Science & Environment

How tree rings can help explain earthquake risk, and stem cells could regrow tooth enamel

By Jes Burns (OPB)
Oct. 19, 2023 1 p.m.

Five of the top illuminating, inspiring and just plain cool Pacific Northwest science stories from “All Science. No Fiction.”

A U.S. Geological Survey diver checks for bark buried in the sediment around a 1000-year-old Douglas fir stump on the Olympic Peninsula in Washington. The ancient wood will help scientists date the earthquake that created Price Lake.

A U.S. Geological Survey diver checks for bark buried in the sediment around a 1000-year-old Douglas fir stump on the Olympic Peninsula in Washington. The ancient wood will help scientists date the earthquake that created Price Lake.

Stephani Gordon / OPB

What tree rings can tell us about earthquake risk

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The Pacific Northwest is considered a seismically active area. Geologically speaking, earthquakes are the norm. Still, we haven’t seen a large quake here in a couple decades. That makes understanding our local network of fault lines and actual earthquake risk all the more difficult.

Researchers in the U.S. Geological Survey Earthquake Science Center in Seattle and the University of Arizona are looking much further back in the geologic record to understand our risk. The scientists collected preserved trees believed to have been killed by massive earthquakes along two shallow fault lines in the Puget Sound region from Lake Washington to Price Lake on the Olympic Peninsula (using an underwater chainsaw!).

One tree ring equals one year of growth. Consequently, the rings can be used as a timeline. And in certain years, cosmic radiation spikes are recorded in the rings. The researchers IDed one of these carbon 14 spikes — from A.D. 774-75 — in the tree rings they sampled. They then counted forward to the final ring on the preserved trees.

They found that the trees died between the years 923 and 924, meaning both of the faults triggered earthquakes at about the same time. It would have been one massive 7.8 magnitude earthquake or two slightly smaller quakes in relatively quick succession. The study suggests the two faults are linked in some way, and the resulting earthquake risk from these local, shallow faults is much higher than we thought.

Read the results in the journal Science Advances here.

Rebuilding tooth enamel

Tooth enamel is the hardest substance produced by the body. But once your teeth are formed, the cells responsible for making the substance — called ameloblasts —- take an early retirement and are never heard from again. Consequently, once your enamel breaks down, there’s no getting it back.

But now researchers at the University of Washington have made a discovery that could eventually change tooth repair forever. The scientists have figured out how to turn stem cells (basic cells that can transform into specialized cells under the right conditions) into ameloblasts. When grouped with other dental cells, the ameloblasts started producing rudimentary tooth enamel.

The researchers say these cells may one day be used to create “living fillings” that could patch up cavities with actual enamel. Or, further down the road, allow the production of lab-grown teeth that a dentist could use to replace lost or seriously damaged teeth in people.

Read more about the discovery in the journal Developmental Cell here.

In this lab image of a developing incisor released by the University of Washington, colors identify which genes are being expressed at each stage of development.

In this lab image of a developing incisor released by the University of Washington, colors identify which genes are being expressed at each stage of development.

UW Dental Organoid Research Team

Money to the people

There are countless reasons why people experience homelessness, but topping the list is something pretty straightforward: a lack of money. As a society we’ve devised ways to try to treat the crisis, but directly addressing the cash shortfall has never gained much traction.

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Research out of the University of British Columbia asked: What would happen if we handed over a chunk of cash — no strings attached? The researchers provided a one-time unconditional cash transfer of $7,500 Canadian dollars to 50 individuals experiencing homelessness in Vancouver, BC. They enrolled another 65 people in the study as a no-cash control. They then tracked spending, the number of days in shelter beds versus stable housing and other measures connected to personal wellbeing.

The researchers found that spending on food, rent and transportation increased for those getting the cash, although spending on things like alcohol, drugs and cigarettes showed no appreciable change. In addition, over the course of a year, the people receiving the cash spent an average of 99 fewer days in shelters, and 55 more days in stable (not transitional) housing.

The reduction in shelter stays alone created a savings to society of more than CA$8,277 — a net benefit of CA$777.

Read more in the Proceedings of the National Academy of Sciences here.

Ballots that were mailed in preparation for the Oregon Primary Election that took place on May 17, 2022.

Ballots that were mailed in preparation for the Oregon Primary Election that took place on May 17, 2022.

Kristyna Wentz-Graff / OPB

Postal speed and voter turnout

Oregon and Washington have some of the highest voter turnout rates in the country. It’s likely connected to how easy it is for us to vote by mail. Other states are turning to mail-in ballots now too, but some continue to put substantial restrictions in place, making voting more difficult.

A researcher at Washington State University examined factors that could affect voter turnout in vote-by-mail systems. He found that the speed of the local postal service played a surprisingly large role — especially in states where voter rules are more restrictive. The more efficient the mail delivery system, the more likely ballots arrive in time to be counted.

Looking at U.S. Postal Service efficiency rates (the average amount first-class mail delivered on time) and each state’s voting laws, the scientist calculated the impact on voter turnout. An efficient local postal service increased the likelihood someone would vote by nearly 3.5% in areas with more restrictive voting laws. The increase for easy-vote states like Oregon and Washington was positive, but far smaller. Although in a close election, even a small increase in turnout could shift the result.

Read more about the work in Election Law Journal here.

Pacific Northwest weather outlook

The planet is warming, and human-caused climate change is the primary driver. But what does that actually mean for future weather in the Pacific Northwest?

Researchers at Portland State University have used computer models and machine learning to get a peek at what’s to come under the global warming trajectory we’re currently on. What they found was a little surprising: The larger atmospheric circulation patterns that influence local weather are not expected to shift all that much, especially in winter. But the weather we experience because of those larger patterns will be warmer and often wetter than it is right now.

For example, we won’t have more insane heat dome events like the one over the Pacific Northwest in 2021, but the heat we get when they do happen will be more intense than it would be if we weren’t screwing up the climate. The amount of rain we get will increase as well — except in summer, when we need it most.

Read the paper in the Journal of Climate here.


In this monthly rundown from OPB, “All Science. No Fiction.” creator Jes Burns features the most interesting, wondrous and hopeful science coming out of the Pacific Northwest.

And remember: Science builds on the science that came before. No one study tells the whole story.

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