The effect is created using a world building application called Mojoworld, which generates 3d planetary landscapes. I generate one that has parameters I like and then export a slice of land into two files of the same pixel size, one is the height map, pictured first and the second is the texture of the land. This can be done using any app that can give you a white to black height field and a corresponding ground texture.
Then I start a new file in Gimp and add both as separate layers. Its often convenient to make the bump map invisible while you work. Select the ground texture layer and choose "filters", "map", "bump Map" from the menus. This open the bump mapping screen. Be sure to select the heightfield layer as the bump map in the dropdown menu. There are various sliders to play with but the two most important for present purposes are "elevation" and "depth". Lowering the elevation and increasing the depth will give you more dramatic contours.
The result is the third pic below. Looks like a decent place for a ski resort. I have applied a slight blur to the texture map and once the two were combined I increased the brightness slightly. I hope this is useful to someone.