81. What is the MOHO? 



MOHO is the name commonly used for the /V7o/7orovicic dis- 

 continuity, the boundary between the earth's crust and mantle. It was 

 named from the Yugoslav seismologist who discovered its existence. 



The crust is the surface layer of rock, averaging 125,000 feet in 

 thickness under the continents; under the oceans it is only 15,000 to 

 20,000 feet thick. This is why the planned Mohole was to be drilled 

 through the ocean floor. 



At the Mohorovicic discontinuity, the speed of earthquake waves 

 changes abruptly, indicating a difference between rocks of the crust and 

 of the mantle. 



The objective of the Mohole Project (now discontinued) was to drill 

 through the MOHO and obtain samples of the mantle rock. Some of the 

 questions which led to the project are: How did the rocks of the oceanic 

 crust become separated from the rocks of the continental crust? How 

 was the crust differentiated? And from where did the layers of oceanic 

 crust come? 



Achievements that arose from the Mohole Project included develop- 

 ment of ways to core the ocean bottom in deep water, a better under- 

 standing of the geophysics of several ocean areas, and improvement of 

 drilling instruments and techniques. 



Bascom, Willard 



A Hole in the Bottom of the Sea, Doubleday, 1961 . 

 Ericson, David B. and Goesta Wollin 



The Deep and the Past, Alfred A. Knopf, 1964. 

 Yasso, Warren E. 



Oceanography, A Study of Inner Space, Holt, Rinehart and 



Winston, 1965. 



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