2020 Kirk Bryan Award

Presented to Martha Cary (Missy) Eppes and Russell Keanini

Martha Cary (Missy) Eppes
Russell Keanini

Martha Cary (Missy) Eppes and Russell Keanini

Awarded for: 2017, Mechanical weathering and rock erosion by climate-dependent subcritical cracking: Reviews of Geophysics, 55, 470-508.


Citation by Frank Pazzaglia, Lehigh University

On behalf of co-nominator Ellen Wohl and ten supporting letter writers, it is an honor to present the 2020 Kirk Bryan Award to my friend and colleague Martha Cary Eppes and co-author Russell Keanini for Mechanical weathering and rock erosion by climate dependent subcritical cracking published in Reviews of Geophysics in 2017. In summary, the research presented in this paper is transformative. As geomorphologists we have a general understanding of mechanical weathering processes, and we tend to hold these separate from other processes that chemically alter rocks and minerals. Now because of Eppes and Keanini, our understanding of weathering is at best dated, and at worst, wrong. Here’s why. Eppes and Keanini convincingly demonstrate, using field and numerical modeling results, that extraordinary or extreme temperature ranges are not necessary to fracture rocks. Nor is water expansion in pre-existing cracks necessary and sufficient. It turns out that when you rigorously apply fracture mechanics to the problem, you learn that weathering in virtually all rock types progresses by moisture-, that is climate-dependent, sub-critical fracturing under virtually all Earth surface and near-surface environmental conditions. Eppes and Keanini provide a framework for unifying chemophysical weathering processes and like all good science, it is testable and will inspire a new generation of research. Given that rock fragments are found everywhere on the planet, why did it take so long for the Eppes and Keanini discoveries? I feel that the answer lies in the unusual courage that Eppes and Keanini demonstrated in tackling the seemingly mundane problem of why rocks crack, in stepping outside of their normal research comfort zones, and in forging a collaboration that reaches across disciplines. It is a lesson for all of us in how excellent science needs to be done, and how process geomorphology can help us understand and manage the environmental consequences of a rapidly changing world.



To receive the Kirk Bryan Award in the year 2020, with its extreme duress, elicits a cascade of conflicting emotions and thoughts. My overwhelming feelings of honor and gratification reside side-by-side with my profound sadness in not receiving this recognition under the same roof as the very friends and colleagues who put me here. By that, I refer not just to Ellen and Frank for their nomination – for which I am deeply grateful, but also to all of you – too many to name - who generously gave the critiques, hard questions, skepticism, encouragement, long talks, and yes, even the crack jokes that led to this paper and its ideas. 2020 is the first year since 1995 that I am not physically present with you at GSA, receiving these annual gifts that ultimately made this paper possible.

Another irony is that Eppes and Keanini (2017) contains no field data when, for my entire career, I have unambiguously and wholeheartedly operated as a field scientist. With this work I departed my comfortable realm of field-based soil geomorphology for an enthralling, and sometimes intimidating, world of fracture mechanics and modeling. But, field observations do make an important appearance in the paper, as support of the brilliant simplifications and assumptions that Russ intuitively built into his physical models. As such, our work together was an enormously satisfying marriage of my – and my students’ - decades of unexplained field observations, and Russ’s modeling - with his dexterity for harnessing the power of basic physical theory and principles. This work was, and continues to be, so much fun.

I want to acknowledge, though, the extent to which this award also arose from luck and privilege; particularly being born to a larger-than-life Judge and to an oh-so-gracious, hard-as-nails Mamma. They had no idea what being a geologist entailed, but they were nevertheless role models who gave me the freedom, inspiration, and tools necessary to pursue my passions – and to acquire supportive mentors. My advisors Les McFadden and Bruce Harrison were especially so. It was Bruce who taught me how physical labor, and tediously acquired data, can reap amazing intellectual profit. And it was Les - with his dazzling knack for solving mechanism-based, desert process problems - that instilled my, possibly preternatural, obsession with cracks in the first place. My luck continues to this day in many forms, but most especially in my fiercely independent husband Jake, and my children Lawson and Oakley. They are always there for me when I need them most.

And finally, I offer up one last seemingly conflicting origin of this paper. After my kids were born, I was forced, for both my sake and theirs, to harshly limit ‘doing my best’ to a single activity in my career - turning my crack ideas into crack papers. In doing so, I found I could focus on research like I never had before. We are all exhausted right now working, schooling and parenting at home, but this award, given for this particular paper that was written on the heels of some very hard years, should bring us all hope. My most sincere thanks to GSA, to QG&G, to Ellen and Frank, to my family and to all of you for this honor.