JOHNSON: GRAND CANON DISTRICT. 141 
from occasional heavy rains drops from the surface of the lava down 
to tlie bottom of the limestone gorge from which the lava has been 
largely removed (Davis, '01, fig. 13). 
A few miles farther west is another north and south line of cliffs, 
developed in limestone, and dissected by small ravines which open 
on steep alluvial cones well up the face of the cliff. This line of 
cliffs faces east, and forms the west side of a valley which has less 
regular limestone cliffs, of less altitude, on its eastern side. The rela- 
tions suggest a north-south fault with a downthrow toward the east. 
Toward the northern end of the east-facing scarp there is a low hill in 
front of the cliffs which seems to be a down-faulted block. Toward 
the southern end a side valley from the west enters through the cliffs. 
From this side valley lava has entered the main valley and floored it 
with igneous rock in very recent geological time. Lava has also entered 
the main valley through shallow ravines cut in the face of the cliffs. 
The amount of disjilacement in both of these north-south faults is 
small. 
If our observations are correctly interpreted, there are disj)lace- 
ments south of the Grand Canon in greater number than has generally 
been supposed, but less extensive and much more irregularly devel- 
oped than the great displacements north of the Canon. Careful field 
work will be necessary before the detailed relations can be ascertained. 
Echo Cliffs JNIoxocline. 
Of our observations along the Echo Cliffs Monocline, only those 
which bear on the origin of the })eculiar form of certain })arts of the 
cliffs need be noted here. Brief mention, however, may be made of 
the remarkable landslides which begin toward the northern end of the 
cliffs and continue around the base of the Paria Plateau to House 
Rock Valley, a distance of some fifty miles (pi. 18, fig. 1). These land- 
slides have been described by Davis ('01, p. 121-120) who believes 
them to be the result of a revival of erosive activity following the up- 
lift of the region which permitted the incision of the present Canon. 
We did not observe the slides until we reached a point south of Bitter 
Spring, where a branch of the Colorado River first reaches eastward 
to the foot of the cliffs. The sudden development of landslide topog- 
raphy at this point is in accordance with the interpretation quoted 
above. 
