Dr. Mathez is an igneous petrologist and geochemist. He has written on a range of topics, such as how basaltic magmas differentiate and solidify, how platinum group element deposits form, and how carbon in rocks influences physical properties. He has had a long interest in the character and evolution of early Earth and issues associated with climate change. His interests have led him to do field work in various parts of the globe, from North America to South Africa and from Greenland to the deep ocean. He was the lead curator of the Gottesman Hall of Planet Earth and co-curated the temporary exhibition Climate Change: The Threat to Life and a New Energy Future.