A little bit of educated guessing on my part:

The purple frames have a bunch of gradients to white, which looks a lot like what happens when the infrared filter on most color cameras is removed and a bunch of IR light is shone into then. For some reason the green cells are less sensitive to IR, which results in a purple-ish hue. So in this case, perhaps the lava striking the camera melted through the lens holder and shifted the IR filter out of place, or is just able to shine intense IR light into the gap between the filter and the sensor.

In those same frames, the dark areas with noisy borders are I believe an artifact of the CMOS sensor digitization process when cells get strongly overwhelmed. I've seen the same patterns on cameras where an extremely intense light (e.g. a laser pointer) is shone into them. It's like the cells get so overwhelmed they roll around back to zero.

The amorphous shapes at the very end are clearly from the lens being totally detached / moved out of position, allowing defocused light to hit the sensor. I didn't spot any interesting sensor or encoder death frames before the video ends, so likely the lava severed the ethernet cable or destroyed the electronics at that point.