Tree-Growth Rings Reveal Ancient History

The unearthing of ancient ruins gives scientists details about the history of our planet — but what about an ancient tree? Excavation of a geothermal power plant lead scientists to recently discover a magnetic event that occurred thousands of years ago. This could not have been possible without analyzing tree-growth rings.

The tree, called kauri, was unearthed in New Zealand and measured 8 feet in diameter and 65 feet long. Lying 26 feet beneath the earth, an examination of the trunk revealed a lifespan of around 1,500 years. It’s estimated that this tree was alive somewhere “between 41,000 and 42,500 years ago.”

A dramatic shift in magnetic fields links to “extinction events” as a result of climate change. Growth rings found on tree trunks keep track of different weather patterns and events that occur in the span of a tree’s life. According to scientist Chris Turney, studying the kauri tree gave scientists enough of the “detailed measurements of the radioactive form of carbon through the tree rings” to conclude a shift in magnetic fields occurred. Based on the evidence found on the tree, a shift in magnetic poles will happen again. Uncovering the kauri tree opened the doors to outstanding discoveries about the past and insight of the future.

cross section of a treeThe Meaning Behind the Rings

So, how do scientists read tree-growth rings to determine the climate changes recorded year after year?

The science of tree-growth rings, or dendrochronology, reveals different events that occur in a tree’s lifespan. The rings record changes in temperature, the age of the tree, and the rate in which the tree grows. The different colors of the rings each have their own meaning. “Thinner, darker ring(s)” occur in mid to higher altitudes due to colder weather which slows growth. “Light ring(s) of new growth to its trunk during the spring and early summer” reveal times of significant growth.

Tropical trees do not experience the same climate changes throughout the year. Their rings are difficult to see because they, “grow year-round adding wood to their trunk at an almost constant rate.” Due to the climate staying particularly the same, “trees from the tropics show little or no alternating dark and light growth patterns.” If the climate is particularly rainy, and the tree depends heavily on moisture, wider rings indicate an abundance of growth. Narrow rings reveal a dry spell in which the tree had very little growth.

According to the National Centers for Environmental Information, more rings on a tree result in more information scientists can extract regarding climate patterns. Larger trees reveal information dating back to hundreds or even thousands of years, a time before climate change was recorded with the accuracy of modern technology, as seen with the kauri tree.


Want to learn more about tree-growth rings and climate change? Check out this article!

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