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Post by Chicago Astronomer Joe on Aug 26, 2005 21:04:41 GMT -6
Earth's core rotates faster than surface
August 25, 2005 Scientists at Columbia University's Lamont-Doherty Earth Observatory and the University of Illinois at Urbana-Champaign have ended a nine-year debate over whether the Earth's inner core is undergoing changes that can be detected on a human timescale. Their work, which appears in the August 26 issue of the journal Science, measured differences in the time it took seismic waves generated by nearly identical earthquakes up to 35 years apart to travel through the Earth's inner core.
"Our observations confirm the change of inner core travel times, which was first claimed by Song and Richards in 1996," said Jian Zhang, a doctoral student in seismology at Lamont-Doherty and one of the study's co-lead authors. "This should settle the debate on whether these changes are real or an artifact of the original measurement method, and get us back to the work of understanding the history and dynamics of our planet."
Earth's core consists of a solid inner core about 1,500 miles (2,400 km) in diameter and a fluid outer core about 4,200 miles (7,000 km) across. The inner core plays an important role in the geodynamo that generates Earth's magnetic field.