The floor has absorbed moisture, expanded, and buckled.

There could be a water leak, the flooring not acclimated adequately before being laid, or simply laid to tight when the humidity was low.

Unless you want to tear up a lot of floor and lay it over (and replace the pieces that get damaged during removal) simply removing the buckled strips, ripping one down, and then replacing them (some face nailing will be needed) is about all you can do.

Floorguy -

I was thinking it could be an expansion issue. That's why I asked about removing his baseboards, in case the floor needs to be cut under them to allow for expansion.

However, after seeing that last photo, I wonder if giving space to expand under the baseboards will do any good. It looks like the floor is nailed down and so how would it be able to expand if the nails are preventing it?

That is why I feel it is an acclimation issue, or someone closed the home up and turned the HVAC off, or way down.

A well nailed floor will buckle out in the middle, if it has not been acclimated, or is allowed to gain moisture from high humidity. The expansion space at the perimeter will still be there. The weakest point will let go.

A strip floor with individually nailed strips allows each and every strip to expand and contract separately.

Having a large expansion at the edges is of no real benefit.

An floor with glued pieces fastened to each other acts as a single very large pieces of wood.
these floors need expansion room at the edges.

Each of thestrips in a floor might move les than 1/16 of an inch accross their 3 inch width.

But acoraas a room that is 10 feet wide there are 40 strips.

If they all moved as a single piece you are looking at 40/16 inch of movement, or about 2.5 inches.

If you left 1.25 at each side things would be fine.

A nailed strip floor only needs the 1/16 at each edge, since that is all a single board moves anyway (and one side of every board is nailed and cannot move very much at all).
The gaps between the strips open ad close to allow for the separate movement of each strip.

It does take some practice to lay strip floors through out the year, even after the wood has acclimated.

Lay it too tight in the winter when it has acclimated and shrunk and it can buckle in the summer wen the humidity is higher.

Lay it to loose when expanded and you have wider than desired joints throughout the dry parts of the year.

And you say you want wood floors in your home...huh? Take it from people who know just about all there is to know about solid wood flooring...it comes with a personality.

My floor looks a lot like the one in the picture and its been down for at least 10 years with no buckling anywhere this just happened in the last week

"My floor looks a lot like the one in the picture and its been down for at least 10 years with no buckling anywhere this just happened in the last week"

Check for some sort of water leak.