Analysis reveals Hawai’i’s undersea volcano, Kama’ehu, erupted 5 occasions in previous 150 years

Kamaʻehuakanaloa (previously Lōʻihi Seamount), a submarine Hawaiian volcano situated about 20 miles off the south coast of the Large Island of Hawai’i, has erupted no less than 5 occasions within the final 150 years, in accordance with new analysis led by Earth scientists on the College of Hawai’i at Mānoa. For the primary time, scientists had been in a position to estimate the ages of the newest eruptions of Kamaʻehu, in addition to the ages of eight extra older eruptions at this volcano going again about 2,000 years. Their findings had been revealed lately in Geology.

Hawaiian volcanoes are thought to transition by means of a sequence of progress phases. Kamaʻehu is presently within the earliest submarine “pre-shield” stage of progress, whereas the lively neighboring volcano Kīlauea is in its important shield-building stage.

“Kamaʻehu is the one lively and uncovered instance of a pre-shield Hawaiian volcano,” mentioned Aaron Pietruszka, lead writer of the examine and affiliate professor within the Division of Earth Sciences on the UH Mānoa College of Ocean and Earth Science and Know-how (SOEST). “On the opposite Hawaiian volcanoes, this early a part of the volcanic historical past is roofed by the nice outpouring of lava that happens throughout the defend stage. Thus, there’s nice curiosity in studying in regards to the progress and evolution of Kama’ehu.”

Kama’ehu’s historical past revealed with chemistry and underwater movies

Beforehand, the one recognized and confirmed eruption of Kamaʻehu was the one which occurred in 1996, an occasion that was solely found as a result of it coincided with a big swarm of earthquakes that had been detected remotely by seismometers on the Large Island.

“Seismometers can solely be used to detect the continuing lively eruptions of submarine volcanoes as a result of earthquakes are transient,” mentioned Pietruszka. “With the intention to decide the ages of older eruptions at Kamaʻehu, we took a unique strategy. We used a mass spectrometer to measure tiny quantities of the isotope radium-226 in items of quenched glassy lava that had been sampled from the seafloor outcrops of Kamaʻehu utilizing a submersible.”

Magma naturally incorporates radium-226, which radioactively decays at a predictable charge. So, Pietruzska and co-authors used the quantity of radium-226 in every pattern to deduce the approximate time elapsed because the lava was erupted on the seafloor, that’s, the eruption age of the pattern.

Pietruszka began this investigation a few years in the past as a postdoctoral researcher on the Carnegie Establishment for Science, simply after ending his doctoral diploma in Earth science from SOEST. As soon as he returned to UH Mānoa in 2019, he received entry to submersible dive movies and pictures round Kama’ehu and had the knowledge he wanted to complete connecting the dots.

“The submersible dive pictures and movies supplied unbiased affirmation of our estimates of eruption ages,” mentioned Pietruszka. “The lavas with the freshest look additionally had essentially the most radium-226, and vice versa for the lavas with the ‘older’ look, that’s, fractured and damaged, and/or lined with marine sediment. I used to be stunned to find that Kama’ehu had erupted 5 occasions throughout the final ~150 years, which means a frequency of ~30 years between eruptions at this volcano. That is a lot slower than at Kīlauea, which erupts virtually constantly (with rare pauses of only some years).”

Chemical modifications in lava over time

The chemistry of the lava erupted from Hawaiian volcanoes modifications over time. The brand new eruption ages for the lavas from Kama’ehu, coupled with measurements of lava chemistry, reveal that the timescale of variation in lava chemistry at this pre-shield volcano is about 1200 years. In distinction, Kīlauea lava chemistry modifications over a timescale of only some years to many years, with an entire cycle over about 200 years.

“We expect that the origin of this distinction is said to the place of the 2 volcanoes over the Hawaiian hotspot,” mentioned Pietruszka. “That is an space of Earth’s mantle that’s rising towards the floor—a “mantle plume” that in the end melts to type the magma that provides Hawaiian volcanoes. Fashions and different isotope knowledge from thorium-230 counsel that the middle of a mantle plume ought to rise sooner than its margin. Our outcomes—particularly, the issue of six longer timescale of variation in lava chemistry at Kama’ehu—gives unbiased affirmation of this concept.”

The analysis crew hopes to higher perceive how Hawaiian volcanoes work from their earliest progress phases to their full, and steadily lively, maturity to assist them perceive the deep controls on volcanic eruptions that provoke throughout the mysterious, upwelling mantle plume underneath the Hawaiian hotspot.