How can you tell how old a tree is?

Scientists can tell the age of a tree by examining it. Researchers call this area of study dendrochronology, which is a combination of several Greek root words: dendro, meaning “tree”; chrono, meaning “time”; and ology, meaning “the study of.” Scientists have several ways to tell how old a tree is. First, they count the whorls around it. A whorl is the circular growth of branches in the same spot around the tree trunk. As the tree gets older, it will loose its whorls and markings will be left behind. They count from the bottom whorl up to tell how old it is. Sometimes, they will use a boring tool to drill into the core of the tree to tell its age. (A boring tool is a T-shaped tool with a long, thin hollow plug that drills into the tree to take a sample of the core.) Scientists count the rings on the sample to determine the age of the tree and then cover the hole to keep the tree alive. If a tree is cut down, they look inside the core for circles, called annual circles. The circles start off very small in circumference and get larger with each ring. Each ring represents one year of life for the tree researchers begin with the innermost part of the core (called the pith) and count outward toward the bark until they determine the age.


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