start by splattering several polygon 2 shapes with different settings to create a basic amount of primitives. slope blur it (32, 0.1, Min) according to a splattered squeeze cloud.
Duplicate this whole setup, turn it into something less vertically shaped and subtract it on the first setup to create medium shapes. slope blur it according to a blurred cloud and then from a fractal sum base to sculpt the surface. invert the result and blend it in subtract mode on an empty output.
connect the result to a height output. now drag and drop this graph into the master graph, plug your main height in it and destroy some parts!