Distribution of U and Th and Their Nuclear Fission in the Outer Core of the Earth and Their effects on the Geodynamics

Abstract

Here we propose that there is a lot of heat producing elements U and Th in the outer core of the Earth. The heat released from them may be the major energy source for driving the material movement within the interior of Earth, including plate motion. According to seismic tomography, the hottest area is the mantle under the central Pacific Ocean. Combined with geomagnetic data, it is derived that the magnetic and heat convection centers deviate from the geographic center to the Pacific direction for 400 km. Therefore, U and Th may be more concentrated in a position close to the equator in the lower outer core under the central Pacific Ocean, and have formed a large U, Th-rich center there. Another small U, Th-rich center may be located in a position close to the equator in the lower outer core under Africa, which is directly opposite of the large U, Th-rich center past the solid inner core. The two U, Th-rich centers may have led to the formation of the Pacific and Africa super-plumes and are offering energy to run the plate tectonic system. It also could have caused the temperature of the western hemisphere to be higher than that of the eastern hemisphere of the inner core, which may be the cause for the east-west hemispherical elastic anisotropy of the inner core. Periodical nuclear fissions of U and Th in the outer core may have occurred in the geological history of the Earth, and also might have triggered geomagnetic superchrons and reversals. At the same time, the energy released from the outer core during these events might have also triggered strong and extensive global geological and volcanic activities, and caused mass extinctions on the surface.