Blender rock formation help?

Hey all,
I've been trying for a few weeks now to create a cliff in blender which looks similar to these ones:
Experiments with the fractal, noise and displace functions didn't work- the results were too angular and not long enough (I'm aiming for a curved, flowing look). Does anyone know of any ways to make rock of this shape?
Thanks,
ardent red
I've been trying for a few weeks now to create a cliff in blender which looks similar to these ones:

Thanks,
ardent red