Tag: Hawaiian hotspot chain

Two continent- sized “hot zones” (Large Low Seismic Velocity Provinces, or LLSVPs) in the lowermost mantle near Earth’s core appear to fuel much of the volcanic activity that builds seamounts on the ocean floor.

Researchers Clint Conrad and Mathew Domeier (University of Oslo, Centre for Planetary Habitability / Department of Geosciences) published the findings in Nature Geoscience (2026).

The associated University of Oslo news article, written by Gunn Kristin Tjoflot, frames the work around seamounts as a window into Earth’s deep interior.

Key points

• What the LLSVPs are: Two enormous, relatively hot and less- rigid structures sit at the base of the mantle (near the core– mantle boundary), one beneath Africa and one beneath the Pacific. Seismic S- waves travel more slowly through them. They are thought to have persisted for a very long time (possibly billions of years).⁠
• Link to seamounts: Seamounts are mostly extinct underwater volcanoes (Earth’s oceans contain tens of thousands of them). Analysis of seamount catalogues shows that volcanic output is significantly more voluminous on seafloor that has previously passed over these LLSVPs. The effect is present for both structures but stronger above the Pacific LLSVP and has declined since the mid- Cretaceous.⁠
• Proposed mechanism: Weak mantle plumes rise from the hotter, less- rigid LLSVPs. These plumes interact with the oceanic lithosphere and promote intraplate volcanism, producing scattered seamounts (as well as other forms of intraplate volcanism such as hotspot chains). The Pacific enhancement may reflect higher mantle temperatures, greater transition- zone hydration, and- or more vigorous convection in that hemisphere.⁠
• Broader significance: The work supports the idea that heat carried upward from the LLSVPs accounts for most oceanic intraplate volcanism, including dispersed seamounts outside classic hotspot tracks. Because seamount volcanism records this deep connection, it can help constrain how the dynamics of Earth’s deepest mantle have changed over geological time. Classic examples such as the Hawaiian- Emperor chain illustrate the process as plates drift over an LLSVP- related zone.

Seamounts themselves matter beyond geology: they create unique deep- sea habitats, influence ocean currents and nutrient mixing, serve as stopovers for migratory species, and can pose navigational hazards.⁠

In short, the research ties ordinary- looking underwater volcanoes on the seafloor to two long- lived thermal anomalies sitting almost 3,000 km down, near the core.

The Hawaiian hotspot chain (Hawaiian Emperor seamount chain) is one of the best- studied examples of intraplate volcanism driven by a deep mantle plume. It stretches ~6,200 km across the northern Pacific Ocean and records more than 80 million years of volcanic activity.

Overview and Structure

• The chain consists of over 80 identified volcanoes (islands, atolls, seamounts, and guyots).
• Youngest section (Hawaiian Islands and Windward Isles): Ages from ~0 to ~5 Ma. Includes the Big Island of Hawaiʻi (with active volcanoes Kīlauea, Mauna Loa, Hualālai, and Mauna Kea) and Maui (Haleakalā). The next volcano in the chain is the submarine Kamaʻehuakanaloa Seamount (formerly Lōʻihi), ~35 km southeast of the Big Island, currently in the pre- shield stage with a summit ~975- 1,000 m below sea level. It shows ongoing seismic activity and hydrothermal venting.⁠
• Northwestern Hawaiian Islands (Leeward Isles): Ages ~7- 28 Ma; mostly eroded to atolls and reefs (e.g., Midway, Kure, the northernmost atoll on Earth).
• Emperor Seamounts: Oldest section (~39- 85 and more Ma), fully submerged, trending more northward. Named after Japanese emperors; the chain ends near the Kuril- Kamchatka Trench.

The Pacific Plate moves northwestward over the relatively fixed (or slowly moving) Hawaiian hotspot at roughly 7- 10 cm/year, producing a clear age progression: volcanoes become older and more eroded with distance from the hotspot.

Formation Mechanism

John Tuzo Wilson proposed the classic hotspot model in 1963: a relatively stationary mantle plume rises from deep in the mantle, melting as it nears the surface and building volcanoes that are then carried away by plate motion.⁠

The plume is widely linked to the edge of the Pacific Large Low Shear Velocity Province (LLSVP)—one of the two continent- sized “hot zones” near the core-mantle boundary discussed in the prior conversation.

Geochemical evidence (especially the Loa vs. Kea trends in younger Hawaiian volcanoes) supports sampling of material from the LLSVP (more enriched “Loa” component) and ambient lower mantle (“Kea” component). Recent models suggest the plume originates near LLSVP ridges or edges, influenced by slab push, and can exhibit bilateral zoning or even conduit splitting.

The Famous Bend

A sharp ~60° bend (Hawaiian- Emperor Bend or HEB) occurs around 47- 50 Ma. It was long attributed solely to a sudden change in Pacific Plate motion (from more northerly to northwesterly).

However, paleomagnetic data show the hotspot itself drifted southward significantly (up to ~10- 15° or more) during formation of the Emperor Seamounts (~80- 47 Ma), at rates that may have reached ~40- 50 mm/year at times.⁠

Current consensus leans toward a combined explanation: both plate- motion change (linked to subduction reorganization, including the end of certain northern Pacific subduction forces and new western Pacific subduction) and hotspot motion (influenced by ridge- plume interaction earlier and deeper interaction with the Pacific LLSVP).

Recent modeling indicates plate rotation contributed roughly 30– 35° of the bend angle, with hotspot drift (including longitudinal components) accounting for the rest.

Current Activity and Broader Significance

• The hotspot remains highly active. Kīlauea and Mauna Loa are among the world’s most closely monitored volcanoes. Recent studies even suggest the plume has heated up over the past ~47 million years (counter to the usual expectation of progressive cooling), with heat surges contributing to especially large volcanoes.⁠
• Kamaʻehuakanaloa continues low- level unrest (earthquake swarms, hydrothermal activity) but is not currently erupting on a major scale.
• The chain provides key constraints on absolute plate motions, mantle convection, plume dynamics, and the longevity and mobility of LLSVPs. It is a classic case linking surface volcanoes to deep- Earth structures.

In the context of the earlier discussion on LLSVPs and seamount volcanism, the Hawaiian chain is a prime example of how weak- to- strong plumes rising from (or near) these basal mantle structures interact with the oceanic lithosphere to produce long- lived intraplate volcanism.

Seamount volcanism associated with Earth’s basal mantle structures

While mid- ocean ridge spreading and subduction account for most oceanic volcanism, intraplate volcanism (including scattered seamounts) requires a deeper explanation.

The authors show that seamount volcanism is systematically more voluminous on seafloor that has previously passed above the two large low- shear- velocity provinces (LLSVPs), the continent- sized “hot zones” at the base of the mantle beneath Africa and the Pacific.

Key Results

• Seamount equivalent lithospheric thickness (SELT, a measure of volcanic volume) is higher on seafloor that has spent more time (higher residence time, RT) above the LLSVPs or their margins.
• The enhancement occurs above both LLSVPs but is stronger above the Pacific LLSVP.
• The effect has declined since the mid- Cretaceous.
• Even after excluding known hotspot tracks, the Pacific association remains robust (roughly a factor- of- two amplification in some analyses).

The authors propose that weak mantle plumes rise from both LLSVPs (or their edges). These plumes interact with the base of the oceanic lithosphere and promote melting and seamount formation. The stronger Pacific signal may reflect:

• Higher mantle temperatures,
• Greater transition- zone hydration, and/or
• More vigorous convection in the Pacific hemisphere.

This supports the broader hypothesis that heat transported upward from the LLSVPs drives most oceanic intraplate volcanism, not only classic hotspot chains and large igneous provinces, but also the thousands of dispersed seamounts scattered across the ocean floor.

Because seamount distribution records this deep connection, it can serve as a sensitive indicator of how the dynamics of Earth’s deepest mantle (including the evolution and mobility of the LLSVPs) have changed through geological time.

The study uses modern seamount catalogues (including G23 and KW11), plate-motion models (M16 and T19), and seafloor-age grids.

The authors compute residence times of seafloor above LLSVP interiors and margins using GPlates- PyGPlates reconstructions. Supporting data and code notebooks are available on Zenodo.

This is the peer- reviewed paper that underlies the University of Oslo news release (“Two hot zones near Earth’s core may fuel volcanoes beneath oceans”) and the earlier discussion of seamounts linked to LLSVPs.

Title: Seamount volcanism associated with Earth’s basal mantle structures

Journal: Nature Geoscience, volume 19, pages 822–827 (2026)

DOI: 10.1038/s41561-026-02007-z

Published: 10 June 2026

Provided: University of Oslo

Published: 10 June 2026

Authors: Clinton P. Conrad &
Mathew Domeier

Abstract

While seafloor spreading and subduction explain much of the volcanic activity in Earth’s oceans, magmatism occurring within tectonic plate interiors requires a deeper mantle explanation. Various types of oceanic intraplate volcanism, including oceanic plateaus and hotspot-associated seamount chains, have been attributed to plumes rising from the margins of two continent-sized structures termed large low-shear-velocity provinces (LLSVPs) in the lowermost mantle beneath Africa and the Pacific Ocean. Here we analyse seamount catalogues and show that seamount volcanism is more voluminous on seafloor that has passed above a LLSVP. We find that this volcanic enhancement is evident above both LLSVPs, but is greater above the Pacific one and has declined since the mid-Cretaceous. We suggest that weak plumes rising from both LLSVPs interact with oceanic lithosphere to promote seamount volcanism. This process may be enhanced for the Pacific because of elevated mantle temperature, transition zone hydration and/or convective vigour in the Pacific hemisphere. Our findings provide additional support for the hypothesis that plumes carrying heat from the LLSVPs are responsible for most oceanic intraplate volcanism, including dispersed seamounts. This deep mantle connection means that seamount volcanism is sensitive to, and thus may constrain, the time-dependent dynamics of Earth’s deepest mantle.