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Department of Mineral Sciences

Izalco Volcano

  • William G. Melson
  • Senior Scientist Emeritus, Division of Petrology and Volcanology
  • Phone:   (202) 633-1809
  • Fax:   (202) 357-2476
  • E-mail Address:   melsonw atsiedu
  • Mailing Address:
    Smithsonian Institution
    PO Box 37012, MRC 119
    Washington, DC 20013-7012
  • Shipping Address:
    Smithsonian Institution
    National Museum of Natural History
    10th & Constitution NW
    Washington, DC 20560-0119


Ph.D. Princeton University (1964)

Research Interests

Papers and abstract published or in press over the past five years deal with three areas of research:

Volcanology: I have been designing and using automated seismic and acoustic monitoring equipment installed at Arenal Volcano, Costa Rica, Central America's most active volcano. This and earlier research on explosive volcanism contributes to pure research on the mechanisms and patterns of volcanic eruptions and to applied research on volcanic hazards. The latter includes consulting to the Nuclear Waste Technical Review Board re volcanic hazards to the proposed high-level nuclear waste repository at Yucca Mountain, Nevada. In a second area of volcanology, a paper was presented to the Journal of Geophysical Research on the composition of submarine volcanic glasses from seafloor spreading centers, data important in the interpretation of the processes that produce ocean basins, an area of research throughout my career at the Museum.

Geoarcheology. One of the real benefits of being at MNH for me is the opportunity for inderdisciplinary research. Thus, I have pursued studies mainly with my archaeological colleagues. Recent work integrates material science aspects into a number of archaeological problems. A publication is in press in the Journal of Archaeological Sciences concerning the origin of reddened to partially molten sediments at a Homo Erectus site at Olorgesalie, Kenya, with Richard Potts, and in a paper with Gus Van Beek on the site of manufacture of Assyrian Palace Ware from 6th Century BC, Tell Jemmeh, Israel. The fruitful merging of disciplines is one of the most important aspects of this research.

Geological History of the Central Appalachians. This project involves reconstructing some major events in the volcanic and plate tectonic processes that shaped the modern Appalachians. The importance of this work derives from bringing into focus specific processes and their timing. An abstract at this Fall's American Geophysical Union by intern Dawn Stodden and me on the Cambro-Ordovician collision of an oceanic trench with eastern North America is the most recent contribution to this project.


Petrology, Geology and Geophysics of the Oceanic Lithosphere

1966. Melson, W.G., Bowen, V.T., Van Andel, Tj. H., and Siever, R., Greenstones from the Central Valley of the Mid-Atlantic Ridge. Nature, v. 209, 604-605.

1966. Melson, W.G., Van Andel, Tj. and Jarosewich, E., 1966. Metamorphism in the Mid-Atlantic Ridge. Marine Geology, v. 4, 165-186.

1966. Melson, W.G., Geologic significance of St. Paul's Rocks. Oceanus, v.7, 8-12.

1967. Luyendyck, B.P. and Melson, W.G., 1967. Magnetic properties and petrology of rocks near the crest of the Mid-Atlantic Ridge. Nature, v. 215, no. 5097, 147-149.

1967. Pierce, J.W., and Melson, W.G., Dolomite from the continental slope off southern California. Journal of Sedimentary Petrology, Sept., 963-966.

1967. Melson, W.G., Jarosewich, E., and Cifelli, R., Alkali olivine basalt dredged near St. Paul's Rocks, Mid-Atlantic Ridge: Nature, v. 215, no. 5099, 381-382.

1967. Melson, W.G., Jarosewich, E., Bowen, V.T., and Thompson, G., St. Peter and St. Paul's Rocks: a high-temperature mantle-derived intrusion. Science, v. 177, 1532-1535.

1968. Cifelli, C., Blow, W., and Melson, W.G., Paleogene sediment dredged from a fracture zone of the Mid-Atlantic Ridge. Journal of Marine Research, v. 26, no. 2, 105-109.

1968. Thompson, G., Melson, W.G., Cifelli, R., and Bowen, V.T., Lithified carbonates from the Equatorial Atlantic, Journ. Sedimentary Petrology, v.38, no. 4, 1305-1317.

1968. Melson, W.G., Thompson, G. and Van Andel, Tj., 1968. Volcanism and metamorphism in the Mid-Atlantic Ridge: 22 N. Latitude. Journal of Geophysical Research, v. 73, no. 18, 5925-5941.

1969. Melson, W.G., Preliminary results of a geophysical survey of the Jun de Fuca Ridge and Blanco Trough. Technical memorandum 6, C&GSTMS, ESSA, 33 p.

1970. Switzer, G., Melson, W.G. and Thompson, G., 1970. Garnet from the Mid-Atlantic Ridge near 43 N. latitude: Bulletin Geological Society of America, v. 81, 895-898.

1970. Melson, W.G. and Thomspon, G., Layered basic complex in oceanic crust, Equatorial Atlantic. Science, v. 168, 817-820.

1970. Thompson, G. and Melson, W.G., 1970. Boron contents of serpentinties and metabasalts in the oceanic crust: Implications for the boron cycle. Earth and Planetary Science Letters, v. 8, 61-65.

1970. Melson, W.G. and Thompson, G., 1971, Petrology of a transform fault zone and adjacent ridge segments. Philosophical Transactions Royal Society, London, A: v. 268, 423-441.

1972. Switzer, G., Melson, W.G., and Thompson, G., 1972. Olivine crystals from the floor of the Mid-Atlantic Ridge near 22 N. latitude. Smithsonian Contributions to Earth Sciences, no. 9, 43-46.

1972. Melson, W.G., Hart, S.R., Thompson, G., 1972. St. Paul's Rocks, Equatorial Atlantic: petrogenesis, radiometric ages and implications on sea-floor spreading. Geological Society of America Memoire 132, 241-272.

1972. Thompson,G. and Melson, W.G., Petrology of oceanic crust across fracture zones: evidence of a new kind of sea-floor spreading. Journal of Geology, v. 80, 526-538.

1972. Melson, W.G., Volcanic rocks recovered from Leg 6 of the Deep Sea Drilling Project: Initial Reports of the Deep Sea Drilling Project, (6) 1110-1120.

1972. Wright, T.L., Benson, W.E., Melson, W.G. and Hart, S.R. 1972. Petrology of basaltic rocks collected from Leg 14. (14) Initial Reports of the Deep Sea Drilling Project.

1972. Melson, W.G., Glassy abyssal basalts, Atlantic sea floor near St. Paul's Rocks: Petrography and composition of secondary clay minerals. Bulletin Geological Society of America, (84), 703-716.

1973. Melson, W.G., Note on high-alumina basalt dredged near the Aleutian Trench. Smithsonian Contributions to Earth Sciences, (14), 21-24.

1973. Melson, W.G., 1973. Basaltic glasses from the Deep Sea Drilling Project: Chemical characteristics, fission track ages, and alteration products: EOS, (54) 1011-1016.

1973. Donnelly, T.W., and W. Melson. Chemical studies of amphiboles, pyroxene, and other mineralsfrom Caribbean deep-sea sedimets, Leg 15. Chapter 28 in Initial reporst of the Deep-sea Drilling Project, (13), 963-968.

1973. Donnelly, T.W., W. Melson, R. Kay, and J.J.W. Rogers. Basalts and dolerites of late Cretaceous age from the centr caribbean. Chapter 30 in Initial reporst of the Deep-sea Drilling Project, (13), 989-1011.

1974. Melson, W.G., Aumento,F., and the Shipboard Party, Deep Sea Drilling Project: Leg 37 - The Volcanic Layer. Geotimes, Dec., 16-18.

1976. Hyndman, R.D., Aumento, F., Melson, W.G. et al., Seismic structure of the oceanic crust from deep drilling on the mid-Atlantic Ridge. Geophysical Research Letters, v. 3, 201-204.

1976. Rabinowitz, P., Melson, W.G. and Shipboard Party, 1976. Challenger drills on Leg 45 along the mid-Atlantic Ridge: Geotimes. April, 20-23.

1976. Byerly, G., Melson, W.G. and Vogt, P.R., Rhyodacites, andesites, ferro-basalts and oceanic tholeiites from the Galapagos Spreading Center. Earth and Planetary Science Letters, v. 30, 215-221.

1976. Melson, W.G., Vallier, T., Wright, T.L., Byerly, G. and Nelen, J., Chemical diversity of abyssal volcanic glass erupted along sea-floor spreading centers. Journal Geophysical Research Monograph 19, 351-368.

1977. Byerly, G., Melson, W.G., Nelen, J., and Jarosewich, E., 1977. Abyssal volcanic glasses as indicators of magma compositions. Smithsonian Contributions to the Earth Sciences, V. 19, 22-29.

1977. Aumento, F., Melson, W.G. and Shipboard Party, Initial Reports of the Deep Sea Drilling Project, Leg 37. 1008 pp., U.S. Government Printing Office, Washington D.C.

1977. Melson, W.G., Byerly, G., Nelen, J., O'Hearn, T., Wright, T.L. and Vallier, T., A catalog of the major element chemistry of abyssal volcanic glasses. Smithsonian Contributions to the Earth Sciences, no. 19, 31-60.

1978. Melson, W.G., Rabinowitz, P., and Shipboard Party, Deep crustal drilling results near 22N, Mid-Atlantic Ridge. Initial Reports of the Deep Sea Drilling Project. v. 45. 717 pp. U.S. Government Printing Office.

1979. Melson, W.G. and O'Hearn, T., Basaltic glasses erupted along the mid-Atlantic Ridge between 0-37 N latitude: correlations between composition and latitude. American Geophysical Union Monograph 48, 249-261.

1980. Thompson, G., Bryan, W.B. and Melson, W.G., Geological and geophysical investigation of the mid-Cayman Rise Spreading center: geochemical variations and petrogenesis of basaltic glasses. Journal Geology, v. 88, 41-55.

1980. Natland, J.H., and Melson, W.G., 1980. Compositions of basaltic glasses from the East Pacific Rise. Initial Reports of the Deep Sea Drilling Project, v. 54, 705-723.

1980. Humphris, S.E., Melson, W.G. and Thompson, R.N., 1980. Basalt weathering on the East Pacific Rise and the Galapagos Spreading Center, Deep Sea Drilling Project Leg 54. in V. 54, Initial Reports of the Deep Sea Drilling Project, Rosendahl, B.R. and Hekinian, R. et al., 773-787.

1983. Natland, J.H., Adamson, A.C., Laverne, C., Melson, W.G. and O'Hearn, 1983. A compositionally zoned nearly steady state magma chamber at the Costa Rica Rift: evidence from basalt glass and mineral data, Deep Sea Drilling Project Sites 501, 504, and 505. Initial Reports of the Deep Sea Drilling Project, v. 69. U.S. Government Printing Office.

1983. Robinson, P.T., Melson, W.G., O'Hearn, T., and Schmincke, H-U., Volcanic glass compositions of the Troodos Opiolite, Cyprus. Geology, v. 11, no. 7, 400-404.

1984. Roden, M.K., Hart, S.R., Frey, F.A.,and Melson, W.G., Sr, Nd, and Pb isotopic and REE geochemistry of St. Paul's Rocks: the metamorphic and metasomatic development of an alkali basalt source. Contributions to Mineralogy and Petrology, v. 85, 376-390.

1984. Natland, J.H., Tarney, J., Marsh, N.G., Melson, W.G. and O'Hearn, T., Compositions, stratigraphy and alteration of pillow basalts, Hole 543A, near the Barbados Ridge. Initial Reports of the Deep Sea Drilling Project, 78, 393- 399.

1984. Dmitriev, L.V., Sobolev, A.V., Uchanov, A.V., Malysheva, T.V., and Melson, W.G., Primary differences in oxygen fugacity and depth of melting in mantle source regions for oceanic basalts, Earth and Planetary Science Letters, v. 70, 303-310.

1985. G. Thompson, W.B. Bryan, R. Ballard, K. Hanuro, and W.G. Melson. Axial processes along a segment of the East Pacific Rise, 10o-12o N. Nature (318, 6045), 429-433.

1986. Melson, W.G. and O'Hearn, T., Zero-age variations in the composition of abyssal volcanic rocks along the axial zone of the mid-Atlantic Ridge: Decade of North American Geology series-The North Atlantic Sea Floor, B. Tucholke and P. Vogt, Editors, Geological Society of America, Vol. M., Ch. 8, 117-136.

1987. Melson, W.G., Background to "Metamorphism in the mid-Atlantic Ridge", Citation Classic, in Current Contents, v. 18, no. 12, p. 16.

1988. Melson, W.G., O'Hearn and Fredriksson, K., Composition and origin of basaltic glass spherules in pelagic clay from the eastern Pacific. Marine Geology. v. 83, 253-271.

1989. Batiza, R., Fox, P.J., Vogt, P.R., Cande, S.C., Grindlay, N.R., Melson, W.G. and O'Hearn,T., Morphology, abundance, and chemistry of near-ridge seamounts in the vicinity of the mid-Atlantic Ridge @26oS. Jour. Geology. 97:209-200.

2002. Melson, W., O'Hearn T. and Jarosewich, 2002, A data brief on the Smithsonian Abyssal Volcanic Glass Data File, Geochemistry, Geophysics and Geosystems, 3 (4) No. 10.1029/2001GC000249


1968. Melson, W.G., and Saenz, R., Preliminary results of investigations of the 1968 eruption of Arenal Volcano, Costa Rica. Smithsonian Center for Short-Lived Phenomena Reports, Nov.

1968. Moore, J. and Melson, W.G., Nuees ardentes of the 1968 eruption of Mayon Volcano, Philippines. Bulletin of Volcanology, v. 33, 600-621.

1969. MacDonald, W.D. and Melson, W.G., 1969. A late Cenozoic volcanic province in Hispaniola: Caribbean Journ. Science, v. 9, 81-91.

1970. Melson, W.G., Jarosewich, E., and Lundquist, C.A., Volcanic eruptions at Metis Shoals, Tonga. Smithsonian Contributions to the Earth Sciences, no. 4, 18 pp.

1971. Fudali, R., and Melson, W.G., 1972. Ejecta velocities, magma chamber pressure and kinetic energy associated with the 1968 eruption of Arenal Volcano, Costa Rica. Bulletin of Volcanology, v. 35, 383-401.

1972. Melson, W.G., Jarosewich, E., Switzer, G. and Thompson, G., Basaltic nuess ardentes of the 1970 eruption of Ulawun Volcano, Papua New Guinea. Smithsonian Contributions to Earth Sciences, no. 9, 15-32.

1973. Melson, W.G. and Saenz, R., Volume, energy and cyclicity of eruptions of Arenal Volcano, Costa Rica. Bulletin Volcanologique, V. 37-3, 416-437.

1978. Melson, W.G., Eruption of Arenal Volcano, Costa Rica. National Geographic Research Reports for 1969, 433-446.

1981. Melson, W.G. and Hopson, C.A., Pre-eruption temperatures and oxygen fugacities in the 1980 eruptive sequence: in "The 1980 Eruptions of Mt. St. Helens", U. S. Geological Survey Professional Paper 1280, 641-648.

1982. Bennett, J.T., Krishnaswami,S., Turekian, K.K., Melson, W.G. and Hopson, C.A., The uranium and thorium decay series nuclides in Mt. St. Helens effusives. Earth and Planetary Science Letters, v. 60, 61-69.

1982. Melson, W.G., The cyclical nature of explosive volcanism: a petrological approach to volcano forecasting: California Division of Mines and Geology, Special Paper 63- "Status of volcanic prediction and emergency response capabilities in volcanic hazard zones in California", 99-118.

1982. Melson, W.G., 1982, Alternation between acidic and basic magmas in major explosive eruptions of Arenal Volcano, Costa Rica: Boletin de Vulcanologia, Univesidad Nacional, Heredia, Costa Rica, no. 14, pp. 65-74.

1983. Melson, Monitoring of the 1980-82 eruptions of Mount St. Helens: Compositions and abundances of glass. Science. 221, p.1387-1391.

1983. Newhall, C.G. and Melson, W.G., Explosive activity associated with the growth of volcanic domes: Volcanology and Geothermal Research, v. 17, 111-113.

1984. Melson, W.G., Pre-historic eruptions of Arenal Volcano, Costa Rica, Vinculos (Museo Nacional, San Jose, Costa Rica) 10:20-35.

1985. Murase, M., McBirney, A.R. and Melson, W.G., Viscosity of the dome of Mount St. Helens: Journal of Volcanology and Geothermal Research, v. 24, pp. 193-204.

1985. Melson, W.G., Allan, J.F., Jerez, D., Nelen, J.,Calavache, M.L., Williams, S.N., Fournelle, J., and Perfit, M., Water contents, temperatures and diversity of the catastrophic eruption of Nevado del Ruiz, Colombia, November 13, 1985: Journ. Vol. Geotherm. Research., v. 41, 97-126.

1986. Melson, W.G., Barquero, J., Saenz, R., and Fernandez, E., Erupciones explosivas de importancia en volcanes de Costa Rica, Boletin Volcanologia (Universidad Nacional, Heredia, Costa Rica) 16:15-22.

1988. Melson, W.G., Saenz, R., Barquero, J. and Fernandez, E., Edad relativo de las erupciones del Cerro Congo y Laguna Hule, Boletin de Vulcanologia, 19 (8-10), Univesidad Nacional, Heredia, Costa Rica.

1988. Borgia, A., Poore, C., Carr, M.J., Melson, W.G. and Albarado, G.F., Structrural, stratigraphic, and petrologic aspects of the Arenal-Cerro Chato volcanic system: evolution of a young stratvolcano complex. Bull. Volcanology. 50:86-105.

1989. Funk, V.A. and Melson, W.G., Volcanological and Biological Observatory at Arenal Volcano (Alajuela Province, Costa Rica). Biotropica 21(1): 95-96.

1990. Hopson, C.A. and Melson, W.G. 1990. Compositional trends and eruptive cycles at Mount St. Helens. Geoscience Canada 17(3) 131-141.

1992. Melson, W.G., The eruption of 1968 and tephra stratigraphy of Arenal Volcano, Costa Rica. pp. 24-47. In Archaeology, Volcanism and Remote Sensing in the Arenal Region, Costa Rica. Edited by P. Sheets and B. McKee. 350 pp. Texas University Press, Austin.

1995. Haynes, J.T., Melson, W.G., and Kunk, M.J., Composition of biotite phenocrysts in Ordovician tephra casts doubt on the proposed trans-Atlantic correlation of the Millbrig K-bentonite (United States) and the Kinnekulle K-bentonite (Sweden). Geology (23-9), 847-850

1996. Haynes, J.T., Melson, W.G., and Goggin, K.E., Biotite phenocryst compositions shows that two K-bentonites in the Little Oak Limestone (Ordovician) at the Old North Ragland Quarry, Alabama, are the same structurally repeated tephra layer. Southeastern Geology (36-2), 1-14.

1997, Haynes, J.T. and Melson, W.G. SEM and EMX study of titaniferous minerals in the Ordovician Deicke K-bentonite of southwestern Virginia. Virginia Minerals 43(1). 8 pp.

1998. Haynes, J.T., Melson, W.G., O'Hearn, T., Goggin, K.E. and Hubbell, R., A High-potassium Mid-Ordovician Shale of the Central Appalachian Foredeep: Implications for Reconstructing Taconian Explosive Volcanism. Pp. 129-141. In Shales and Mudstones II, Schweizerbart'sche Verlagsbuchhandlung, Stuttgart, Germary.


1969. Melson, W.G., Note on the petrography of potsherds from Hajar Bin Humeid and other south Arabian localities: in Hajar Bin Humeid: Investigations of a Pre-Islamic Site in South Arabia, by Gus Van Beek et al., Johns Hopkins University Press, 409-413.

1983. Melson, W.G., and Van Beek, G., Properties, cultural selection, and provenance of pumice from Tell Gemmeh, Israel. Society for Archaeological Sciences Research Reports, 4, 3-6.

1986. De Atley, S.P.,and Melson, W.G., Evaluating prehistoric ceramic clays, Research Report No. 8, Society for Archaeological Sciences, v. 9, no. 3, pp. 3-7.

1991. Melson, W.G. and Van Beek, V.B., Geology and the loessial soils, Tell Gemmeh. Israel. Geoarchaeology. V. 7(2). 121-147.

1992. Sheets, P., Hoopes, J., Melson, W.G., McKee, B., Sever, T., Mueller, M., Chenault, M. and Bradley, J. 1992. Prehistory and volcanism in the Arenal area, Costa Rica. Journal of Field Archaeology 18, 445-465.

2002. Melson, W.G. and Potts, R. Combustion metamorphism in the sediments of the Pleistocene Olorgesailie Basin, Southern Kenya Rift. Journal of Archaeological Science, 29, 307-316.

The Lunar Rocks

1970. Mason, B., and Melson, W.G., Comparison of lunar rocks with basalts and stony meteorites. Proceedings of the Apollo 11 Lunar Science Conference, v. 1, 661-671.

1970. Mason, B. and Melson, W.G., The Lunar Rocks. John Wiley and Sons, New York. 192 pp.

1970. Mason, B., Fredriksson, K., Henderson, E.P., Jarosewich, E., Melson, W.G., Towe, K.M., and White, J.S. Jr. 1970. Mineralogy and petrography of lunar samples. Science, v. 167. pp. 656-659.

1970. Fredriksson, K., Nelen, J., and Melson, W.G., Petrography and origin of lunar breccias and glasses. Proceedings of the Apollo 11 Lunar Sceince Conference, v. 1. pp. 419-432.

1970. Fredrikkson, K., Nelen, J., Melson, W.G., Henderson, E.P., and Andersen, C.A. Lunar glasses and microbreccias: properties and origin. Science, v. 167. pp. 664-666.

1971. Melson, W.G. and Mason, B., Lunar "basalts": some comparisons with terrestrial basalts and meteoritic analogs, and a proposed classification and nomenclature. Proceedings of the Apollo 12 Lunar Science Conference, v. 1, 459-467.

1971. Preliminary Examination Team, 1971. Preliminary Examination of the Apollo 14 samples. Science. v. 173. pp. 681-693.

1972. Mason, B., Melson, W.G., Henderson, E.P., Jarosewich, E. and Nelen, J., Mineralogy and petrography of some Apollo 12 samples. Smithsonian Contributions to Earth Sciences, no. 9, 1-4.

Geology of Montana

1971. Melson, W.G., 1971. Geology of the Lincoln area, Lewis and Clarke Co., Montana. Smithsonian Contributions to the Earth Sciences, no. 7, 29 pp.

Popular Articles

1970. Melson, W.G., 1970, America's sleeping volcanoes: National Wildlife Mag., Dec.-Jan.

1979. Melson, W.G., Shenandoah roots. The American land, Smithsonian Exposition Books, pp. 60-67, Smithsonian Insitution, Wash. D.C.

1997. Melson, W.G.; Post, J.E.; Wise, M.A.; Sorensen, S.S.; Fiske, R.S.; Luhr, James; MacPherson, G.J., McCoy, T., Diamonds to diamonds: a tour of the Smithsonian's new Geology, Gems, & Minerals Hall. Geotimes, 42(12), 16-21.

2000. Melson, W.G., Global Synergies. In "Forces of Change, A New View of Nature", National Geographic Press, 79-92.


1972. Switzer, G. and Melson, W.G., Origin and composition of rock fulgurite glass. Smithsonian Contributions to Earth Sciences, no. 9, 47-51.

Petrology and Ore Collections, U.S. National Museum, Smithsonian Institution

1985. Melson, W.G., and Banks, H., The Dale Jackson collection, Geotimes, v. 30, no.4,p. 5.

1988. Melson, W.G., National Collection of Rocks and Ores, in Collections for the Future: Archivists, Curators, historians, Bibliographers Speak, 18 (26-36). Geoscience Information Society.

Appalachian Geology

1998. Melson, W.G., Haynes, J.T., O'Hearn, T., Hubbell, R., Goggin, K.E., Locke, D. and Ross, D., K-shales of the central Appalachian Paleozoic: Properties and Origin. In Progress in Shale Research, pp. 143-160. Springer-Verlag.

Metamorphic Petrology

1966. Melson, W.G., Phase equilibria in calc-silicate hornfels, Lewis and Clarke County, Montana: American Mineralogist, v. 51, 402-421.

1966. Melson, W.G. and Switzer, G., Plagioclase-spinel-graphite xenoliths in metallic iron-bearing basalts, Disko Island, Greenland. American Mineralogist, v. 51, 664-676.

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