In northwest Lake County a low tilted-fault-block ridge divides the Summer Lake basin (a remnant of Lake Chewaucan) from the Fort Rock/Silver Lake basin. Even during the high stands of the late glacial maximum, about 18,000 years ago, the pluvial lakes were never joined.
This dynamic geologic and hydrologic intersection became an important cultural intersection. To the south the Paisley Five-Mile caves and to the north the Fort Rock region, both studied by Luther Cressman in the 1930s, are now known to have been occupied by early peoples over 12,000 years ago.
Petroglyphs in this region are diverse and distinctive, ranging from archaic (early Anthropocene) to later Anthropocene (the last 3000 years.) The ridge divide is now called Picture Rock Pass. There are many varieties petroglyphs on sub-ridges and low basalt rims and boulders within a mile of the Highway 31 road cut and within six miles: along the south edge of Silver Lake, to the north; and south of the divide along the northern periphery of the Summer Lake basin near Ana Springs, now a reservoir.
Many petroglyphs have been minimal recorded, yet despite this significant location, there has not been a systematic study. In part, most archaeologists do not consider petroglyphs scientifically relevant due to difficulties with dating and establishing cultural context. Revelation awaits.
Meanwhile, view striking examples of this important cultural crossroads: Picture Rock Pass