intransitive. Mineralogy and Geology. Of a stratum, vein, etc.: To come up to the surface; to come out and appear on the side of a slope, etc.

Of strata: To crop out at the surface.

Of strata: To crop out.

figurative. to crop up: to come up or turn up unexpectedly or incidentally, in the field of action, conversation, or thought.

intransitive. Of a rock stratum, mineral vein, etc.: to be visible at the surface of the ground; to crop out (see crop, v. 10a).

figurative. to crop out (rarely forth): to come out, appear, or disclose itself incidentally.

transitive and intransitive. Geology (chiefly British). With on to. Of an upper stratum or sequence of an unconformity: to extend over…