September was a month of hydrothermal activity at Yellowstone, the Yellowstone Volcano Observatory said in their monthly update released October 1, 2018.
Steamboat geyser experienced water eruptions on September 1, 7, 12, 17, 24, and 30, bringing the total number of Steamboat eruptions in 2018 to 21.
In addition, a rare eruption of Ear Spring (6 - 9 m / 20 - 30 feet), a normally docile hot pool, in the Upper Geyser Basin, not far from Old Faithful, occurred on September 15 and was accompanied by changes to springs and geysers in the Geyser Hill area. The eruption ejected not only rocks, but also material that had fallen or been thrown into the geyser in years past, like coins, old cans, and other human debris. The last known similar-sized eruption of the spring was in 1957, although smaller eruptions occurred as recently as 2004.
A new thermal feature also formed at that time nearby, spouting scalding water that necessitated the closure of the boardwalk through the area.
Scientists from Yellowstone National Park deployed temperature sensors and cameras in the area to monitor the activity, and the University of Utah deployed 29 seismic sensors around the region to measure whether or not significant changes in the subsurface plumbing system occurred relative to data collected from the area in November 2017.
During September 2018, the University of Utah Seismograph Stations, responsible for the operation and analysis of the Yellowstone Seismic Network, located 57 earthquakes in the Yellowstone National Park region. The largest event was a microearthquake of magnitude 2.9 located about 25.7 km (16 miles) ESE of Mammoth, WY, on September 11 at 13:30 UTC.
No swarm activity occurred during the month of September and Yellowstone earthquake activity remains at background levels.
Featured image: Rare eruption of Ear Spring in the Upper Geyser Basin on September 15, 2018. Credit: Geyser Observation and Study Association