Washington, Aug 3: Nearly half of the earth's heat comes from the radioactive decay that can practically move mountains and sea floors and cause eruption of volcanoes.
 Itaru Shimizu of Tohoku University in Japan and collaborating physicist Horton Smith, associate professor of physics at Kansas State University, made the measurement using the KamLAND neutrino detector in Japan.
 Previous research has shown that earth's total heat output is about 44 terawatts or trillion watts, the journal Nature Geoscience reports.
 KamLAND researchers found that 29 terawatts come from radioactive decay of uranium, thorium and other materials, meaning more than 50 percent of the earth's heat comes from geoneutrinos (neutrinos from a geological source).
 Researchers estimate that the other half of the earth's heat comes from primordial sources left over when the earth formed and from other sources of heat, according to a Tohoku statement.
 KamLAND, short for Kamioka Liquid-Scintillator Antineutrino Detector, is an experiment at the Kamioka Observatory, an underground neutrino observatory in Toyama, Japan.
 Neutrinos are neutral elementary particles that come from nuclear reactions or radioactive decay. Because of their small size, large detectors are needed to capture and measure them.
 "It is a high enough precision measurement that we can make a good estimate of the total amount of heat being produced by these fissions going on in naturally occurring uranium and thorium," Horton Smith said.
 Horton Smith was part of a team collecting some of the most precise measurements of earth's radioactivity by observing the activity of subatomic particles -- particularly uranium, thorium and potassium. IANS

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