This is something that might cause people to turn to fantastical explanation, but the rational mind knows to calm down and use Science! to find the answer.
So, what we need Norway to do is take a look around their country and answer these following questions to lead us to a logical answer:
Do people around you look the same but act differently? If so, then the spiral is the beginning of an alien attack and they are replacing everyone with pod people.
Have you run into someone who looks like you except with a goatee and is evil? Then the spiral is most likely a portal to the mirror universe.
Have all the annoying, preachy people disappeared? Then it was probably the rapture. Finally, we can do Science! without their interference!
Is there techno music playing, and is everyone around you dancing? Then it’s probably a laser light show as part of a music concert. Dance! Dance!
Remember, being logical leads to answers. Thus says Science!, and thus say we all.