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Enormous 'mega-blob' under Hawaii is solid rock and iron, not gooey — and it may fuel a hotspot

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Enormous 'mega-blob' under Hawaii is solid rock and iron, not gooey — and it may fuel a hotspot
  1. Planet Earth
  2. Geology
Enormous 'mega-blob' under Hawaii is solid rock and iron, not gooey — and it may fuel a hotspot

News By Stephanie Pappas published 2 February 2026

A new study reveals a detailed look at what lies beneath the Hawaiian hotspot.

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Scenic view of sea against sky, Kaaawa, Hawaii, United States, USA A "mega-blob" deep beneath Hawaii may be fueling a volcanic hotspot, according to a new study. (Image credit: Warren Ishii / 500px via Getty Images)
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A massive blob deep under Hawaii seems to be solid and iron-rich, new research finds.

This blob — scientifically known as a mega-ultralow velocity zone — may anchor the Hawaii hotspot, an area where hot material rises through the mantle and drives the volcanic activity that created the Hawaiian Islands.

"Because it's iron-rich material, it is going to be electrically more conductive, and that will actually promote thermal conduction — so it will actually help localize the plume to last longer," said Doyeon Kim, a seismologist at Imperial College London and the first author of the new study, published Jan. 28 in the journal Science Advances.

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Ultralow velocity zones (ULVZs) are giant hunks of the planet that sit near the boundary of the mantle and the core, at about 1,800 miles (2,900 kilometers) below the Earth's surface. They get their name from the fact that seismic waves from earthquakes slow down dramatically in these regions. Mega-ultralow velocity zones are the largest of these regions, which often span hundreds of kilometers. They're often found near volcanic hotspots, such as Hawaii, Iceland and the Marquesas Islands of the South Pacific.

"It actually makes them one of our few direct windows into deep-Earth composition and dynamics," Kim told Live Science.

Because these blobs are so deep, scientists typically study them using compressional waves generated by earthquakes. But these pressure waves, or P waves, provide limited information. So Kim and his colleagues used a method they developed in 2020 that could also incorporate S waves, or shear waves, which create vertical motion. By combining data from both types of waves and then modeling rocks and minerals that could match those data, the researchers could get a clearer picture of why the waves slow down in those zones.

They found that the mega-ULVZ under Hawaii is likely rich in iron and solid rock. That largely rules out a competing hypothesis that suggested the area might be extra-melty.

Sign up for the Live Science daily newsletter nowContact me with news and offers from other Future brandsReceive email from us on behalf of our trusted partners or sponsorsBy submitting your information you agree to the Terms & Conditions and Privacy Policy and are aged 16 or over.RELATED STORIES

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With this information, "we can think about where it is coming from," Kim said. "It could be coming from the relics of Earth's earliest evolution, particularly from the crystallization of a basal magma ocean or recrystallized melt from past mantle melting."

Not every mega-ULVZ may be created equally, Kim added. Some might form from the subduction of water-rich oceanic crust deep into the mantle. Perhaps others involve material from the core itself. The approach in the new paper can help differentiate these types of ULVZs worldwide, he said, as well as shedding light on how planets form in the first place.

"We have to first clearly understand what's happening on Earth to understand fully what's happening on other planets," he said.

Article Sources

Kim, D., Song, J.-H., Dobrosavljevic, V. V., & Lekić, V. (2026). Seismic and mineralogical evidence for an iron-rich mega–ultralow-velocity zone beneath Hawai'i. Science Advances, 12(5). https://doi.org/10.1126/sciadv.adz1962

TOPICS hawaii Stephanie PappasStephanie PappasSocial Links NavigationLive Science Contributor

Stephanie Pappas is a contributing writer for Live Science, covering topics ranging from geoscience to archaeology to the human brain and behavior. She was previously a senior writer for Live Science but is now a freelancer based in Denver, Colorado, and regularly contributes to Scientific American and The Monitor, the monthly magazine of the American Psychological Association. Stephanie received a bachelor's degree in psychology from the University of South Carolina and a graduate certificate in science communication from the University of California, Santa Cruz. 

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