How to trim the jagged edges off of this solid I am a total newbie to Blender. I'm trying to make a solid model of a piece of terrain, cut into a circle, on a cylindrical base, for 3D printing.

Below is what I have so far. I got there by importing a square piece of terrain surface, then I drew a circle and extruded it through that terrain, and then I did a Boolean intersect between the two, and solidified it (inwards), so that both the top surface and the sidewalls have some thickness for the printing.

However, the solidify made some ugly jagged things protruding through the outside of the cylinder, these are probably offsets from parts of the terrain.

How can I trim these off so the cylinder is smooth on the outside? I've tried making other solid cylinders and doing Boolean operations to subtract these bumps, but the Boolean operations are always refused.

File is here.
Try applying a solidify modifier to your cylinder prior to adding your boolean modifier to the terrain object. 

For me, I have better luck with the boolean modifier when there is thickness to the extracting mesh.