Bulletin of Volcanology

, Volume 53, Issue 8, pp 579–596 | Cite as

The roles of magma and groundwater in the phreatic eurptions at Inyo Craters, Long Valley Caldera, California

  • Larry G Mastin


The Inyo Craters (North Inyo Crater and South Inyo Crater), and a third crater, Summit Crater, are the largest of more than a dozen 650- to 550-yr-B.p. phreatic craters that lie in a 1-km-square area at the south end of the Inyo Volcanic Chain, on the west side of the Long Valley Caldera in eastern California. The three craters are aligned within a 1-km-long northsouth system of fissures and normal faults, and coincide in age with aligned magmatic vents farther north in the Inyo Volcanic Chain, suggesting that they were all produced by intrusion of one or more dikes. To study the sequence and mechanisms of the eruptions, the deposits were mapped, sampled, and compared with subsurface stratigraphy obtained from the core of a slant hole drilled directly below the center of South Inyo Crater from the southwest. The deposits from the two Inyo Craters are fine-grained (median diameter less than 1 mm), are several meters thick at the crater walls, and cover at most a few km2 of ground surface. Stratigraphic relationships between the Inyo Craters and Summit Crater indicate that the eruptions proceeded from north to south, overlapped slightly in time, and produced indistinctly plane-parallel bedded, poorly sorted deposits, containing debris derived primarily from within 450 m of the surface. Debris from the deepest identifiable unit (whose top is at 450 m depth) is present at the very base of both Inyo Craters deposits, suggesting that the eruptive vents were open and tapping debris from at least that depth, probably along preexisting fractures, even at their inception. According to ballistic studies, the greatest velocity of ejected blocks was of the order of 100 m/s. All eruptions, particularly the least powerful, selectively removed debris from the finest-grained, most easily eroded subsurface units. Although juvenile fragments have been previously identified in these deposits, they are confined primarily to the grain-size fraction smaller than 0.25 mm dia. and probably did not constitute more than several percent of the deposit. It is therefore suggested that these juvenile fragments were not the main source of heat for the eruptions, and that the eruptions were caused either by: (1) heating of water by fragmented magma that was not ejected before the eruption shut off; (2) slow heating (over months to years) of groundwater under confined conditions without fragmentation of magma, followed by a second process (pressure buildup, seismic faulting, or intrusions) that breached the confinement; or (3) breach of a pre-existing confined geothermal aquifer.


Stratigraphy Slow Heating Pressure Buildup Seismic Fault Crater Wall 
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. Bailey RA (1989) Geologic map of the Long Valley Caldera, Mono-Inyo Craters Volcanic Chain, and Vicinity, eastern California. US Geol Surv Misc Invest Map I-1933Google Scholar
  2. Bailey RA, Dalrymple GB, Lanphere MA (1976) Volcanism, structure, and geochronology of Long Valley Caldera, Mono County, California. J Geophys Res 81: 725–744Google Scholar
  3. Bailey RA, MacDonald RA Thomas JE (1983) The Inyo-Mono Craters: products of an actively differentiating rhyolite magma chamber, eastern California. Eos 64: 336Google Scholar
  4. Bird RB, Stewart WE, Lightfoot EN (1960) Transport phenomena. John Wiley and Sons, New York, pp 1–780Google Scholar
  5. Christiansen RL, Peterson DW (1981) Chronology of the 1980 eruptive activity. In: The 1980 eruptions of Mt St Helens, Washington. US Geol Surv Prof Paper 1250Google Scholar
  6. Delaney PT (1982) Rapid intrusion of magma into wet rock: groundwater flow due to pore pressure increases. J Geophys Res 87: 7739–7756Google Scholar
  7. Delaney PT (1987) Heat transfer during emplacement and cooling of mafic dykes. In: Geol Assoc Canada Spec Paper on Mafic Dyke Swarms, pp 31–46Google Scholar
  8. Eichelberger JC, Vogel TA, Younker LW, Miller CD, Heiken GH, Wohletz KH (1988) Structure and stratigraphy beneath a young phreatic vent: South Inyo Crater, Long Valley Caldera, California. J Geophys Res 93: 13208–13220Google Scholar
  9. Feuillard M, Allegre CJ, Brandeis G, Gaulon R, Le Mouel JL, Mercier JC, Pozzi JC, Semet MP (1983) The 1975–1977 crisis of La Soufriere de Guadeloupe (F.W.I): a still-born magmatic eruption. J Volcanol Geotherm Res 16: 317–334Google Scholar
  10. Fink JH (1985) The geometry of silicic dikes beneath the Inyo domes, California. J Geophys Res 90 11127–11133Google Scholar
  11. Finch RH (1943) Lava surgings in Halemaumau and the explosive eruptions in 1924. Volcano Lett 479: 1–4Google Scholar
  12. Fisher RV (1968) Puu Hou littoral cones, Hawaii. Geol Rundsch 57: 837–864Google Scholar
  13. Fisher RV, Schmincke H-U (1984) Pyroclastic rocks. Springer, Berlin Heidelberg New York, pp 1–472Google Scholar
  14. Fudali RF, Melson WG (1972) Ejecta velocities, magma chamber pressure and kinetic energy associated with the 1968 eruption of Arenal volcano. Bull Volcanol 35: 383–401Google Scholar
  15. Hedenquist JW, Henley RW (1985) Hydrothermal eruptions in the Waiotapu Geothermal System, New Zealand: their origin, associated breccias, and relation to precious metal mineralization. Econ Geol 80: 1640–1668Google Scholar
  16. Gorshkov GS (1959) Gigantic eruption of the Bezymianny volcano. Bull Volcanol 2: 20Google Scholar
  17. Heiken GH, Goff F, Stix J, Tamanyu S, Shafiqullah M, Garcia S, Hagan R (1986) Intracaldera volcanic activity, Toledo Caldera and Embayment, Jemez Mountains, New Mexico. J Geophys Res 91: 1799–1815Google Scholar
  18. Huber NK, Rinehart CD (1965) Geologic map of the Devil's Postpile quadrangle, Sierra Nevada, California. US Geol Surv Map GQ-437Google Scholar
  19. Le Guern F, Bernard A, Chevrier RM (1980) Soufriere of Guadeloupe 1976–77 eruption-mass and energy transfer and volcanic health hazards. Bull Volcanol 43–3: 577–593Google Scholar
  20. Lloyd EF (1959) The hot springs and hydrothermal eruptions of Waiotapu. New Zealand J Geol Geophys 2: 141–176Google Scholar
  21. Lorenz V (1970) Some aspects of the eruption mechanism of the Big Hole Maar, central Oregon. Bull Geol Soc Am 81: 1823–1830Google Scholar
  22. Lorenz V (1973) On the formation of maars. Bull Volcanol 37: 183–204Google Scholar
  23. Lorenz V (1986) On the growth of maars and diatremes and its relevance to the formation of tuffurings. Bull Volcanol 48: 265–274Google Scholar
  24. Mastin LG, Pollard DD (1988) Surface deformation and shallow dike intrusion processes at Inyo Craters, Long Valley, CA. J Geophys Res 93: 13 221–13 235Google Scholar
  25. Metz JM, Mahood GA (1985) Precursors to the Bishop Tuff eruption: Glass Mountain, Long Valley, California. J Geophys Res 90: 11 121–11 126Google Scholar
  26. Miller CD (1985) Holocene eruptions at the Inyo Volcanic Chain, California — Implications for possible eruptions in Long Valley Caldera, Geology 13: 14–17Google Scholar
  27. Minakami T (1942) On the distribution of volcanic ejecta (part I). The distributions of volcanic bombs ejected by the recent explosions of Asama. Bull Earthquake Res Inst Tokyo 20: 65–91Google Scholar
  28. Moore JG, Nakamura K, Alcaraz A (1966) The 1965 eruption of Taal Volcano, Science 151: 955–960Google Scholar
  29. Muffler LJP, White DE, Truesdell AH (1971) Hydrothermal explosion craters in Yellowstone National Park. Geol Soc Am Bull 82: 723–740Google Scholar
  30. Nairn IA (1979) Rotomahana-Waimangu eruption, 1886: base surge and basalt magma. New Zealand J Geol Geophys 22: 363–378Google Scholar
  31. Nairn IA, Wiradiradja S (1980) Lae quaternary hydrothermal explosion breccias at Kawerau Geothermal Field, New Zealand. Bull Volcanol 43: 1–13Google Scholar
  32. Nairn IA, Wood CP, Hewson CAY (1979) Phreatic eruption of Ruapehu: April 1975. N Zealand J Geol Geophys 22: 155–173Google Scholar
  33. Nakamura K (1964) Volcano-stratigraphic study of Oshima Volcano Izu. Bull Earthquake Res Inst, Tokyo 42: 649–728Google Scholar
  34. Nelson CE, Giles DL (1985) Hydrothermal eruption mechanisms and hot spring gold deposits. Econ Geol 80: 1633–1639Google Scholar
  35. Pollard DD, Fink JH, Delaney PT (1984) Igneous dikes at Long Valley, CA: emplacement mechanisms and associated geologic structures, US Geol Surv Open File Rep 84-939: 130–146Google Scholar
  36. Prinz M (1970) Idaho rift system, Snake River Plain, Idaho. Bull Geol Soc Am 81: 941–948Google Scholar
  37. Sampson DE, Cameron KL (1987) The geochemistry of the Inyo Volcanic Chain: Multiple magma systems in the Long Valley region, eastern California. J Geophys Res 92: 10 403–10 421Google Scholar
  38. Self S, Sparks RSJ (1978) Characteristics of wide-spread pyroclastic deposits formed by the interaction of silicic magma and water. Bull Volcanol 41: 196–212Google Scholar
  39. Self S, Kienle J, Huot JP (1980) Ukinrek maars, Alaska, II. Deposits and formation of the 1977 craters. J Volcanol Geotherm Res 7: 39–65Google Scholar
  40. Shepherd JB, Sigurdsson H (1982) Mechanism of the 1979 explosive eruption of Soufriere volcano, St. Vincent. J Volcanol Geotherm Res 13: 119–130Google Scholar
  41. Sheridan MF, Wohletz KH (1983) Hydrovolcanism: Basis considerations and review. J Volcanol Geotherm Res 17: 1–29Google Scholar
  42. Sherwood AE (1967) Effect of air drag on particles ejected during explosive cratering. J Geophys Res 72: 1783–1791Google Scholar
  43. Sieh K, Bursik M (1986) Most recent eruption of the Mono Craters, eastern central California. J Geophys Res 91: 12539–13571Google Scholar
  44. Sorey ML (1985) Evolution and present state of the hydrothermal system in Long Valley Caldera. J Geophys Res 90: 11219–11228Google Scholar
  45. Sorey ML, Suemnicht GA, Sturchio NC, Nordquist GA (1991) New evidence on the hydrothermal system in Long Valley Caldera, California from wells, fluid sampling, electrical geophysics, and age determinations of hot-spring deposits. J Volc Geotherm Res. in pressGoogle Scholar
  46. Steinberg GS (1977) On the determination of the energy and depth of volcanic explosions. Bull Volcanol 40: 116–120Google Scholar
  47. Suemnicht GA (1987) Results of deep drilling in the western moat of Long Valley, California. Eos 68: 785–798Google Scholar
  48. Suemnicht GA, Varga RJ (1988) Basement structure and implications for hydrothermal circulation patterns in the western moat of Long Valley Caldera, California. J Geophys Res 93: 13191–13207Google Scholar
  49. Walker GPL (1971) Grain-size characteristics of pyroclastic deposits. J Geol 79: 696–714Google Scholar
  50. White DE (1955) Violent mud-volcano eruptions of Lake City Hot Springs, northeastern California. Bull Geol Soc Am 66: 1109–1130Google Scholar
  51. Whyte F (1968) Lower Carboniferous volcanic vents in the west of Scotland. Bull Volcanol 32: 253–268Google Scholar
  52. Williams H, McBirney AR (1979) Volcanology. Freeman, San Francisco, pp 1–391Google Scholar
  53. Wilson L, Head JW III (1981) Ascent and eruption of basaltic magma on the Earth and moon. J Geophys Res 86: 2971–3001Google Scholar
  54. Wohletz KH (1986) Explosive magma-water interactions: thermodynamics, explosion mechanisms, and field studies. Bull Volcanol 48: 245–264Google Scholar
  55. Wohletz KH, McQueen RG (1984) Experimental studies of hydromagmatic volcanism. In: Explosive volcanism: inception, evolution, and hazards. National Academy Press, Washington, pp 158–169Google Scholar
  56. Wohletz KH, Sheridan MF (1983) Hydrovolcanic explosions II. Evolution of basaltic tuff rings and tuff cones. Am J Sci 283: 385–413Google Scholar
  57. Wood S (1977) Distribution, correlation, and radiometric dating of late Holocene tephra, Mono and Inyo Craters, eastern California. Geol Soc Am Bull 88: 89–95Google Scholar
  58. Yokoyama I (1956) Energetics in active volcanoes. 1st paper. (Activities of volcano Mihara, Ooshima Island during the period 1953–54). Tokyo Univ Bull Earthquake Res Inst 34: 190–195Google Scholar
  59. Yokoyama I Energetics in active volcanoes. 2nd paper. Tokyo Univ Bull Earthquake Res Inst 35: 75–97Google Scholar

Copyright information

© Springer-Verlag 1991

Authors and Affiliations

  • Larry G Mastin
    • 1
  1. 1.Department of Applied Earth SciencesStanford UniversityUSA

Personalised recommendations