Figure 2.08. Old Faithful Geyser. This is one of more than 500 geysers in Yellowstone National Park, USA. Geysers erupt due to the nucleation and growth of steam bubbles due to heating and decompression of groundwater. You can see videos of the eruptions of some Yellowstone geysers by clicking these links: Yellowstone Geysers, Grand Geyser, Fountain Geyser. Links to some other geyser videos: Geysers del Tatio. If you would like to make a model geyer that erupts every few minutes, follow the instructions in the article by Forrester and Thune (1942) interpreted by Marshall Schalk in this drawing. A short video example of the geyser model erupting is shown here. John Brady photo.