Learning Family studies geysers at Yellowstone Sunday, June 14, 1998

Yellowstone is famous for its "Thermal Features." We learned that there are four kinds of thermal features: mud pots, fumaroles, hot springs and geysers. Yellowstone has about 10,000 thermal features, which include over 300 geysers. Geysers, which are close cousins of volcanoes, are made by water seeping down throught the ground, then gets heated by a hot spot of magma many miles below the surface. This water is heated past boiling temperatures, and rises up again as hot steam. This steam builds up pressure until it comes out through holes making a thermal feature. It takes 5 years for water to go from precipitation to geyser eruption. This picture of the Lowere Geyser Basin shows just how many there are.

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Silex Spring. Hot springs are made by the same forces as geysers, but they have wide openings in their plumbing, so they don't build up any pressure as the hot water rises from deep within the earth.

A Fumarole is also like a geyser, but it doesn't have enough water to make an eruption. Only hot steam and gas come out, making a hissing sound. Sometimes it has a sulfer smell, which comes from the

Some geysers have predictable eruptions. Old Faithful Geyser is the most famous geyser in the world, because of its predictability. Some of the factors that are needed to predict Old Faithful eruptions: the starting time of the last eruption, its duration. Geysers have narrow and long plumbing, which makes the pressure of the hot water build, until an eruption occurs.

Here's an old black and white of a group on Old Faithful. The picture was contributed by one of our friends. I think it is his grandfather's family on a trip before preservation of the park was a priority.

Wildlife at Yellowstone