Explore Yellowstone | West Thumb Basin

Explore Yellowstone: West Thumb Geyser Basin |||Entering Yellowstone from the south gate, the first main scenic area you will see is the West Thumb Geyser Basin. Located on the west side of Yellowstone Lake, West Thumb is named after the thumb-like protrusion into the lake. This basin was formed by a volcanic eruption about 174,000 years ago, and later filled with water from Yellowstone Lake, creating the West Bay we see today. As a result, active geysers can still be seen in the lake water along the shore. Dozens of intermittent springs and hot springs of the West Thumb Geyser Basin are distributed around a circular boardwalk that runs southeast to northwest. Park your car and take a counterclockwise stroll. At the southern end of the plank road, there are two pools called Seismograph Pool P2 and Blue Bell Pool P3. These two pools were originally called Blue Pool. After the 7.5 magnitude earthquake in Yellowstone in 1959, some people believed that the current Seismograph Pool may have recorded abnormal activity during the earthquake, so it was given the two names it has now. The hot springs here range from over 30 degrees to over 93 degrees. Don't be fooled by the calm lake-side P4 hot spring, there may be hidden dangers. The two protruding banks on the shore are the intermittent spring P5 between the lake banks, which had a maximum eruption of 15 meters in the early last century. At the corner of the boardwalk, there is a black pool P6. Originally, thermophilic bacteria in black-green and brown grew in the pool, so the pool looked black. However, in the summer of 1991, the water temperature of the pool rose and killed these bacteria. Now the black pool we see is sapphire blue. Across from Black Pool is a beautiful deep pool called P7-9, which reaches a depth of 16 meters and is one of the deepest hot springs in Yellowstone National Park. The water temperature of the pool reaches 77 degrees and the color changes between emerald green, sapphire blue, and other colors with time and light.