Final answer:
Intersecting joint planes in a rock cliff that point downward and outward typically form an anticline, identifiable by examining the rock's strike and dip.
Step-by-step explanation:
Two joint planes in a rock cliff intersecting in a line pointing down and out of the cliff face form what is known as an anticline or a ridge-like fold in the rock layers. The intersecting joint planes would typically dip away from the crest of the anticline, which is consistent with the description of them pointing down and out of the cliff face. This geological feature can be identified through careful analysis of the rock's strike and dip, where strike represents the horizontal line of intersection between a rock layer and the Earth's surface, and dip indicates the steepest angle of the rock layer's descent relative to a horizontal plane.