Geological WondersYellowstone National Park
For a few, Yellowstone is Earth’s door to Hell, for others, like the many microbiologists who visit the park in pilgrimage, this place is like going to Heaven. Bacteria and blue-green algae adapt to the various properties of the hot springs, probably under similar conditions in which early stages of life occurred on Earth.
Yellowstone National Park is currently sitting on top of a Hot Spot, where semi molten rock sits quietly just a few miles below ground, providing geothermal heat expressed in many forms throughout the park. Most of the rocks in the area have magmatic origin and many episodes of extreme active volcanism has occurred. Such rocks contain significant quantities of rare minerals ready to be dissolved in the groundwater.
Yellowstone is one of the few places in the world where geysers occur. The essentials for geysers and hot springs exist here. Snow and rainfall provide water to fill the ground water, heat from the deep magma chamber warms the rock and water above it, and fractures in the rock provide the “plumbing” through which the water circulates.
A geyser’s channels have constrictions that prevent the water from circulating freely to the surface where the heat would escape. Pressure builds. When the bubble point is reached, steam forms and is trapped in the liquid phase in the rock pores, by constrictions and overlying cooler fluids. At a critical point, the confined steam lifts the cooler water and causes the geyser to overflow or splash. Pressure release continues, more steam rises and forces water out of the vent. The eruption begins.
Minerals such as sulfur are dissolved in the hot water and steam, which can then get precipitated in the pools surrounding the geysers. Mixed with bacteria, it creates beautiful basins but may also deliver less attractive smells.
Hot springs are very similar to geysers but have no constrictions in their plumbing. Convection prevents the spring from erupting like geysers do. Water cools down in contact with the colder atmosphere temperature and circulates down to underlying rock pipes, replaced by the hotter water rising, making a perfect geothermal system.
Any modifications of the plumbing system, through earthquakes or obstructions may transfer a peaceful hot spring into a raging geyser without any warning.
Travertine or minerals can be deposited around springs and pools, depending on water chemistry.
When the water supply diminishes, fumaroles may form in the presence of a vent in the Earth’s crust to allow steam to escape when hot water comes in contact with hot rocks underground.
Hydrogen sulfide rising from deep within the Earth can be converted into sulfuric acid by specific microorganisms. The acid dissolves surrounding rocks into clay. Mixed with rising steam and groundwater, it forms muddiest of varying colors and consistencies.
Anemone Geyser, Upper Geyser Basin
If Anemone Geyser if drained when you walk by, wait a few minutes to watch the stages of a typical eruption. The pool fills, overflows, and large bubbles rise to the surface. Suddenly, Anemone erupts 2m or more. The water then drains back with a gurgling sound into the vent.
Hot Springs, Yellowstone National Park
(from top left to bottom right: Rainbow Pool, Black Sand Basin; Aurum Geyser, Upper Geyser Basin; Pendant Spring, Upper Geyser Basin; Palette Spring, Mammoth Hot Spring; Black Pool, West Thumb Geyser Basin; Heart Spring, Upper Geyser Basin; Pendant Spring, Upper Geyser Basin; Palette Spring, Mammoth Hot Spring; Black Pool, West Thumb Geyser Basin; Silex Spring, Lower Geyser Basin; Doublet Pool, Upper Geyser Basin)
Map, Yellowstone National Park