Devereux surf break pictures

[Joseph Berkovitz]

During the pandemic my wife and I have started going to Devereux Beach early every morning when few people are around. This morning’s visit coincided with fairly low water of -0.77 feet and much of the surf break at the East end of the beach was exposed. It’s an unusual feature: a shallow tongue of bottom that sticks out at right angles to the much more substantial spit on top of which lies the causeway to Marblehead Neck. 

Thanks to the breaking onshore wind waves you can clearly see how the tongue extends well out past the part that’s visible. I originally thought I would walk out on this tongue for a picture, but no: it’s made of unwalkable slimy seaweed covered cobbles:

I wonder why this feature is here - a sort of spit hanging off another larger spit. Unlike the causeway though, this one is made of large cobbles and rocks rather than fine gravel. A number of larger rocks extend right up onto the sand beach, although these may just be riprap dislodged by the waves near this break at high water.  There is a NE-SW fault running down the center of the harbor which probably goes roughly parallel to this feature. Maybe there’s a relationship? Mysteries abound!

It’s visible as the intertidal bulge to the south of the causeway here:

Notice that the feature is just east of a parallel depression in the bottom that runs in the same direction. Perhaps there is some geology at work here, it doesn’t seem to be drifting sediment. 

Edited July 7, 2020 by Joseph Berkovitz

[Dan Foster]

I was going to suggest that maybe this tongue of cobbles is all that remains of some prehistoric breach in the causeway and the outflow of material flowing from north to south. But given the protected harbor to the north, I'd suspect any breach would result in waves flushing TO the north. I also wondered if the causeway was man-made and there used to be a breach there. But this suggests no: https://patch.com/massachusetts/marblehead/when-was-the-causeway-built

Looking at the bigger picture, it's also in-line with the transition from deep to shallow blue water that extends out on the nautical chart. Looking at the aerial, I'd swear there's a culvert or some sort of outflow creating your "parallel depression to the east". But there isn't, right? I wonder if the lifeguards see rip currents setting up there.

Edited July 7, 2020 by Dan Foster
Tidal rip?

[Joseph Berkovitz]

No, there is definitely no culvert. Pre-road, the causeway was originally a tombolo which is a landform we see a lot around here (Nahant Beach is another one).

The dark appearance in the satellite photo is due to the dark algae covered cobbles of the raised tongue. On either side there is light-colored sand.