Dr. Quest's balloon breaks away with a long cable trailing, but when it reaches the plateau, the cable is missing; however, the cable is back when the balloon falls into the fissure.
It's never shown how a tribe of all-male cavemen and an ex-Nazi officer survive atop an inescapable, barren plateau without plant or animal life to sustain them (nor how logs happen to be inside a cave, nor how a long-dead tree just happens to be at the fissure to snag the escaped balloon, nor how the cavemen come by wooden clubs or their presumably animal-skin clothing and that presumably 20+ year old German grenades could be in working condition).