At work, so no time for a detailed answer, but what you'd have to do is lerp between a line and circle formula.
If t is a value between 0 and 1, that represents represents the path around the circumference of a circle, or the path along the line from beginning to end where it wraps.
Then for each point on the perlin plan you get a height value, and use this added to the minimum radius for the circle. Calculate the angle of that point from the circle.
On the line version angle would just be 0
Using distance as a factor lerp the two together to get the x and y coordinates of the nonnoised surface, and interpolate the angles to get the correct angle to offset that point in the land from the surface. If none of this makes sense let me know and ill explain in greater detail when I have a chance
As far as visualization, id say it'd have to be distortmaps
Tho in my experience on a mass scale like this, its best to modify the sprite plug to take distortion commands from another plugin to avoid the event overhead