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[Comment on Seismology in the Days of Old by Inge Lehmann] The Eos, Vol. 68, No. 46, November 17, 1987 stratosphere, and a program to measure bio­ ed for a complete picture of present-day U.S.-Soviet Climate genic methane produced in permafrost areas world climate, a requirement for accurate of the United States and the Soviet Union. forecasting of future climatic trends. Two of Research: More, The protocol, signed in preliminary form the proposed activities involve monitoring of November 2, 1987, by representatives of both chloroflourocarbon levels in Lake Baikal, Better countries, is the latest update of a bilateral north of Mongolia, and measuring aerosols PAGE 1593 agreement in place since 1972. Ultimate ap­ and ozone on Heiss Island, within 10° of the proval of the protocol should come in the North Pole. The draft of an agreement for cooperative next few months, in the form of a final sign­ Another important function of cooperation U.S.-Soviet climate research contains a num­ ing by Environmental Protection Agency is confirming data. "We can reinforce each ber of proposed projects that should lead to (EPA) Administrator Lee Thomas and the other's conclusions," says Robert Etkins, as­ unprecedented knowledge of the worldwide head of the equivalent ministry in the Soviet sistant director of the National Climate Office atmospheric distribution of trace gases and Union, Yuri Izrael. in Boulder, Colo. International standards for their effect on climate change. Activities The rationale for the protocol since its im­ measurement of trace gases will be essential named in the document include the shared plementation has been that the study of cli­ to the future of the multinational Montreal measurement of Antarctica's ozone hole, a mate and the atmosphere is a global job. agreement on CFC production completed in joint experiment to investigate the relation­ Knowledge of the large part of the planet September. Soviet and U.S. lidars used to ship between aerosols and ozone in the Arctic that lies in or near the Soviet Union is need- measure stratospheric aerosols would be cali- Forum Development of floor spreading, continental drift, and a con­ ary 20, 1987, p. 33; see also Bolt [1987, servative earth surface through what is now 1982]) remind us that this outstanding Plate Tectonics called subduction. All the critical pieces were Earth scientist is now in her 100th year. then put into place. I have long found it sur­ The inner core boundary (ICB) is one of Theory: The prising that a paper I found so important to the three great seismic-compositional dis­ Missing Piece my acceptance of plate tectonics, and one of continuities that divide Earth into crust, the most exciting papers I have read in my mantle, core, and inner core. The other PAGE 1593 career, is so little cited in the scientific litera­ two discontinuities are well known by The recent article by Jean-Claude Mares- ture and so little discussed in the historical lit­ names honoring their discoverers, Andrija chal ("Plate Tectonics: Scientific Revolution erature. Mohorovicic and Beno Gutenberg. In this or Scientific Program?" in Eos, May 19, 1987, It also seems to me that development of tradition, it is fitting that the ICB be p. 529) adds to the interesting literature on the theory of subduction deserves "equal called the Lehmann Discontinuity in hon­ the evolution of the theory of plate tectonics. time" with seafloor spreading and transform or of its discoverer. It is curious that an aspect of the general the­ faults in the considerations of the develop­ This title was used informally with re­ ory that seems to be little considered and ment of the theory of plate tectonics. Histori­ spect to a discontinuity in the mantle at mentioned by Mareschal or others who write ans can figure out which people deserve pri­ 190-250 km [Anderson, 1979, 1981]. Leh- about the history of development of the the­ ority, but the Coats, Oliver and Isacks, and mann's work on discontinuities in the up­ ory, but that was vitally important in my own Isacks et al. papers were the ones that were per mantle stems from 1959 and later, but acceptance of the theory, was the discovery of important to me. It is, perhaps, also a matter she proposed the inner core model in subduction and, to a lesser extent, abduction. of some significance that all three of these 1936. The use of her name for features of Earth's surface is essentially conservative papers were in publications of the American the upper mantle has been sparse. Prece­ over^periods of millions of years, and if conti­ Geophysical Union. dence should be accorded the earlier and more fundamental discovery of the inner nents were drifting, what was happening to References the rigid oceanic crust? The concern only was core, which is surely a feature of central exacerbated by seafloor spreading. I was well Coats, R. R., Magma type and crustal struc­ importance in the dynamic Earth. We aware of Benioff seismic zones (as they were ture in the Aleutian arc, in Crust of the Pa­ therefore consider that the name Leh­ referred to in the United States during the cific Basin, Geophys. Monogr. Ser., vol. 6, edit­ mann Discontinuity is most appropriate 1950s) but had not connected them to foun­ ed by G. A. MacDonald and H. Kuno, pp. for the inner core boundary. dering oceanic crust. In this regard, I found 92-109, AGU, Washington, D.C., 1962. a paper by Coats [1962] to be very interesting Doe, B. R., Cenozoic volcanism in the south­ but did not connect it, for some reason, with ern Rocky Mountains, Q. Colo. School Mines, References the overall picture. In this paper, Coats gave 63, 149, 1968. evidence of underthrusting of the oceanic Isacks, B., J. Oliver, and L. R. Sykes, Seismol­ Anderson, D. L., The deep structure of crust under the Aleutians and used it to ex­ ogy and the new global tectonics, J. Geophys. the continents,/. Geophys. Res., 84, 7555, plain andesitic volcanism. A number of years Res., 73, 5855, 1968. 1979. later, I found it impressive that Oliver and Oliver, J., and B. Isacks, Deep earthquake Anderson, D. L., Discontinuities in the hacks [1967] also found seismic evidence of zones, anomalous structures in the upper mantle (abstract), Eos Trans. AGU, 62, foundered oceanic crust. mantle, and lithosphere, /. Geophys. Res., 1073, 1981. It was not until early 1968, when I was 72, 4259, 1967. Bolt, B., Inside the Earth, W. H. Freeman, talking to the late Paul Gast about a manu­ Bruce R. Doe San Francisco, 1982. script I was preparing on the isotopic signa­ Assistant Director for Research, Bolt, B., 50 years of studies on the inner tures of lead and strontium in the tectonic U.S. Geological Survey, core, Eos Trans. AGU, 68, 73, 1987. environments from oceans ridges to conti­ Reston, Va. nental cratons [Doe, 1968], that my concerns began to be resolved. Paul suggested that I D. L. Anderson come to the Lamont-Doherty Geological Obv- Seismological Laboratory, servatory (Palisades, N.Y.) and get together The Lehmann California Institute of Technology, Pasadena with Lynn Sykes to discuss a manuscript he Discontinuity B. A. Bolt was involved in. I did this just prior to the Seismographic Station, AGU Annual Meeting in 1968 and learned PAGE 1593 University of Calfifomia, Berkeley about the "New Global Tectonics" [hacks et ai, 1968], which is a little-cited paper that Recent reflections by Inge Lehmann on S. A. Morse presented a unified model allowing for sea- her discovery of the inner core (Eos, Janu- University of Massachusetts, Amherst This page may be freely copied. .
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