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Source: The Conversation – USA – By Barbara Clark Smith, Curator, Division of Political History, Smithsonian Institution

As the nation observes its 250th birthday, historians can help settle one present-day dispute: Is the United States a democracy or a republic?

For years, advocates have argued the point.

Yet the question itself is misleading. It assumes that the categories constructed by political theorists neatly describe actual practice.

As a historian of early America, I know this nation has always been unwieldy, its institutions hammered out from conflicting ideals and the pragmatic lessons of lived experience. Just as Britain today is both a monarchy and a democracy, so the U.S. has always been a hybrid.

Ideals of both republicanism and democracy have shaped the nation. To understand how requires a history lesson.

No purity

Let’s start with a famous definition. Here is the often-quoted “Father of the Constitution,” James Madison, urging Americans to ratify the new frame of government proposed by the Constitutional Convention in 1787.

In Federalist essay No. 10, Madison distinguished two sorts of governments for his readers.

One was a “pure democracy,” which he described as “a society consisting of a small number of citizens, who assemble and administer the government in person.” A New England town meeting might qualify for this definition, where voters assembled to choose town officers and approve local bylaws.

The other type of government was a “republic,” defined as “a government in which the scheme of representation takes place”
– meaning where the people’s chosen representatives made governing decisions for them.

That seems cut and dried. Surely no one thought the entire population of 13 states could work like a town meeting.

But Madison here was saying only that the possibility of a “pure” democracy was impractical. He was by no means banishing all democratic ideas and institutions.

As the French theorist Montesquieu had noted, republics were of varying sorts. Some republics were aristocratic, controlled by a relative few who were set above the rest. Other republics were democratic, engaging many more in the ongoing affairs of government.

What was at stake in the U.S. in 1787 wasn’t a “pure” democracy nor a “pure” republic. The issue was how aristocratic – and how democratic – the American scheme of representation would be.

Who would be represented – the many or the few?

‘Actual’ representation

America had never been the home of an aristocracy in the British sense. Besides, the Revolution had discredited the very idea of hereditary power. There would be no House of Lords, filled with titled men born into political power and a special set of legal privileges denied to ordinary people. The people alone would be sovereign, and all authority to govern derived, directly or indirectly, from them.

Even so, the problem of aristocracy remained. After all, it had been the lower house of Parliament – the House of Commons, not of Lords – that had sparked the imperial debate when it tried to tax and legislate for the Colonists.

Not nobility, members of the Commons still formed a remote and ambitious elite. None was elected by American voters or even necessarily informed about the Colonists’ lives. Apologists for Parliament claimed that the Commons “virtually” represented the Colonies anyway.

But the Colonists watched the Commons ignore American grievances while favoring private interests – East India Company shareholders, for example – that served wealthy British gentlemen such as themselves.

Many concluded that the members of the House of Commons did not “actually” represent either the poor of Britain or the growing population of the continental Colonies.

In contrast, “patriot” Americans pointed to the legislative assemblies established in each colony soon after its founding.

Needing to attract British settlers, and following the British model, each colony established an elected house of the legislature to provide a check to governors and upper houses that were appointed by the king or a wealthy Colonial proprietor.

Law and custom required that delegates to these assemblies live among their constituents. Although they were men of some fortune and standing in their districts, assemblymen might plausibly “actually represent” their lesser neighbors.

In the lead-up to the Revolution, patriots used new measures to ensure their representatives’ fidelity: They called for vigilant popular oversight of government decision, publicized those decisions in the press, wrote constituent instructions for legislators and winnowed out noncompliant officeholders at election time.

Individual and collective liberties

With independence, Americans created a patchwork of new, representative state governments. South Carolina empowered its wealthy planter elite by setting a high property-holding requirement for voters and a higher one for officeholders. Pennsylvania and Vermont adopted unprecedentedly democratic systems that allowed a large proportion of the white male population to participate in government.

By 1787, some Americans thought there was too much popular democracy – too much power given to nonelite members of society, especially within state governments.

The Constitution adopted restraints on democracy – a Senate appointed by state legislatures, an electoral college that put the choice of president at a remove from the people, a supremacy clause that allowed national laws to supersede, or contravene, state laws.

At the same time, a commitment to democracy was also evident in the U.S. frame of government.

The Constitution set no property requirements for federal officeholders. It left suffrage requirements up to individual states, some of which already extended the vote to all male taxpayers.

Equally important, the ratification process produced a consensus that a bill of rights was necessary to protect ordinary people’s rights and liberties from government overreach.

These first 10 amendments would defend individual rights but also collective rights of the people, such as their right to assemble, to petition the government or even to change it.

The Bill of Rights also protected a free press. It ensured that ordinary free men would still serve in armed militias when their state needed protection. And they would still sit on grand and petit juries to enforce the law or prevent its overreach.

These were the sorts of institutions that the lawyer John Adams called “democratical.”

More and better democracy

Within a few decades, the common phrase for the American system became “democracy.”

Madison had been inconsistent in how he used the term. In the 1790s and 1800s he called himself a “Democratic Republican,” in opposition to the allegedly aristocratic party, the Federalists.
Decades later, Madison was frustrated when pushed to define the U.S. government more precisely. Ordinary “political vocabulary” fell short, he wrote. The American system was “so unexampled in its origin, so complex in its structure, and so peculiar in some of its features” that it was best understood as something new.

How aristocratic? How democratic? The question of 1787 has returned repeatedly to face Americans.

Elites with aristocratic aspirations have repeatedly tried to build permanent governing hierarchies. American history is partly the story of these contests – Free-Soilers against a slaveholding elite, reformers against wealthy “barons” of the Gilded Age, critics of inequality against billionaires who shape government policies today. In such cases, Americans have often turned to more and better democracy, their necessary resource for pressing their political leaders to actually represent the people.

Following Madison’s advice, Americans today can refuse to be misled into describing the U.S. in a single, inadequate term.

They might prize both of these historic commitments: to a republic that insists on the people’s right to be represented rather than ruled, and to a democracy that ensures that ordinary people might collectively make it so.

Barbara Clark Smith does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

– ref. A democracy or a republic? History shows that some Americans are asking the wrong question – https://theconversation.com/a-democracy-or-a-republic-history-shows-that-some-americans-are-asking-the-wrong-question-274798

Source: The Conversation – USA (2) – By Moncef Krarti, Professor of Civil, Environmental and Architectural Engineering, University of Colorado Boulder

Somewhere between 5% and 7% of U.S. households have rooftop solar panels. Many more Americans want them, but high costs, building locations and landlord restrictions are key obstacles.

As someone who has designed and evaluated a wide range of building energy efficiency technologies, including integrated photovoltaic systems, I know that other options are available elsewhere in the world – and are becoming available in the U.S. Plug-in solar systems, also referred to as balcony solar systems, are alternatives to rooftop panels that still generate electricity from sunlight, but without complex and expensive installations.

Plug-in solar systems are designed to be used without requiring specialized technicians, construction permits or permission from electricity utility companies. A typical system consists of small photovoltaic panels that can be placed on a balcony, in a backyard or on a deck or roof area. They are connected to the home’s electrical system by simply plugging them into a regular power outlet.

European popularity

In Europe, systems like this have been legal for more than a decade. They are wildly popular, especially for renters who do not have permission to install permanent solar panels on their buildings.

In Germany, the introduction of balcony solar raised the share of households with solar panels to about 10%.

Germans can buy plug-in solar kits in local retail stores and set them up quickly at home, with no help or oversight from technicians or utility companies. Estimates find that with current electricity prices in Germany, the systems generate enough power to pay for themselves in less than three years.

Legal changes afoot in the US

In the U.S., the main barrier to widespread availability and adoption of plug-in solar systems is that current laws and regulations do not distinguish them from larger rooftop panel systems.

In most cases, solar panels on buildings that are connected to the power grid must be installed by professionals, because they typically require additional equipment that prevents too much of the home-generated power from entering the grid. This process also requires a permit from a state or local government.

For balcony solar systems, the grid-protection equipment is built in to what consumers buy at the store. But in most states, the laws don’t recognize a difference and still require permits and professional installation for any solar panels at all.

However, in 2025, Utah passed a law that removes those requirements for plug-in solar panel systems that generate less than 1,200 watts of power. Maine has enacted a similar law, and one in Colorado awaits the governor’s signature. Both are slated to take effect at different points in 2026. The Vermont Senate passed one too, and the state’s General Assembly is considering it now. And lawmakers in 25 other states are considering similar legislation.

In addition, in early 2026, UL Solutions, an independent safety certification company, announced a new standard for plug-in solar systems in the U.S., which can help consumers feel confident they are buying something that is safe for them to use in their homes.

Costs and benefits

The potential benefits of balcony solar systems vary primarily with the local cost of electricity. Buying these systems can cost between US$1,200 and $2,000, but they can generate enough power to save several hundred dollars in electric bills each year.

They can’t power a whole home, but they can power relatively low loads, like refrigerators, LED lights, laptop computers, phone chargers, televisions and fans, even when a grid power outage occurs.

Depending on their configurations, balcony solar systems can offer additional benefits. Mounting them to movable bases that track the Sun’s path through the sky can boost power generation. Mounting the panels on overhangs can create shade, reducing the need for air conditioning, especially in hot climates.

Adding battery storage to balcony solar systems can also help households store extra energy from the daytime and use it at night, further lowering their utility bills, though buying batteries would raise the costs.

I expect U.S. demand for balcony solar systems to be significant, especially in places with lots of sunlight and high electricity prices. Householders will still need to select their equipment and its location carefully to maximize their power generation and cost savings.

Moncef Krarti does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

– ref. How balcony solar can help renters and homeowners save money – https://theconversation.com/how-balcony-solar-can-help-renters-and-homeowners-save-money-281620

Source: The Conversation – USA (2) – By Qingqing Yang, Research Scientist of Education, University at Albany, State University of New York

About 1 in 4 elementary students in the United States reports being bullied at least once during a given school year.

Children who are frequently bullied are more likely to struggle in school, experience poorer physical health and face higher risks of depression, anxiety and substance use as they age. These effects can persist into adulthood, contributing to unemployment and financial instability.

Most bullying research focuses on children’s individual traits, such as whether they display signs of aggressiveness or whether their parents physically punish them at home. Children who experience non-physical but harsh or punitive discipline at home may also be more likely to engage in bullying.

Overall, bullying rates vary widely across classrooms.

New research I conducted with colleagues at the University at Albany and other schools finds that classroom environments play an important role in bullying. Children have a slightly higher risk of being bullied when they are in classrooms that are frequently disrupted by student misbehavior, or are chaotic – even after considering individual factors, like a child’s personality and family experiences.

Our findings show that bullying is not only influenced by who children are, but by the environments they are exposed to at school.

Evaluating classroom environments

We analyzed teacher and student surveys collected by the U.S. Department of Education’s National Center for Education Statistics from 2014 through 2016. This nationwide data looked at teachers and children who were in the third, fourth and fifth grades.

Teachers evaluated whether their classroom environment was disruptive by reporting how many students struggled to pay attention, behave appropriately or follow instructions. They also gave an overall rating of classroom misbehavior. Students reported how frequently they were bullied, including being teased, called names, intentionally excluded from play or subjected to physical aggression like pushing and hitting.

To make sure the findings reflected a real pattern and not a coincidence, we used a statistical method that tests whether the same students reported more or less bullying when they were in more or less disruptive or chaotic classrooms across different grades.

In other words, we looked at how changes in a child’s classroom environment were linked to changes in their own experiences of bullying. This approach helps separate the effects of a classroom environment from differences between children’s personal characteristics and experiences at home.

Reducing classroom chaos

Traditionally, anti-bullying efforts target individual students’ behaviors or family dynamics. Interventions might include teaching social skills or giving parents more support and training in responding to their kids’ behavior.

However, programs that target only bullies or victims are not always effective at preventing bullying.

Our findings suggest that reducing classroom chaos is a viable path toward decreasing bullying. The effects we observed are small but consistent, meaning the pattern held even under strict tests. We think awareness of this connection could help make a meaningful difference across a classroom.

Teachers reporting that classrooms are disruptive reflects both students’ behavior and the challenges teachers face in overseeing a classroom full of students. These challenges include keeping students focused, encouraging appropriate behavior and ensuring that students follow instruction.

In more chaotic classrooms, students may be talking over one another, leaving their seats or struggling to stay on task. This creates an environment where it is harder to maintain order and can lead to a “spillover effect,” in which negative behaviors spread. As a result, aggression can become more common and even be reinforced within the peer group, increasing the likelihood of bullying.

Managing a chaotic classroom can also be demanding and emotionally exhausting for teachers. They must spend more time handling disruptions and keeping students on task. This can limit not only the time and energy they have to prevent or respond to bullying but also their ability to notice it in the first place.

At the same time, it is important to recognize that chaotic or disruptive classrooms often reflect broader challenges, such as large class sizes, limited school funding and students dealing with difficulties outside of school, such as poverty, housing instability or trauma.

Supporting educators with professional development options, like offering training on how to support students emotionally and connecting rules to positive or negative consequences, can help to reduce the likelihood that children will misbehave in class.

The impact of classroom chaos also intersects with broader social inequalities.

Previous studies show that students from low-income families, racial and ethnic minority backgrounds and those with disabilities face higher risks of being bullied. Our study helps explain why: These students are more likely to be in chaotic classrooms.

This is not because they are deliberately placed in such environments, but because they are more likely to attend schools with low budgets that might have large class sizes, fewer experienced staff and less specialized kinds of support for students.

Next steps

Bullying is a serious issue that often occurs in elementary schools, making prevention an urgent priority. Our findings shift the focus from students’ individual characteristics and backgrounds to the broader classroom environment.

Our findings suggest that reducing classroom chaos may be one promising approach to addressing bullying. Further research is needed to identify additional classroom factors that capture the complexity of classroom dynamics and how they contribute to bullying.

Qingqing Yang receives funding from Spencer Foundation.

– ref. Bullying is common in elementary school – and it’s more likely to happen in classrooms that are chaotic – https://theconversation.com/bullying-is-common-in-elementary-school-and-its-more-likely-to-happen-in-classrooms-that-are-chaotic-280872

Source: The Conversation – USA (2) – By Marie Helweg-Larsen, Professor of Psychology, Dickinson College

Much has been written about Denmark’s consistently high scores in global happiness rankings, so it might not come as a surprise that Denmark is also rated the best place to raise children, according to U.S. News and World Report. The small Scandinavian nation also scores near the top for child well-being, a measure of physical health, mental health, education and social relationships.

Government policies like generous parental leave, robust public investment in education and universal healthcare have certainly played a role in these rankings. Danes also score high on social trust, with 74% of Danes agreeing that most people can be trusted, whereas only 37% of Americans say the same.

But another factor could be contributing to Danish children’s well-being: They’re often encouraged to take part in risky, unstructured play.

This might seem at odds with a parent’s desire to do what they can to keep their kids safe. But as a native of Denmark and a psychologist, I’ve explored how the country’s hands-off parenting style may be one key to raising more resilient, self-reliant kids.

The benefits of unstructured play

Danes have two words for the English word “play.” There’s “leg,” which refers to unstructured play; and “spille,” which is used for games or activities with pre-established rules, such as playing soccer, chess or the violin.

Each type of play has benefits. But studies have shown that unstructured, spontaneous play requires more compromise and creativity, since kids have the freedom to change or make up the rules. Children learn to take turns and work through problems – skills that are harder to develop when adults step in or when the rules are predetermined.

Then there’s risky play, a form of unstructured play that involves exciting activities with a possibility of physical injury. On a playground, this might mean climbing tall towers, going headfirst down a slide or roughhousing. Off the playground it might involve building a fire, swimming, biking or using tools like saws, hammers and knives.

Norwegian early childhood education researcher Ellen Beate Hansen Sandseter
pioneered the study of risky play. She’s explored its evolutionary functions – specifically, how it helps children become competent, independent adults. Other researchers have shown that risky play boosts mental health by teaching children to be more resilient and manage their emotions.

Positive risks vs. negative ones

When it comes to risky play, it’s useful to distinguish between positive risks and negative ones.

On a playground, a positive risk is a challenge that a child can recognize and decide to take. They can weigh if they want to try a zip line, or determine when they’ve reached their limit while ascending a climbing net for the first time. The goal is for the child to explore boundaries and learn to manage emotions like fear and anxiety. Sure, there’s the risk of scrapes and bumps. But success can breed more self-confidence.

A negative risk, on the other hand, is a danger that the child does not have the experience or knowledge to foresee. Using playground equipment that has rotted wood, wielding a tool like a drill without proper instruction or swimming in rapids could lead to serious accidents without any learning benefits.

Many playgrounds in Denmark are designed to encourage positive risks. The country has become known for its junk playgrounds, the first of which was created during World War II. These are play areas built with discarded tires, boards and ropes instead of fixed equipment. Kids are often given access to tools so they can build structures and remake the space on their own terms.

The point ultimately isn’t to put kids in harm’s way. It’s to let them explore on their own, test their limits and try new things.

The competent child

Of course, no parent wants to see their child get injured. But research suggests that Danish parents and American parents have distinct perceptions of risk – and different thresholds for what they consider dangerous.

One study compared U.S. and Danish mothers’ reactions to pictures showing a child engaged in 30 different types of play, such as sledding, biking, using a saw to cut wood and climbing a tall tree. It found that Danish mothers, on average, were more likely to say that they would be comfortable with their own child in these situations. In subsequent interviews, Danish mothers were also more likely to talk about practicing risky activities with their kids, such as how to use tools. (One described how she showed her 5-year-old to use an axe to chop wood.)

In fact, Danish daycares often teach children how to use a sharp knife, with some handing out knife diplomas once children have learned the skill. Learning how to ride a bike, meanwhile, can be practiced on what are known as “traffic playgrounds,” which have child-sized streets, bike lanes, traffic lights and signs.

This difference in risk tolerance could stem from differences in parenting approaches. Danish parents see their children as innately competent, meaning they trust their ability to navigate risks and challenges. Adults, in turn, try to create environments for these natural competencies to flourish; they work to encourage cooperation instead of using control.

In contrast, American parents are more likely to see kids as vulnerable and in need of protection. Mental health is a major concern, with 40% of American parents extremely or very worried that their child will suffer from anxiety or depression at some point, according to a 2023 Pew Research Survey. Somewhat ironically, kids who have less independence are more likely to have mental health challenges.

When permissiveness goes too far

Letting kids take the lead can work well, but sometimes they can’t see or anticipate certain risks.

Danish youth, for example, drink more alcohol than their European peers. A recent survey showed that almost 7 out of 10 Danish ninth grade students had consumed alcohol in the last month, and 1 out of 3 had been drunk in the past month. One study found that Danish parents who are stricter about alcohol consumption are less likely to have teens who frequently drink. Danish culture, overall, has a very permissive attitude toward drinking alcohol, so those parents are few and far between.

Furthermore, Danish 10-year-olds have among the highest rate of smartphone ownership in the world, even as studies have shown that smartphone ownership among children is associated with higher rates of depression, stress and anxiety, as well as less sleep.

But these statistics don’t relate to risky play, which even emergency physicians and nurses champion. Instead, they show how permissive parenting styles can sometimes have negative effects.

The benefits of risky play – like learning to tolerate failure, distress and uncertainty – aren’t just important parts of being a kid. They’re important parts of being human.

Marie Helweg-Larsen has received funding from the National Institutes of Health.

– ref. Denmark’s ‘hands-off’ approach to parenting could offer a blueprint for raising more resilient, self-reliant kids – https://theconversation.com/denmarks-hands-off-approach-to-parenting-could-offer-a-blueprint-for-raising-more-resilient-self-reliant-kids-281485

Source: The Conversation – USA (3) – By Christian Franck, Bjorn Borgen Professor of Mechanical Engineering and Director of the Center for Traumatic Brain Injury, University of Wisconsin-Madison

Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to CuriousKidsUS@theconversation.com.

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Why do you have to wear a helmet when you’re skateboarding? – Artie, age 13, Queens, New York

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Back when I was 13, I was an avid skateboarder – the kickflip was my go-to trick. And I didn’t see why I needed to strap on a helmet before practicing my ollies.

But now, doing the work I do, I get it.

My research is centered on understanding how physical forces cause brain injury and how to best protect against it. So I spend a lot of time thinking about how the brain gets hurt and how to improve helmets. This includes work focusing on protecting members of the United States military in training and active combat zones.

So why is it so important to wear a helmet when skateboarding, and also riding your bike, and really any sport or activity where your head could get hurt?

Your very own supercomputer

Inside your head sits probably your most amazing organ – your brain. It allows you to do everything you love, such as tasting ice cream, watching movies, listening to music and, of course, skateboarding.

Your brain is the world’s mightiest supercomputer. Everything it does requires billions of tiny brain cells, called neurons, working together in unison. These cells send messages to the rest of your body that regulate everything from body processes you’re not even aware of – such as your heartbeat – to moving your muscles, to helping you think and talk.

Some researchers estimate that humans have about 86 billion neurons, although scientists are still working on finding the exact number. That’s more than 10 times the number of all the people living on earth. And they’re all crammed inside a space the size of a melon, working together tirelessly, day in and day out.

Of course, your brain is not just made up of neurons. There are a lot of other cells supporting the neurons, including astrocytes and microglia, which are important helper cells to the neurons.

But as busy as your brain cells are, they are also incredibly soft and squishy. In fact, your brain has the consistency of jello. And like jello, it is very vulnerable, especially to physical forces, such as a fall or a sudden jolt.

The physical forces of a fall

Now, you might be thinking, doesn’t my skull protect my brain? And, yes, it does offer some protection. But your skull is a layer of cortical bone only about .28 inches (7 millimeters) thick, making it a useful barrier that prevents dirt and other objects from getting into your brain, but it’s too thin and too stiff to keep your brain safe in case of a fall while skateboarding.

Why is that? It helps to break down what happens when your unprotected head hits the pavement: Upon impact, your skull deforms, or changes shape, and often rotates. But your skull is not capable of fully absorbing that impact. So the remaining energy is transferred through the hard bone of your skull and absorbed by your soft, squishy brain.

Imagine squeezing and wiggling a block of jello to change its shape. This is similar to what happens to your brain: Like the block of jello, when your skull deforms, your brain can be compressed and change shape. This can cause your neurons to stretch and move in ways they aren’t designed to, causing damage.

This is why wearing a helmet is so important. If you look at your helmet, you will see that it has two parts – an outer shell that is usually hard and an inner shell liner, usually made from stiff foam. The shell is meant to protect your brain from penetrating objects. It also holds the liner, which is there to absorb most of the energy from an impact so it doesn’t reach your brain.

Recovering from a brain injury

If you fall off your skateboard and you’re not wearing knee and wrist pads, you might skin your knee or break your wrist. But unlike your skin and bones, your brain doesn’t tend to heal easily.

Without a helmet, much of the energy from your fall gets absorbed by your brain. Depending on the amount of energy that enters your brain, your brain cells can be injured. Even a mild traumatic brain injury, such as a concussion, can cause significant damage to the cells inside your brain. This could mean that you lose some of those brain cells or that they won’t work properly anymore.

If too many of your brain cells are damaged or die, you may lose really important brain functions, such as walking, talking or seeing clearly. The brain cells you have now are largely the same ones you had when you were born. And once you lose them, there is no way to get them back.

When you lose brain cells, the remaining cells have to work extra hard to keep your brain function intact. While modern medicine has gotten really good at repairing most of the tissues and organs in your body, the brain is still a major challenge for researchers.

This is why researchers like me spend so much time trying to find ways to protect the brain from trauma: A protected brain doesn’t need to be healed. In fact, according to one study of bicyclists, those who wear helmets are 65% to 88% less likely to get a brain injury.

So next time you step onto your skateboard, remember that you need your brain to do all the amazing things it does for you, and do what you can to protect it. Helmet on!

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Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to CuriousKidsUS@theconversation.com. Please tell us your name, age and the city where you live.

And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.

Christian Franck is director of the Office of Naval Research sponsored PANTHER program through which his research group at UW-Madison receives funding.

– ref. Why do you have to wear a helmet when you’re skateboarding? – https://theconversation.com/why-do-you-have-to-wear-a-helmet-when-youre-skateboarding-279956

Source: The Conversation – USA – By Yinchu Li, Ph.D. Candidate in Marine Geology, Georgia Institute of Technology

Not all earthquake faults behave the same. Some stick and snap, causing earthquakes. Others move slowly over time.

For years, the leading explanation for slow-moving faults has been that high-pressure fluids along the fault lubricate it, allowing the slabs to slide steadily rather than building up stress until that stress is eventually released in a large, destructive earthquake.

But in a new study of the Shumagin Gap, a quiet section of the Alaska-Aleutian subduction zone – the area where one tectonic plate dives below another – my colleagues and I found that the fault does not contain enough fluid to explain why it slides slowly. Scientists may need to rethink this assumption about subduction zones around the world.

Pinning down why faults creep matters for how scientists build models of the world’s most powerful earthquake zones to assess long-term earthquake and tsunami hazards, from Alaska to Japan to the Pacific Northwest. Knowing how earthquakes are likely to behave is essential for helping communities decide where and how to build homes and other infrastructure so they can withstand an earthquake and tsunami.

How earthquakes happen along faults

An earthquake fault is a break in Earth’s outer rock layer where two blocks of rock slide past each other. The way they slide determines what kind of shaking, if any, reaches the surface.

Some faults are “locked.” They do not budge until stress builds to a breaking point, then they release it all at once in a sudden rupture. This is what happens during most damaging earthquakes. Other faults “creep.” They glide past each other steadily, releasing stress gradually.

The biggest and most destructive earthquakes on Earth happen along subduction zones, where one tectonic plate dives beneath another. The Alaska-Aleutian margin, the Japan Trench, the subduction zone off Chile and the Pacific Northwest’s Cascadia zone are all examples. When a locked patch of a subduction fault suddenly slips, the seafloor can jolt upward and a tsunami can follow.

A quiet fault challenges a common assumption

Deep underground, fault behavior is hard to see directly, especially offshore where faults often sit beneath kilometers of seawater and sediment.

Scientists rely on measurements from GPS stations, seismometers and seafloor sensors, and then build computer models of what must be happening below. For decades, the leading explanation for creeping faults has been that high-pressure fluids along the fault reduce friction, the way a film of water causes tires to hydroplane.

Testing that idea requires seeing the fluids, and that’s where our team came in.

We use marine electromagnetic imaging, a method that maps how easily underground materials conduct electricity. A ship tows an instrument close to the seafloor, sending electromagnetic signals into the rocks below, while other instruments on the seabed record the response. Different materials beneath the seafloor conduct electricity differently, and that shows up in the measurements. Because salty water conducts electricity very well, the method is especially good at mapping where fluids are and where they aren’t.

We surveyed a 75-mile (120-kilometer) stretch of seafloor across the Shumagin Gap, a section of the Alaska-Aleutian subduction zone that has been creeping for more than a century. The Shumagin Gap had long been considered a quiet part of the margin, even though neighboring segments have produced magnitude 8 and larger earthquakes.

To our surprise, the fault at the Shumagin Gap was not as fluid-rich as the leading explanation would predict.

Our images show that the shallow part of the fault, closest to the ocean, has little open space in the rock for fluid to occupy. And the fluid that is there is under roughly normal pressure, not the high pressure that the “slippery fluid” model predicts.

The fault surface is bumpy and rugged. The upper plate appears to be a patchwork of stronger and weaker material, and we found possible pathways where fluids may drain into the rock above the fault.

In other words, this quiet fault isn’t quiet because it’s well lubricated. Something else is keeping it stable, most likely a combination of rough fault surface, varying rock strength and, in some places, fluid.

What this means for assessing earthquake risks

Our findings about this fault have consequences for assessing earthquake and tsunami hazards more broadly.

Many models lean on the idea that fluid pressure helps determine whether a subduction fault slips suddenly or creeps. If fluid isn’t the main control keeping the Shumagin Gap quiet, other quiet faults might similarly lack fluid, raising questions about how stable those faults really are.

Understanding these mechanisms matters for assessing coastal communities’ earthquake and tsunami risks. A shallow slip near a trench is what drives the most destructive tsunamis. Tsunamis from Alaska–Aleutian earthquakes have reached distant coasts before. Large earthquakes in 1946, 1957 and 1964 generated tsunamis that damaged the coasts of Hawaii and California.

As our results show, there isn’t a single, simple story explaining slow-sliding faults. More and better offshore data will help scientists more accurately assess earthquake and tsunami hazards around the world and help communities well beyond Alaska prepare.

This research was funded by the National Science Foundation under grants OCE-1654652 and OCE-1654619.

– ref. A quiet Alaska fault is missing the fluids scientists expected – and it’s changing what we know about earthquake zones – https://theconversation.com/a-quiet-alaska-fault-is-missing-the-fluids-scientists-expected-and-its-changing-what-we-know-about-earthquake-zones-281510

Source: The Conversation – USA – By Idan Shalev, Associate Professor of Biobehavioral Health, Penn State

Imagine receiving a test result that tells you your body is biologically five years older than your chronological age. You exercise regularly, get good sleep, eat healthy meals and have a happy personal life. What have you been doing wrong? Can this test be trusted?

Dozens of companies are marketing products that promise to reveal a person’s “true” biological age – that is, how well your body is functioning – for a price ranging from around US$30 to over $1,000. These products are based on epigenetic aging clocks, which are research tools that estimate age based on a person’s DNA. These clocks are reshaping how scientists study aging and how the public thinks about it.

But while epigenetic clocks are highly effective research tools to study aging at the population level, they aren’t designed to make claims about the health of individuals.

We are biobehavioral health scientists who study how early development and environmental factors across the lifespan shape biological aging, influencing health and disease decades later. As researchers who use epigenetic clocks in our work, we have found them to be highly informative tools when studying large numbers of people. But these clocks can provide faulty results at the individual level, and they do not meet the standards required of common medical tests.

What are epigenetic clocks?

Measuring reversible chemical changes to DNA, known as epigenetic marks, can provide information about how your body is aging.

Using DNA obtained from routine blood draws, researchers can measure millions of these epigenetic marks in an individual. Running statistical algorithms on this information can produce a single value that represents that person’s epigenetic age, analogous to chronological age.

Epigenetic clocks work because the chemical marks on DNA can shift over time and are influenced by lifestyle, stress and the environment. These changes capture aspects of aging that chronological age alone may not reflect.

In this way, epigenetic clocks help scientists identify the experiences, exposures and behaviors that may accelerate or slow biological aging.

Not for individual health decisions

Why can’t epigenetic clocks provide reliable results about biological age for individual people?

First, there are dozens of different types of epigenetic clocks, each designed for a specific purpose. Some are used to predict a person’s age, while others are used to predict how fast someone is aging or how many years until they die. These different clocks do not always agree with one another, even when used on the same person.

Second, epigenetic changes are dynamic, making age predictions sensitive to short-term fluctuations in diet, environmental exposures, illness, time of day and other transient factors. As a result, estimated age could vary substantially depending on when someone is tested.

Third, constructing epigenetic clocks is technically challenging, and there is no established gold-standard method for generating clocks across laboratories. For example, testing epigenetic age in saliva versus blood samples can yield substantially different results for the same person. The technologies used to measure epigenetic marks have also evolved over time and will likely continue to improve. As these methods change, the original algorithms designed for specific measurement platforms may not perform the same way.

Fourth, scientists do not universally agree on what aging means, in part because it is a very complex process. Reducing that complexity to a single number, such as an epigenetic age, can be misleading.

Finally, epigenetic clocks are influenced by a person’s history of trauma, discrimination and early life adversity. This makes their use at the individual level potentially problematic. On average, marginalized communities tend to show signs of accelerated aging when assessed with epigenetic clocks. If insurance companies began using epigenetic age estimates to set premiums, many people could face higher costs for biological differences shaped by circumstances beyond their control, potentially deepening existing health disparities.

Studying how aging unfolds over time

While epigenetic clocks are not appropriate tools for individual health decisions, this does not mean they lack value.

Researchers have used epigenetic clocks to discover lifestyle habits that can, on average, slow down aging. Some examples include reducing daily calorie intake, exercising regularly, maintaining a healthy diet, getting enough sleep and avoiding smoking.

Epigenetic clocks can also help test new drug therapies aimed at slowing down specific aging processes. For example, researchers have shown that rapamycin, a drug connected to various aging processes, can reduce the epigenetic age of human skin cells. There is also some evidence that a treatment designed to regenerate the thymus may slow or even reverse epigenetic aging after one year of treatment. However, researchers have seen these effects only when looking at groups rather than individuals.

Epigenetic clocks are helping scientists advance scientific research on the aging processes, but they aren’t medical tests to measure individual health. In the future, epigenetic measurements may play a useful role in guiding personal health decisions. But for now, epigenetic clocks sold as biological age tests are best used and refined by researchers who are studying populations rather than individual people.

Idan Shalev receives funding from The National Institutes of Health.

Abner Apsley receives funding from the National Institutes of Health and the National Science Foundation.

– ref. Biological age tests reveal what slows or hastens aging – but they’re useful only for researchers, not consumers – https://theconversation.com/biological-age-tests-reveal-what-slows-or-hastens-aging-but-theyre-useful-only-for-researchers-not-consumers-275974