Colby Tucker and Emily Quinton
Geology 112 Term Paper
Geysers: Not to be Overlooked Despite Their Rarity
There are many unique features that can be found in areas where geothermal heat is close
to the surface to the earth. Included in this list are volcanoes, hot springs, geysers, fumeroles and
mud pots. Geysers, a rare type of hot spring, are vents that periodically eject hot water and
steam. While some geysers, such as Old Faithful in Yellowstone National Park and Geysir in
Iceland, are well-known, there are other areas that attract a lot of attention for their geysers. The
accessibility of geysers to research and visitors, however, is sometimes limited by geothermal
power developments in the surrounding area. The eruption process of geysers has been known
since the 1940s and knowledge about geysers has not changed a significant amount since then
because research on geysers has been limited by the geological nature of their systems; however
efforts have been made to better understand these eruptions. Studies on geysers have focused
primarily on the periodicity of eruptions and both internal and external factors that affect the
timing and size of eruptions. These studies are important for better understanding the geological
processes that occur in geyser areas.
Hot springs are a geological feature that can arise in areas where water is able to be
heated deep below the earth’s crust. Geyser fields, however, arise under more limited conditions
and that is why there are only five main geyser fields in the world. These five fields are located
in North America at Yellowstone National Park, at the Geysir area and Strokkur in Iceland, at
Pohutu Geyser and Waimangu in New Zealand, at El Tatio in Chile and on the Kamchatka
Peninsula in Russia (see Appendix A for world map of geyser locations). Geysers have also been
studied in other various locations, including Nevada, but in some places the geysers have been
lost to geothermal power developments (Bryan, 2005).
About half of the geysers on Earth are located in Yellowstone. Approximately 500
geysers are located here and the protection provided by the national park service has helped to
preserve this number and foster long term research opportunities (Cross, 1996). Old Faithful is
Yellowstone’s most famous geyser, erupting approximately 10,000 – 12,000 gallons of water
every 30 – 90 minutes (“Geothermal Energy and Geysers, EIA). New Zealand has approximately
70 active geysers, with Waimangu being perhaps its most famous one, as it was once the world’s
largest (Cody, 1999). Iceland’s most famous geyser – Geysir, is the namesake of these rare forms
of hot springs. The name comes from the Icelandic word “to gush” (Reynolds, 1941).
Geysers are located in one of two areas. They are either located at plate boundaries,
where the earth’s plates are either converging or diverging, or they are located on a geological
hot spot. Yellowstone and Iceland are both located on hot spots. Unlike plate boundaries that are
moving relative to one another, hot spots are fixed locations beneath the lithosphere where a
plume of magma is close to the surface creating features like volcanic arcs (Marshak, 2008).
Despite the differences between the two types of locations where geysers are found, the
important aspect is that heat is available close the surface of the earth.
It is no coincidence that geysers are a rarity on Earth—they require quite a bit of luck in
their formation. Not only are there two very specific locations where they can form, but also they
require proximity to a heat source, certain rock chemistry, water volume (and holding capacity),
and specific plumbing. The heat source is the basis of the energy within the geyser system and
the rock chemistry and plumbing is what contains the energy inside the system. The rocks within
a geyser are dominated by geyserite, a special kind of rock made of silicon dioxide that covers
the pores in the rocks and makes the system pressure tight. The plumbing of geysers is a network
of fractures and channels allowing water to flow freely like in the plumbing system of a house
(see Appendix B). The water can flow uninhibited from the source to the surface, but it is
thought to take at least 1,100 years (Bryan, 2005).
An eruption occurs by water seeping through the ground until it meets rocks heated by
magma. Water pools and begins to rise through the plumbing. There are likely to be several
sitting pools of boiling water throughout the plumbing that help feed the system and the eruption,
especially for the recharge of the geyser. The heat then rises by convection through the plumbing
of the geyser. Since the water on the surface is cooler and therefore denser, it presses down on
the system. Some of the hot water turns to steam, causing an initial overflow or bulge of water at
the top. The bulging reduces some of the pressure and allows the convection current to continue
to rise. The bulge will fall and as the heated water nears the surface the convection currents begin
to fail as the plumbing narrows, though the process of the surface water bulging and falling may
occur several times. Throughout this process, the water becomes superheated like in a pressure
cooker with no release valve (Bryan, 2005). As the heat and pressure increases, the water bulges
up one final time and finally erupts.
The recharge of the geyser begins immediately as water beneath the eruption fills the
vacant area with the water returning back down. Some of the water, however, has been ejected so
far that it will likely not return to the surface of the geyser, but rather percolate down through the
soil and porous rocks until it is fed back into the system via the geyser’s plumbing and ground
water interactions. It is this water that Bryan (2005) says will take another 1,100 years to reach
the surface. Yet, for all the natural circumstances people have found geysers to require for their
existence, many geysers are very unpredictable in their eruption intervals. This mystery has been
the focus of many people’s research, as geysers display a curiously chaotic nature (Nichol et al,
1994).
Stuart Rojstaczer and S.E. Ingebristen are today’s authorities on geyser activity and
behavior. In their most recent co-authored paper (2003), the authors collected “high-quality
geyser-frequency time series” from six geysers in Yellowstone National Park. Using this data in
conjunction with meteorological data and the time series from the other geysers, the authors were
able to suggest and rule out factors that may be related to the frequency of geyser eruptions
(Rojstaczer and Ingebristen, 2003). Firstly, elastic deformation, which is a rock’s response to
stress in the form of bending, was once thought to be a major factor in the eruptive timing. This
theory, which stated that the rock’s compressibility within the plumbing was at least partially
responsible for the variable timing of eruptions, is now thought to be less significant (Rojstaczer
and Ingebristen, 2003). The authors proposed that the long distance interconnections (up to 1.5
km) between geysers are a stronger influence in the eruptive timing than rock compressibility.
Secondly, as suggested by some, but found to be insignificant, are Earth-tide influences and
atmospheric pressure changes on a daily basis (Rojstaczer and Ingebristen, 2003). Over a longer
period of time, on the order of weeks, atmospheric pressure changes over 5 mBars was correlated
to the eruptive timings of four of the six geysers studied. The other two geysers, while not
directly affected by the atmospheric changes were influenced by the eruptions of at least one of
the other affected geysers, making every geyser eruption at least indirectly related to atmospheric
pressure changes above 5 mBars (Rojstaczer and Ingebristen, 2003). The difficulty in being
certain with the relationship of a single variable to the timing of eruptions must not be
overlooked. Geyser systems are complex and dynamic (especially on the geologic timescale).
They cannot be reduced to a single controlling factor or even several static factors.
Research on geysers has been fairly limited in scope, which may be related to the
difficulty in studying geysers. The general definition of a geyser and information on how it
erupts has not evolved much and a quick overview of the type of research that has been done on
geysers does not show that much progress either. After learning about geysers, however, it is
clear to see the importance of these systems and why research on what affects geysers is
important. By definition, geysers are rare. This aspect makes them an important geological
feature because it makes the areas in which they are located special (“Geothermal Energy and
Geysers, EIA). Research on whether geysers respond to certain internal and external forces and
variables could be helpful once these responses are better understood. Knowledge about what
affects a geyser could be helpful in examining the types of forces that occur in the volcanic areas
they are situated in.
The rarity of geysers also means that efforts should be made not to destroy them. While
natural processes that lead to the inactivity of a geyser are unavoidable, human influences can be
changed. Geothermal power developments changing the water table have led to the extinction of
geysers. Littering by visitors can block the geyser conduit (Bryan, 2005). While littering is an
issue that can easily be stopped, geyser presence may not always be considered in geothermal
power developments.
Scientific studies and textbooks reveal surprisingly little information about geysers
beyond their definition and eruption process. While this reflects the difficulty in studying these
systems, it also reaffirms the importance of continuing to study geysers. As a very rare
geological feature found on land, geysers can reveal information about certain natural processes.
Further research will focus more on the factors discussed that affect the periodicity of eruptions
and will hopefully lead to increased understanding of the places where geysers are found.
Considering that 70% of the planet is covered with water, there may realistically be geysers in
the oceans that are still too difficult to find.
Bryan, Scott T. Geysers: What They Are and How They Work, 2nd ed, Mountain Press
Publishing Company, Missoula, MT, 2005.
Cody, A., Present-day geysers of New Zealand, Newsletter – Geological Society of New
Zealand, 118:9-13, 1999.
Cross, Jeff. Geyser Studies in Yellowstone National Park, Geological Society of America,
28(7):ABSTRACT #144, 1996.
“Geothermal Energy and Geysers”. Sponsored by the Energy Information Association.
<http://www.eia.doe.gov/cneaf/solar.renewables/renewable.energy.annual/appc.html> last
modified 23 January 2003, visited 7 October 2008.
Manga, M., and Brodsky, E., Seismic triggering of eruptions in the far field: volcanoes and
geysers, Annual Review of Earth and Planetary Sciences, 34:263-291, 2006.
Marshak, Steven. Earth: Portrait of a Planet, 3rd ed., Norton & Company, New York. pg. 104;
674-675, 2008.
Nichol, M. J, Wheatcraft, S. W., Tyler, S. W., Berkowitz, B., Is Old Faithful a strange attractor?
Journal of Geophysical Research, 99(B3), 4495-4503, 1994.
Reynolds, S. H., Fumeroles, hot springs and geysers, Bristol Naturalists’ Society, 9(2):251-263,
1941.
Appendix A: The map of geyser locations and geyser fields worldwide (Bryan, 2005).
Appendix B: The plumbing system of a geyser (Bryan, 2005).