What caused the 1964 tsunami?

The ’64 Alaska Earthquake: When the World Rocked and the Waves Roared

The Great Alaska Earthquake of 1964, hitting on Good Friday, wasn’t just a tremor; it was a full-blown assault by Mother Nature. Picture this: 5:36 PM AKST, March 27th, 1964. The ground starts to rumble, and then… well, then all hell breaks loose. This wasn’t just any earthquake; it was a magnitude 9.2 monster, the kind that rewrites landscapes and etches itself into history. And what followed? A tsunami, a wall of water that swept across the Pacific, leaving devastation in its wake from Alaska to California, even reaching Hawaii and as far as Antarctica. It’s a story of immense power, but also of how we learned to better understand and prepare for these terrifying events.

So, what unleashed this watery nightmare? It all boils down to a megathrust earthquake. Think of Alaska as being caught in a slow-motion tug-of-war between tectonic plates. The Pacific Plate is constantly trying to shove itself under the North American Plate – a process called subduction. This happens along the Aleutian Megathrust, basically a gigantic, creaky fault line. On that Good Friday, a huge chunk of this fault, almost 600 miles long, finally gave way. The earth split open about 15 miles beneath the surface, a bit west of Valdez and east of Anchorage. It shook for nearly four and a half minutes, an eternity when the ground is bucking beneath your feet. The energy released was mind-boggling, the most ever recorded in North America and second-most worldwide since we started measuring these things properly.

But here’s the crucial part: this wasn’t just a side-to-side jolt. The earthquake caused the seafloor to heave up and down, like a giant flexing its muscles. Imagine the ocean floor suddenly rising or sinking across an area the size of Oregon – about 110,000 square miles! That’s a whole lot of water being pushed around, and that’s precisely what created the tsunami. These aren’t your average beach waves; they’re more like moving mountains of water, radiating out from the epicenter. The biggest one? A staggering 220 feet tall, crashing into Shoup Bay near Valdez. Unimaginable.

Now, the earthquake was the main villain, but it had some nasty accomplices: landslides. The shaking was so intense that it triggered underwater and above-ground landslides, which in turn generated their own, smaller but still deadly, tsunamis. Take Port Valdez, for example. A massive underwater landslide there claimed 32 lives. Or Chenega, a village wiped out by a landslide-induced wave, killing 23 out of 68 residents. Recent mapping of the seafloor confirms just how big a role these underwater landslides played. These local tsunamis were particularly brutal because they struck almost immediately, giving people no chance to escape.

And it wasn’t just landslides. The shaking also caused liquefaction, turning solid ground into something akin to quicksand. This made the landslide problem even worse and caused buildings to sink and collapse. I remember reading accounts of houses simply disappearing into the earth.

The devastation was widespread. Towns like Seward, Whittier, and Kodiak were hammered by the earthquake, the sinking ground, and the tsunami. Crescent City, California, also suffered terribly. In the end, around 139 people lost their lives.

But from this tragedy came progress. The ’64 earthquake forced us to rethink our understanding of plate tectonics and how tsunamis are born. It led to the creation of better tsunami warning systems, including the Alaska Tsunami Warning Center in 1967. It’s a grim reminder, but also a testament to our ability to learn and adapt, to try and protect ourselves from the raw power of our planet. The lessons learned that day continue to shape earthquake preparedness and tsunami mitigation efforts around the globe.