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

Here we propose that there is a lot of heat producing elements U and Th in the Earth’s outer core. The heat released from them is the major energy source for driving the material movement within Earth's interior, 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 Earth’s geographic center to the Pacific direction for 400 km. Therefore, U and Th are more concentrated in a position close to the equator in the lower outer core (from the middle to bottom of the outer core) under the central Pacific Ocean, and have formed a large U, Th-rich center there. Another small U, Th-rich center is 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 may have occurred in the outer core in Earth’s geological history. This kind of natural fission of U and Th may be similar to the spontaneous fissions that occurred in Precambrian uranium mines. This is also supported by planetary quality and luminosity relation studies. Another piece of evidence comes from noble gases from volcanic rocks and their xenoliths in Pacific volcanic hot spots; since some of these noble gases could only be produced by nuclear fission of U and Th. Periodical U, Th fissions in the outer core 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. It may have also led to Earth’s cyclical expansions in its