Tree ring cross dating
The downslope parts of the rings grow wider than the upslope ones, and in studies carried out in Poland, Malgorzata Wistuba and colleagues found that those tilts are in evidence between three and fifteen years prior to catastrophic collapse.
It had long been known that three 9th century Viking period boat-grave mounds near Oslo, Norway (Gokstad, Oseberg, and Tune) had been broken into at some point in antiquity.
Some historical sources had reported the Qinghai route was abandoned by the 6th century AD: dendrochronological analysis of 14 tombs along the route identified a continuing use through the late 8th century.In this activity, you will use a digital software program called Image J to measure the width of digital tree-ring samples from the three sites that you already explored in Part 2.You will produce a time-series graph from this data and combine your measurements with those of your classmates to produce a preliminary tree-ring record for each of the three tree-ring sites.Tree-ring dating works because a tree grows larger—not just height but gains girth—in measurable rings each year in its lifetime.
The rings are the cambium layer, a ring of cells that lies between the wood and bark and from which new bark and wood cells originate; each year a new cambium is created leaving the previous one in place.
How large the cambium's cells grow in each year, measured as the width of each ring, depends on temperature and moisture—how warm or cool, dry or wet each year's seasons were.