My daughter is doing a Volcano project at school. We designed this as a cut-away so she could show how the magma comes up by painting it on. I kept a 15mm tube so we could fill it with Hydrogen Peroxide, Dawn, Yeast and some water. For this model she will be adding clay on the outside to make it feel more realistic.

The Volcano is hollow and I left the top area intentionally off to cut down on the need for any supports. I designed this from 123d Design and came out great. No "FIX" needed.