Composition of the Earth at a Depth of 500–700 km

Abstract

Price and Lahiri¹ announce interesting results of their study of the electrical conductivity, ϰ, of the earth from terrestrial magnetic variations. They confirm the finding of Chapman and Price that there is a considerable increase in ϰ with increasing depth beyond 150 km. below the earth's surface, and further, express the view that the really important increase in ϰ occurs at a depth of about 700 km.; and they accordingly suggest a change in the composition of the earth in the vicinity of this depth. This result is specially interesting in view of recent progress in other branches of geophysics, and the purpose of this note is to direct attention to the extent of agreement indicated.