Terraform filters

I have a question about the terraform tools, namely how to get them to work. It doesn't seem to matter what I do, but lets say I add Smoothing to the list of actions. The minimap shows an estimate of waht should happen once I hit apply, but whatever I set up, my world always ends up completely flat. When I use the canyon fractal, which to my understanding would create canyons, the same happens, just like the other options.

Do I need to set something else up first?

Thanks in advance.