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GSA TODAY | FEBRUARY 2016 Bob Garrels conducting fieldwork in the late 1930s or early 1940s. Sedimentary Rocks, which reinvigorated the concept of global
Photo courtesy Cynthia Garrels.
Robert M. Garrels
Lee R. Kump, Dept. of Geosciences, The Pennsylvania State
University, University Park, Pennsylvania 16802, USA, lkump@psu.edu
An obvious way to begin this article would have been,
“It’s hard to imagine a more influential geochemist
than Robert Minard Garrels,” but one of many pieces
of advice Garrels (1916–1988) gave his students was,
“If you find yourself saying ‘it’s hard to imagine …’ imagine
harder!” Imagining hard is what characterized Garrels’ approach
to the earth sciences.
Garrels’ contributions to the fields of geology and geochemistry
are immense, for which he received many honors. With Mary
Thompson, he pioneered the use of the ion-pairing model to
understand the behavior of the elements in seawater. With
William Krumbein (1952) and later Charles Christ, he explained,
through many examples, how redox potential (Eh) and acidity
(pH) can be used to characterize natural environments and to
predict the minerals that occur stably in them. With Fred
Mackenzie he proposed that seawater chemistry was strongly
affected by equilibria with newly formed silicate minerals (the
concept of reverse weathering). The collaboration with Mackenzie
led to a series of papers and a 1971 textbook, Evolution of
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cycling of the elements. Garrels came to imagine that the chem-
istry of the oceans and atmosphere were in a dynamically steady
state rather than in equilibrium, and this led to a series of papers
that transformed these ideas into ordinary differential equations
(box models), as classically presented in the BLAG model (for
Berner, Lasaga, and Garrels; Berner et al., 1983). His textbooks
are classics, and his publications impactful, still to be mined for
treasured insights.
What made Bob Garrels so uniquely able to see order in the
chaos of nature and to present it in a way that was accessible even
to less chemically oriented geologists? Like so many of us, his early
experiences and great mentors along the way had tremendous
influence. His father was a chemical engineer who worked for a
chemical company that used local salt and limestone in its
processes. Garrels credits his father’s interest and the local salt
deposits and fossil-rich rocks as factors that set him on the path
toward a career in earth science. A neighbor who excelled in
astronomy took the time to instill a sense of wonder about the
universe in young Garrels and his friends. Bob liked to play with
his mother’s lye (which she used for making soap) because it felt so
slippery, and he learned the hard lesson that bases can be as
caustic as acids when his fingernails fell off. At Michigan, where
he obtained his undergraduate degree, Garrels was turned off to
chemistry by a poor teacher and settled on geology.
Upon graduation in 1937, Garrels found that continuing on for
an advanced degree at Northwestern paid almost as well as avail-
able jobs and took the offer of a teaching assistantship in the
geology department. Having taken all the geology courses
offered, he enrolled in chemistry courses, which “to [his] amaze-
ment, [were] fascinating and useful” (quoted in Berner, 1992).
From a geology professor, John T. Stark, he learned to question
tacit assumptions and to adopt the position of devil’s advocate,
an approach he is said to have used with great pleasure. He
learned from a chemistry professor (F.T. Gucker Jr.) not to under-
estimate students, but rather to challenge them with problems
that seemed beyond their abilities, and to “make [them] under-
stand that it was unthinkable for [the students] not to solve
them.” To Garrels own students’ immediate dismay but enduring
benefit, they experienced this teaching pedagogy many times in
the geochemistry classroom.
Garrels moved many times during his career (Sloss and Berner,
1989). After receiving his Ph.D. in 1941, he remained at
Northwestern until 1952, excepting a one-year stint in the mili-
tary mapping beaches in the Pacific. He left Northwestern for the
U.S. Geological Survey to work on the geochemistry of uranium,
an element of great interest in the post-war atomic age and Cold
War, but longed for a return to academic life and so in 1955
accepted a position at Harvard. In 1965, fleeing the administrative
duties of department chairman, he returned to Northwestern.
Four years later, he moved to Scripps, then two years later to the
University of Hawaii, then two years later back to Northwestern
for five years, and finally to the University of South Florida.
Garrels always welcomed new ideas, and because of this he
struck up a deep friendship with James Lovelock, originator of the
controversial “Gaia Hypothesis” that imagines Earth as a living
organism, able to regulate important state variables such as
temperature and ocean composition. Lovelock wanted to test his