230 DOUGLAS WILSON JOHNSON 
apparent continuation of the cone slopes unbroken into the basin 
indicates that in considerable part at least the eruptions followed 
the faulting. A mud flow from the Crater Lake volcano came 
recently enough to descend the already formed Anna Creek valley, 
and even to spread out over the floor of the basin for some distance 
if one may judge from topography alone. No sections were 
observed out in the basin, but farther up the valley Anna Creek 
Fic. 1.—Joint structure in volcanic ash, Anna Creek valley. (Photo by D. W. 
Johnson.) 
has trenched the flow, revealing a beautifully jointed ash deposit 
(Fig. 1). A sufficient number of lateral tributaries greatly to 
dissect the deposit has not yet been developed; partly, no doubt, 
because of the porosity of the ash. 
On the east side of the Klamath basin is a lower scarp remark- 
able for its straightness and for the small extent to which it has 
suffered from the agents of erosion. It is far more youthful in 
appearance than the higher Cascade scarp. Because of its steep- 
ness the low, west-facing scarp is in striking contrast with the 
very gentle slope which declines eastward from its crest, and of 
