News this week that geologists led by Steven Jacobsen of Northwestern University in Evanston, Illinois, USA, may have discovered a vast amount of water locked up in hydrated minerals deep in Earth's mantle. Estimates put the amount of water at some three times the combined volumes of Earth's oceans. Were this volume of water to be on the surface of Earth only the tops of mountains would be dry land.
The high water storage capacity of minerals in Earth’s mantle transition zone (410- to 660-kilometer depth) implies the possibility of a deep H2O reservoir, which could cause dehydration melting of vertically flowing mantle. We examined the effects of downwelling from the transition zone into the lower mantle with high-pressure laboratory experiments, numerical modeling, and seismic P-to-S conversions recorded by a dense seismic array in North America. In experiments, the transition of hydrous ringwoodite to perovskite and (Mg,Fe)O produces intergranular melt. Detections of abrupt decreases in seismic velocity where downwelling mantle is inferred are consistent with partial melt below 660 kilometers. These results suggest hydration of a large region of the transition zone and that dehydration melting may act to trap H2O in the transition zone.
Brandon Schmandt, Steven D. Jacobsen, Thorsten W. Becker, Zhenxian Liu, Kenneth G. Dueker
Dehydration melting at the top of the lower mantle; Science 13 June 2014: Vol. 344 no. 6189 pp. 1265-1268 DOI: 10.1126/science.1253358
The significance of this find is that it suggests the origin of Earth's ocean water was not comets but that they oozed out of the mantle and now exist in an equilibrium with this subterranean reserve. Water is known to be pulled down into Earth's mantle along the subduction zones as plate tectonics pushes one plate down and below another taking the ocean floor sediment with it. Despite this loss, the volume of surface water has remained more or less constant even when sea levels have risen or fallen due to climate change and more or less extensive ice-sheets. The assumption is that this mantle water acts as a buffer.
What's the betting that, if someone hasn't already done so, one or more creationist frauds will be misrepresenting this discovery as the discovery of a vast ocean of liquid water, and proclaiming the craved-for scientific proof of the Noah's flood myth by explaining where all the water came from - the 'fountains of the deep', no less?
Of course it's no such thing. Not only does the paper only establish that there may be this reserve of water in the mantle but there is no sense in which this water could fountain up to vastly increase the volume of the oceans even if it proves to be there. Nor is there sufficient volume to cover Earth to a depth of over 8,800 meters as would have been required to cover the highest hills as the myth claims.
Sorry creationists, but this discovery doesn't rescue your favourite creation myth and save it from a deserved ridicule; it simply increases your difficulty by denying you a possible source for all the water and an explanation of where it all went. The 'vast ocean of water' is not liquid water but water locked up in hydrated minerals. If your creation pseudo-scientists tell you otherwise they are lying to you again.