Aleisha Johnson

PhD Candidate

I’m a 4th year geochemistry graduate student in the School of Earth and Space Exploration at Arizona State University working with Dr. Ariel Anbar and Dr. Christy Till.

My primary research investigates mineral oxidation rates to understand how Earth’s early atmosphere interacted with continental crust before the Great Oxidation Event and how these interactions might be recorded by paleoredox proxies. My current project focuses on the mobilization of molybdenum as a potential oxidative weathering signature in the 2.5 Ga Mount McRae Shale from Western Australia, which I investigate with aqueous sulfide oxidation experiments and weathering models. To this end, we hope to develop molybdenum as a paleooxybarometer and further quantify the first oxygenation of Earth’s atmosphere.


My secondary research project with Christy Till is working to develop a fractional crystallization correction for modestly hydrous magmas in subduction zones. This will allow us to calculate the pressure and temperature at which a given arc magma was last in equilibrium with the mantle, using only their major element compositions.

I kicked off my graduate school career by abandoning the cold winters of the midwest for sunny Arizona. Since then, I’ve become an avid cactus-photographer, swing dancer, rock climber, hiker, and sometimes I even pretend to be a chemist. I love that my research allows me to travel the world, including Switzerland, Denmark, Japan, and France. I joke that I’ve always wanted to be a geochemist, of all things, which is why my dissertation ranges from petrology to the kinetics of mineral oxidation. You can contact me at