Transcript: Tidal heating is another consequence of gravity acting on moons of planets. The tidal force is the differential force or stretching force on a moon orbiting a planet. Tidal force increases with increasing moon size and decreasing distance from the planet. If the tidal force is too large, the moon will be disrupted, but even a moderate tidal force is enough to cause heating of a moon. Basically the stretching force, in particular in an elliptical orbit where the stretching force changes during the orbit, will cause a flexing of the moon which leads to an increase in its temperature inside. Imagine flexing a tennis ball by squeezing it and letting it go, squeezing it and letting it go. Eventually the tennis ball would warm up. In the same way, tidal forces can cause heating of moons in close orbits around planets, and in extreme cases this tidal heating can lead to volcanic activity.