The Relation Between Decadal Droughts and Eruptions of Steamboat Geyser in Yellowstone National Park, USA.

In the past century, most eruptions of Steamboat Geyser in Yellowstone National Park's Norris Geyser Basin were mainly clustered in three episodes: 1961–1969, 1982–1984, and ongoing since 2018. These eruptive episodes resulted in extensive disturbance to surrounding trees. To characterize tree response over time as an indicator of geyser activity adjustments to climate variability, aerial and ground images were analyzed to document changes in tree coverage around the geyser since 1954. Radiocarbon dating of silicified tree remnants from within 14 m of the geyser vent was used to examine geyser response to possible variations in decadal to centennial precipitation patterns. We searched for atypical or absent growth rings in cores from live trees in years associated with large geyser eruptions. Photographs indicate that active eruptive phases have adversely affected trees up to 30 m from the vent, primarily in the dominant downwind direction. Radiocarbon dates indicate that the geyser formed before 1878, in contrast to the birthdate reported in historical documents. Further, the ages of the silicified trees cluster within three episodes that are temporally correlated with periods of relative drought in the Yellowstone region during the 15th–17th centuries. The discontinuous growth of trees around the geyser suggests that changes in eruptive patterns occur in response to decadal to multidecadal droughts. This inference is supported by the lack of silicified specimens with more than 20 annual rings and by the existence of atypical or missing rings in live trees during periods of extended geyser activity. Plain Language Summary: Steamboat Geyser, in Yellowstone National Park's Norris Geyser Basin, has the tallest eruptions among the world's active geysers. To examine whether eruptions impact trees in the vicinity of the geyser, we analyzed aerial photos acquired since 1954 which indicate that prior periods of frequent eruptions have adversely affected trees up to 30 m from the vent, primarily in the dominant wind direction. To examine if the limited availability of water may have caused the geyser to stop erupting in past centuries, we dated silicified tree remnants with radiocarbon. Results suggest that trees were growing near Steamboat during three periods when the geyser was not erupting because of prolonged droughts in the Yellowstone region during the 15th–17th centuries. This inference is supported by observations that none of the silicified tree specimens had more than 20 annual rings, implying that the trees did not grow for long periods, and by the presence of atypical or missing rings in live trees during periods of geyser activity. Key Points: Aerial photos indicate that recent eruptive phases of Steamboat Geyser have adversely impacted trees up to 30 m from the vent14C dates of silicified trees cluster in three periods that temporally correlate with regional droughts during the 15th–17th centuriesAtypical or absent tree‐rings suggest that prolonged eruption episodes impacted tree growth around Steamboat Geyser [ABSTRACT FROM AUTHOR]