g-rh (04/16/83)
"Mohole, project proposed during the International Geophysical Year
(1957-59) to drill a hole through a shallow part of the Earth's crust
somwehere in the ocean floor through the Mohorovicic Discontinuity into
the upper mantle of the Earth. This project was never completed for
several reasons, including the enormous cost of the project and insuf-
ficient technological expertise for drilling beyond the continental
shelf to depths of six to eight kilometres (four to five miles) into
the oceanic crust."
Encyclopedia Brittanica, 1979
There is a well defined dicontinuity between the Earth's crust
and the upper mantle. The average depth is about 30 kilometres. How-
ever it is much shallower under the ocean beds. The proposal was of
considerable geophysical interest because the only knowledge we have
of the mantle is inferential from seismic data.
The drilling depth was not (and is not) the problem; holes that
deep have been drilled. Th problem was that in the 50's the technology
of deep sea drilling was not very advanced.