National Geographic : 1934 Jul
rnouograpn uyu.t.uratil, courtesy iNauOuna rarK oervice THE COLORADO RIVER HAS CUT THROUGH ROCKS OF THREE GEOLOGIC AGES Rising from the swirling stream to the left is the steep gorge of the earliest, or Archaean, period of the earth'smaking, barren ofany remnants ofanimal life. Above it lie the teeming chapters of the Paleozoic era of "old life," of which a poet wrote "When you were atadpole and Iwas afish." The geologist would describe it under such prosaic headings as the Tonto Platform, the slopes of shale, the red walls and terraces, the white sandstone and thebuff cliffs ofKaibab lime stone forming the surface binding of this rocky volume of terrestrial history. Between the vast span of the Archaan and thePaleozoic lieAlgonkian strata, which do not appear in this view.