Sunday, April 2, 2017


So yesterday I bought a rock and some driftwood at a sidewalk sale.  I guess I’m giving away my geographic location here.  Who but a Californian would go to a garage sale or whatever and pay good money for rocks and sticks?  But that’s what I did.  Here are pictures…

The driftwood makes me think of Bristlecone pines – the world’s oldest living things.  (Or is that oldest living trees?)  Anyway, I’m sure my driftwood is not a Bristlecone.  It’s most likely some random root of a much more common tree.

But the rock…  Clearly sandstone, but why the waffly, holey, appearance?  And what was the process by which it attained this state?

So I “Used the Duck.”  Which is to say, Duck Duck Go.  I don’t use Google as my search engine.

Here’s what I found:

They’re called Moon Rocks.

from: Wikipedia 

The rocks of Salt Point are sedimentary, mainly sandstone. All of these rocks are tilted, exposing older rocks. The rocks at the north end of the park's coast are younger than the rocks at of the southern end. Salt Point is named for the tafoni where the ocean water crystallizes in the honeycomb like crevices. This tafoni is caused when the salt crystals interact with the sandstone making parts of the sandstone harden while other parts soften.

...and more from Wikipedia

Tafoni (singular: tafone) are small cave-like features found in granular rock such as sandstone, granite, and sandy-limestone with rounded entrances and smooth concave walls, often connected, adjacent, and/or networked. They often occur in groups that can riddle a hillside, cliff, or other rock formation. They can be found in all climate types, but are most abundant in intertidal areas and semi-arid and arid deserts. Explanations of their formation include salt weathering, differential cementation, structural variation in permeability, wetting-drying, and freezing-thawing cycles, variability in lithology, case hardening and core softening, and/or micro-climate changes and variation (that is, moisture availability). Tafoni have also been called fretting, stonelace, stone lattice, honeycomb weathering, and alveolar weathering.

Tafoni features have been found across the Earth, with dramatic forms found in the Jodhpur-Ajmer section of India's Thar Desert, Petra, Jordan, Coastal California and Australia, and even in the Arctic regions, and Antarctica (Paradise 2011).

The etymology of the word "tafoni" is unclear. Tafoni may come from the Greek word taphos, "tomb", or it may stem from a Corsican or Sicilian word for "holes", taffoni, or from tafonare meaning "to perforate". The earliest known publication of the term “tafoni” was in 1882. Conventionally, the word 'tafoni' is the plural form of 'tafone'.

My rock may have come from Salt Point State Park, CA, or it may have come from Bean Hollow Pebble Beach, Pescadero, CA.  Or it may have come from neither.  But isn’t it cool?

Here’s more photos from the Bean Hollow Pebble Beach page.

Here's another one from Wikipedia:

No comments: