A cluster of earthquakes rattled the seafloor south of the Island of Hawaiʻi in August 2026, drawing scientific attention to one of the archipelago’s least-visible volcanoes. The tremors came from Kamaʻehuakanaloa, the submarine volcano formerly known as Lōʻihi Seamount, whose summit sits roughly 3,200 feet beneath the ocean surface and which marks the newest addition to the Hawaiian chain.
The unrest was strong enough to be felt on land but posed no tsunami threat, and scientists were quick to place it in a long historical context of similar swarms that came and went without an eruption. The episode is a reminder that the same volcanic hot spot building the Big Island is still at work offshore, slowly assembling a future island out of sight.
An earthquake swarm beneath the sea
The seismic sequence began around August 9, 2026, and peaked two days later with a magnitude-5.2 earthquake on August 11. That quake struck beneath Kamaʻehuakanaloa about 26 miles east-southeast of Nāʻālehu, at a depth of roughly 7 miles below sea level. A separate strong shock in the same swarm, recorded at magnitude 5.1, prompted officials to confirm that no tsunami was expected from the offshore activity.
Swarms like this one consist of many earthquakes clustered in time and space without a single dominant mainshock followed by a tapering aftershock sequence. That signature is often associated with the movement of magma or fluids underground, which is why geologists monitor them closely even when, as here, no eruption follows.
The volcano once called Lōʻihi
Kamaʻehuakanaloa rises from the seafloor on the southeastern flank of the Hawaiian hot spot, the plume of hot rock that has produced the entire island chain as the Pacific Plate drifts slowly over it. Because it is the youngest Hawaiian volcano, it is still submerged, its summit thousands of feet underwater. Over tens of thousands of years, continued eruptions are expected to build it upward until it eventually breaches the surface to become a new island or merges with the Big Island.
The volcano was renamed from Lōʻihi Seamount to Kamaʻehuakanaloa in recognition of its place in Hawaiian tradition, and it remains a subject of active study by the Hawaiian Volcano Observatory, part of the U.S. Geological Survey. Its remote, deep-water setting makes it far harder to observe than the subaerial volcanoes of Kīlauea and Mauna Loa.
Why monitoring the summit is so difficult
Unlike the well-instrumented volcanoes on land, Kamaʻehuakanaloa has no working monitoring equipment installed at its summit. Scientists therefore track its behavior largely through the regional seismic network that surrounds the Big Island, inferring what is happening from the earthquakes it detects rather than from direct measurements at the source.
That network cannot capture every event. Analyses of the August 2026 swarm suggested that instruments were registering only a fraction of the total seismicity, with the smallest quakes going undetected at such depth and distance. As a result, the swarm was almost certainly larger in raw numbers than the felt and cataloged earthquakes alone would indicate.
A pattern seen many times before
The 2026 sequence closely resembled earlier bouts of unrest that did not culminate in an eruption, including swarms recorded in 2020, 2022 and 2024. The most energetic episode on record came in the summer of 1996, when the volcano produced more than 4,000 earthquakes, including nearly 300 events stronger than magnitude 3.0 and dozens in the magnitude-4 range. That 1996 swarm was associated with a collapse near the summit but still did not send lava to any level that threatened people.
Read against that history, the August 2026 activity looked typical rather than exceptional. Observatory scientists reported no indicators of an imminent eruption, and the swarm was consistent with the intermittent pulses of magma movement that have characterized the volcano’s monitored history.
What the unrest signals about a growing island
Even without an eruption, the swarm is evidence that Kamaʻehuakanaloa remains geologically alive. Each pulse of seismicity reflects magma shifting within or beneath the edifice, the incremental process by which the volcano adds material and, over immense spans of time, grows taller. The Hawaiian hot spot has repeated this cycle for millions of years, producing island after island in a northwest-trending line.
For people on the Big Island, the practical significance of the 2026 episode was limited: strong but deep earthquakes, no tsunami, and no change to daily life. For scientists, it was another data point in a slow-motion story of island birth, one that will continue playing out on the seafloor long after the current generation of monitoring instruments has been retired.
What an eruption would look like
Were Kamaʻehuakanaloa to erupt, the event would differ sharply from the fiery fountains and ash plumes of Hawaiʻi’s land volcanoes. At depths of thousands of feet, the immense pressure of the overlying water suppresses the violent expansion of volcanic gases, so submarine eruptions at the summit tend to produce pillow lava, rounded lobes of rock that form as molten material chills instantly on contact with cold seawater. Explosive activity, if any, would be muted compared with a surface eruption.
Such an eruption would pose little direct danger to people, given the volcano’s remoteness and depth, though it could affect the surrounding marine environment and the unusual microbial communities that thrive around its hydrothermal vents. Those vent ecosystems, sustained by chemistry rather than sunlight, are part of what makes the volcano scientifically valuable and a reason researchers keep returning to study it despite the challenges of working so far below the surface.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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