What a bore

There are so many misused terms regarding natural phenomena it makes your head spin. For instance the term tidal wave. A tidal wave can be a tsunami, the Japanese word meaning harbor wave. Tsunamis are caused by the displacement of undersea crust that displaces a large body of water. Another tidal wave is a bore, the wave caused by a rising tide traveling into a gradually restricted space, such as moving up a river. The picture above shows a tidal bore.

In the early 1980s during a period of significant seismic activity nearby, I experienced a micro tsunami at Florence Lake. I was piloting the ferry boat on the first run of the day at 8:30 AM. In early morning the lake is usually glass-smooth since there is no wind. As I headed across the still waters I noticed a line of raised water traveling in the same direction as the boat. The leading edge of the wave matched the shape of the shoreline behind me. What had happened was the occurrence of another of the many earthquakes that were occurring at Mammoth Mountain, 20 miles to the northeast. The quake shocked the rock that surrounds the lake and shoved the water in a shape matching the surrounding terrain.

At Florence Lake we can never experience a bore. A bore takes a tide to create it. What happens is the moon travels over the ocean and its gravity causes the water to lift. The rising tide travels toward a space that incrementally restricts it laterally. The water piles up into a wave that moves into a more restricted space. The result? Boring. But interesting.

Photo from Spaceweather.com