Why do rocks start flying when high levels of chakra are being used? When people in Naruto begin using high levels of chakra--such as when Naruto's Kyuubi chakra comes out, rocks or other pieces of the terrain begin levitating, as shown in this picture:



Some of the rocks are circled to make them clear.

Why does this happen?
The nerd in me says:

Specifically, in the case Naruto, the anime goes out of their way to explain the chakras of the body.  They even go as far to explain the flow of energy through the chakras.  As such, as they draw energy into their chakras (both from inside and outside their body), debris (rocks in this particular case) also have that "draw" motion upwards.

Furthermore, since the movement of energy creates heat (evident in what happens later in the series when Naruto generates too much energy and he burns himself - trying not to spoil here), it stands to reason that the air around him would also heat up - so debris again would already with the added chakra pull + the hot air above it + color air below it, would help to lift it off the ground.  Similar to a hot air balloon (hot air balloons explained)

The adult in me says: 

Dramatic visual effects.  There is no rationale behind it, just a common theme you see in animes.  But it's fun to make up reasons why!