Yellowstone National Park has more than 10,000 hydrothermal features, including over half the world’s geysers! These unique features led to Yellowstone becoming the world’s first national park.
The first super volcanic eruption in the area was 2.1 million years ago followed by two more super eruptions. Five types of hydrothermal features exist in the park – these prove Yellowstone’s volcano is still active today.
Rain seeps through bedrock and becomes superheated by the magma below. The way this heated water interacts with the surface is what differentiates the types.
Fumaroles
Also called steam vents, fumaroles constantly release hot steam due to a low supply of water – the water boils away before it reaches the surface.
A great example of fumaroles is Roaring Mountain. In the early 1900s, its fumaroles were loud enough to be heard for miles, hence its name. Another is Black Growler in Norris Geyser Basin.
Geysers
These are hot springs with constrictions that prevent water from circulating freely to the surface; this causes periodic eruptions to release the built-up pressure. Geysers get their name from Geysir, a geyser in Iceland.
The most famous feature in Yellowstone is Old Faithful. Old Faithful is one of six geysers in the park that rangers can regularly predict eruption times. The others are Castle, Grand, Daisy, Riverside, and Great Fountain.
Upper Geyser Basin has at least 150 geysers within one square mile.
Hot Springs
Hot springs are pools of hydrothermally heated water. They are the most common hydrothermal feature in the park. Superheated water cools as it reaches the surface, then sinks and is replaced by hotter water from below. This flow prevents it from erupting.
Hot springs may have bright colors which are due to different species of thermophiles – heat-eating bacteria and algae – living in the water.
My favorite hot spring in Yellowstone, and the largest one in the United States, is Grand Prismatic Spring. Midway Geyser Basin and Black Sand Basin each have four main hot springs.
Mudpots
Surface water collected in shallow depressions forms mudpots. Thermal water below causes steam to rise through the ground and heat the surface water. Sulfuric acid breaks the surrounding rock into clay.
The gooey mix gurgles and bubbles, dancing in a rhythm all its own. Paint pots are mudpots that are tinted different colors by minerals.
Artists’ Paintpots has colorful hot springs and two large mudpots. Thumb Paint Pots in West Thumb Geyser Basin shows its colors.
Travertine Terraces
Travertine terraces are hot springs that rise up through limestone. Thermal water dissolves the calcium carbonate, depositing calcite which forms the white terraces. Colorful formations are caused by thermophiles.
The most popular travertine terrace in Yellowstone is Mammoth Hot Springs.
It is easy to see all these hydrothermal features throughout Yellowstone National Park. Most are located just next to boardwalks, making it perfect for a family trip!
Very, very good info, I wish I’d had it many years ago when we visited Yellowstone. Thank you.