Seen from the air
On a recent transatlantic flight as pax from the UK to the USA, we flew over Northern Canada. While looking out of the window, I saw a load of very long straight lines seeingly carved into the rock. There was snow on the ground and they were all white - looking almost like long, frozen canals. The ran kind of North - South but changed direction every few miles. I was just wondering if anybody could tell me what they are?