Wednesday, November 27, 2013

Black's Beach

Black's Beach, named for the family that once ranched above the bluffs where the over-the-top mansions of La Jolla Farms now perch, and sometimes referred to as Torrey Pines City Beach, lies below the high bluffs described in the previous two posts. Unlike much of the San Diego coastline, where natural sediment sources (particularly from bluffs) have largely dried up (or been entombed), these bluffs are still dumping large amounts of sand onto the beach (those landslides in the Torrey Pines photos). This material gets transported south toward La Jolla where it is lost into the offshore canyons.

The promontory that marks the south end of the beach (and separates it from Scripps and La Jolla Shores) is associated with a volcanic dike on the platform that is more resistant to erosion than the surrounding sedimentary rocks.  It is also marked by the old NMFS buildling described in an earlier post (Scripps) and a crazy guest house (called the mushroom house) at the bottom of a steep tramway.


The sand on this beach contains a lot more than just quartz. Heavier dark minerals and shiny golden ones (muscovite?) are abundant and each swash erases the previous pattern and creates a new one. The dark grains form little cusps that open seaward during the backwash. The light ones tend to spread out more evenly.  A study in density and subtle differences in fine-scale transport characteristics. If it is muscovite, I suspect that suggests that the beach is composed of pretty fresh bluff - I doubt the muscovite would persist long in this setting. Interestingly, some accounts of Black's Beach describe it as Black Beach and credit this to the dark sands.

Beach wrack, mainly torn up kelp, was distributed in small and large piles across the beach and was crawling (hopping, actually) with small critters and attracting birds.  I suppose as it breaks down, some of material and nutrients get washed back out into the nearshore. These are probably far more complex ecosystems than sandy beaches are normally given credit for.

I watched dolphins follow a stand-up paddle boarder (couldn't get photos) - maybe if the waves had been bigger they would have been surfing (check this out on YouTube).

Black's Beach is best known for surfing - I guess the break is enhanced by the head of the Scripps submarine canyon lying just offshore - and as a clothing-optional beach, although that portion lies a little farther north.  I guess that's good thing, since it might be a little awkward to be a middle-aged guy taking a ton of pictures in the midst of the sunbathers and volleyball games.

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