YELLOWSTONE NATIONAL PARK — On June 30, 1975, a magnitude six earthquake became the largest earthquake recorded in Yellowstone National Park (YNP).
According to U.S. Geological Survey (USGS) Volcanoes, the epicenter of the earthquake was along the north-central boundary of Yellowstone Caldera, a few miles southeast of Norris Geyser Basin. The well-known 1959 magnitude 7.3 earthquake had its epicenter just outside the western boundary of YNP, so is not considered the largest within the Park itself.
While USGS Volcanoes says there were reports of a damaged chimney, a rockfall that closed the road between Norris and Madison Junction overnight and a temporary telephone service outage in West Yellowstone, Old Faithful and Madison, no injuries were reported and all Park campgrounds and facilities remained open.
“Changes were noted in several thermal features in Norris Geyser Basin, and the average interval between eruptions of Old Faithful Geyser increased by about three minutes,” USGS Volcanoes posted on their Facebook page in honor of the anniversary. “Water levels decreased and turbidity increased temporarily at a few thermal features in Norris Geyser Basin and there were a few new breakouts of thermal fluids, and some nearby rivers turned muddy for a few days due to increased sediment loads.”
The earthquake was most significant not because of its impact on the landscape but because of its impact on the scientific understanding of YNP. The mid-1970s research findings that Yellowstone is still an active volcano was a direct result of the post-earthquake survey to learn whether there had been any measurable ground disruption, TSGS Volcanoes confirms.
USGS Volcanoes encourages people to remember that “earthquakes don’t trigger Yellowstone eruptions!”
