Hot Springs and Geysers
Hot Springs form above areas of the earth’s crust where the crust is thin enough, due to subduction or hotspots, to allow pockets of hot magma to be near the surface. As rainwater or groundwater seep into the underlying rock layers, it is heated by the magma and percolated back up to the surface. As the hot water rises up, it tends to dissolve minerals in the rock thus providing a variety of color, odor and composition of mineral deposits.
Geyser activity occurs in a small percentage of these areas and can only happen if the right combination of factors occurs. Scientists believe the crucial factors are the right combination of heat, intruding water, and most importantly the shape and size of the cavities and fractures in the underlying rock layers.
Basically what is required is a cycle of heating that reaches a critical temperature and pressure that cause formation of steam and superheated water. At some point, the pressure cannot be contained and is released as a geyser of steam and water. After the pressure is released, the geyser stops and ground water flows back into the cavity to be heated and the cycle starts all over.
This explanation is very basic and it should be noted that scientists have identified at least 6 types of formations. They are all different from one another depending on the shape of the cavities, the type, and temperature and flow rate of the water flowing into the geyser.
The geyser system you see here is an example of the construction of a typical fountain geyser such as the ones found on Yellowstone National Park. “Old Faithful”, the best known Geyser in the world, is also a fountain geyser but it is believed to have a somewhat different shape, this results in a single, regularly spaced eruption, as opposed to a series of eruptions, demonstrating what you would get from a geyser formation such as the one shown on cross section here. Other factors that influence geyser eruptions include the presence of underground gases, seasonal rainfall, barometric pressure, earth’s tides, and earthquakes.
Other interesting formations that occur in the same areas as geysers are steam vents. These are water pockets that do not erupt but constantly release pressure as steam. Mud pots are heated water that is saturated with silt or clay and hot pools are the result of water that is heated but not to the point of steam.
Thermally active areas, such as Yellowstone in the United States and Iceland, can be useful in providing people with a source of energy. Thermal energy can be used directly to heat buildings and in some cases produce electrical energy. This source of energy is being utilized today in a number of countries and holds the promise of providing a clean, renewable source of our ever-increasing demand for energy.