Cactus Rock is a rock formation in Upper Rockridge. It is located at 6240 Acacia Avenue. Oakland Geology described it as a knocker of the Franciscan Complex. A knocker is a small body of bedrock, surrounded by a matrix of softer rocks, that protrudes from the ground surface. Cactus Rock may have served as the influence for Rockridge to be named "Rock Ridge," in the late 19th century.

photo CC BY-SA 2.0 by rbotman01
photo CC BY-SA 2.0 by rbotman01photo CC BY-SA 2.0 by rbotman01