Find out by clicking and dragging on the terrain using your mouse or by breaking out of auto-pilot and navigating with the W A S D keys on your keyboard. Look at locations to learn about them. If you have a VR headset, then use that instead.
The black sand forms mounds that are tallest in cities with the greatest amount of dislike for the smug croissant. Cities are areas with 10K or more people. Modulo the clearly fake data, the city-level data is from here. The contour map below is draggable and will help you orient yourself.