Hi Don,

I see you've been doing your homework again. :-> I think sharing what we saw over last weekend might shed a little light on the Sonoma Volcanics, you might agree?

Don and I have taken a couple of trips to the local dump the past two weekends and though one might not think going to the dump would help one study geology, this is to the contrary in this area.

What we saw was a hillside that was excavated down about forty feet and so one can see exactly the layers of different soils. Approximately the top ten feet is brown soil, however, below that the entire area is all gray ash. We were very surprised to see this and marveled over it with each visit. When time is not so pressing we will go and take some photographs so we can share them and let you have a look at this excavation.

Just outside the town of Calistoga is the Petrified Forest. Somehow a volcanic eruption with much ash occurred and caused the petrification. However, to this day no one knows where this volcanic ash came from. Knowing this and having seen the excavation at the dump makes it quite obvious, it wasn't limited to just Calistoga. Calistoga is about 11 miles NE from Petaluma.

Also as a final note, I'm sure I've said before that most of the volcanic action in Sonoma County was a result of oozing volcanoes, however, there are many places which have huge volcanic rocks that were placed upon the land by explosive eruptions, so it appears further research into this realm should be undertaken in the future. Of course that's when funding returns.

Petra