Old Faithful is a geyser in Yellowstone National Park, named after its regularity in erupting hot water and steam, fed by the geothermal activity of the Yellowstone supervolcano underneath.
In the last several decades, scientists have observed that Old Faithful’s interval between eruptions has changed considerably, stretching from about 60-65 minutes in the 1950s to about 90-94 minutes since 2001.
A geyser’s eruption is feed by a complex, underground vent system filled with water. As the magma in the underground heats up the groundwater, steam pressure will build up until it is sufficient to trigger a steam eruption on the surface. According to the scientists, no major changes have occurred in the thermal state of Yellowstone, excluding this factor as an explanation for the delay in Old Faithful’s eruptions. Another possible factor controlling geyser activity