The map shows that Obsidian Creek runs through hydrothermal zones at Sites
3 and 4!
What difference does that make?
All the difference in the world! Yellowstone has over ten thousand hot
springs, mudpots, geysers, and steam vents. If water from a hydrothermal
system mixes with water in a stream, the stream’s temperature, water
chemistry, and ecology are all affected. At Site 4, where stream conditions
are most severe, Obsidian Creek flows by Roaring Mountain, an area that’s
very hot and acidic. Therefore, the creek also becomes hotter and more
acidic at this location.