The arched formation is 'natural' in the fractal. Indeed it's strangely smooth, compared to the chaotic mess of the grassy parts, but it just happened!
It's probably a very dense part of the fractal shape, given the effect of the color map on it; at least this is my interpretation.
I used a single color map, and while the hues change smoothly on the rocks and vegetation, they are very densely packed in there. When I saw the effect I tried to compromise between a nice green on the vegetation, a decent rocky hue for the mountain and an interesting rainbow pattern on the distant fields.
The color management on this picture was mostly about increasing vibrance on foreground parts, for the color map was too weak.
The white haze comes from fog settings in MB3D.
Yes, the title means: Rainbow Fields, in Maltese language.