Eos,Vol. 84, No. 9, 4 March 2003

Schubert Receives 2002Harry H. Hess Medal

Gerald Schubert was awarded the Hess Medalat the AGU Fall Meeting Honors Ceremony,whichwas held on 8 December 2002,in San Francisco,California.The medal is given for outstandingachievements in research in the constitutionand evolution of Earth and sister planets.

Citation

“It is good we are here this evening,not onlyto honor our friend and colleague JerrySchubert, but also,perhaps as important, to setthe record straight. Otherwise, it is likely thatcenturies from now historians will struggle with

the mystery of whether Gerald Schubert wasone person or, rather more plausibly, a pseudo-nym for a group of individuals. Great effortcould be expended on this enigma, tracts writ-ten,conferences held,university departmentscreated,and countless academics gainfully em-ployed. But we here tonight can save them allthe trouble and expense.

“For although Jerry Schubert is an incompa-rable polymath,with a list of major contributionsto make us seethe with jealousy, we can attestto the fact that he is indeed just one man.How-ever,Jerry’s prodigiousness and diversity aside,what is most remarkable is that so many of hiscontributions have endured to become classicsof geophysics. Many of us would be happy tomake a lasting impression in one field; but tohave made such an impression in so many fieldsis simply extraordinary, not to mention intimi-dating.Since Jerry has more papers than words

‘officially’allowed in this citation,I will give youonly a brief flavor of some of his major con-tributions.

“Jerry began his career in aeronautical engi-neering in the 1960s, but was coaxed first intoastrophysics, and then later into planetary

ABOUT AGU

PAGES 80-81

Stochastic Methods for Flow in PorousMedia, Coping withUncertainties

DONGXIAO ZHANGAcademic Press; San Diego,California;

ISBN 0-12-779621-5; xiv + 350 pp.; 2002; $79.95.

Flow of water in sub-surface geologic envi-ronments takes place through an array of inter-connected pore spaces, the spatial distributionof which eludes us.The presence of complexvariations in water pathways and geologic cha-racteristics produces large spatio-temporal fluc-tuations in the values of the variables describingwater flow and/or transport of contaminants.The situation is accentuated by the small num-ber of measurements that are usually availablein groundwater studies, the dependence ofparameter values onto instruments’ resolution,measurement and interpretation errors duringsampling procedures,and model uncertaintiesin the description of a hydrologic system.

Traditionally,analyses of groundwater problemsrelied on solution of partial differential equationsthat required precise definition of parameters,water sources or sinks, and conditions at theboundaries of the hydrogeologic system.How-ever,and in addition to the hydrogeologic para-meters’ variation,one typically has to estimatewater inputs or outputs to aquifers from agri-cultural activities, leakage from lagoons, lakes,or other sources of surficial water in an area,and to a large extent hypothesize the hydraulicconditions at the boundaries of aquifers.Thiscombination of spatio-temporal variation,measurement error, and uncertainty has ledin the last 30 years to the development of sto-chastic sub-surface hydrology.

The stochastic framework views parametersand variables no longer as deterministic, butrather, it treats them as exhibiting random fluc-tuations from one point to another.At the sametime,due to the underlying geologic continuity,it views them as remaining correlated overdistances and with each other; or, as definedin geostatistical terminology,as random fields.Stochastic Methods for Flow in Porous Media,Coping with Uncertainties, written by one ofthe most active researchers in the area of sto-chastic hydrology, surveys a broad range ofapproaches used by scientists in the sub-surfacehydrologic community, and presents some ofthe most recent accomplishments in the deve-lopment of stochastic methods.

The book commences with a discussion ofone-dimensional saturated and unsaturated flows,and uses these two simple cases to illuminatethe influence of various sources of uncertainty.This task is accomplished by separately ana-lyzing cases of uncertain water inputs or sinks,such as those encountered during agriculturalapplications; cases of varying boundary con-ditions, such as of aquifers connected to riversof fluctuating stages; or by investigating casesof heterogeneous hydraulic conductivity fields.The book thus highlights early on the need forstochastic concepts and techniques to real flowproblems and naturally introduces the readerto these topics.

Although the book requires some mathemati-cal sophistication, the topics are presented ina tutorial way so that knowledge of the theoryof stochastic processes is not an a priori re-quirement.The brief overview of random fieldtheory should suffice for helping readers followthe development of methods presented in sub-sequent chapters.

The introductory material is expanded inchapters 3 and 4 to cover the more generalcases of three-dimensional, steady-state, andtransient saturated flows, respectively.Chapters5 and 6 present three-dimensional unsaturated(both steady-state and transient) and two-phase

flows,respectively; while chapter 7 is dedicatedto flow in fractured porous media.Uncertaintyis introduced in all cases by the presence ofheterogeneous material through which flowtakes place,as well as from uncertain sources/sinks and boundary conditions.

The chapters introduce a number of stochasticmethods that allow computation of the statisticalmoments for variables, such as hydraulic headand flux,which are of interest to hydrogeologicstudies.Techniques such as perturbation expansions, spectral methods, adjoint meth-ods, Green’s function methods,and closureapproximations—which have been used inthe hydrologic literature to develop solutions—are covered extensively.Numerical applicationsand a large number of examples are an addedbonus that this book offers,as these help illus-trate the practical use of mathematical tech-niques.

Given the complexity of the topic, the booksucceeds admirably in presenting the materialin as straightforward and reader-friendly amanner as possible,by illustrating the advantagesand limitations of each technique to the problemat hand, or by showing that results can be developed independently through differentapproaches. In that respect, both an advancedaudience that has been exposed to the stochastic groundwater literature, and anovice reader of this material have a lot togain by exposure to the arsenal of toolsutilized today in the field of stochastic hydrology.Perhaps the most important aspect offered bythe book is the complete and authoritativemanner with which the topics are covered,thus allowing stochastic sub-surface hydrologyto claim that it has outgrown the research envi-ronment,and is ready for use by practicinghydrologists.

—EVANGELOS K. PALEOLOGOS, University of South

Carolina, Columbia

PAGE 84

Eos,Vol. 84, No. 9, 4 March 2003

physics.Early in his career, in the 1960s and 70s,Jerry was one of the primary investigators forthe Apollo program’s lunar magnetometer in-struments,which were used to infer lunar crustalmagnetism.As is typical in Jerry’s career,he hascome full circle and recently used apparentmagnetic lineations on Mars to constrain theonset and demise of the Martian dynamo.

“Also in the 1960s,when seismology and min-eral physics suggested the existence of phasetransitions in the mantle at 410 and 660 kmdepths, Jerry presented several pioneeringstudies on how phase transitions could eitherinhibit or facilitate whole mantle convection.And again later in the 1990s, Jerry was at theforefront of similar studies involving catastrophicmantle overturn events.However,before leavingthe 1960s,Jerry’s ‘moving-flame model’providedwhat remains one of the primary theories toexplain why Venus’s atmosphere moves fasterthan,but opposite to, the planet’s slow rotation.

“Jerry was also one of the pioneers of plan-etary thermal history models and was one ofthe first people to propose that secular coolingcontributed to Earth’s heat loss,which is there-fore not, as was commonly assumed, in equi-librium with the heat produced by radioactivity.Similarly,Jerry was involved in work with DavidStevenson that explained the lack of a strongmagnetic field on Venus as being due to a cen-tral temperature too high and pressure too lowto initiate freezing of an inner core. Jerry’s con-tribution to global-scale mantle dynamics alsoentailed many of the first papers on three-dimen-sional spherical convection which showed thateven simple convection had many of the featureswe associate with plate tectonics. Jerry’s workon the physics of mantle plumes offered someof the first strongly nonlinear analyses of plumeinitiation,conduit solitary waves (possibly lead-ing to discrete island formation),and the natureof lithospheric thinning by plumes.His studieson the thermal structure of subducting litho-sphere,the lifting force on slabs associated withmantle corner flow, lithospheric flexure attrenches, migration of slabs, and subductioninitiation are all fundamental to our presentunderstanding of subduction zones.Moreover,Jerry’s hypothesis that Venus’s coronae are thesites of Venusian subduction generated con-siderable excitement during the height of theMagellan program.

“Jerry’s seminal studies of the propagation ofcontinental freeboard gave the first estimatesof Phanerozoic and Precrambrian crustal pro-duction. His investigation of river morphologywas one of the first attempts to quantify the non-linear processes behind meandering and fluvialerosion.His papers on glacial surges due to shearheating and melting provided a model for theevolution and motion of large ice sheets duringclimate changes.And his many works on flowand convection in porous media are still con-sidered fundamental studies of geothermalprocesses.

“After the discovery of intense volcanism onJupiter’s innermost moon Io,Jerry and studentsinvestigated the role of tidal heating in a modelof Io accounting for both an elastic lithosphere

and a partially molten asthenosphere.Theirpapers predicted a heat flow pattern on Io thatwas born out nearly 15 years later by telescopicand satellite measurements.Jerry and colleaguesalso provided the most recent models of tidalheating in Europa,and have presented evidenceof subsurface oceans on both Europa andCallisto with obvious relevance to the existenceof extraterrestrial life.

“Jerry has worked at length on the effect ofupper atmosphere gravity waves and tidal forcingon OH nightglow and ozone, on topography-driven gravity waves on Venus, and on wavedisturbances induced by the impact of CometShoemaker-Levy with Jupiter. Jerry led one ofthe first groups to numerically simulate zonalwinds as on Jupiter from deep convection ina rapidly rotating atmosphere.And, becauseJerry Schubert hasn’t worked on enough pro-blems, he has lately become involved in geo-dynamo studies which led to the discovery ofa new phenomenon called ‘teleconvection.’

“However, perhaps one of Jerry Schubert’sgreatest contributions is that he, with a fewothers, was a pioneer in bringing a classicalphysicist’s perspective to the many fields of geo-logy and planetary science.The use of a simplefirst-principles approach to solving geophysicalproblems has flourished and thus proven aninvaluable gift to our community.There is per-haps no greater testimony of this gift than thebook he co-authored with Don Turcotte, Geo-dynamics,one of the most highly cherished textsin our field. Recently, Jerry, with Don Turcotteand Peter Olson, produced a new text, MantleConvection in the Earth and Planets,whichpromises to be the magnum opus of mantledynamics.

“Finally, Jerry Schubert has tirelessly servedthe AGU community through his excellenceas a teacher and advisor,evident in the numberof his students, essentially all still active in sci-ence. He has been a conscientious citizenthrough his participation in space experiments,his large number of editorial appointments,hischairmanship of the Earth and Space SciencesDepartment at UCLA, and most recently, hiselection to president of AGU’s Planetary SciencesSection. I should also note that this has beena good two years for Jerry; in addition to thishonor we are presenting tonight,Jerry was alsoinducted into both the American Academy ofArts and Sciences and the National Academyof Sciences.

“In the end, it is clear that Jerry Schubert hasmade,and will undoubtedly continue to make,a profound and lasting impact on our funda-mental understanding of the Earth and planetsthat is nothing short of astounding,and for whichwe in the AGU are both proud and honored topresent to him the Harry H. Hess Medal.”

—DAVID A. BERCOVICI, Yale University

Response

“Mr. President, ladies and gentlemen, col-leagues, friends, and family members: I have anumber of thanks to offer, so let me begin by

thanking David Bercovici for his kind and ge-nerous remarks and his friendship. It was only6 years ago that Dave and I shared the samestage, but in a reversal of our present roles ascitationist and medalist.Thanks also to the HessMedal Committee for selecting me, and to thecolleagues who put my name forward andsupported my nomination for this special honor.Idid not know Harry Hess personally; he diedjust a couple of years after I entered geophysics.But this recognition means a great deal to mebecause I have known almost all of the recipi-ents of this medal since it was established in1984,and I’m proud to be included among them.

“Harry Hess participated in one of the greatrevolutions in Earth science. Indeed,he playeda major role in establishing the theory of sea-floor spreading and plate tectonics. I have noclaim of any similar paradigm-setting contri-bution, but I did follow on from Harry’s ideasand spent much of my career studying mantleconvection, the cause of seafloor spreading. Ihave also been fortunate to have participatedin the great age of close-up exploration of thesolar system, an age Harry Hess anticipatedand helped plan when he was at the helm ofthe Space Studies Board.The thrill of discoveryis unparalleled,and it’s one I have experiencedseveral times in the Apollo missions to the Moon,the Pioneer and Magellan missions to Venus,and the Galileo mission to Jupiter and itssatellites.

“In the last few months, I’ve done a lot ofreading about Harry Hess. I found out that wenot only had research interests in common,butwe also both served in the Navy and we bothmanaged to get some science done duringthat service. Harry managed to collect data on the bathymetry of the seafloor while com-mander of a troop transport in the Pacific duringWWII.Again my accomplishment pales in com-parison,but I managed to write a Ph.D. thesiswhile on duty at the U.S.Naval Nuclear PowerSchool near Berkeley.

“All of us stand considerably taller on theshoulders of students and colleagues,and I’vebeen very fortunate to have worked with thevery best.You’d be very impatient with me if Itried to name all of them.I won’t,of course,butI must acknowledge Don Turcotte,who helpedme obtain a master’s degree at Cornell in 1961and with whom I’ve had an active collaborationand friendship ever since.Don recently enteredthe eighth decade of his life, and he’s beenhonored at this meeting as the Lorenz lecturerand by a special Union session. I also mustmention Bill Kaula,my former UCLA colleague,who encouraged and supported me throughoutthe years.If he were with us today,he’d take somesatisfaction in a prediction he made some 27years ago at an AGU event like this one.

“The last but most important person I’ll singleout for thanks is my wife, Joyce. She’s made itpossible for me to focus my energies on science,and for that I’m especially grateful.

—GERALD SCHUBERT, University of California,Los Angeles