Kenneth C. Macdonald

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Kenneth C. Macdonald
Ken Macdonald.jpg
Ken Macdonald at the Columbia River, OR, USA
Born1947
NationalityAmerican
Alma materUC Berkeley MIT
Known forocean spreading centers deep sea hydrothermal vents
Awards
  • Fellow Geological Soc. America
  • Fellow Amer. Geophys. Union
  • Fellow Amer. Assoc. Adv. Science
  • Member, American Academy of Arts and Sciences
  • Cody Medal
  • Newcomb Cleveland Prize of Amer. Assoc. Adv. Science
Scientific career
Institutions
Doctoral advisorBruce Luyendyk, Tanya Atwater
Websitewww.geol.ucsb.edu/faculty/macdonald/index.php

Kenneth Craig Macdonald is an American oceanographer and marine geophysicist born in San Francisco, CA in 1947. As of 2018 he is Professor Emeritus at the Department of Earth Science and the Marine Sciences Institute at the University of California, Santa Barbara (UCSB). His work focuses on the tectonics and geophysics of the global mid-oceanic ridge including its spreading centers and transform faults, two of the three types of plate boundaries central to the theory of plate tectonics. His work has taken him to the north and south Atlantic oceans, the north and south Pacific oceans, the Indian Ocean, the Red Sea and the Sea of Cortez, as well as to the deep seafloor on over 50 dives in the research submersible ALVIN. Macdonald has participated in over 40 deep sea expeditions, and was Chief- or Co-Chief Scientist on 31 expeditions.

Early life and education[edit]

Macdonald grew up in El Cerrito and Richmond, California, and graduated from Harry Ells High School in 1966. He attended UC Berkeley graduating with a B.S. in Engineering in 1970. Funded by a National Science Foundation Graduate Fellowship, he attended the Massachusetts Institute of Technology in 1970, graduating from the MIT/Woods Hole Oceanographic Institution Joint Program in Oceanography specializing in marine geophysics in 1975. He was awarded a Cecil H. and Ida Green Research Fellowship to work at the Institute of Geophysics and Planetary Physics with Dr. James Brune in 1975. He joined the research staff at the Scripps Institution of Oceanography in 1976 as Research Geophysicist working with Dr. Fred Spiess. In 1979, he joined the faculty of the Department of Geological Sciences at UCSB and the Marine Sciences Institute as an Associate Professor and Research Geophysicist.

Career and impact[edit]

His PhD work focused on the tectonic and magnetic properties of the Mid-Atlantic Ridge on an expedition led by Dr. Bruce Luyendyk.[1][2][3] (his other primary advisor was Dr. Tanya Atwater[4][5]).

He was Co-Chief Scientist of the expedition which discovered superheated "black smoker" hydrothermal vents on the East Pacific Rise in 1979,[6] and was the first to calculate their contribution to global geothermal heat flux.[7] He was also chief scientist and lead diver on the expedition which documented in situ, the recording of magnetic reversals in the volcanic rocks of the deep seafloor, an important aspect of proving seafloor spreading and plate tectonics.[8][9]

Macdonald led expeditions which mapped the Vema and Tamayo Transform faults, showing that the plate boundary intersection of an oceanic ridge and transform fault is sharp, only a few km in area, and documenting that these two types of plate boundaries are narrow.[10][11] Their work demonstrated that the inside corner region is an area of diffuse deformation caused by extreme tectonic extension.[12]

He was Chief Scientist on the expedition which discovered “Overlapping Spreading Centers” (OSCs).[13] In this geometry two active spreading centers overlap, apparently pushing against each other, which would violate one of the rules of plate tectonics: plates are rigid. This paradox is solved by the fact that the OSCs are non-steady-state, and propagate along the ridge; as one segment lengthens, the neighboring segment shortens, and the overlapped region migrates.[14]

Previous to this discovery, it was thought that mid-ocean ridges were offset only by transform faults, usually at right angles. The expedition found that the ridge is segmented on a length scale of hundreds of kilometers by transform faults, but also at much shorter scales, km to tens of kilometers, by Overlapping Spreading Centers and other types of nontransform discontinuities.[15] The long segments persist for millions of years, while the finer scale segments are shorter-lived, hundreds of thousands of years or less. The shorter segments are important because they define the scale at which individual volcanoes function on the ridge, which, in turn, control the creation of new oceanic crust and hydrothermal activity[16][17]

Awards and Honors[edit]

In recognition of his work he was the first marine geophysicist to be awarded the Cody gold medal and prize for his outstanding work and leadership in the Ocean Sciences as well as election as Fellow to the American Academy of Arts and Sciences, Fellow of the American Association for the Advancement of Science, Fellow of the American Geophysical Union (1995), Fellow of the Geological Society of America (1995) and co-recipient of the Newcomb Cleveland Prize for the most important article published in Science magazine in 1980 for the discovery and analysis of black smoker vents.

Leadership in the profession[edit]

He has contributed to the advancement of ocean sciences by serving on the Ocean Studies Board of the National Academy of Sciences (1980–83), the Oceanic Lithosphere Panel for the Advanced Drilling Project (Deep Sea Drilling Project) (1983–85), member of the ALVIN Review Committee (1979–82), founding member of the RIDGE Steering Committee (1987–90), member of the U.S. Geodynamics Committee (of the National Research Council) (1999-2000), Chairman National Undersea Research Panel of the National Undersea Research Program (NOAA) (2002), member of the Woods Hole Oceanographic Institution Corporation, and numerous panels and future planning committees for the National Science Foundation, in particular for NSF Ocean Sciences program.

He has also served in the following editorial capacities: Associate Editor, Journal of Geophysical Research; Associate Editor, Earth and Planetary Science Letters; Co-Editor, Marine Geophysical Researches; Section Editor, Encyclopedia of Ocean Sciences; Section Editor, Encyclopedia of Geology.

Selected Works[edit]

  • The crest of the East Pacific Rise, Scientific American 244:100-117, 1981, Macdonald, K.C. and B.P. Luyendyk.
  • Mid-ocean ridges: Fine scale tectonic, volcanic and hydrothermal processes within the plate boundary zone, Annu. Rev. Earth Planet. Sci. 10:155-190, 1982, Macdonald, K.C.
  • East Pacific Rise from Siqueiros to Orozco fracture zones: Along-strike continuity of axial neovolcanic zone and structure and evolution of overlapping spreading centers, J. Geophys. Res. 89:6049-6069 and 6301-6306, 1984, Macdonald, K.C., J.-C. Sempere and P.J. Fox.
  • A new view of the mid-ocean ridge from the behaviour of ridge axis discontinuities, Nature 335:217-225, 1988, Macdonald, K.C., P.J. Fox, L.J. Perram, M.F. Eisen, R.M. Haymon, S.P. Miller, S.M. Carbotte, M.-H. Cormier and A.N. Shor.
  • The mid-ocean ridge, Scientific American 262:72-79, 1990, Macdonald, K.C. and P.J. Fox.
  • Mid-ocean ridges: Discontinuities, segments and giant cracks, Science 253:986-994, 1991, Macdonald, K.C., D.S. Scheirer and S.M. Carbotte.
  • Hydrothermal vent distribution along the East Pacific Rise crest (9°09'-54'N) and its relationship to magmatic and tectonic processes on fast-spreading mid-ocean ridges, Earth Planet. Sci. Lett. 104:513-534, 1991, Haymon, R.M., D.J. Fornari, M.H. Edwards, S. Carbotte, D. Wright and K.C. Macdonald.
  • East Pacific Rise 8°-10°30'N: Evolution of ridge segments and discontinuities from SeaMARC II and three-dimensional magnetic studies, J. Geophys. Res. 97: 6959-6982, 1992, Carbotte, S. and K. Macdonald.
  • Volcanic growth faults and the origin of Pacific abyssal hills, Nature 380:125-129, 1996, Macdonald, K.C., P.J. Fox, R.T. Alexander, R. Pockalny, and P. Gente.
  • Seafloor Spreading: Mid-Ocean Ridge Tectonics, in Encyclopedia of Ocean Sciences (eds. J. Steele, S. Thorpe, K. Turekian), Academic Press, p. 1798-1813, 2001 (updated 2017), Macdonald, Ken C.

References[edit]

  1. ^ Luyendyk, B.P. and K.C. Macdonald (1977). "Physiography and structure of the Famous Rift Valley inner floor observed with a deep towed instrument package". Bull. Geol. Soc. Am. 88 (5): 648–663. doi:10.1130/0016-7606(1977)88<648:PASOTI>2.0.CO;2.
  2. ^ Macdonald, K.C. (1977). "Near-bottom magnetic anomalies, asymmetric spreading, oblique spreading, and tectonics of the Mid-Atlantic Ridge (37°N)". Bull. Geol. Soc. Am. 88 (4): 541–555. doi:10.1130/0016-7606(1977)88<541:NMAASO>2.0.CO;2.
  3. ^ Macdonald, K.C. and B.P. Luyendyk (1977). "Deep-tow studies of the structure of the Mid-Atlantic Ridge crest near 37°N (Famous)". Bull. Geol. Soc. Am. 88 (5): 621–636. doi:10.1130/0016-7606(1977)88<621:DSOTSO>2.0.CO;2.
  4. ^ Atwater, T.M. and K.C. Macdonald (1977). "Are spreading centres perpendicular to their transform faults?". Nature. 270 (5639): 715–719. doi:10.1038/270715a0.
  5. ^ Macdonald, K.C. and T.M. Atwater (1978). "Evolution of rifted ocean ridges". Earth Planet. Sci. Lett. 39 (3): 319–327. doi:10.1016/0012-821X(78)90017-1.
  6. ^ Spiess, F.N.; K.C. Macdonald; et al. (1980). "East Pacific Rise: Hot springs and geophysical experiments". Science. 207 (4438): 1421–1433. doi:10.1126/science.207.4438.1421. PMID 17779602.
  7. ^ Macdonald, K.C., K. Becker, F.N. Spiess and R. Ballard (1980). "Hydrothermal heat flux of the black smoker vents on the East Pacific Rise". Earth Planet. Sci. Lett. 48: 1–7. doi:10.1016/0012-821X(80)90163-6.CS1 maint: Multiple names: authors list (link)
  8. ^ Macdonald, K.C., S.P. Miller, B.P. Luyendyk, T.M. Atwater and L. Shure (1983). "Investigation of a Vine-Matthews magnetic lineation from a submersible: The source and character of marine magnetic anomalies, 1983". J. Geophys. Res. 88: 3403–3418. doi:10.1029/JB088iB04p03403.CS1 maint: Multiple names: authors list (link)
  9. ^ Cann, J.R. (1983). "Magnetic Reversals from a Submersible". Nature. 305 (5930): 100. doi:10.1038/305100a0.
  10. ^ Macdonald, K.C., K. Kastens, S.P. Miller and F.N. Spiess (1979). "Deep-tow studies of the Tamayo transform fault". Mar. Geophys. Res. 4: 37–70. doi:10.1007/BF00286145.CS1 maint: Multiple names: authors list (link)
  11. ^ Macdonald, K.C., D.A. Castillo, S.P. Miller, P.J. Fox, K.A. Kastens and E. Bonatti (1986). "Deep-tow studies of the Vema fracture zone I. Tectonics of a major slow slipping transform fault and its intersection with the Mid-Atlantic Ridge". J. Geophys. Res. 91: 3334–3354. doi:10.1029/JB091iB03p03334.CS1 maint: Multiple names: authors list (link)
  12. ^ Searle, R C (2013). Mid-ocean ridges. New York: Cambridge University Press. 318 pp.
  13. ^ Macdonald, K.C. and P.J. Fox (1983). "Overlapping spreading centers: New accretion geometry on the East Pacific Rise". Nature. 301 (5903): 55–58. doi:10.1038/302055a0.
  14. ^ Macdonald, K.C., J.-C. Sempere ,P.J. Fox and R. Tyce (1987). "Tectonic evolution of ridge axis discontinuities by the meeting, linking or self-decapitation of neighboring ridge segments". Geology. 15 (11): 993–997. doi:10.1130/0091-7613(1987)15<993:TEORDB>2.0.CO;2.CS1 maint: Multiple names: authors list (link)
  15. ^ Langmuir, CH, JF Bender, and R Batiza (1986). "Petrological and tectonic segmentation of the East Pacific Rise, 5 30′–14 30′ N". Nature. 322 (6078): 422–429. doi:10.1038/322422a0.CS1 maint: Multiple names: authors list (link)
  16. ^ SM Carbotte, DK Smith, M Cannat, EM Klein (2016). "Tectonic and magmatic segmentation of the Global Ocean Ridge System: A synthesis of observations". Geological Society, London, Special Publications. 420 (1): 249–295. doi:10.1144/SP420.5.CS1 maint: Multiple names: authors list (link)
  17. ^ RM Haymon, SM White (2004). "Fine-scale segmentation of volcanic/hydrothermal systems along fast-spreading ridge crests". Earth and Planetary Science Letters. 226 (3): 367–382. doi:10.1016/j.epsl.2004.08.002.