A master of the earth: H.D. Holland and his contributions to geochemistry

- H.D. Holland was one of the great geochemists of modern times.
- Economic geology, hydrothermal processes, and evolution of the atmosphere and oceans.
- Changes in the composition of seawater through geologic time.
- The rise of oxygen in Earth's atmosphere.

H.D. Holland was one of the great geochemists of modern times. As a Professor at Princeton University for 22 years and at Harvard for 33, he mentored 24 graduate students and 24 postdoctoral researchers. He was a member of the U.S. National Academy of Sciences and a President of the Geochemical Society. He co-authored 179 publications in 64 years from 1949 to 2012, including four books. He edited one other book and, with Karl Turekian, co-edited the ten-volume Treatise on Geochemistry. His contributions to geochemistry were mainly in economic geology, hydrothermal processes, and especially the chemistry and evolution of the Earth's atmosphere and oceans, a topic to which he devoted nearly half of his publications. His most significant contributions documented changes in the composition of seawater through geologic time and the rise of oxygen in Earth's atmosphere. He pioneered the use of mineral sequences in marine evaporite deposits and fluid inclusions in evaporite minerals to determine the composition of ancient seawater. He collected extensive data on paleosols and used them to calibrate the oxygen content of the ancient atmosphere, documenting its rise in the Great Oxidation Event that peaked between 2.41 and 2.32 Ga, and writing extensively about the causes of this event, one of the most significant in Earth history.