A little tip I discovered playing around with this recently, to get extra crags and roughness in the face of a hill you can take the ramp tool, dial it down to smallest, then find a point on the hill click, drag a couple of millimetres, and let go, this creates a ragged, jagged piece, which you can then use the blend tool to make the surface look a little more jagged and natural.
Here's a pic of what I got in literally three seconds doing this (a bit more time and care can get it way better):
i5, NV960 2GB, 16GB memory, 2x 2TB Hybrid, Win10.
i3 , Intel integrated graphics, 6GB memory, 512GB Generic SATAIII Win8.1.
Intel Celeron (duel Core), Radeon integrated graphics, 4GB memory, 180gB Generic SATAII, WinVista.
Q6600, Intel integrated graphics, 8GB memory, 512GB Generic SATAII, Win7.
