Hardwood floor split and bulge
You stated this is red oak.  Are you sure it isn't engineered flooring with a thin red oak veneer?  It looks to have some sort of particle or pressed fiber board under the veneer.  Either of the latter is subject to warping via moisture expansion but I don't think that's your situation.  I think the fractional expansion of all the boards across the room are expressing themselves at this one length where it meets an anchored (nailed) section.

I would consider using a circular saw, since these don't appear tongue &amp; groove (T&amp;G), to slightly widen the current gap.  Using the saw, while the boards are uplifted, should widen the gap less that the width of the saw blade but be just enough to let the boards lie flat.  A second pass might be necessary to allow the boards to lie flat afterward.

At some point, during the Winter, there might be a noticeable gap.  If so, I'd suggest using either: a) clear or tinted rubbery caulk (not wood filler...which doesn't allow for expansion/contaction) or, b) sufficiently thick twine stained in matching floor stain and pressed into crack.