NGDIR News Section-- Natural geysers are rare on Earth; there are fewer than 1,000 worldwide, and about half of them are in Yellowstone National Park. Geysers, whose eruptions range from small bubbling pools, to roaring jets of water and steam that can reach a few hundred meters high, fascinate all who have the good fortune of witnessing one.
In a newly published paper, U. S. Geological Survey hydrologist, Shaul Hurwitz and his coauthor, geology professor Michael Manga at the University of California, Berkeley, synthesize the current state of knowledge about geysers. The authors review past research, and point the way to answering future questions. The "Annual Review of Earth and Planetary Sciences" is published once a year, and includes articles written by invitation only. The newly-published article about the science of geysers attempts to bring all the knowledge of geysers that has been gathered by scientists since the early 19th century together in one place and to improve our understanding of the influence of changing technology on scientific knowledge.
Because many of the processes associated with geyser eruptions are similar to those operating in volcanoes, understanding the mechanics of geysers and how they operate can lead to better understanding and predictions of volcanic eruptions. And because geyser eruptions are smaller and more frequent than volcanic eruptions, there is an opportunity to collect more data and develop approaches for integrating and interpreting geophysical and hydrological measurements to understand their geology, chemistry, underground "plumbing," and the physical processes that control their behavior.
A better quantitative understanding of the processes that control geyser eruptions is also critical for their preservation, and can guide the protection and preservation of the unique and diverse geysers on Earth.
Through monitoring eruption intervals, analyzing geophysical data, taking measurements within geyser conduits, performing numerical simulations, and constructing laboratory models, some of these questions have been addressed. Geysers are uncommon because they require a rare combination of abundant water recharge, magmatism (a source of heat), and large fractures and cavities in the rock. Geyser eruptions are driven by the conversion of thermal to kinetic energy during decompression. In other words, water deep in the ground is heated up by nearby hot rocks, and when conditions are just right, and the pressure of the overlying rocks is released, the water will erupt out of the ground as a geyser. Larger and deeper cavities within the rock permit larger eruptions and promote regularity by isolating water from weather variations at the Earth's surface.
"Geysers are exceedingly complex hot springs, no two of which are alike," said the late USGS geologist Donald White, who established the modern scientific definition for word, "geyser" in 1967. The English word "geyser" is derived from Geysir, a name given by Icelanders in the seventeenth century to an intermittently discharging hot spring in southwest Iceland. Some of the earliest studies that led to the scientific understanding of geysers were done in Iceland by Robert Bunsen (of laboratory burner fame) in 1847.