It makes perfect sense when you plug the numbers. They're talking about a thin layer of extremely dry, hot rocks in the earth's mantle. Something like 1-2% wat

It makes perfect sense when you plug the numbers. They're talking about a thin layer of extremely dry, hot rocks in the earth's mantle. Something like 1-2% water by weight [0] in ringwoodite -- about 35-80 grams/liter. (Liquid water at the surface is >1,000 grams/liter). The catch is, it's a staggering volume: the earth's mantle is ~3,000 km thick, and the comparatively "thin" layer they're looking at, the transition zone, is ~250 km [1] -- this compared to the oceans' depth of ~4 km [2]. "The water storage capacity of the upper and lower mantles is less than 0.2 wt%. The transition zone has a storage capacity of approximately 0.5–1 wt% due to a water solubility of about 1–3 wt% in wadsleyite and ringwoodite, which are the major con- stituents of the transition zone. Thus, the transition zone may be a major water reservoir in the Earth’s interior." [0] http://mon.univ-montp2.fr/claroline/backends/download.php?url=L1N1amV0c19leHBvc%2BlzL09jZWFuc19kdV9tYW50ZWF1L1ZvbGF0aWxzLWVhdSBkYW5zIGxlIG1hbnRlYXUuZnVsbC5wZGY%3D&cidReset=true&cidReq=GLST202 http://mon.univ-montp2.fr/claroline/backends/download.php?ur... [1] https://en.wikipedia.org/wiki/Transition_zone_%28Earth%29 https://en.wikipedia.org/wiki/Transition_zone_%28Earth%29 [2] https://xkcd.com/1040/ https://xkcd.com/1040/