A:
1" cracks you say! That is not a crack. It's a drainage ditch. Sorry.
Couldn't resist.
That is a big gap. Can I assume that this is not tongue and groove, and
there is no sub floor beneath this pine?
What I am thinking is that you could make a stiff paste with fine wood dust
and wood glue and press it into the gaps. I am not sure that it would not
sink through. It would have to be really a stiff mix. Perhaps jamming some
paper into the gaps first or cutting tight fitting wood strips and banging
them in would give this paste something to sit on. Before doing this, I
would apply painters tape to each side of the gap so you don't smear the
glue-dust mix all over the surface of the floor boards. If the colour is
going to be significantly different, make sure you push the mix below the
top of the boards so that when it hardens you can perhaps apply another
colour matched latex filler on top. Then when all of that is done, you may
want to have the floor lightly buffed with a polisher and fine screen pad,
and recoated.
If you can come up with a more workable solution, please let me know.
I hope this helps.

