You are right, spunky.
In addition, almost any forest service employee will laugh when you 'tell' him that trees only develop one ring a year.
In the tropics NO rings are produced.
In young pines, up to three may be produced annually, although two is more common.
Rings depend on rain and sun cycles. A warm spring followed by a cool, rainy summer, with an end of summer and beginning of autumn that is warmer and dryer (not terribly uncommon in the mountains) will easily produce two rings in most trees, as they will have two growth spurts. The second ring is almost always thinner than the first, which gives a good clue often overlooked by those involved in dating, that both rings were the products of one year.
I do urge those who are interested in this subject to take the time to enjoy the following links. Different arguments are presented:
http://www.mystae.com/restricted/stream ... ating.html
from here (http://geography.otago.ac.nz/Courses/28 ... asics.html) , which is a very good site explaining dendrochronology comes this reminder:
The growth of trees can be affected by slope gradient, sun, wind, soil properties, temperature and snow accumulation. The more a trees rate of growth has been limited by such environmental factors, the more variation in ring to ring growth will be present. This variation is referred to as sensitivity and the lack of ring variability is called complacency. Trees showing sensitive rings are those affected by conditions like slope gradient, poor soils, little moisture. Those showing complacent rings have generally constant climatic conditions such as a high water table, good soil, or protected locations.
also from that webpage is the following:
This principle is important to dendrochronology because ring widths can be crossdated only if one or more environmental factor become critically limiting, persists sufficiently long and acts over a wide enough geographic area to cause ring widths or other features to vary the same way in many trees.
The principle spoken of is uniformitarianism -- that things go on basically the same way they have since the beginning.
However there is something else to consideer. In our old home, we planted about eight birch trees in a small 'grove' outside the front door. They all started the same size, were all paper bark weeping European birches, and were all planted the same day.
Two were situated over the septic tank. The others were only a few feet away, to the west.
In fifteen years, the trunks of those over the septic tank were about six inches in diameter and the trees were at least fifty feet tall. Arborists used to stop by and ask us how we did that! The ones to the west ranged from 1-3 inches in diameter. When we moved, last spring, they ranged from about 30-30 feet tall. They received the same amount of water from the same sprinklers.
And NO ONE who has ever studied dendrochronology would, given cross sections or bores of these eight trees, have guessed they were from the same place, planted at the same time.
In other words, there are a LOT of factors affecting tree growth, including growing in the shade of other like trees. Dendrochronology is NOT something I would put any faith in at all! It's fun, but not necessarily at all accurate.
As far as the volcanoes go, it should be remembered that uniformitarianism does not apply here, either. There is evidence from the Pacific Ring of Fire that there have been times in the past when massive volcanism has occurred all at once.