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The crust is about 40 kilometres ( 25 miles ) thick in continental regions and is
highly heterogeneous , composed largely of rocks varying in composition
between granite and basalt . Beneath the deep oceanic basins , the crust is about
stable between depths of approximately 70 and 350 kilometres ( 40 and 200
miles ) ; no further phase transformations occur in this region . Regions of
occurrence of plagioclase and amphibole pyrolites are limited in the uppermost
Between about 450 and 600 kilometres ( 300 and 400 miles ) the rate of increase
of seismic velocities is not indicative of further phase transformations .
Experimental studies reveal that the spinels and garnets formed near 400
kilometres ( 250 ...
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LibraryThing ReviewUser Review - keylawk - LibraryThing
This is the 198215th Edition, in two halves, with the Macropaedia and the Micropaedia. First published in 1768, the publisher is the oldest English-language encyclopedia still in print. Two Scottish ... Read full review