Any tsunami video I look at barely looks like a 20 feet wave hitting shore. But wikipedia tells me there have been dozens of 100+ feet tsunamis even in the last 10 years.
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A Tsunami is made by tectonic activity beneath the ocean floor. When a large amount of the plate comes up, it pushes the ocean up. This pushes a Whole BUNCH of the ocean in one direction, generally towards some shoreline.
At its peak, the risen ocean wave may be 100 feet high. An earthquake can last for several minutes, remember. The longer it lasts and the more the plate moves upwards, the more ocean it will be pushing away from it.
So if you have a 300 meter long tectonic plate movement/ crack happening with ocean moving up, all that water is getting pushed at the same time.
All that water goes to the opposite shore. Its a HUGE amount of water, and the wave can come so fast, it has to go to the surface to spread out also, which probably slows the wave action somewhat.
However, water is very heavy, weighing 5 lbs a gallon, so we are talking about billions or trillions of gallons of water being moved.
Anyways, a 100 foot wave is going to look like a “rogue wave” aka an unusually large wave, at sea, but once the bottom part of that wave hits the 130 foot depth, it breaks, turning it into what appears to be a 30 foot wave, from the surface view.
Remember, though, that waves themselves are generally just on the surface of the water. A Tsunami is not merely a wave. It is a top to bottom of the deep ocean floor, movement of water also.
So that “broken” wave is just expanded out to miles and miles in width, and all the ocean beneath it is still moving also, because its not just a wave, its a fraction of the ocean, surface to ocean bottom, being pushed onto land.
In this respect, you end up having miles and miles worth of tsunami ocean water that is all pushed onshore.
That is why there is so much more water than you would expect. I hope that helps.
Edit:
And though you didnt ask, a more common issue for beachgoers is rip currents.
If you ever see lines going out, from the shore to the sea, or coming in, its probably a rip current.
To break “the grip of the rip” as we call it, nobody, not even Michael Phelps, on his best day, can swim against the current, strongly enough, to not be swept out to sea.
Instead, the best thing to do is to swim parallel to the shore, sideways, so to speak. This is the best chance at staying within view of the shore, and breaking out of the rip current.
This is more relevant to everyone lmao because anyone who goes to the beach is at risk of suddenly getting caught in a rip. Just an add on. 🙂 Just in case.
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