How Gravity Changes On Kīlauea Acted As An Early Indicator Of The 2018 Eruption

A new USGS video explains the science and the importance of monitoring subtle changes in gravity on our volcanoes. Prior to the 2018 eruption of Kīlauea that forever changed the Lower East Rift Zone, as lava level in Puʻuʻōʻō began to rapidly drop, the largest drop in gravity on earth was recorded. Volcanologists monitoring the volcano were then able to use the subtle decreases in gravity, combined with other 3-D models, to show the opening of a dry crack as lava withdrew from Puʻuʻōʻō, followed by an increase in gravity representing magma filling the newly opened crack days before the May 3rd eruption. Early indicators of volcanic activity, particularly the movement of magma from the summit into populated rift zones on Kīlauea and Mauna Loa, are invaluable when the time comes and another eruption inevitably happens in a populated area and people's livelihoods are once again at stake. Small changes in gravity are measured by a gravimeter, which is relatively new and are still quite expensive, with quality gravimeters costing roughly $100,000. But, as with other technologies, it can be expected that the price will decrease over time and gravimeters may become the next monitoring network used to monitor our volcanoes. “Anyplace where magma is shallow and changes can happen quickly, it can be outstanding” said Dr. Mike Poland, who presented the research. “It's not so great where magma is deep and changes are gradual. And I think the pre-collapse time series for Puʻuʻōʻō demonstrates that the gravity signal was much stronger and less ambiguous than the contemporary tilt signal. That might make it easier to interpret changes as they happen -- if you have a more obvious signal to look at.” Full presentation from the American Geophysical Union Fall Meeting 2020: https://www.youtube.com/watch?v=MbaUV36b0Qg