BLOCK FAULTING IN THE KLAMATH LAKES REGION 231 
which one may catch an occasional glimpse from the automobile 
road. The topographic relations clearly indicate a very young 
block mountain with steep fault face on the west and gentle back- 
slope on the east. For convenience we may call this the ‘Fort 
Klamath block” from the little settlement of that name near the 
base of the west-facing scarp. The northern portion, at least, of 
the Klamath Lakes basin, bounded as it is by higher fault blocks 
on both the east and the west, would therefore appear to represent a 
graben, if this term may properly be applied to a relatively depressed 
block between two faults of different date. We will in any case 
refer to it simply as the “Klamath graben.’ 
Toward the north the fault scarp of the Fort Klamath block 
appears to swing westward to intersect the Cascade scarp under the 
mass of the Crater Lake volcano. Indeed it would seem that the 
intersection of the two supposed fault fissures most probably lies 
beneath the surface of Crater Lake itself. Toward the south the 
Fort Klamath block dies out, to be replaced by the Modoc Point 
block described below. 
One feature associated with the young Fort Klamath block 
deserves special attention. It is well understood that if a block 
mountain is raised across the path of a transverse stream so slowly 
that the stream is able to cut down its channel as fast as uplift 
occurs, the stream will maintain its antecedent course through the 
mountain. The transverse gorge of the Sevier River through the 
Cafion Range in Utah appears to be of this origin. On the other 
hand, if successive slight uplifts occur in too rapid succession, or 
if a single uplift is sufficiently great in amount, the river may be 
defeated in its purpose and turned aside. Somewhere, accord- 
ing to theory, we might reasonably expect to find one or more 
examples in which the river maintained its antecedent course 
for a long time, say until the block was raised halfway to its 
present altitude, but was then turned aside by a period of too- 
rapid uplift. 
The Fort Klamath region seems to present just such a case. 
South of Fort Klamath settlement one sees from the automobile 
road what at first appears to be a hanging valley opening in the 
face of the fault scarp about halfway between crest and base 
