Culture & History

Big Island Tsunamis: A History of an Unseen Coastal Force

The beautiful coastlines of Hawaiʻi Island have a powerful and sometimes tragic history shaped by tsunamis. Understanding this history and knowing the modern warning signs is essential for any visitor.

September 26, 2026 • 9 min read • by Big Island Tours Editorial

Hawaiʻi's position in the middle of the Pacific Ocean makes it a paradise, but its location within the seismically active "Ring of Fire" also exposes it to the powerful force of tsunamis. While they are infrequent, their impact on the Big Island's history, particularly in the city of Hilo, is undeniable. Understanding the risk, the warning signs, and the proper response is a crucial part of responsible travel to Hawaiʻi Island.

This isn't about causing alarm, but about fostering awareness. The state and county have robust systems in place, but the most effective safety tool is your own knowledge. A few minutes of preparation can ensure you know exactly what to do in the unlikely event of a tsunami alert during your visit.

What Exactly is a Tsunami?

A tsunami is not a single tidal wave, but a series of powerful ocean waves caused by large-scale disturbances of the seafloor, most commonly large earthquakes. According to the U.S. Geological Survey (USGS), these events displace a massive volume of water, generating waves that can travel across entire oceans at speeds comparable to a jet airliner.

As these waves approach shallow coastal waters, they slow down and their height increases dramatically. What might be an imperceptible swell in the deep ocean can transform into a destructive wall of water, flooding land far from the normal shoreline. It's crucial to remember a tsunami is a series of waves, and the first wave is often not the largest.

There are two main types of tsunamis that can affect Hawaiʻi:

Distant (or Teletsunami): Generated by a faraway earthquake, such as those in Alaska, Chile, or Japan. These are the most common type to affect Hawaiʻi. The key advantage is time; these tsunamis take several hours to cross the ocean, allowing for official warnings and orderly evacuations.
Local Tsunami: Generated by a nearby event, typically a major earthquake and/or an underwater landslide along the Hawaiian Islands chain itself. These are far more dangerous because they can arrive at the coast within minutes, often before any official warning can be issued.

A History Written in Water: Major Big Island Tsunamis

The Big Island, especially its eastern-facing Hilo coast, has been tragically shaped by tsunamis. Visiting Hilo's downtown and waterfront parks today, you are seeing a city that was literally rebuilt with these events in mind.

The 1946 April Fools' Day Tsunami

Generated by a magnitude 8.6 earthquake in the Aleutian Islands of Alaska, this tsunami caught Hawaiʻi completely by surprise. There was no tsunami warning system in place at the time. Waves reaching heights of up to 55 feet in some areas slammed into the islands. Hilo was hit particularly hard, with a series of massive waves flooding the downtown area, destroying the bayfront, and killing 96 people on the Big Island (159 statewide). This disaster was the catalyst for creating the Pacific Tsunami Warning Center.

The 1960 Chilean Tsunami

The most powerful earthquake ever recorded—a magnitude 9.5 in Chile—generated a teletsunami that radiated across the entire Pacific. This time, the warning system was in place, and sirens sounded in Hilo. However, a combination of factors, including a lack of public understanding and the fact that the first waves were small, led many to believe the danger had passed. Tragically, a larger, more destructive wave arrived later, killing 61 people in Hilo and obliterating the Waiākea neighborhood.

The 1975 Local Tsunami

On November 29, 1975, a magnitude 7.2 earthquake centered in the Kalapana region on the Big Island's southeast coast triggered a local tsunami. A huge section of the coast subsided, generating waves that arrived almost immediately. At Halapē, within what is now Hawaiʻi Volcanoes National Park, two campers were killed. This event was a stark reminder that the Big Island can generate its own tsunamis, offering almost no time for official warnings.

How to Know a Tsunami is Coming

Knowing the signs—both official and natural—is the most critical part of tsunami safety. Heed all warnings immediately.

Official Warnings

All-Hazard Sirens: Hawaiʻi has a statewide system of sirens. You may hear them tested on the first business day of each month at 11:45 AM with a steady one-minute tone. In a real emergency, including a tsunami warning, you will hear a wailing tone (up-and-down siren) for three minutes. This is your signal to immediately tune into a local radio or TV station or check official online sources for instructions.
Wireless Emergency Alerts (WEA): Tsunami Warnings are pushed to all compatible cell phones in the affected area. This may be the first and most direct warning you receive.
Emergency Alert System (EAS): Local radio and television stations will broadcast detailed information and instructions from authorities.

A Tsunami Watch means a distant earthquake has occurred that could generate a tsunami. Stay informed and be prepared to act. A Tsunami Warning means a tsunami is imminent or expected. Evacuate the warning zone immediately.

Natural Warning Signs

For a local tsunami, you will not have the luxury of waiting for an official siren. Nature provides the most urgent clues:

Strong Ground Shaking: If you are near the coast and feel an earthquake so strong it is difficult to stand up, a tsunami could be minutes away. Do not wait for a siren. Immediately move to higher ground as far inland as possible.
Sudden Sea Level Change: A sudden, unusual fall or rise in sea level is a classic sign of an approaching tsunami. The ocean may recede far beyond the lowest tide line, exposing the sea floor. This is a signal to run.
A Loud Ocean Roar: Survivors of past tsunamis often describe an unusual, loud roar coming from the ocean, sometimes compared to a freight train or a jet engine. This is the sound of the approaching wave.

Tsunami Evacuation Zones & Safety Procedures

Coastal areas of the Big Island are mapped into Tsunami Evacuation Zones. These are the areas most at risk of inundation.

Know Your Zone: When you check into your hotel or vacation rental, ask if you are in a tsunami evacuation zone. Look for the evacuation maps, which are often posted in lobbies and are available on the Hawaiʻi County Civil Defense website.
Plan Your Route: Identify your evacuation route beforehand. The goal is simple: get to high ground, as far inland as you can. Roads will be congested. If you are close, walking or running may be your best option.
Heed the Signs: Blue and white signs throughout coastal communities indicate evacuation routes. Follow them.

During a warning, authorities will direct a coordinated evacuation. The key is to move calmly and quickly away from the coast. Do not go to the shore to watch the wave; it moves faster than you can run and can carry deadly debris.

Hilo: The City That Remembers

Hilo is a living lesson in tsunami resilience. The devastating events of 1946 and 1960 led to a complete redesign of the city's relationship with the ocean.

The Bayfront: The beautiful green space and parks that line Hilo Bay today exist where a bustling commercial district once stood. This area now serves as a protective buffer zone.
The Pacific Tsunami Museum: Located in a historic bank building that survived the tsunamis, this excellent museum is a must-visit. It tells the human stories behind the science and preserves the memory of those who were lost. It's a powerful and educational experience.

Understanding this history gives you a deeper appreciation for Hilo and the immense power of the Pacific. You can learn more about general Big Island trip planning at our guide on High End Hawaii.

While the thought of a tsunami can be unsettling, these events are rare. Being informed is the best way to feel secure and enjoy your time on the beautiful, dynamic, and powerful island of Hawaiʻi.

Related Reading:

A Guide to Seeing Lava on the Big Island: /blog/seeing-lava-big-island-guide
Stargazing on Mauna Kea: /blog/mauna-kea-stargazing-guide
Big Island Hurricane Season: What Travelers Should Know: /blog/big-island-hurricane-season-preparedness

Frequently asked questions

What's the difference between a Tsunami Watch and a Tsunami Warning?

A Tsunami Watch is issued when a distant earthquake occurs that *could* generate a tsunami. It means you should stay informed and be prepared to act. A Tsunami Warning is issued when a dangerous tsunami is imminent or expected, and it means you must evacuate the designated coastal zones immediately.

How often do damaging tsunamis hit the Big Island?

Damaging tsunamis are relatively rare. The last two major destructive events were in 1946 and 1960. Smaller, non-damaging tsunamis occur more frequently, but robust warning systems are in place to monitor all potential threats across the Pacific.

What should I do if I hear a tsunami warning siren?

If you hear the wailing (up-and-down) siren for a sustained period, it is a signal to take action. Immediately turn on a local radio station, TV, or check official county alerts on your phone for instructions. If you are in a designated Tsunami Evacuation Zone, evacuate to higher ground.

Is it safe to stay in a hotel on the coast?

Yes, it is generally safe. Coastal hotels are aware of the risks and have established evacuation procedures. Upon check-in, familiarize yourself with their plan and know your evacuation route to higher ground.

Where can I find tsunami evacuation zone maps?

Official Tsunami Evacuation Zone maps are provided by Hawaiʻi County Civil Defense. You can find them on their website. Many hotels and rental properties in coastal areas also post these maps for guest awareness.

Can Big Island volcanoes cause tsunamis?

Yes, it's possible. The 1975 Kalapana earthquake, linked to volcanic and tectonic activity, caused a local tsunami. While a massive flank collapse of Kīlauea is a theoretical long-term hazard, the more immediate risk is from local tsunamis generated by large, coastline-shifting earthquakes.

What is the Pacific Tsunami Museum in Hilo?

The Pacific Tsunami Museum is a fascinating museum in downtown Hilo dedicated to the history and science of tsunamis, particularly the 1946 and 1960 events that reshaped the city. It serves as both a memorial and an educational center, and it's highly recommended for understanding the island's history.