Power lines looks like the possible "culprit" here.
If they go into voids, you might consider remnants of the latest Ice Age. I know here in Sweden we have something called "rullstensåsar". They are collections of stones deposited by the melting ice. Some of these can be seen from the air although most of them are overgrown. I guess they would be more clearly seen in an environment of snow and tundra since the treetops won't obscure your view. They can be surprisingly straight.
Happy hunting, please let us know what you find!