“On the other Hawaiian volcanoes, this early part of the volcanic history is covered by the excellent profusion of lava that happens throughout the shield phase. “The lavas with the best look also had the most radium-226, and vice versa for the lavas with the older appearance, that is, fractured and damaged, and/or covered with marine sediment. The chemistry of the lava erupted from Hawaiian volcanoes changes over time. The new eruption ages for the lavas from Kamaehu, paired with measurements of lava chemistry, reveal that the timescale of variation in lava chemistry at this pre-shield volcano is about 1200 years. Our outcomes– particularly, the factor of 6 longer timescales of variation in lava chemistry at Kamaehu– supply independent verification of this idea.”.
Undersea images of lava from Kamaehu volcano, contrasting fresh-looking young lavas (top) versus older sediment-covered lavas (bottom). Credit: The two images on the bottom are courtesy of JAMSTEC.
The submarine Hawaiian volcano Kamaʻehuakanaloa, previously understood as Lōʻihi Seamount, positioned approximately 20 miles from the southern shore of Hawaiis Big Island, has actually experienced a minimum of five eruptions in the past century and a half, according to current research carried out by Earth researchers at the University of Hawaii at Mānoa.
Researchers have, for the very first time, estimated the ages of Kamaʻehus latest eruptions, in addition to the ages of 8 more ancient eruptions from this volcano, tracing back nearly 2,000 years. Their findings were released just recently in the journal Geology.
Hawaiian volcanoes are believed to shift through a series of growth phases. Kamaʻehu is currently in the earliest submarine “pre-shield” stage of growth, whereas the active neighboring volcano Kīlauea is in its main shield-building stage.
” Kamaʻehu is the just active and exposed example of a pre-shield Hawaiian volcano,” stated Aaron Pietruszka, lead author of the research study and associate professor in the Department of Earth Sciences at the UH Mānoa School of Ocean and Earth Science and Technology (SOEST). “On the other Hawaiian volcanoes, this early part of the volcanic history is covered by the excellent profusion of lava that happens throughout the guard phase. Hence, there is terrific interest in finding out about the growth and advancement of Kamaehu.”
Kamaehus history exposed with chemistry and undersea videos
Previously, the just recognized and confirmed eruption of Kamaʻehu was the one that happened in 1996, an event that was just discovered since it accompanied a big swarm of earthquakes that were discovered from another location by seismometers on the Big Island.
” Seismometers can only be utilized to discover the continuous active eruptions of submarine volcanoes due to the fact that earthquakes are short-term,” said Pietruszka. “In order to determine the ages of older eruptions at Kamaʻehu, we took a various technique. We utilized a mass spectrometer to measure tiny quantities of the isotope radium-226 in pieces of quenched glassy lava that were sampled from the seafloor outcrops of Kamaʻehu utilizing a submersible.”
Magma naturally consists of radium-226, which radioactively decomposes at a foreseeable rate. Pietruzska and co-authors used the amount of radium-226 in each sample to infer the approximate time elapsed given that the lava erupted on the seafloor, that is, the eruption age of the sample.
Pietruszka started this examination several years ago as a postdoctoral researcher at the Carnegie Institution for Science, just after completing his doctoral degree in Earth science from SOEST. He got access to submersible dive videos and images around Kamaehu and had the info he needed to finish linking the dots when he returned to UH Mānoa in 2019.
“The lavas with the freshest appearance likewise had the most radium-226, and vice versa for the lavas with the older appearance, that is, damaged and fractured, and/or covered with marine sediment. I was amazed to find that Kamaehu had actually emerged 5 times within the last ~ 150 years, which suggests a frequency of ~ 30 years in between eruptions at this volcano.
Chemical changes in lava in time.
The chemistry of the lava emerged from Hawaiian volcanoes modifications gradually. The brand-new eruption ages for the lavas from Kamaehu, paired with measurements of lava chemistry, reveal that the timescale of variation in lava chemistry at this pre-shield volcano is about 1200 years. On the other hand, Kīlauea lava chemistry changes over a timescale of only a couple of years to years, with a complete cycle over about 200 years.
” We believe that the origin of this distinction is related to the position of the two volcanoes over the Hawaiian hotspot,” said Pietruszka. “This is a location of Earths mantle that is increasing towards the surface area– a “mantle plume” that ultimately melts to form the lava that supplies Hawaiian volcanoes. Models and other isotope data from thorium-230 recommend that the center of a mantle plume need to rise faster than its margin. Our results– specifically, the aspect of six longer timescales of variation in lava chemistry at Kamaehu– supply independent confirmation of this idea.”.
The research group wants to much better understand how Hawaiian volcanoes work from their earliest development stages to their complete, and frequently active, maturity to help them understand the deep controls on volcanic eruptions that initiate within the mystical, upwelling mantle plume under the Hawaiian hotspot.
Referral: “Slow modifications in lava chemistry at Kamaehuakanaloa linked to sluggish mantle upwelling on the margin of the Hawaiian plume” by Aaron J. Pietruszka, Michael O. Garcia, Richard W. Carlson and Erik H. Hauri, 26 May 2023, Geology.DOI: 10.1130/ G51350.1.
The study was funded by the Carnegie Institution for Science and National Science Foundation.