Deposits formed at shallow depths are related to extrusive rocks and to intrusives near the surface.
"The Economic Aspect of Geology"
C. K. Leith
All this experience was valuable, but it was not the languages-save in so far indeed as it was the English, which we hadn't in advance so much aimed at, yet which more or less, and very interestingly, came; it at any rate perhaps broke our fall a little that French, of a sort, continued to be with us in the remarkably erect person of Mademoiselle Cusin, the Swiss governess who had accompanied us from Geneva, whose quite sharply extrusive but on the whole exhilarating presence I associate with this winter, and who led in that longish procession of more or less similar domesticated presences which was to keep the torch, that is the accent, among us, fairly alight.
"A Small Boy and Others"
Henry James