This is kind of the question I was asking myself before I learned about the thermal features of this unbelievable place. Why are they found here? No where are there as many geysers. A volcano is the answer. Hundreds of thousands of years ago huge volcanic eruptions happened here. This caused some of the geographic features we see today. The heat from magma underground powers the parks geysers, hot springs, fumaroles and mudpots. Grand Prismatic Spring was the most memorable for us. Ranger Rick told us where to hike to get the best view and he was right on the money. The little specks down on the board walk are people. We had to climb to get this awesome view.
All of the thermal water features are unique in their own way. Heat loving microorganisms grow in different colors depending on the temperature. Hot springs are the most common in Yellowstone. They can be muddied and boiling to clear and calm. All are heated by the magma under the earths surface.
The travertine terraces found at Mammoth Hot Springs are the result of water and limestone. It is so interesting how they form in different patterns depending on the way the water flows.
At Old Faithful we learned how geysers form. The park ranger led us through the stages before the geyser erupts. Geysers are hot springs with narrow spaces in there plumbing. These prevent the water from freely coming to the surface where the heat could escape. The water temperature exceeds the boiling point. The pressure increases the deeper it is. This pressure keeps the water from boiling even though it is hot enough to. As the hot water moves toward the surface steam forms. Bubbling upward, the steam expands as it nears the surface until there are too many big bubbles to pass through the small opening. The confined bubbles lift the water causing the geyser to overflow. This decreases the pressure on the whole system and the water can now boil. When it boils tremendous amounts of steam force water out of the opening and the eruption begins! We were there a few times when Old Faithful erupted. We also were able to simulate the eruption in the visitor center with a model.