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"Diagram to illustrate the inferred structure in the vicinity of the "Triangle." Arkose conglomerate is represented by lines and ellipses, anterior basalt by the black areas, anterior shale by parallel lines, and main basalt by cross-hachure areas. The finer hachuring (and hence the deeper shade) corresponds to the higher blocks of the basalt." -Walcott, 1901

Basalt Diagram

"Diagram to illustrate the inferred structure in the vicinity of the "Triangle." Arkose conglomerate…