We have a fair bit of geothermal energy/heating in my local area. I've always assumed that it is exchanging heat from underground, heat comes up and cool goes d

We have a fair bit of geothermal energy/heating in my local area. I've always assumed that it is exchanging heat from underground, heat comes up and cool goes down. The cooling is slowly seeping out through the rock into the magma causing it to solidify. This solid spike of rock now grows as the geothermal exchange continues, the spike grows into a sail, a giant rock sail poking down into the slowly moving magma. Eventually the magma current pushes against the rock sail which is attached to the town above causing the whole lot to flip over like an iceberg.