From what I have gathered it is permanent as long as we don't pump too much cold water down in vents and use it sparingly. There are a few places in the world such as in Japan, New Zealand, The Philippines, and the United States, and these are countries that have really only scratched the surface in developing geothermal energy. Water is pumped into vents down to hot rocks heated by underground sources such as volcanic lava deep underground. The water is pumped back up and refined by removing chemicals that may cause it to become encrusted with matter that prevents successful removal of the heated water. New Zealand and Japan have been using this form of energy for longer periods of time than in the U.S. and we have a readily available source of energy that has no residual polluting effects on the environment. Geothermal energy is one of another of the available natural energy sources to be further developed around the world and offers a successful way in heating and operation of power plants that provide electricity, as well. As long as there is water available, and the center of the planet is full of hot magma, then we will have this source of energy. I suspect before the earth's core burns down, we, as a human race, will have migrated to new solar systems in our galaxy. The earth is around 5.4 billion years old, according to scientists, and most likely it will take several more billion years to burn out. How important now is NASA and the space program?