Hawaii Formed Differently than Believed, Study Suggests

Hawaii formed through the eruptions of lava on the surface, also known as extrusion, rather than through the internal emplacement of magma, as previously believed.

These were the findings of a recent study carried out by scientists from the University of Hawaii, Manoa (UHM) School of Ocean and Earth Science and Technology and the University of Rhode Island (URI).

Together, the researchers compiled historical land-based gravity surveys with more recent surveys taken on the Big Island and Kauai, in addition to marine surveys from the National Geophysical Data Center and from the R/V Kilo Moana, a vessel owned by the US Navy and operated by the University of Hawaii Marine Center.

By piecing together the information each contributed, the scientists were able to infer processes played out over the years.

Before this study, most believed the Hawaiian volcanoes grew internally for the most part, as magma intruded into rock and solidified before reaching the surface

However, while this does occur, the results showed that this does necessarily represent the overall formation of the Hawaiian Islands.

"The discrepancy we see between our estimate and these past estimates emphasizes that the short term processes we currently see in Hawaii (which tend to be more intrusive) do not represent the predominant character of their volcanic activity," Ashton Flinders, lead author and graduate student at URI, said in a statement.

Based on this, Garrett Ito, professor of geology and geophysics at UHM stated: "This could imply that over the long-term, Kilauea's [East Rift Zone] will see less seismic activity and more eruptive activity that previously thought. The 3-decade-old eruption along Kilauea's [East Rift Zone] could last for many, many more decades to come."

Knowing that intrusive magma is more dense and structurally sound than lava, Flinders argues that one of the greatest implications of the new theory is how it impacts the stability of the volcano's flank.

"Collapses occur over a range of scales from as large as the whole flank of a volcano, to bench collapses on the south coast of Big Island, to small rock falls," he said. "If the bulk of the islands are made from these weak extrusive flows then this would account for some of the collapses that have been documented, but this is mainly just speculation as of now."

Going forward, the researchers hope to use the new model as a starting point for more crustal studies in the region.