Misconceptions of Sea Glass and Wave Formation

Over the last two years, I have noticed that the landscape of the beach changes every single day. Sometimes it is very subtle and other times quite dramatic. It never fails to surprise me how the sea can take large heavy boulders and re-distribute them to another part of the beach. I feel like tagging them to see where they end up. Donkey's voice off Shrek the movie is popping into my head now. 'Boulder, that is a nice boulder'. Moving swiftly on...

There is a general misconception that sea glass is brought in with every tide, which is not entirely true. Sometimes the sea glass is already sitting beneath the surface of the sand and pebbles, and is only revealed by an onshore wind or a particularly high tide taking more of the surface away.

Another misconception is that waves are caused by the movement of water when in fact, it is energy that passes through water which causes the water to move in a circular movement.

Here is a great piece from https://oceanexplorer.noaa.gov/facts/waves.html# who explain it far better than I can. Check out their website too, they are doing some great work.

Waves are actually energy passing through the water, causing it to move in a circular motion. When a wave encounters a surface object, the object appears to lurch forward and upward with the wave, but then falls down and back in an orbital rotation as the wave continues by, ending up in the same position as before the wave came by. If one imagines wave water itself following this same pattern, it is easier to understand ocean waves as simply the outward manifestation of kinetic energy propagating through seawater. In reality, the water in waves doesn’t travel much at all. The only thing waves do transmit across the sea is energy.

The idea of waves being energy movement rather than water movement makes sense in the open ocean, but what about on the coast, where waves are clearly seen crashing dramatically onto shore? This phenomenon is a result of the wave’s orbital motion being disturbed by the seafloor. As a wave passes through water, not only does the surface water follow an orbital motion, but a column of water below it (down to half of the wave’s wavelength) completes the same movement. The approach of the bottom in shallow areas causes the lower portion of the wave to slow down and compress, forcing the wave’s crest higher in the air. Eventually this imbalance in the wave reaches a breaking point, and the crest comes crashing down as wave energy is dissipated into the surf.

Where does a wave's energy come from? There are a few types of ocean waves and they are generally classified by the energy source that creates them. Most common are surface waves, caused by wind blowing along the air-water interface, creating a disturbance that steadily builds as wind continues to blow and the wave crest rises. Surface waves occur constantly all over the globe, and are the waves you see at the beach under normal conditions.

Adverse weather or natural events often produce larger and potentially hazardous waves. Severe storms moving inland often create a storm surge, a long wave caused by high winds and a continued low pressure area. Submarine earthquakes or landslides can displace a large amount of water very quickly, creating a series of very long waves called tsunamis. Storm surges and tsunamis do not create a typical crashing wave but rather a massive rise in sea level upon reaching shore, and they can be extremely destructive to coastal environments.