Gradient tool, shape "radial"
layer modes
  Europe.xcf.7z (Size: 478.42 KB / Downloads: 204)
Screenshot below and .xcf above, should be self explanatory, increase contrast for a sharper effect, check out the compressed .xcf for the different layer modes (Layer with the mask is in "Darken only" mode)
   
	
	
	
	
layer modes
  Europe.xcf.7z (Size: 478.42 KB / Downloads: 204)
Screenshot below and .xcf above, should be self explanatory, increase contrast for a sharper effect, check out the compressed .xcf for the different layer modes (Layer with the mask is in "Darken only" mode)

