“Volcanoes of the Eastern Sierra Nevada”

Dendrochronology is a process that involves studying tree-ring growth and tree-ring dating in order to piece together a timeline of past events. These events are marked by changes in climate throughout our history, which are reflected in the size and coloration of tree-rings. Today’s technology, combined with tedious work being carried out by scores of persistent researchers, has allowed us to accurately date changes in climate far into the past. In fact, dendrochronologists have gathered data dating back nearly 9,000 years, all the way to 7,000 B.C.E., with help from the chronology created through studying and sampling ancient bristlecone pine trees and their dead wood, which can, and often does, remain intact for thousands of years, if left undisturbed by the numerous researchers and hikers who visit the few sites where these immaculate wonders exist and thrive. (Miller, 1995-2003) Discovered by A.E. Douglass of the University of Arizona, this technique was first implemented in the early part of the 20th century by botanists, foresters, and archeologists. Douglass noticed that during wet years, certain trees would produce wider rings than normal. In drier years, the rings would be much more narrow. Tree rings are created as new cells are produced starting at the beginning of the growing season. These new cells become the lighter colored portion of the wood when viewing a cross-section of a tree, and grow from the cambium layer in between the layer of old wood from the previous season and the outer bark of the tree. This separation of layers allows for the rings to be easily counted and dated. (Miller, 1995-2003) As shown in the graphic below, the early-wood of a living tree is made up of many cells with thin cell walls and large diameters, with a lighter appearance in color, as aforementioned. The late-wood has cells with thicker walls and smaller diameters, causing their color to be darker