Earth's deep water reservoir

摘要

How well do we know what lies deep inside Earth, more than 500 kilometres below our feet? Surprisingly well, according to a paper by Pearson et al. on page 221 of this issue. The authors describe the first sample of an unusual mineral from Earth's mantle transition zone, which is located between depths of 410 and 660 km. Their study suggests that the sample is rich in water, supporting the hypothesis that the transition zone is a hydrous region. Observations of earthquakes show that the velocity of seismic waves changes abruptly at some discontinuities that separate the upper mantle from the transition zone and the lower mantle.