Since protons and neutrons weigh about the same, the atomic mass of ordinary carbon is 6 6 = 12.
The second goal is to collect new tree-ring specimens from back-country cliff sites that still contain datable wood.The ITRDB was initially established by Hal Fritts through the Laboratory of Tree-Ring Research at the University of Arizona through a grant from the US National Science Foundation after the First International Workshop on Dendrochronology in 1974.Specific information is required for uploading data to the data base, such as the raw tree ring measurements, an indication of the type of measurement (full ring widths, earlywood, latewood), and the location, but the types of data and the rules for accuracy and precision of the primary data, tree-ring width measurements, are decided by the dendrochronologists who are contributing the data rather than by the NOAA or another governing organization.It has a radio half-life (T 1/2) of 5,730 years and is a low energy beta emitter with a radioactive range in air of ten inches.It is produced currently at a fairly constant rate in the upper atmosphere through the action of cosmic radiation on Nitrogen-14.These rings are physical manifestations of the tree’s growth from the beginning of the year when the tree develops a wide thin-walled cellular structure and the end of the year as the tree’s cell structure changes in the fall and winter, creating light and dark fluctuations: ‘rings’ ~which extend outward from the tree’s heart. Changes in sunlight and water availability can further increase or decrease the width of a tree’s rings, providing valuable indicators for solar variations in the earth’s movement around the sun and other environmental indicators such as drought. By creating databases of rings with known dates, new samples can be compared to sets of previously collected samples in order to find the time period in which the rings from the new sample and the database match each other.Dendrochronology is used in a variety of modern studies, ranging from environmental studies on the decline of species of wood in certain areas, like the deforestation of the area around the ancient Mayan city of Tikal.In addition to the five well known Mesa Verde cliff dwellings that are open to the public (Balcony House, Long House, and Step House on Wetherill Mesa; Cliff Palace and Spruce Tree House on Chapin Mesa), there are nearly 600 documented cliff sites within the park boundaries, ranging from small masonry granaries, to large cliff sites.Of these, roughly 250 are known to contain wood, but only about one tenth (24) of those contain wood from secure contexts that are likely to be datable.Since 2006, I have been involved in an archeological tree-ring dating program that focuses on collecting samples from some of the last datable beams remaining in the park. The first goals is to ensure that all previously collected but unanalyzed tree-ring specimens collected at Mesa Verde NP have been analyzed and, hopefully, dated by specialists at the Laboratory of Tree-Ring Research (LTTR), University of Arizona.Approximately 400 previously unanalyzed specimens have been located and sent to the LTTR.