On May 22, 1960, the most powerful earthquake ever recorded struck off the coast of southern Chile. After the tremors subsided, Denis García, a resident of Corral, noticed an anomaly: the bay’s waters had receded, exposing the seabed. His investigation led to a harrowing encounter with a 40-foot tsunami. García’s experience highlights the unpredictable and devastating nature of these mega-waves. This article explores the extent to which a tsunami can travel inland, emphasizing the critical need for preparedness and awareness.
Around 80% of tsunamis are triggered in the Pacific Ocean’s “Ring of Fire.” While Hawaii, Alaska, and the US West Coast face the highest risk, tsunamis can occur in any ocean, traveling vast distances approximately twice per decade. While García survived, most who are caught in a tsunami do not. Being aware of the risks and taking proactive steps is crucial for survival.
“It’s easy to say, ‘That’s not going to be my problem ever,’ and it’s also easy to throw up your hands and say, ‘It’s going to be so bad that there’s really nothing I can do,’” says Carrie Garrison-Laney, a tsunami and coastal hazard expert at the Washington Sea Grant office in Seattle. “Yes, it will be bad, but…there are some things you can do to be prepared in the event that it happens.”
Understanding Tsunami Formation and Characteristics
Most tsunamis originate from undersea earthquakes that displace significant water volumes. Volcanic eruptions, landslides, and even meteor impacts can also cause these devastating waves.
In the open ocean, tsunami waves can stretch hundreds of miles in length but are often only a few feet high, traveling at speeds of up to 500 mph. As they approach shallower coastal waters, their speed decreases to 20-30 mph, and their height dramatically increases.
While most tsunamis are less than 10 feet high upon landfall, they can reach heights exceeding 100 feet. Areas within a mile of the coast and below 25 feet above sea level are at the greatest risk. However, tsunamis have been known to surge up to 10 miles inland. According to Garrison-Laney, tsunamis are relentless, with water continuously flowing inland for extended periods.
Tsunami approaching land, showing the wave height and potential inundation area
The appearance of a tsunami is often not what many expect. Instead of a breaking wave, it typically manifests as a rapidly rising flood of turbulent water. It’s crucial to recognize warning signs, both natural and official.
Recognizing Warning Signs and Taking Immediate Action
Following a strong coastal earthquake, evacuate to higher ground immediately, even without an official tsunami warning. Local tsunamis can arrive within minutes. The ocean receding unexpectedly, as García witnessed, is another critical warning sign. A loud roaring sound, similar to a train or jet plane, can also indicate an approaching tsunami.
Tsunami tracking centers, such as the Pacific Tsunami Warning Center and the National Tsunami Warning Center, issue alerts. Stay informed through official warnings, sirens, and local authorities. Hesitation can be fatal.
Laura Kong, director of the International Tsunami Information Center in Honolulu, emphasizes the importance of prompt action: “You don’t want to hesitate if you know a warning’s been issued or you’ve felt the ground shaking. You want to get going.”
Evacuation Strategies: Reaching Safety
If you are on a boat in the open ocean, remain there. On land, the primary goal is to evacuate away from the coast, aiming for locations at least 100 feet above sea level or two miles inland.
If time allows, gather a disaster kit and bring your pets. Follow evacuation signs and instructions from emergency personnel, who may recommend specific routes. When in doubt, continue moving uphill. Avoid rivers and streams, as tsunamis can surge up them rapidly. Evacuate on foot to avoid traffic congestion. Be cautious of downed power lines and unstable structures.
If reaching high ground is impossible, seek shelter in a sturdy, reinforced concrete building. Ascend to the highest possible level, preferably the roof. In the absence of buildings, climbing a tree may provide temporary refuge.
Surviving the Impact: What to Do When the Wave Hits
In the event of being caught in the wave, grab onto floating debris. Some individuals have survived by using roofs as makeshift rafts. Survival in the turbulent water filled with debris is largely a matter of chance.
Garrison-Laney describes the experience: “A person will be just swept up in it and carried along as debris; there’s no swimming out of a tsunami. There’s so much debris in the water that you’ll probably get crushed.”
Remember that a tsunami consists of a series of waves, with the first wave not necessarily being the largest. Remain in a safe location until emergency personnel issue an all-clear. The coastline may be devastated, with flooding, damaged buildings, and debris fires. Structures weakened by the tsunami may collapse.
Preparedness and Risk Awareness: Protecting Coastal Communities
Tsunamis possess immense power, capable of moving boulders and demolishing buildings due to the entire water column from seafloor to surface being in motion. A significant portion of the global population lives near coastlines, increasing the potential for catastrophic impact.
Preparedness is essential. Coastal residents should have a family plan and know their tsunami evacuation zone. Practice evacuation routes and maintain an emergency kit. Understand community disaster plans.
Tourists should also be aware of tsunami risks and plan accordingly. A simple flashlight can be invaluable during a nighttime evacuation. Scientists continuously analyze tsunami events to improve understanding and preparedness, running simulations to predict vulnerable areas and develop evacuation plans.
The 2004 Indian Ocean Tsunami highlighted the critical need for warning systems. Today, nations bordering the Indian Ocean are better prepared. Yet, tsunamis remain unpredictable, as demonstrated by the rare tsunami that struck Greenland. Even Japan, known for its earthquake preparedness, suffered greatly from the 2011 tsunami.
Coastal communities must prepare for worst-case scenarios, even in regions with infrequent tsunamis. The key unknown is where the next tsunami will strike. Garrison-Laney concludes: “It’s really just up to coastal communities to make sure that they’re ready, and hopefully it won’t happen before everyone’s ready.”
Conclusion: The Importance of Understanding Tsunami Risks
Understanding how far a tsunami can travel inland is paramount for coastal communities and individuals. By recognizing warning signs, developing evacuation plans, and staying informed, we can mitigate the devastating impact of these natural disasters. Preparedness, awareness, and prompt action are crucial for survival when facing the threat of a tsunami.
