Inside the Earth
Surface runoff, from rain and snow, seeps down into the Earth through cracks and crevices. This cooler surface water eventually percolates down to rock heated up by contact with a magma chamber. The water then becomes superheated, at times even to above the boiling point. A convection current starts circulating as the incoming cold water sinks and the outward bound hot water rises (just like air) through cracks, crevices, and weaker rock. At the surface, a hot pool of water forms. Unlike geysers, hot springs contain an unrestricted plumbing system. Air and water can access hot springs freely so heat energy releases in a relatively slow, constant manner. The distribution of water through numerous cracks and crevices decreases pressure. Pressure in a hot spring’s plumbing system cannot build up enough to a full eruption. Although, some hot springs are known to burst boiling water up into the air similar to a geyser. Just as silica deposits on the surface, known as geyserite or sinter, form geyser cones, it also creates interesting patterned edges around hot springs. Depending on water and air temperatures at a hot spring’s surface, steam may or may not be present.
Hot springs can also form when no magma body is present. This occurs when water seeps into cracks and crevices far below the Earth's surface. If water goes deep enough, the internal heat coming from the core can heat up the water.
Surface Colors
Hot springs come in a myriad of colors, from everyday clear water to sapphire blue to emerald green. Color depends on what wavelength of sunlight we see reflected off the pool’s surface.
The sinter around the edge of hot springs comes in all colors, as well. In fact, water temperature can be estimated by the colors. Different microbes are present at different water temperatures. These microbes create the colors. “Cooler” temperature water is habitat for microbes creating darker colors. Microbes are colored by pigments like chlorophyll in green plants and carotene found in carrots. These microbes are known as thermophiles because they love heat (root therm as related to heat).
Recipe for a Mudpot
Unlike the regular supply of hot water to a hot spring, the hot water supply to a mud pot is limited. The limited supply of hot water combines with hydrogen sulfide gas sulfuric to form sulfuric acid which chemically erodes the surrounding rock into finer clays and silica. A little water is churned into the clay and silica, producing a “pot” of boiling mud. Many mudpots are shades of white and gray but red hues are common when oxides are present. Thickness of the mud depends on the available water supply. For example, Yellowstone may have an above average snowfall one year. The excess runoff will increase the mud pot’s water supply so mud will be thin. Likewise, less snowfall will provide less runoff so mud will be thicker.
Enjoy Nature’s Gifts
While soaking in a natural hot spring, think about the Earthly process that made the warm spring possible. Geysers erupting are exciting and hot springs are colorful but scientifically mudpots are just as fascinating. Both hot springs and mudpots are intriguing signs of an ever changing, volcanically active Earth.
Related Article:
Geysers: Rare Geologic Wonders
About Microbes:
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