Looks like an extract with steeping grains batch (I hope the oats aren't in the FV)
Not mixed well or at all and the top up water sits atop the denser layer of sugar rich wort. As fermentation has begun you are seeing krausen on the upper layer of the dense sugar rich wort layer as it tries to break through to the surface. You have a hydocline in the FV for want of a better term.
Looks very odd. Never seen this. But I'm inexperienced with extract brews. Given enough time the whole thing should become homogenous.
That's my theory anyway.
If the oats are in the FV no bueno. I'm almost sure they are not.