Abstract: Herewith are methods and embodiment of an apparatus for using geothermal heat for pyrolysis. In some embodiments, a pyrolysis reaction chamber is lowered into a well, where the pyrolysis reaction can be driven by geothermal heat. In some embodiments the reaction chamber is connected to second chamber to contain the gas reaction products produced by the pyrolysis reaction. In some embodiments, the reaction chamber and the gas collection chamber are separated by some distance in the well, and are connected by a long hose or conduit. A spallation drilling apparatus is also disclosed that uses jets of hot fluid for drilling. This is compatible with drilling wells in high temperature zones, such as a lava dome. A simplified pyrolysis reactor for use in a lava dome is also disclosed, in which the dome functions to contain the reaction, and the apparatus to facilitate pyrolysis is far more compact.