Perhaps this is why the water in those Idaho hot springs is boiling.
“As the North American Plate has moved WSW over the hotspot that is now Yellowstone it has left a deep trail of connected magma chambers under the landscape,” says reader Andrew Stranglen.
“The older magma chambers to the West are cooled and extinct, while the recent ones closer to Yellowstone are more than likely still quite hot.”
“The Heise Volcanic Field deep magma chambers are probably responsible for this particular Hot Spring.”
According to Wikipedia, the Yellowstone hotspot, also known as the Snake River Plain-Yellowstone hotspot, is responsible for large scale volcanism in Oregon, Nevada, Idaho, and Wyoming, United States. It created the eastern Snake River Plain through a succession of caldera forming eruptions.
Thanks to Andrew Stranglen for this link