Science of dating trees

Before the advent of absolute dating methods in the twentieth century, nearly all dating was relative.

The main relative dating method is stratigraphy (pronounced stra-TI-gra-fee), which is the study of layers of rocks or the objects embedded within those layers.

When we stand in an ancient forest and look upwards, admiring the trees soaring above our heads, a common question often pops up – how long have these trees been here?

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By counting the dark ring segments, scientists can tell a tree’s age if the cross section of the trunk is complete. Based at the University of Arizona in Tucson, Douglass wanted to know how sun spot activity affected climate, and his research soon led him to pioneering tree-ring analysis.

Because the width of tree rings varies with growing conditions, scientists also learn about local climate during the tree’s lifetime by comparing the rings’ different widths. For instance, higher rainfall and a longer growing season produces a wider ring than a year with low rainfall and prolonged cold. Douglass was among the first to notice that trees in a geographic area develop the same growth-ring patterns because they experience the same climatic conditions.

These age-old guardians have fascinated people around the world since time immemorial, but for people in modern times, there is a great deal of curiosity about accurately calculating the age of trees. Short Answer: The only guaranteed method is knowing when the tree was planted, but tree growth rings are also highly accurate – to a point – in determining the age of a tree.

These growth rings can be counted when the tree is either alive or dead, in addition to various other non-invasive methods to roughly predict a tree’s age.

Now you will use the master chronology to date two samples of wood from ancient cliff dwellings. The left edge of each plot represents when the tree started growing.

The right edge of each plot represents when it was cut.

(den-droh-cruh-NOL-uh-gee) means “the study of tree time.” Usually called tree-ring dating, dendrochronology is a science based on the fact that every growth season a tree adds a new layer of wood to its trunk.

Over time, these yearly growth layers form a series of light and dark concentric circles, or tree rings, that are visible on cross sections of felled trees.

Visible rings result from the change in growth speed through the seasons of the year, thus, one ring usually marks the passage of one year in the life of the tree.

The rings are more visible in temperate zones, where the seasons differ more markedly.

The most popular method of determining the age of a tree is through dendrochronology – the science of dating tree rings – but this is a rather new field of study.

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