Another explosive episode of Kilauea’s volcanic activity came and went Wednesday after Episode 28 of the ongoing eruption in Halemaumau Crater saw eight hours of high fountaining.

Essentially, gas pistoning is a shallow, degassing-driven rise and fall of a lava surface. Often these pistons occur in narrow conduits — although they can happen in larger lava lakes and even in lava channels — and in bunches, as part of a series.