Tree Rings Give Scientists Insight to Earthquake History

It’s something we’ve all probably heard through the grapevine – the ‘looming’ earthquake that is going to hit the Vancouver region. After the recent devastation on Japan, one may be led to wonder, how are the effects seen down the road? Will the anguish still be prevalent hundreds, or even thousands of years from now?

In a recent conversation with Tom Balakshin (a friend and avid geologist) about the earthquake history in the Pacific Northwest, he enlightened me on how scientists track the history of seismic activity – specifically noting an earthquake that occurred in Northwest Washington approximately 1000 years ago. Though physical traits such as an abrupt uplift in shorelines, and evidence of a deposition from a tsunami, one of the most fascinating discoveries looks past the land formations, and to the vegetation of the surrounding land.

Prehistoric rock avalanches (believed to be the product of forceful seismic activity) in the Olympic Mountains between 1000 and 1300 years ago caused surrounding trees and plants to be completely submerged in water – trapping them in by rock dams. Scientists were able to determine the trees that drowned during the avalanche by observing tree rings. Trees that were underwater showed patterns uncharacteristic of those in normal conditions, such as diminished wood quality and varying ring spacing due to the death of outer layers. Analysis of the dead wood allowed scientists to determine that the avalanche predated the last ring about 100 years, as well as also indicating which season the trees died in.

Who would’ve thought that the rings of a tree could not only tell age, but also the environmental conditions that were present at that time? Even though the memories of those victimized through these devastations never fade, this just goes to show the Earth itself has its own way of keeping track of these natural catastrophes.

Check out this brief video on how scientists actually use the rings to reveal the tree’s history!

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