Firehole Spring Splash
Firehole Lake Drive is a loop road north of Old Faithful, near the Lower Geyser Basin. It is not a "household name" like several other geyser areas at Yellowstone, but has some impressive geothermal features.
Firehole Spring erupts nearly continuously, shooting boiling water a few feet into the air. The hottest water is on the right side, where the splashing occurs; the water then cools as it runs off to the left and behind the spring, where thermophilic bacteria and algae thrive. These create the beautiful yellow, orange and brown mats seen here.