DAVIS : THE GRAND CANYON OF THE COLORADO. 125 



noted ; but when the slides advance far enough to fall over the bench, 

 they flow down its froutal slope and sprawl out on the platform beneath 

 like gigantic lava floods, as in Figure 5. The streams of rock-waste 

 sometimes descend by a re-entrant notch in the front of the bench, like 

 the lava flows in the notches of the upper Aubrey cliffs on the west side 

 of Toroweap valley ; they sometimes advance in large volume and 

 cascade over the front of the bench, smothering salient as well as re- 

 entrant of the Shinarump. The different colors of successive strata are 

 normally arranged in ordei'ly bands on the face of the cliffs ; reddish 

 gray sandstones at the top, then red-and-yellow-brown sandstones — 

 vermilion seemed to us too strong a name for these cliffs, and " freight- 

 car red" was suggested as a substitute — blue in the lower Triassic clays, 

 chocolate brown in the Shinarump cliff, and banded creamy gray in the 

 upper Permian slope. Something of banded colors may still be seen in 

 the slides that have moved down and forward in orderly fashion to form 

 the monoclinal ridges, but the color bauds in the slides of greater forward 

 advance become greatly confused when the slides sprawl down the Shina- 

 rump bench, and a most curious patchwork of reds, yellows, blues, grays, 

 and browns is the result. Most of the slides seem to be old enough to 

 have suffered some erosion since their descent, yet they are young and 

 large enough to be very conspicuous elements in the landscape. They 

 are easily recognized when seen at a distance of eight or ten miles from 

 the summit of the Kaibab, where the road crosses it westward from 

 House-rock spring. 



If we now cross the river and go some twenty miles south of Lee's 

 Ferry, the blue clays are concealed under the evenly graded floor of 

 a monoclinal valley that follows the foot of the Echo cliffs ; the Shina- 

 rump sandstone rises on the western side of the monoclinal valley, so as 

 to overlap the eastern part of the Marble platform. The Triassic sand- 

 stones are, however, bolder in this part of the Echo cliff's than in the 

 Vermilion cliffs of the northern part of the House-rock valley; they 

 here expose a larger proportion of bare rock cluttered over with scanty 

 and very coarse waste, not of orderly enough arrangement to be called 

 a talus. Passing northward towards the river, the Shinarump sandstone 

 crosses the valley obliquely as a low ridge, thus shifting from a cuesta- 

 like attachment on the border of the Marble platform to a basal bench 

 and cliff at the foot of the Echo cliffs ; at the same time, the monoclinal 

 valley shifts from the blue clays of the lower Trias to the weak Permian 

 strata. Thus the blue clays come to outcrop on the slopes beneath 

 the red sandstones of the Echo cliffs, and at once the landslides begin. 



