Geysers: Rare Geologic Wonders

The Scientific Process Behind Geysers

Sep 5, 2007 Lisa A. Bessasparis

Millions of visitors travel to Yellowstone National Park and Iceland to watch geysers. Here is look at the science behind them.

What Is A Geyser?

A geyser is basically a hot spring with an air- and watertight plumbing system. This system allows internal pressure to build up until eruption is necessary to relieve the pressure. Some geysers erupt nearly continuously, while others lie dormant for many years. Duration and height of eruptions are also very different for each geyser.

Invisible Forces At Work

Geyserite, a rhyolite-derived mineral, cements the plumbing system. Geyserite deposits on the surface form cones and a myriad of interesting formations. Magma heats up reservoirs of water below the Earth‘s surface. These reservoirs are supplied with water by underground aquifers through cracks and crevices. Magma heat the surrounding rock, the rock heats the water, and a convection current now circulates the water. Eventually, all of the water in the reservoir is heated up to above the boiling point and steam escapes. Water coming into the spring from the surface is cooler. The boiling water expands at the same time the surface water is running down into the internal plumbing, filling up the system. Excessive steam and water running over the sides of geyser cones or excessively bubbling springs are seen.

Water Pressure Increases

Pressure builds up as underground boiling water tries to expand but is hindered by the narrow opening. Longer, narrower openings allow more pressure build-up and perhaps a more spectacular eruption than a shorter, larger diameter opening does. Rocks or foreign objects encountered along the way up allow more pressure build-up because the opening is restricted.

Boiling Water

In the process of boiling, the higher the temperature the faster the molecules are moving. Along with the restrictive opening, the temperature of the water factors in how much pressure will build up. The steam we see on the surface is from gas bubbles reaching the surface. The liquid water reached vaporization and is now a gas. The molecules of liquid water were closer together; in gaseous state water molecules are far apart from each other. At first, smaller bubbles are formed, but as the water heats up larger bubbles form. It is harder to fit the larger bubbles through a small opening so again pressure is building up. The bubbles escape as a shower of water.

At this moment, pressure is lowered but the rest of the bubbles need to push through. Bubbles keep building up and releasing in this manner as long as there is sufficient heat. At first, it is in smaller bursts. The shower reaches a maximum height and fades out with smaller and smaller showers until all of the trapped bubbles have escaped and the heat is not sufficient enough anymore.

The Final Show

Seated tourists patiently wait. Steam begins to rise up out of the ground, increasing as time progresses. Small bursts of water appear as the steam continues. The bursts progressively increase in height and frequency. Finally, a grand column of water shoots out of the ground and into the sky. The crowd is awed, frantically photographing, until the geyser’s cycle is complete. Another 90 minutes or so and Old Faithful replays the show. What a magnificent planet we live on!

Related Suite 101 Articles:

Hot Springs and Mudpots

Fumaroles: Steamy Volcanism

Geyser-Related Links:

National Park Service: Old Faithful Webcam

Geyser Observation and Study Association

The copyright of the article Geysers: Rare Geologic Wonders in Geology/Ecology is owned by Lisa A. Bessasparis. Permission to republish Geysers: Rare Geologic Wonders in print or online must be granted by the author in writing.

A Distant Old Faithful

In Upper Geyser Basin