Slick Ridge
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Slick Ridge


Slick Ridge
33 bedrock mortars, numerous slicks, and multiple housepits on a ridge between Blue Oak and Volvon Trails.
Many of these mortars are pot or pan-shaped, relative rarities in Volvon territory.

We call this Slick Ridge because of all the flat rocks with shallow indentations we’ve found here. It’s hard to tell sometimes what’s a slick and what’s a natural formation.

One indicator of slickhood is the presence of a bedrock mortar in the putative slick. There’s a small cone ground into the center of this one.


This rock is a strange one. Two bowls are visible from this angle as is part of a trough-like slick that flows over the surface of the rock like a spillway. The slick is 8 1/2″ deep at its deepest and has a shallow bowl (about 3″ deep) at its low end, which is out of sight in this picture. Heaven only know what was processed here.


Ernest Johnson in “The Stone Mortars of Contra Costa County,” American Antiquity, Vol. 7, No. 3 (Jan. 1942), pp. 322-326, describes rare mortars with interior cavities that “flare outward a short distance below the opening, making a cavity of larger diameter at this point than at the rim” (p. 325). Johnson calls this type of mortar the “Olla” type. He implies these mortars never occur in bedrock when he claims (p. 325) that all Contra Costa County bedrock mortars he’s seen have V-shaped (cone-shaped) interiors. You should have hiked up into Morgan Territory Ernie!

Bob admires a perfect Olla bowl (or pan, since it has a flat bottom). Note the rounded rim.


There are great sightlines from this ridge.


The omnipresent Mt. Diablo.