Picture this: You're jolted awake by the earth roaring beneath you, buildings crumbling, and then, without warning, a monstrous wave of water surges in to claim lives and reshape the land—this is the terrifying legacy of the Kalapana earthquake, which struck 50 years ago and left an indelible mark on Hawaii. But don't worry, we're diving deep into the science and stories behind it, so stick around for insights that might just change how you think about volcanic islands and natural disasters. If you're new to this, think of earthquakes as the Earth's way of releasing built-up pressure, much like popping a balloon—suddenly and unpredictably.
This piece comes from Volcano Watch, a weekly update crafted by experts at the U.S. Geological Survey's Hawaiian Volcano Observatory (HVO). You can find more at https://volcanoes.usgs.gov/hvo/hvovolcanowatch.html. This week's edition is penned by HVO geologist Katie Mulliken.
Dubbed the 'Kalapana earthquake' due to its epicenter close to the town of Kalapana on the southeastern coast of the Big Island of Hawaiʻi, this seismic event unfolded roughly 5 miles (9 kilometers) below the surface. It wasn't an isolated outburst; it was heralded by smaller tremors called foreshocks—think of them as warning signals—ranging from magnitude 4 to 5, which began a full month prior. The most significant of these precursors was a magnitude-5.7 quake at 3:36 a.m. HST on November 29, 1975.
Just over an hour later, at 4:48 a.m., the main event—a whopping magnitude-7.7 earthquake—hit with a vengeance. The violent shaking persisted for more than 30 seconds, rattling the entire island and even reaching as far as Maui and Oahu. The financial toll? An estimated $2.7 million in damages, concentrated in Hilo, where roads cracked, water pipes burst, walls split, chimneys toppled, water tanks collapsed, rock walls and fences gave way, windows shattered, and shelves spilled their contents onto the floor.
Yet, the quake itself was overshadowed by the deadlier tsunami that followed swiftly. Campers at Halapē, tucked along the south coast within Hawaiʻi Volcanoes National Park, were roused not only by the tremors but also by boulders tumbling from the cliffs above, triggered by the shaking. As detailed in a USGS report (https://pubs.usgs.gov/publication/cir740) compiling survivor testimonies, these campers wisely recognized the tsunami risk—remember, big earthquakes near the coast often precede these waves. They spotted the ocean rising alarmingly and bolted for higher ground, but the water caught up fast. Describing the ordeal, one survivor likened being caught in the tsunami's multiple waves to tumbling inside a giant washing machine. The water ebbed about 10 minutes post-quake, but tragically, one camper was carried away and never recovered, another perished from drowning or battering waves, and seven more required hospitalization.
The tsunami encircled the Big Island, wreaking havoc: It battered docks and piers, left boats stranded or sunken, razed homes and businesses in Punaluʻu, and inundated Aliʻi Drive in Kona. The tallest wave crested at around 48 feet (14.6 meters) above the shoreline east of Halapē, leaving behind a stark marker of uprooted vegetation, stones, and debris. Overall, tsunami damages added up to about $1.4 million, bringing the combined cost of the quake and wave to $4.1 million.
For context, tsunami waves slammed into Hilo a mere 20 minutes after the earthquake—a speed that's vital to grasp for beginners. This is lightning-fast compared to tsunamis from distant sources, like the magnitude-8.8 quake off Russia's Kamchatka Peninsula on July 29, 2025. In that case, the Pacific Tsunami Warning Center predicted waves would reach Hawaii over five hours later, allowing ample time for coastal evacuations.
And this is the part most people miss: In Hawaii, intense shaking serves as your immediate tsunami alert. If you're near the shore, head uphill right away—no waiting for sirens or alerts. Local tsunamis, spawned by nearby quakes, can strike before official warnings even go out. Why? Because they depend on substantial vertical shifts of the seafloor during the earthquake.
In 1975, sections of the south coast from Honuʻapo to Kaimū shifted horizontally by up to 26 feet (8 meters) and sank vertically by as much as 11.5 feet (3.5 meters), drowning plants and swamping the old shoreline. The quake also fractured a 15-mile (25-kilometer) segment of the Hilina fault system, with vertical displacements reaching 5 feet (1.5 meters).
Interestingly, Kīlauea Volcano was highly pressurized in November 1975, and the earthquake sparked a brief, small-scale eruption inside Kaluapele, the summit caldera. This mini-outburst started under an hour after the quake and fizzled out within 24 hours.
While lava eruptions frequently alter parts of the Big Island's landscape, rarer massive earthquakes and ground deformations can overhaul entire coastlines and inflict widespread harm. For earthquake readiness tips, visit https://www.shakeout.org/hawaii/. Next week, we'll explore how our knowledge and surveillance of Kīlauea's south flank—and the dangers tied to its shifts—have evolved since 1975. Plus, on Saturday, November 29, the Pacific Tsunami Museum in Hilo is hosting commemorative events—check details at https://tsunami.org/events/.
But here's where it gets controversial: Some argue that with better monitoring, such disasters could be mitigated, while others believe nature's fury is ultimately unstoppable. Do you think human ingenuity can outpace these volcanic and seismic threats? Is it fair to blame outdated tech for past tragedies, or should we accept that living on active volcanoes comes with inherent risks? Share your thoughts in the comments—do you agree that preparedness is key, or disagree that we can ever fully control such forces?
Volcano Activity Updates
Kīlauea has been experiencing intermittent eruptions inside its summit caldera since December 23, 2024. Its alert status from the USGS is WATCH. For a refresher, a caldera is basically a large crater formed by volcanic collapse, often signaling ongoing activity.
The most recent episode, number 36, featured lava fountaining for 5 hours on Sunday, November 4. Nighttime glow from the vents has been visible in recent days. The summit is swelling again, and predictive models suggest episode 37 could kick off between November 21 and 26. No odd happenings along Kīlauea's East Rift Zone or Southwest Rift Zone.
Mauna Loa remains dormant, with its USGS alert level at NORMAL.
No noticeable earthquakes were felt across the Hawaiian Islands last week.
HVO remains vigilant, keeping a close eye on both Kīlauea and Mauna Loa.
For archives of Volcano Watch pieces, the latest on Kīlauea and Mauna Loa, stunning photos, maps, earthquake data, and more, head to HVO’s website. Got questions? Shoot an email to askHVO@usgs.gov.
