Neutrino Geophysics Conference Introduction

Long distance detection of electron anti-neutrinos from reactors at distances of order 200 km has been achieved with the 1000 ton liquid scintillator-based KamLAND instrument in Japan. In summer 2005 the KamLAND group reported the first detection of anti-neutrinos from the natural radioactivity of the earth. These measurements are due to uranium and thorium decays dominantly from the nearby crust in Japan, and are expected to have only a small contribution from the earth’s mantle (and core). Several new detectors are under consideration around the world for measurements which when taken together can reveal the location of these heavy elements, which are expected to contribute a major share of the internal earth’s heating via their radioactivity. This heating is of course associated with providing the power to drive the geomagnetic field and plate tectonics. Geologists have only indirect evidence about the deep earth, mostly from seismic wave velocity and inferences from a few meteorites. Anti-neutrino detection, on the other hand, yields direct information about earth’s interior. The location and magnitude of the earth’s uranium and thorium are crucial to understanding the origin and evolution of the earth and present day activity. Lead Article in Proceedings of Neutrino Sciences 2005