It’s a hot summer day on the beach when the sea starts to recede. In a matter of minutes, a wall of water 50 feet high rushes towards the shore at 40 miles per hour. Confused beach-goers, families and teenagers start to scream as they race away from the wave pounding towards them.
This scenario sounds like a scene out of a high-budget Hollywood summer blockbuster. However, for millions of people on the western coast of the United States, it is a threat they live with on a daily basis.
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To better understand the threat of a tsunami, it helps to have a basic understanding of plate tectonics. This refers to the continually dynamic adjustments of earth layers that lie between the Earth’s crust, the continents, the oceans and all living creatures on the planet, and the extremely hot, semi-solid mantle that makes up over three quarters of the Earth’s mass. Rather than comprising a single, contiguous sheet, the crust is broken up into various fragments known as plates. And, because these plates are sitting on top of a dense liquid, the mantle, they float around. When these plates move, so do the Earth’s oceans and continents.
At the boundaries of these plates is where the action occurs. We’re all familiar with the most obvious effect of a shift between two tectonic plates: earthquakes. But they also create tsunamis, which have resulted in some of the biggest global disasters in recent memory, including the 2004 Indian Ocean tsunami, which killed a quarter of a million people.
Two plates that pose significant risk for Americans on the West Coast are the North American plate and the Juan de Fuca. This plate boundary hasn’t moved in over 300 years. As time passes, more pressure builds beneath the surface. When the plate finally does move, the consequences will be devastating.
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It will start with an enormous mountain of water being forced into the air. When the wall collapses again into the ocean, the force will send two enormous waves of water out across the Pacific Ocean. This is similar to the effect of throwing a rock into a pond and watching the ripples head towards the edge. In the case of a tsunami, one of these ripples represents a deep wall of water moving at 500 miles per hour through the Pacific Ocean.
When it reaches the coast, that wave could reach as high as 100 feet in places. And the only warning residents will have is the earthquake caused by the same plate shift that created the tsunami, which will reach them only a few minutes before the wave. Earthquakes originating near Japan or Alaska, or even under-ocean landslides can cause tsunamis. These distant tsunamis may not be preceded by noticeable ground shaking. In either case, if you live on the coast, getting to high ground in that brief window of time between the initial shock of the earthquake and when the tsunami makes landfall will be the difference between life and death.
Locals know that Cannon Beach, Oregon, is one of the most beautiful coastal towns in the country. Every summer, tourists flock to their beaches to take in the sun, admire the 235-foot Haystack Rock and walk through the town’s friendly main streets. Despite this benign appearance, the year-round residents of Cannon Beach also know that their town is in the middle of a tsunami inundation zone. They were struck unawares by a violent tsunami following the Great Alaska Earthquake of 1964, which resulted in the deaths of four children. After this early tragedy, Cannon Beach has emerged as a leader in promoting the safety of its citizens.
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If you drive around the town of Cannon Beach, you’ll notice tsunami evacuation signs depicting a person racing away from a towering wave. These are not meant to scare residents or passing tourists; rather, these provide essential information in the event that the Juan de Fuca plate sets off a major tsunami—the evacuation route. After the initial shocks of the earthquake pass, the citizens of Cannon Beach will have 10 to 15 minutes to reach high ground.
In 2014, the city hosted the inaugural “Race The Wave” fun run to promote citizen awareness. The path follows one of the actual evacuation routes leading from the beach, through the city center and up into the hills to one of the emergency cache sites. There, race participants had the opportunity to learn more about what they can do to protect themselves and their families.
As tsunami inundation zones go, Cannon Beach is a fairly safe place to live. The hills behind the town rise hundreds of feet above sea level, offering a safe haven to retreat to when the ground stops shaking. Residents of Grays Harbor County in Washington State have no such luxury. Thousands of at-risk residents live miles from the nearest hill. With only 15 to 30 minutes to reach high ground after a quake, there simply isn’t enough time to outrun the earthquake.
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To combat this problem, the residents of Westport and Grayland decided in 2013 to build a new gymnasium for the local school system that would double as a tsunami tower, the nation’s first human-made, vertical tsunami refuge. The concept here is simple but lifesaving: Build a gymnasium strong enough to withstand both the initial 9.0 earthquake and the blast of the tsunami wave, and high enough that it’s above the highest wave predicted by current models. Under construction now, the building will hold 1,000 or more people once complete, making it a safe haven for both the 400 children in the Ocosta School District and nearby residents.
If you live in a tsunami danger zone, take steps to prepare your family in advance of a disaster. Start by considering your relative distance from the ocean, the elevation of your home and what the fastest route to higher ground would be. Since tsunamis can hit with minimal warning at any time, practice evacuating so that you’ll be able to execute your plan under inclement conditions or in the middle of the night. You’ll need to be able to reach your safe location in 15 minutes or less, so it may take a couple of practice runs to feel comfortable with your evacuation plan.
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Have your emergency kit ready to go. If a tsunami strikes your house, there may be little left to salvage, so ensure that there are sufficient provisions to get you through the immediate disaster. Having a portable radio will be useful for learning about the tsunami threat as it develops.
Also discuss what steps to take in the event that you are not at home when a tsunami strikes. Consider what your evacuation plan should be from your place of work, and make sure your children know what to do if they are at school. If family members end up evacuating to different areas, decide on a safe meeting point to rendezvous at once the threat has passed. Tsunamis are one of nature’s deadliest disasters, but with the right preparation you can maximize your chances of survival. Race the wave and find the high ground.
Make Your Community Tsunami Ready
Schools, playgrounds, hospitals and homes are often built in areas vulnerable to tsunamis. The National Weather Service created the TsunamiReady program to help cities in coastal areas prepare for potential consequences of a tsunami and minimize losses to vital community strongholds.
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View the TsunamiReady Communities map to see if your community is one of the 180 that are participating in the program. To be recognized as TsunamiReady, communities must meet several requirements, including establishing a 24-hour warning point and emergency operations center, having more than one way to receive tsunami warnings to alert the public and developing a formal tsunami plan. For the full list of criteria and to download an application, visit tsunamiready.noaa.gov. Source: ready.gov
This article was originally published in the SURVIVOR’S EDGE™ Winter 2016 edition. Subscription is available in print and digital editions here.