A common question particularly asked by those students looking for science fair ideas. Geyser experiments are described on my science fair project page in the student section of this site. All of the experiments listed need adult supervision. The word geyser is an eponym. Find out the origin of the word and what an eponym is on my page, How Geysers Got Their Names .
Geysers are temporary features geologically.
The do not last for millions of years but probably for a few thousand. Geysers require a specific set of geological conditions. Second, a supply of water that can circulate deep enough to be heated by the magma. Third, cavities or pore space in the rocks just below ground level that can act as a pressure chamber. Fourth, silica rich rocks that will provide abundant silica to seal the pressure chamber and keep the pressure contained until a eruption results.