamics of withdrawal from stratified reservoirs. J Volcanol Geotherm Res 27:153–178Google Scholar
  6. Blake S, Ivey GN (1986b) Density and viscosity gradients in zoned magma chambers, and their influence on withdrawal dynamics. J Volcanol Geotherm Res 30:210–230Google Scholar
  7. Boden DR (1989) Evidence for step-function zoning of magma and eruptive dynamics, Toquima caldera complex, Nevada J Volcanol Geotherm Res 37:39–57Google Scholar
  8. Carey S, Sigurdsson H (1985) The May 18, 1980 Eruption of Mount St Helens 2. Modeling of dynamics of the Plinian Phase. J Geophys Res 90:2948–2958Google Scholar
  9. Carey S, Gardner J, Sigurdsson H (1989) Intensity and magnitude of post-glacial Plinian eruptions at Mount St Lelens (abst). In: Continental magmatism. New Mexico Bureau of Mines and Mineral Resources Bull 131:43Google Scholar
  10. Carey S, Sigurdsson H, Gardner JE, Criswell W (1990) Variations in column height and magma discharge during the May 18, 1980 eruption of Mount St Helens. J Volcanol Geotherm Res 43:99–112Google Scholar
  11. Carroll MR, Rutherford MJ (1987) The stability of igneous anhydrite: experimental results and implications for sulfur behavior in the 1982 El Chichon trachyandesite and other evolved magmas. J Petrol 28:781–801Google Scholar
  12. Casadevall TJ, Johnston DA, Harris DM, Rose WI, Malinconico LL, Stoiber RE, Bornhorst TJ, Williams SN, Woodruff L, Thompson JM (1981) SO2 emission rates at Mount St Helens from March 29 through December, 1980. US Geol surv Prof Paper 1250:193–207Google Scholar
  13. Casadevall TJ, Rose W, Gerlach T, Greenland LP, Ewert J, Wunderman R, Symonds R (1983) Gas emissions and the eruptions of Mount St Helens through 1982. Science 221:1383–1384Google Scholar
  14. Cashman KV (1988) Crystallization of Mount St Helens 1980–1986 dacite: a quantitative textural approach. Bull Volcanol 50:194–209Google Scholar
  15. Cashman KV, Taggart JE (1983) Petrologic monitoring of 1981 and 1982 eruptive products from Mount St Helens. Science 221:1385–1387Google Scholar
  16. Chadwick WW Jr, Swanson DA, Iwatsubo EY, Heliker CC, Leighley TA (1983) Deformation monitoring at Mount St Helens in 1981 and 1982. Science 221:1378–1380Google Scholar
  17. Chadwick WW Jr, Archuleta RJ, Swanson DA (1988) The mechanics of ground deformation precursory to dome-building extrusions at Mount St Helens 1981–1982. J Geophys Res 93:B5:4351–4366Google Scholar
  18. Christiansen RL, Peterson DW (1981) Chronology of the 1980 eruptive activity. US Geol Surv Prof Paper 1250:17–30Google Scholar
  19. Crandell DR (1976) Preliminary assessment of potential hazards from future volcanic eruptions in Washington. US Geol Surv Misc Field Studies Map MF-774Google Scholar
  20. Crandell DR (1980) Recent eruptive history of Mount Hood, Oregon, and potential hazards from future eruptions. US Geol Surv Bull 1492:1–81Google Scholar
  21. Crandell DR (1987) Deposits of pre-1980 pyroclastic flows and lahars from Mount St Helens volcano, Washington. US Geol Surv Prof Paper 1444:1–91Google Scholar
  22. Crandell DR, Mullineaux DR (1978) Potential hazards from future eruptions of Mount St Helens. US Geol Surv Bull 1383-C:1–26Google Scholar
  23. Criswell CW (1987) Chronology and pyroclastic stratigraphy of the May 18, 1980 eruption of Mount St Helens, Washington. J Geophys Res 92:10237–10266Google Scholar
  24. Criswell CW (1989) Volumes and compositional variations of the May 18, 1980 eruption of Mount St Helens: implications for eruption forecasts (abst). In: Continental magmatism. New Mexico Bureau of Mines and Mineral Resources Bull 131:62Google Scholar
  25. Delaney PT, Pollard DD, Ziony JI, McKee EH (1986) Field relations between dikes and joints: emplacement processes and paleostress analysis. J Geophys Res 91:4920–4938Google Scholar
  26. Devine JD, Sigurdsson H, Davis AN, Self S (1984) Estimates of sulfur and chlorine yield to the atmosphere from volcanic eruptions and potential climate effects. J Geophys Res 89:6309–6325Google Scholar
  27. Dvorak J, Okamura AT, Mortensen C, Johnson MJS (1981) Summary of electronic tilt studies at Mount St Helens. US Geol Surv Prof Paper 1250:169–174Google Scholar
  28. Endo ET, Dzurisin D, Murray T, Syverson K (1987) The rate of magma ascent during dome-building at Mount St Helens (abst). Abstract volume, Hawaii Symposium on How Volcanoes Work:64Google Scholar
  29. Endo ET, Dzurisin D, Swanson DA (1990) Geophysical and observational constraints for ascent rates of dacitic magma at Mount St Helens In: Ryan MP (ed) Magma transport and storage. Wiley, New York, pp 317–334Google Scholar
  30. Evarts RC, Ashley RP, Smith JG (1987) Geology of the Mount St Helens area: record of discontinuous volcanic and plutonic activity in the Cascade arc of southern Washington. J Geophys Res 92:10155–10169Google Scholar
  31. Fink JH, Malin MS, Anderson SW (1990) Intrusive and extrusive growth of the Mount St Helens lava dome. Nature 348:435–437Google Scholar
  32. Gerlach TM, Casadevall TJ (1986) Fumarole emissions at Mount St Helens volcano, June 1980 to October 1981; degassing of a magma-hydrothermal system. J Volcanol Geotherm Res 28:141–160Google Scholar
  33. Gerlach TM, Westrich HR, Casadevall TJ (1990) High sulfur and chlorine magmas during the 1989–90 eruption of Redoubt volcano, Alaska (abst). Am Geophys Union Trans (EOS) 71:1702Google Scholar
  34. Glicken H, Meyer W, Sabol M (1989) Geology and ground-water hydrology of Spirit Lake blockage, Mount St Helens, Washington, with implications for lake retention. US Geol Surv Bull 1789:1–33Google Scholar
  35. Halliday AN, Fallick AE, Dickin AP, Mackenzie AB, Stephens WE, Hildreth W (1983) The isotopic and chemical evolution of Mount St Helens. Earth Planet Sci Lett 63:241–256Google Scholar
  36. Heliker CC (1984) Inclusions in the 1980–83 dacite of Mount St Helens, Washington. MSc thesis. Western Washington University: 1–185Google Scholar
  37. Hill PM, Rutherford MJ (1989) Experimental study of amphibole breakdown in Mount St Helens dacite with applications to magmatic ascent rate determinations (abst). New Mexico Bureau of Mines and Mineral Resources Bull 131:131Google Scholar
  38. Hoblitt RP (1989) Day 3: The Kalama eruptive period, southwest and south flanks In: Field excursions to volcanic terranes in the western United States II: Cascades and Intermountain West. New Mexico Bureau of Mines and Mineral Resources Memoir 47:65–69Google Scholar
  39. Hoblitt RP, Crandell DR, Mullineaux DR (1980) Mount St Helens eruptive behavior during the past 1,500 yr. Geology 8:555–559Google Scholar
  40. Hoblitt RP, Miller CD, Vallance JW (1981) Origin and stratigraphy of the deposit produced by the May 18 directed blast. US Geol Surv Prof Paper 1250:401–419Google Scholar
  41. Hopson CA, Melson WG (1980) Mount St Helens eruptive cycles since 100 a. d. (abst). American Geophysical Union Trans (EOS) 61:1132–1133Google Scholar
  42. Hopson CA, Melson WG (1984) Eruption cycles and plug-domes at Mount St Helens (abst). Geol Soc Am Abst with Programs 16:544Google Scholar
  43. Hopson CA, Melson WG (1990) Compositional trends and eruptive cycles at Mount St Helens. Geosci Can 17:131–141Google Scholar
  44. Irvine TN (1967) The Duke Island ultramafic complex, southeastern Alaska. In: Wyllie PJ (ed) Ultramafic and related rocks. Wiley, New York, pp 84–96Google Scholar
  45. Jaeger JC (1957) The temperature in the neighborhood of a cooling intrusive sheet. Am J Sci 255:306–316Google Scholar
  46. James OB (1971) Origin and emplacement of the ultramafic rocks of the Emigrant Gap area, California. Jour Petrology 12:523–560Google Scholar
  47. Leeman WP, Smith DR, Hildreth W, Palacz Z, Rogers N (1990) Compositional diversity of Late Cenozoic basalts in a transect across the southern Washington Cascades: Implications for subduction zone magmatism: J Geophys Res 95:19561–19582Google Scholar
  48. Lees JM, Crosson RS (1989) Tomographic inversion for three dimensional velocity structure of Mount St Helens using earthquake data. J Geophys Res 94:5716–5728Google Scholar
  49. Lipman PW, Mullineaux DR (eds) (1981) The 1980 eruptions of Mount St Helens, Washington. US Geol Surv Prof Paper 1250Google Scholar
  50. Lipman PW, Moore JG, Swanson DA (1981a) Bulging of the north flank before the May 18 eruption — geodetic data. US Geol Surv Prof Paper 1250:143–156Google Scholar
  51. Lipman PW, Norton DR, Taggart JE Jr, Brandt EL, Engleman EE (1981b) Compositional variations in 1980 magmatic products. US Geol Surv Prof Paper 1250:631–640Google Scholar
  52. Malone SD (1990) Mount St Helens, the 1980 rewakening and continuing seismic activity. Geosci Can 17:146–149Google Scholar
  53. Mellors RA, Waitt RB, Swanson DA (1988) Generation of pyroclastic flows and surges by hot-rock avalanches from the dome of Mount St Helens volcano, USA. Bul Volcanol 58:14–25Google Scholar
  54. Melson WG (1983) Monitoring the 1980–1982 eruptions of Mount St Helens: compositions and abundances of glass. Science 221:1387–1391Google Scholar
  55. Merzbacher C, Eggler DH (1984) A magmatic geohygrometer: application to Mount St Helens and other dacitic magmas. Geology 12:587–590Google Scholar
  56. Miller CD, Mullineaux DR, Crandell DR (1981) Hazards assessments at Mount St Helens. In: Lipman PW, Mullineaux DR (eds) The 1980 eruptions of Mount St Helens, Washington. US Geol Surv Prof Paper 1250:789–802Google Scholar
  57. Mooney WD, Weaver CS (1989) Regional crustal structure and tectonics of the Pacific coastal states; California, Oregon, and Washington. Geol Soc Am Mem 172:129–161Google Scholar
  58. Moore JG, Albee WC (1981) Topographic and structural changes, March–July 1980 — photogrammetric data. US Geol Surv Prof Paper 1250:123–134Google Scholar
  59. Moran S, Malone SD (1990) Recent micro-seismic activity at Mt St Helens and its implications for the evolution of the deeper magmatic system (abst). Am Geophys Union Trans (EOS) 71:1693–1694Google Scholar
  60. Mullineaux DR (1976) Preliminary map of volcanic hazards in the 48 conterminous United States. US Geol Surv Misc Field Studies Map MF-786Google Scholar
  61. Mullineaux DR (1986) Summary of pre-1980 tephra-fall deposits erupted from Mount St Helens, Washington State, USA. Bull Volcanol 48:17–26Google Scholar
  62. Mullineaux DR, Crandell DR (1981) The eruptive history of Mount St Helens. US Geol Surv Prof Paper 1250:3–15Google Scholar
  63. Nakamura K (1977) Volcanoes as possible indicators of tectonic stress orientation — principle and proposal. J Volcanol Geotherm Res 2:1–16Google Scholar
  64. Newhall CG (1982) A method for estimating intermediate- and long-term risks from volcanic activity, with an example from Mount St Helens, Washington. US Geol Surv Open-File Report 82-396:1–50Google Scholar
  65. Pallister JS, Hoblitt RP (1985) Magma mixing at Mount St Helens (abst). Am Geophys Union Trans (EOS) 66:111Google Scholar
  66. Pallister JS, Heliker C, Hoblitt RP (in press) Glimpses of the active pluton below Mount St. Helens (abst). Am Geophys Union Trans (EOS) 72Google Scholar
  67. Pearce JA (1982) Trace element characteristics of lavas from destructive plate margins. In: Thorpe RS (ed) Andesites. Wiley, New York, pp 525–548Google Scholar
  68. Rutherford MJ (1990) Experimental study of dehydration and crystallization produced by decompression of dacites: implications for magma ascent rates (abst). Goldschmidt Conf Prog Abst 78Google Scholar
  69. Rutherford MJ, Devine JD (1988) The May 18 eruption of Mount St Helens. 3. Stability and chemistry of amphibole in the magma chamber. J Geophys Res 93 B10:11949–11959Google Scholar
  70. Rutherford MJ, Sigurdsson H, Carey S, Davis A (1985) The May 18, 1980, eruption of Mount St Helens 1. Melt composition and experimental phase equilibria. J Geophys Res 90 B4:2929–2947Google Scholar
  71. Sager JW, Chambers DR (1986) Design and construction of the Spirit Lake outlet tunnel, Mount St Helens, Washington. In: Schuster RL (ed) Landslide dams: processes, risk, and mitigation. Am Soc Civil Engineers Geotechnical Special Publication 3:42–58Google Scholar
  72. Sarna-Wojcicki AM, Shipley S, Waitt RB Jr, Dzurisin D, Woods SH (1981) Areal distribution, thickness, mass, volume, and grain size of air-fall ash from the six major eruptions of 1980. US Geol Surv Prof Paper 1250:577–600Google Scholar
  73. Scandone R, Malone SD (1985) Magma supply, magma discharge and readjustment of the feeding system of Mount St Helens during 1980. J Volcanol Geotherm Res 23:239–262Google Scholar
  74. Scarfe CM, Fujii T (1987) Petrology of crystal clots in the pumice of Mount St Helens' March 19, 1982 eruption; significant role of Fe−Ti oxide crystallization. J Volcanol Geotherm Res 34:1–14Google Scholar
  75. Shemeta JE, Weaver CS (1986) Seismicity accompanying the May 18, 1980 eruption of Mount St Helens, Washington. In: Keller SAC (ed) Mount St Helens: five years later. Eastern Washington University Press, Cheney, WA, 44–58Google Scholar
  76. Sigurdsson H (1982) Volcanic pollution and climate: the 1783 Laki eruption. EOS Trans Am Geophys Union 63:601–602Google Scholar
  77. Sillitoe RH (1973) The tops and bottoms of porphyry copper deposits. Econ Geol 68:799–815Google Scholar
  78. Smith DR (1984) The petrology and geochemistry of High Cascade volcanics in southern Washington: Mount St Helens volcano and the Indian Heaven basalt field. Ph D dissertation, Rice University, Houston, Texas: 1–409Google Scholar
  79. Smith DR, Leeman WP (1982) Mineralogy and phase chemistry of Mount St Helens tephra sets W and Y as keys to their identification. Quat Res 17:211–227Google Scholar
  80. Smith DR, Leeman WP (1987) Petrogenesis of Mount St Helens dacitic magmas. J Geophys Res 92. B10:10313–10334Google Scholar
  81. Snoke AW, Sharp WD, Wright JE, Saleeby JB (1982) Significance of mid-Mesozoic periodotitic to dioritic intrusive complexes, Klamath Mountains-western Sierra Nevada, California. Geology 10:160–166Google Scholar
  82. Spera FJ, Yuen DA, Greer JC, Sewell G (1986) Dynamics of magma withdrawal from stratified magma chambers. Geology 14:723–726Google Scholar
  83. Stanley WD, Finn C, Plesha JL (1987) Tectonics and conductivity structures in the southern Washington Cascades. J Geophys Res 92:10179–10193Google Scholar
  84. Swanson DA, Holcomb RT (1990) Regularities in growth of the Mount St Helens dacite dome, 1980–1986. In: Fink JH (ed) Lava flows and domes. Springer, New York, pp 3–24Google Scholar
  85. Swanson DA, Lipman PW, Moore JG, Heliker CC, Yamashita KM (1981) Geodetic monitoring after the May 18 eruption. US Geol Surv Prof Paper 1250:157–168Google Scholar
  86. Swanson DA, Casadevall TJ, Dzurisin D, Malone SD, Newhall CG, Weaver CS (1983) Prediction of eruptions at Mount St Helens, June 1980 through December 1982. Science 221:1369–1376Google Scholar
  87. Swanson DA, Dzurisin D, Holcomb RT, Iwatsubo EY, Chadwick WW, Casadevall TJ, Ewert JW, Heliker CC (1987) Growth of the lava dome at Mount St Helens, Washington (USA) 1981–1983. Geol Soc Am Sp Paper 212:1–16Google Scholar
  88. Taggart JE, Lindsay JR, Scott BA, Vivit DV, Bartel AJ, Stewart KC (1987) Analysis of geologic materials by X-ray fluorescence spectrometry. In: Badecker PA (ed) Methods for geochemical analysis. US Geol Surv Bull 1770. pp E1–E19Google Scholar
  89. Thompson RN, Morrison MA, Dicken AP, Hendry GL (1983) Continental flood basalts ... Arachnids rule OK? In: Hawkes-worth CJ, Norey MJ (ed) Continental basalts and mantle xenoliths. Shiva, Cambridge MA, pp 158–185Google Scholar
  90. US Army Corps of Engineers (1986) Mount St Helens, Washington — Toutle, Cowlitz and Columbia Rivers. Portland District, Sedimentation Design Memorandum 3Google Scholar
  91. Waitt RB Jr, Pierson TC, MacLeod NS, Janda RJ, Voight B, Holcomb RT (1983) Eruption-triggered avalanche, flood, and lahar at Mount St Helens — Effects of winter snowpack. Science 221:1394–1397Google Scholar
  92. Walsh JB (1975) An analysis of local changes in gravity due to deformation. Pure Appl Geophys 113:97–106Google Scholar
  93. Weaver CS, Grant WC, Malone SD, Endo ET (1981) Post-May 18 seismicity: volcanic and tectonic implications. US Geol Surv Prof Paper 1250:109–122Google Scholar
  94. Weaver CS, Zollweg JE, Malone SD (1983) Deep earthquakes beneath Mount St Helens: evidence for magmatic gas transport? Science 221:1391–1394Google Scholar
  95. Weaver CS, Grant WC, Shemeta JE (1987) Local crustal extension at Mount St Helens, Washington. J Geophys Res 92:10170–10178Google Scholar
  96. Williams DL, Abrams C, Finn C, Dzurisin D, Johnson DJ, Denlinger R (1987) Evidence from gravity data for an intrusive complex beneath Mount St Helens. J Geophys Res 92:10207–10222Google Scholar
  97. Wright TL, Doherty PC (1970) A linear programming and least squares method for solving petrologic mixing problems. Geol Soc Am Bull 81:1995–2008Google Scholar
  98. Yamaguchi DK (1983) New tree-ring dates for recent eruptions at Mount St Helens. Quat Res 20:246–250Google Scholar
  99. Yamaguchi DK (1985) Tree-ring evidence for a two-year interval between recent prehistoric explosive eruptions of Mount St Helens. Geology 13:554–557Google Scholar
  100. Yamaguchi DK (1986) Interpretation of cross correlation between tree-ring series. Tree-ring Bull 46:47–54Google Scholar
  101. Yamaguchi DK, Lawrence DB, Hoblitt RP (1990) A new tree-ring date for Mount St Helens' “Floating Island” lava flow. Bull Volcanol 52:545–550Google Scholar

Copyright information

© Springer-Verlag 1992

Authors and Affiliations

  • John S Pallister
    • 1
  • Richard P Hoblitt
    • 2
  • Dwight R Crandell
    • 1
  • Donal R Mullineaux
    • 1
  1. 1.US Geological SurveyDenverUSA
  2. 2.Cascades Volcano ObservatoryUS Geological SurveyVancouverUSA

Personalised recommendations