This is weird. And when they feed on matter, their meal ripples across this surface like when you throw a rock into a pond. These ripples, when they reach the edge of the black hole, can actually cause the black hole to overflow, like a sort of cosmic lake bursting its banks. As Adams puts it:

"We showed that when you throw stuff into a black hole, the surface of the black hole responds like a fluid – and in particular, it can become turbulent. More precisely, the horizon itself becomes a fractal."