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Science Frontiers ONLINE No. 48: Nov-Dec 1986 |
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Water, water: how far down?
The upper 10-15 kilometers of the earth's continental crust is different in several ways from the lower crust. The top layer is electrically resistive, seismically transparent, the source of almost all earthquakes, and responds to stress elastically. In contrast, the lower crust is electrically conductive, contains many reflectors of seismic energy, provides few quakes, and responds like a ductile material to stress.
The diverse characteristics of both regions can be explained if the entire crust contains saline water. In the up-per crust the water is thought to be in separated cavities, while deep down it forms an interconnected film on crystal surfaces.
(Gough, D. Ian; "Seismic Reflectors, Conductivity, Water and Stress in the Continental Crust," Nature, 323:143, 1986.)
In an accompanying commentary, B.W.D. Yardley notes that the Soviet deep borehole on the Kola peninsula has found water down to at least 12 kilome ters.
(Yardley, Bruce W.D.; "Is There Water in the Deep Continental Crust?" Nature, 323:111, 1986.)