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West Thumb
Geyser Basin

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Seismograph and Bluebell Pools

The milky, pale blue water of Seismograph and Bluebell pools steam in the cool autmun air.

These pools used to be known as the "Blue Pools." After the 1959 Hebgen Lake earthquake, which measured 7.5 on the Richter scale, the pools were renamed. At West Thumb, no one recorded the nature of the changes caused by the quake, but perhaps someone thought Seismograph Pool somehow "registered" the earthquakes. (A seismograph measures the intensity and time of earthquakes). These days, Seismograph is sometimes muddy—but not from earthquakes. The mud comes from the runoff of nearby mud pots.

West Thumb Geyser Basin Tour

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Last Updated: Wednesday, 22-Dec-2004 10:11:49 Eastern Standard Time
http://www.nps.gov /archive/yell/tours/westthumb/seismograph.htm