Heaving or settling?

I see this fairly often with older garages, this one was a dandy, probably 40+ years old. I was having a discussion with other colleagues, and there was a debate about whether the sides are sinking (slab edges settling) or the middle is heaving, which is what I think is happening, looks like an abandoned log home with no foundation. The garage had no heat when inspected but a chimney size hole in the roof sheathing says it may have been heated at one time. Climate here would be similar to Minnesota or the Dakotas.
Any opinions? Settling or Heaving?

Subsidence at the side walls. Without proper footings, this will happen. Notice the middle of the slab has not settled, but the side sections have rotated, which are under the weight of the walls and roof.

For your part of the Country, I would have to say that it was a frost heave.

Look for cracking and joint movement in wall cladding and visible framing. If you find that, then the exterior of the slab is moving, if not it is the much more likely the floor heaving

We observed significant movements at the slab and structure. Recommend Service and Repair by a competent foundation and General contractor