Mavericks Beach in Half Moon Bay is a legendary surf spot known worldwide. The beach is something of an anomaly, routinely experiencing giant waves that boggle the mind. The waves can regularly top 25 ft, and can even top out around 60ft. It is hard to predict exactly when the big waves will strike, but they often come after winter storms.
So, how do these giant waves form here and very few other places around the globe? Along with the ocean tide patterns, geologists have discovered a peculiar feature of Mavericks Beach that helps create these massive waves.
Researchers from the US National Oceanic and Atmospheric Administration (NOAA) have revealed that the ocean floor leading up to the bluffs at Pillar Point forms a giant ramp, slowly increasing in elevation. This may sound like any normal sea floor, but this long, narrow ramp is unique. The underlying sea floor actually becomes shallower much further out than the rest of the area, and continues to rise in elevation until reaching the beach. The surrounding seafloor, in contrast, stays deep until abruptly rising close to the shore. The ramp that underlies Mavericks Beach causes the deepest parts of the wave to slow down once they come in contact with the formation. However, due to tidal forces, the shallower part of the waves continue to approach at their same speed. This difference in approach speed forces the deeper water from the wave upwards as it ascends the seafloor ramp, and causes the wave to stand up taller.
Additionally, there are deep troughs on either side of this “ramp.” These deep areas hold water more calmly, which allows these giant waves to draw additional energy from the slow water. This is known as a wave convergence. The deep troughs feed the mega waves as water hits the wall of the trough and gets pushed upwards onto the bedrock ramp.
To log this Earthcache, Please send me a message with the following:
- The name of this earthcache with the number of people in your group.
- What are the current tide conditions during your visit?
- Stand at the coordinates, which bring you to the beach, and face out to the sea. Identify the rocks protruding from the surface offshore. Are these part of the ramp that brings water up to unusually shallow depths?
- Along with the big waves it causes, do you think the daily low and high tide marks are influenced by this underwater ramp?
Have fun, be safe, and please pack out any trash you bring! There are trash cans located at the beach and the parking lots.
Sources:
https://www.newscientist.com/article/dn11667-map-reveals-secret-of-awesome-mavericks-waves/
https://en.wikipedia.org/wiki/Mavericks,_California
https://sanctuaries.noaa.gov/news/press/2007/pr041607_items.html