One can use the same sequence of random numbers and produce islands that
have the same large-scale shape, but with different values of H. The hull
is roughest (that is, the hull dimension is at its highest) when H is around
0.5. These rougher islands look more "arctic".
H=0.3
H=0.4
H=0.45
H=0.5
H=0.6
H=0.7
