Qualla: Hilina Slump

Hilina Slump: Introduction

Thu, 12 Mar 2026 00:00:00 GMT

In 1868, a tsunami rolled over the tops of coconut trees on Hawaii's southeast coast -- "probably 60 feet high," one witness reported -- sweeping houses, livestock, and 46 people out to sea. The source was not a distant earthquake across the Pacific. It was the island itself, breaking apart. The Hilina Slump, a colossal block of Kilauea's south flank, had lurched seaward, and the ocean responded accordingly. More than 150 years later, the slump is still moving -- roughly 10 centimeters per year, pushed by magma injection and pulled by gravity -- and the question of what it might do next remains one of the most consequential in Hawaiian geology.

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Hilina Slump: An Island Falling Sideways

Thu, 12 Mar 2026 00:00:00 GMT

The Hawaiian Islands are shield volcanoes, built by eruptions from a hotspot deep in Earth's mantle. Their broad, gently sloping profiles belie a structural instability that only becomes apparent over time. As each volcano grows, its own weight causes its flanks to stretch and sa...

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Hilina Slump: The Earthquakes It Brings

Thu, 12 Mar 2026 00:00:00 GMT

The slump moves both silently and violently. Much of its seaward creep is aseismic, unnoticed by anyone on the surface. But periodically the friction holding the block in place gives way all at once, producing earthquakes of magnitude 6 or greater. The 1868 event -- estimated bet...

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Hilina Slump: Megatsunami or Overstatement?

Thu, 12 Mar 2026 00:00:00 GMT

Systematic mapping of the Hawaiian seafloor in the late 1980s revealed 17 areas around the islands that appear to be remnants of enormous ancient landslides. The Nuuanu Slide alone is estimated at 5,000 cubic kilometers in volume, with blocks "tens of kilometers" in size transpor...

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Hilina Slump: Magma-Jacking and the Vulnerable Flank

Thu, 12 Mar 2026 00:00:00 GMT

What makes Kilauea's south flank particularly prone to failure is a process called magma-jacking: fresh magma injected into pre-existing fractures or weak rock, with the pressure literally prying the flank apart from within. Smith and Malahoff, in a 1999 paper, noted that Kilauea...

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