I'm rusty.

Yes, I am blog-rusty, but not as rusty as this chunk of tuff situated underneath a drip irrigation emitter.  Stained a curious shade of orange, from the iron present in Vinoland's well water, this fractured hunk of ash-fall tuff distracted me from the job at hand.  (For more on tuff, see here.)  I've been keeping busy stuffing shoots, thinning heads and suckering trunks.  And watching this California Harvester Ant (Pogonomyrmex californicus) bopping around under a Syrah vine, fascinating.  I'm easily distracted.  Situation, normal.

Tuff stuff.

A small excavation in Vinoland has revealed a friendly, neighbourhood igneous rock (everybody should have one).  Tuff, or ash-fall tuff, is extremely variable in its chemical and mineralogical composition.  Vinoland's tuff happens to be extremely light in weight and texture, but there exists some historical references (The Structural and Industrial Materials of California, Bulletin No. 38, State Mining Bureau, 1906), to a brecciated tuff, mined just a mile or so from here, that "...for many years has been used for macadamizing the streets of Napa."  Now, that's tough stuff.
Tuff is a fine grained rock composed of volcanic ash which fell upon this part of the Napa Valley millions of years ago, (vulcanism reached the valley about 7 million years ago), which later hardened into beds of tuff.  Vinoland's tuff is really light in colour (it resembles diatomaceous earth in appearance, though it is denser), includes no clasts (volcanic detritus), rubs off on your fingers like chalk and is usually high in silica. 
Tuff is only found in a small area in the south end of Vinoland, (some Syrah is planted in it, tough stuff for a grapevine to deal with).  I know that at least one of our neighbours over the hill behind Vinoland has a large amount of it, but I don't know how extensive it is in the neighbourhood as a whole.  Some folks claim that the volcanic rock in the Napa Valley is responsible for certain characteristics in the grapes and resulting wine.  However, due to the huge diversity in the types of volcanic rock deposited in the length and breadth of the valley, I am of the opinion that there is little significance you can attribute to just one specific lithology.

The Calistoga AVA.

 

There is no doubt that the Napa Valley is a very picturesque place.  However, a lot of visitors I run into do complain of being disappointed with the town of Napa itself.  I point out to them that Napa is a functioning town that has to support a fairly sizeable population (approx. 80,000 peeps) and therefore it has to service that population with such untouristy features as an auto row, big-box stores and strip malls.
Of all the AVA sign photographs that I have posted up till now, this Calistoga AVA sign, on the corner of Highway 29 and Larkmead Lane, has to have the most unlovely of dispositions.  There are other Calistoga AVA signs that I could have photographed in much prettier settings, but this one makes me laugh.  Like some cavalier afterthought, this sign was plonked down in the most unprepossessing of locations.  I think the oval wine-coloured AVA signs are of a rather fetching design, but this Calistoga sign is being outcompeted by a slightly mangled chain-link fence, the yellow safety shield on a guy-wire (stabilizing a utility pole) and a red sign warning of an underground telephone cable (which I cropped out).  Funny!
Grapevines were first planted in Calistoga (also known for its sparkling water, hot springs and mud baths) in 1862 by Samuel Brannan, a Mormon settler and businessman.  Dominated by a single soil type - volcanic (or, as the successful petition for AVA status reads, "volcanic bedrock overlain with lava flows, ash-fall tuffs, welded tuffs, pyroclastic flows and mudflows"), Calistoga was listed in a viticultural census as long ago as 1893.  Calistoga, in the summer months, has the most dramatic diurnal shift in the Napa Valley, a 50°F (often more) day-to-night change in temperature.
Calistoga was granted AVA status in 2010.  The  contentious petition to the Tax and Trade Bureau (TTB) was initially proposed by Bo Barrett (of Chateau Montelena and Judgement of Paris/Bottle Shock fame) in 2003 and resulted in the temporary cessation of all AVA petitions until the TTB could complete a top-to-bottom review of AVA rules.  Sheesh!  Some people can get so tetchy over alcohol, money and politics.
Notable wineries for me in this AVA are; Clos Pegase Winery, Frank Family Vineyards (I recently had their sparkling wine, they call it Rogue Champagne, which I didn't even know they made and it was delicious), Larkmead Vineyards, Madrigal Family Vineyards, Schramsberg Vineyards and Vincent Arroyo Winery.
Eight down, eight to go