There's no sign of what's causing the glow, instead it just seems like the rock itself is what's causing the glow. Like it's a hollow vessel filled with something magical, but if that was true then why was only this glowing? Why was every inch of the whole ground not glowing? Weird!

Fortunately there's no sign that it's growing, they seem largely stationary. The only odd thing is that none of the cracks seem to have ripped through buildings like fractures from earthquakes do. Instead these rip through paths, roads, parks, all natural areas.

Hopefully Joanna doesn't try to drive anywhere.