- A line of clouds can indicate there are mountains below, as the mountains push warmer air upwards to higher elevations, where it cools and forms clouds. A line of vortices in the ocean, on the other hand, can indicate there are peaks below the surface of the water, perturbing the water's flow.
- There's an optical illusion called relief inversion that can happen with satellite images. Mountains appear to be canyons, or vice versa. The Earth Observatory explains: