But what happens to the vast amount of water attached to a slab that descends to the Earth’s core? Yutaro Tsutsumi and colleagues have now answered that question. Their experimental results suggest that the water does not escape from the slabs at the base of the mantle, as commonly thought, even at high temperatures and pressures (Y. Tsutsumi et al. Nat. Geosci. https://doi.org/10.1038/s41561-024-01464-8; 2024).It is commonly believed that at high temperature and pressures, water is released from the subducting slabs. This process could modify the chemistry of the lowest mantle by hydrating minerals or causing partial melting. However, Tsutsumi and colleagues’ finding challenges this prevailing view. Their results suggest that the subducted water has a minimal effect on the structure and composition of the core–mantle boundary region.
