What Causes Sneaker Waves?

Several factors contribute to the existence of sneaker waves–one of which is seafloor features.  Here on the north coast, we are in the middle of several tectonic plates, leading to quite the topography of our coastal ocean floor– including the San Andreas fault, which is just offshore in the southern area of Humboldt County, the pacific plate, North American plate, the Gorda plate, as well as being located just south of the Cascadia subduction zone. 

A subduction zone refers to anywhere two tectonic plates meet, and one is being subducted, or being pushed underneath the other.  Here, the Juan de Fuca plate is being subducted by the north american plate, creating a trench off our coast.  When you have a trench next to a shallow coastline, that can create sneaker waves.  Those are unexpected waves that quite literally sneak up on you and can sweep you out to sea.

We also have several smaller faults in the area, including the Mad River fault, the Trinidad fault and the Big Lagoon fault.

Pacific ocean swells, fueled by storms churning miles and miles off the coast, also contribute to sneaker waves, as waves are stackable, and the vastness of the pacific gives them plenty of time and space to build up.  Storms out at sea can generate strong winds, and thus, strong waves.  these waves can amplify as they approach our coastline, which adds to the unpredictability of sneaker waves.   Local ocean currents can also increase the likelihood of sneaker waves

If you plan on heading out to the coast in the next few days, avoid jetties, cove beaches or beaches that back up to steep cliffs– and remember, never turn your back on the ocean.