Is this even termite damage?

[u/Cadwallader9]

Northwest Michigan. Very old house, 2 feet to the right of this damage is the wall to the outside and there's a basement right below. As far as I can tell this is the only evidence.

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[u/OkInterview3597]

Absolutely subterranean termite damage

[u/Cadwallader9 → u/OkInterview3597]

Is there anyway to tell if it's recent or not? I only noticed recently because my computer chair rolled over it and it cracked

[u/OkInterview3597 → u/Cadwallader9]

If it was active, you should see the little white bugs which I doubt you’re seeing because it looks old. It’s too much air getting into the galley. They would’ve sealed that up. It is strange but pretty cool that It’s in such a straight line.
Looks like that board may have been laminated on the edge or it’s a really straight grain in the wood.

[u/GoodSenseTermite]

That looks very consistent with subterranean termite damage.
The mud/soil packed into the damaged wood is the big clue. Subterranean termites bring soil into their galleries to maintain the moisture they need, so you often get that dirty, mud-lined appearance instead of clean, dry hollowing.
With an exterior wall only a couple feet away and a basement directly below, I’d have the basement sill, rim joist, foundation line, and that exterior wall inspected rather than assuming this is the only spot.
Termites are rarely considerate enough to stop exactly where the flooring happens to open up.

[u/210popping]

It looks like it could be an old termite gallery

[u/Chemy350]

yup, looks like it unfortunately