Physics: Why does cold water splash the first time it is added to a cup of hot tea, but not the second time?

Question

I take cold water in my tea to cool it down a bit - because I don't drink milk. I've noticed that every time I add the water it splashes very high. But the second time I add the water from exactly the same height, it doesn't splash to anywhere near as high. This always strikes me as a bit strange... Is there some stored energy which exists in undisturbed water and its surface tension, and is released upon the first adding of water, but not the second? Perhaps such an effect could be used to harvest extra energy from free standing water, maybe to build a perpetual motion machine extracting energy from the oceans? Or perhaps the water surface has an intricate fractal energy field, and is an example of a fifth force of nature? There's definitely new physics here.

Answer 1

u cause a ripple with the first drop ...that breaks the fall of the 2nd etc etc

Answer 2

Old physics, I'm afraid. The first drop hits a level surface. The impact creates a circular wave, part of which consists of a large vertical oscillation at the center which can result in a vertical jet. Subsequent impacts on the disturbed surface can't concentrate wave energy at the center because of asymmetry, so the jet, if any, is weaker. A similar thing is thought to happen with direct (vertical) impacts of large meteors or asteroids on planets, which is why many craters have a central peak.
Forget harvesting energy on this basis. Surface tension plays a very minor role in the phenomenon; it's mostly just the usual potential-to-kinetic stuff plus this focusing effect.