February 16, 2005
American Center for Physics
College Park, MD, MD
The origin of the Earth's continental crust, remains a first-order geologic problem. Presently-accepted theories hold that the continents are the result of terrain accretion driven by plate tectonic processes. They are essentially the same concept proposed in the mid-19th century by Dana who argued that continents have grown laterally over geologic time, mountain belts such as the Appalachians being analogous to the growth rings of a tree. Evidence from comparative planetology suggests a different mechanism. The Moon and Mars evidently developed global differentiated crusts, analogous to terrestrial continental crust, by purely igneous processes, not related to plate tectonics. The early lunar crust was aluminum-rich basalt, the early Martian crust a mixture of basalt and andesite.
The speaker proposes that terrestrial continents are the remnants of a primordial global crust, chiefly of andesitic composition, disrupted several billion years ago by major impacts. There has been on balance no significant growth of continental crust since then, except by addition of basalt. It is proposed that basaltic magmatism has been the main petrologic processes in the Earth for the last 4 billion years.
Dr. Paul Lowman is currently a Geophysicist working in the Geodynamics Branch at Goddard Space Flight Center. He received a B.S. in Geology from Rutgers University in 1953 and a Ph. D. in Geology from the University of Colorado in 1963. Dr. Lowman specializes in Comparative Planetology, Lunar Geology, Orbital Remote Sensing, Global Tectonics, Lunar Exploration, and Lunar Bases.
He served as the Principal Investigator or Co-Investigator on many projects since 1963. These include experiments for many of the Apollo, Mariner 9, Voyager, Mercury, and Gemini missions. He has been with NASA- Goddard since 1959 and he was associated with Terrain Photograph in the Mercury, Gemini and Apollo programs and with the Landsat and the Voyager programs.
He is Principal Investigator for the Intraplate Tectonic Study for the Global Earthquake Satellite System (GESS). Dr Lowman has received many honors including the GSFC Linsay Award, NASA's Exceptional Service Medal, 2003, belongs to numerous Technical Societies and has written many books and publication articles.