What is Thermal Activity

Yellowstone is full of geysers, fumeroles, hot springs, and mudpots. All of them involve something called “thermal activity”.

For thermal activity to happen on earth, there must be three things:

  • Heat source
  • Ground water
  • Cracks or “fissures” in the earth

The water for Yellowstone’s geysers comes from ground water – snow and rain. The water seeps down into the ground until it comes in contact with heat.

The heat in Yellowstone comes from a “hot spot” deep under the ground. For some reason that nobody understands, in that particular spot the magma (molten rock) is able to rise up through a channel until it’s almost at the surface of the earth.

The magma heats the water, which then comes to the surface through a series of cracks called fissures in the earth’s crust.

Old Faithful is one of the most predictable geysers in the world.

In essence, all of Yellowstone’s many geothermal features are the same. The only difference is what the earth looks like where the water comes up.

Geysers – the crack the hot water comes up through gets very narrow at some point, which blocks the flow. Pressure builds up until the constriction can’t hold it any more and it blows.

Mudpots – the hot sulfuric water comes to the surface where there happens to be a stone called feldspar. The sulfuric acid dissolves the feldspar to make mud, and the water bubbles up through it.

Fumeroles(steam vents) – hot water turns to steam deep down in the earth. As the steam rises to the surface, it creates a hissing spot in the ground sounding like an angry teapot!

Hotsprings – hot water bubbles up through the fissures and collects in steaming pools on the surface of the earth.

Steam from afar.
Hot spring.
Hot spring joins a river.
A geyser.
Another geyser.
Heat loving microorganisms.

books by Nancy Sathre-Vogel

About Nancy Sathre-Vogel

After 21 years as a classroom teacher, Nancy Sathre-Vogel finally woke up and realized that life was too short to spend it all with other people's kids. She and her husband quit their jobs and, together with their twin sons, climbed aboard bicycles to see the world. They enjoyed four years cycling as a family - three of them riding from Alaska to Argentina and one exploring the USA and Mexico. Now they are back in Idaho, putting down roots, enjoying life at home, and living a different type of adventure. It's a fairly sure bet that you'll find her either writing on her computer or creating fantastical pieces with the beads she's collected all over the world.

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