Why the earth quakes – a closer look at what’s going on under the ground
A man works his way through the rubble of buildings in Marrakesh, Morocco, after a magnitude 6.8 earthquake on Sept. 8, 2023. Fadel Senna/AFP via Getty Images
Earthquakes, large and small, happen every single day along zones that wrap around the world like seams on a baseball. Most don’t bother anybody, so they don’t make the news. But every now and then a catastrophic earthquake hits people somewhere in the world with horrific destruction and immense suffering.
On Sept. 8, 2023, a magnitude 6.8 earthquake in the Atlas Mountains of Morocco shook ancient villages apart, leaving thousands of people dead in the rubble. In February 2023, a large area of Turkey and Syria was devastated by two major earthquakes that hit in close succession.
As a geologist, I study the forces that cause earthquakes. Here’s why some seismic zones are very active while others may be quiet for generations before the stress builds into a catastrophic event.
Earth’s crust crashes into itself and pulls apart
Earthquakes are part of the normal behavior of the Earth. They occur with the movement of the tectonic plates that form the outer layer of the planet.
You can think of the plates as a more or less rigid outer shell that has to shift to allow the Earth to give off its internal heat.
A map of all earthquakes greater than magnitude 5 from 1960 to 2023 clearly shows the outlines of the tectonic plates. USGS/GMRT
These plates carry the continents and the oceans, and they are continuously in slow-motion crashes with one another. The cold and dense oceanic plates dive under continental plates and back into Earth’s mantle in a processknown as subduction. As an oceanic plate sinks, it drags everything behind it and opens a rift somewhere else that is filled by rising hot material from the mantle that then cools. These rifts are long chains of underwater volcanoes, known as mid-ocean ridges.
Earthquakes accompany both subduction and rifting. In fact, that is how the plate boundaries were first discovered.
In the 1950s, when a global seismic network was established to monitor nuclear tests, geophysicists noticed that most earthquakes occur along relatively narrow bands that either fringe the edges of ocean basins, as in the Pacific, or cut right down the middle of basins, as in the Atlantic.
They also noticed that earthquakes along subduction zones are shallow on the oceanic side but get deeper under the continent. If you plot the earthquakes in 3D, they define slablike features that trace the plates sinking into the mantle.
Ten thousand earthquake locations from 1980 to 2009 trace the Pacific Plate as it subducts under northern Japan. The top image is a side view showing the depth of the earthquakes beneath the rectangle on the map. Jaime Toro, CC BY-ND
An experiment: How an earthquake works
To understand what happens during an earthquake, put the palms of your hands together and press with some force. You are modeling a plate boundary fault. Each hand is one plate, and the surface of your hands is the fault. Your muscles are the plate tectonic system.
Now, add some forward force to your right hand. You will find that it will eventually jerk forward when the forward force overcomes the friction between your palms. That sudden forward jerk is the earthquake.
A Google Earth image of creeks offset by movement along the San Andreas fault in southern California as the Pacific Plate moves to the northwest with respect to North America. Jaime Toro
Fast plates move at up to 8 inches (20 centimeters) per year, driven mostly by the oceanic slabs sinking at subduction zones. Over time, they become stuck to each other by friction at the plate boundary. The attempted motion deforms the plate boundary zone elastically, like a loaded spring. At some point, the accumulated elastic energy overcomes the friction and the plate jerks forward, causing an earthquake.
But the plate-driving forces do not stop, so the plate boundary starts to accumulate elastic energy again, which will cause another earthquake – perhaps soon or perhaps far in the future.
In the oceans, plate boundaries are narrow and well defined because the underlying rocks are very stiff. But within the continents, plate boundaries are often broad zones of deformed mountainous terrain crisscrossed by many faults. Those faults may persist for eons, even if the plate boundary becomes inactive. That is why sometimes earthquakes occur far from plate boundaries.
Earthquakes, fast and slow
The cyclic behavior of faults allows seismologists to estimate earthquake risks statistically. Plate boundaries with fast motions, such as the ones along the Pacific rim, accumulate elastic energy rapidly and have the potential for frequent large-magnitude earthquakes.
Slow-moving plate boundary faults take longer to reach a critical state. Along some faults, hundreds or even thousands of years can pass between large earthquakes. This allows time for towns to grow and for people to lose ancestral memory of past earthquakes.
A magnitude 7.8 earthquake that hit Syria and Turkey on Feb. 9, 2023, destroyed buildings and killed more than 50,000 people. Mehmet Kacmaz/Getty Images
The huge belt of mountains that extends from the Atlas of North Africa to the Pyrenees, Alps and most of the mountains across southern Europe and the Middle East is the product of this plate collision. Yet because these plate motions are slow near Morocco, large earthquakes are not so frequent.
Preparing for the big one
An important fact about catastrophic earthquakes is that, in most cases, the earthquakes don’t kill people – falling buildings do.
Most Americans have heard of California’s San Andreas Fault and the seismic risk to San Francisco and Los Angeles. The last major earthquake along the San Andreas Fault hit at Loma Prieta, in the San Francisco Bay area, in 1989. Its magnitude, 6.9, was comparable to that of the earthquake in Morocco, yet 63 people died compared with thousands. That’s largely because building codes in these earthquake-prone U.S. cities are now designed to keep structures standing when the Earth shakes.
The exceptions are tsunamis, the huge waves generated when an earthquake shifts the seafloor, displacing the water above it. A tsunami that hit Japan in 2011 had horrific consequences, regardless of the quality of engineering in coastal towns.
Unfortunately, earthquake scientists can’t predict exactly when an earthquake might occur; they can only estimate the hazard.
theconversation.com – James Wray, Professor of Earth and Atmospheric Sciences, Georgia Institute of Technology – 2024-10-11 12:36:00
The human mind may find it difficult to conceptualize: a cosmic cloud so colossal it surrounds the Sun and eight planets as it extends trillions of miles into deep space.
The spherical shell known as the Oort Cloud is, for all practical purposes, invisible. Its constituent particles are spread so thinly, and so far from the light of any star, including the Sun, that astronomers simply cannot see the cloud, even though it envelops us like a blanket.
It is also theoretical. Astronomers infer the Oort Cloud is there because it’s the only logical explanation for the arrival of a certain class of comets that sporadically visit our solar system. The cloud, it turns out, is basically a gigantic reservoir that may hold billions of icy celestial bodies.
Two of those bodies will pass by Earth in the days leading up to Halloween. Tsuchinshan-ATLAS, also known as Comet C/2023 A3, will be at its brightest, and likely visible to the naked eye, for a week or two after Oct. 12, the day it’s closest to Earth – just look to the western sky shortly after sunset. As the days pass, the comet will get fainter and move to a higher part of the sky.
A view of comet Tsuchinshan-ATLAS from the International Space Station.
The second comet, C/2024 S1 (ATLAS), just discovered on Sept. 27, should be visible around the end of October. The comet will pass closest to Earth on Oct. 24 – look low in the eastern sky just before sunrise. Then, after swinging around the Sun, the comet may reappear in the western night sky right around Halloween. It’s possible, however, that it could disintegrate, in part or in whole, as sometimes happens when comets pass by the Sun – and this one will come within 1 million miles (1.6 million kilometers) of our star.
As a planetary astronomer, I’m particularly curious about the Oort Cloud and the icy bodies inhabiting it. The Cloud’s residents may be a reason why life ignited on Earth; crashing on our planet eons ago, these ice bodies may have supplied at least some of the water that all life requires. At the same time, these same objects pose an ever-present threat to Earth’s continuation – and our survival.
Billions of comets
If an Oort Cloud object finds its way to the inner solar system, its ices vaporize. That process produces a tail of debris that becomes visible as a comet.
Some of these bodies, known as long-period comets, have orbits of hundreds, thousands or even millions of years, like Tsuchinshan-ATLAS. This is unlike the so-called short-period comets, which do not visit the Oort Cloud and have comparatively quick orbits. Halley’s comet, which cuts a path through the solar system and orbits the Sun every 76 years or so, is one of them.
The 20th-century Dutch astronomer Jan Oort, intrigued by the long-period comets, wrote a paper on them in 1950. He noted about 20 of the comets had an average distance from the Sun that was more than 10,000 astronomical units. This was astounding; just one AU is the distance of the Earth from the Sun, which is about 93 million miles. Multiply 93 million by 10,000, and you’ll find these comets come from over a trillion miles away. What’s more, Oort suggested, they were not necessarily the cloud’s outermost objects.
Nearly 75 years after Oort’s paper, astronomers still can’t directly image this part of space. But they do estimate the Oort Cloud spans up to 10 trillion miles from the Sun, which is almost halfway to Proxima Centauri, the next closest star.
The long-period comets spend most of their time at those vast distances, making only brief and rapid visits close to the Sun as they come in from all directions. Oort speculated the cloud contained 100 billion of these icy objects. That may be as numerous as the number of stars in our galaxy.
How did they get there? Oort suggested, and modern simulations have confirmed, that these icy bodies could have initially formed near Jupiter, the solar system’s largest planet. Perhaps these objects had their orbits around the Sun disturbed by Jupiter – similar to how NASA spacecraft bound for destinations from Saturn to Pluto have typically swung by the giant planet to accelerate their journeys outward.
Some of these objects would have escaped the solar system permanently, becoming interstellar objects. But others would have ended up with orbits like those of the long-period comets.
An illustration of the solar system and the Oort Cloud. The numbers on the graph depict AUs, or astronomical units. Note the location of Voyager 2, which will take another 30,000 years to fly out of the Cloud. NASA
Threats to Earth
Long-period comets present a particular potential danger to Earth. Because they are so far from our Sun, their orbits are readily altered by the gravity of other stars. That means scientists have no idea when or where one will appear, until it does, suddenly. By then, it’s typically closer than Jupiter and moving rapidly, at tens of thousands of miles per hour. Indeed, the fictional comet that doomed Earth in the film “Don’t Look Up” came from the Oort Cloud.
New Oort Cloud comets are discovered all the time, a dozen or so per year in recent years. The odds of any of them colliding with Earth are extremely low. But it is possible. The recent success of NASA’s DART mission, which altered the orbit of a small asteroid, demonstrates one plausible approach to fending off these small bodies. But that mission was developed after years of studying its target. A comet from the Oort Cloud may not offer that much time – maybe just months, weeks or even days.
Or no time at all. ‘Oumuamua, the odd little object that visited our solar system in 2017, was discovered not before but after its closest approach to Earth. Although ‘Oumuamua is an interstellar object, and not from the Oort Cloud, the proposition still applies; one of these objects could sneak up on us, and the Earth would be defenseless.
One way to prepare for these objects is to better understand their basic properties, including their size and composition. Toward this end, my colleagues and I work to characterize new long-period comets. The largest known one, Bernardinelli–Bernstein, discovered just three years ago, is roughly 75 miles (120 kilometers) across. Most known comets are much smaller, from one to a few miles, and some smaller ones are too faint for us to see. But newer telescopes are helping. In particular, the Rubin Observatory’s decade-long Legacy Survey of Space and Time, starting up in 2025, may double the list of known Oort Cloud comets, which now stands at about 4,500.
The unpredictability of these objects makes them a challenging target for spacecraft, but the European Space Agency is preparing a mission to do just that: Comet Interceptor. With a launch planned for 2029, the probe will park in space until a suitable target from the Oort Cloud appears. Studying one of these ancient and pristine objects could offer scientists clues about the origins of the solar system.
As for the comets now in Earth’s vicinity, it’s OK to look up. Unlike the comet in the DiCaprio movie, these two will not crash into the Earth. The nearest Tsuchinshan-ATLAS will get to us is about 44 million miles (70 million kilometers); C/2024 S1 (ATLAS), about 80 million miles (130 million kilometers). Sounds like a long way, but in space, that’s a near miss.
theconversation.com – John Sommers-Flanagan, Clinical Psychologist and Professor of Counseling, University of Montana – 2024-10-11 07:32:00
Uncommon Courses is an occasional series from The Conversation U.S. highlighting unconventional approaches to teaching.
Title of Course
Evidence-Based Happiness for Teachers
What prompted the idea for the course?
I was discouraged. For nearly three decades, as a clinical psychologist, I trained mental health professionals on suicide assessment. The work was good but difficult.
I consulted my wife, Rita, who also happens to be my favorite clinical psychologist. We decided to explore the science of happiness. Together, we established the Montana Happiness Project and began offering evidence-based happiness workshops to complement our suicide prevention work.
In 2021, the Arthur M. Blank Family Foundation, through the University of Montana, awarded us a US$150,000 grant to support the state’s K-12 public school teachers, counselors and staff. We’re using the funds to offer these educators low-cost, online graduate courses on happiness. In spring 2023, the foundation awarded us another $150,000 so we could extend the program through December 2025.
What does the course explore?
Using the word “happiness” can be off-putting. Sometimes, people associate happiness with recommendations to just smile, cheer up and suppress negative emotions – which can lead to toxic positivity.
As mental health professionals, my wife and I reject that definition. Instead, we embrace Aristotle’s concept of “eudaimonic happiness”: the daily pursuit of meaning, mutually supportive relationships and becoming the best possible version of yourself.
The heart of the course is an academic, personal and experiential exploration of evidence-based positive psychology interventions. These are intentional practices that can improve mood, optimism, relationships and physical wellness and offer a sense of purpose. Examples include gratitude, acts of kindness, savoring, mindfulness, mood music, practicing forgiveness and journaling about your best possible future self.
Students are required to implement at least 10 of 14 positive psychology interventions, and then to talk and write about their experiences on implementing them.
This exercise helps you focus on what goes right, rather than the things that go wrong.
What’s a critical lesson from the course?
The lesson on sleep is especially powerful for educators. A review of 33 studies from 15 countries reported that 36% to 61% of K-12 teachers suffered from insomnia. Although the rates varied across studies, sleep problems were generally worse when teachers were exposed to classroom violence, had low job satisfaction and were experiencing depressive symptoms.
The sleep lesson includes, along with sleep hygiene strategies, a happiness practice and insomnia intervention called Three Good Things, developed by the renowned positive psychologist Martin Seligman.
I describe the technique, in Seligman’s words: “Write down, for one week, before you go to sleep, three things that went well for you during the day, and then reflect on why they went well.”
Next, I make light of the concept: “I’ve always thought Three Good Things was hokey, simplistic and silly.” I show a video of Seligman saying, “I don’t need to recommend beyond a week, typically … because when you do this, you find you like it so much, most people just keep doing it.” At that point, I roll my eyes and say, “Maybe.”
Then I share that I often awakened for years at 4 a.m. with terribly dark thoughts. Then – funny thing – I tried using Three Good Things in the middle of the night. It wasn’t a perfect solution, but it was a vast improvement over lying helplessly in bed while negative thoughts pummeled me.
The Three Good Things lesson is emblematic of how we encourage teachers in our course – using science, playful cynicism and an open and experimental mindset to apply the evidence-based happiness practices in ways that work for them.
I also encourage students to understand that the strategies I offer are not universally effective. What works for others may not work for them, which is why they should experiment with many different approaches.
What will the course prepare students to do?
The educators leave the course with a written lesson plan they can implement at their school, if they wish. As they deepen their happiness practice, they can also share it with other teachers, their students and their families.
Over the past 16 months, we’ve taught this course to 156 K-12 educators and other school personnel. In a not-yet-published survey that we carried out, more than 30% of the participants scored as clinically depressed prior to starting the class, compared with just under 13% immediately after the class.
The educators also reported overall better health after taking the class. Along with improved sleep, they took fewer sick days, experienced fewer headaches and reported reductions in cold, flu and stomach symptoms.
As resources allow, we plan to tailor these courses to other people with high-stress jobs. Already, we are receiving requests from police officers, health care providers, veterinarians and construction workers.
The 67 million Americans eligible for Medicare make an important decision every October: Should they make changes in their Medicare health insurance plans for the next calendar year?
The decision is complicated. Medicare has an enormous variety of coverage options, with large and varying implications for people’s health and finances, both as beneficiaries and taxpayers. And the decision is consequential – some choices lock beneficiaries out of traditional Medicare.
Beneficiaries choose an insurance plan when they turn 65 or become eligible based on qualifying chronic conditions or disabilities. After the initial sign-up, most beneficiaries can make changes only during the open enrollment period each fall.
The 2024 open enrollment period, which runs from Oct. 15 to Dec. 7, marks an opportunity to reassess options. Given the complicated nature of Medicare and the scarcity of unbiased advisers, however, finding reliable information and understanding the options available can be challenging.
We are health carepolicy experts who study Medicare, and even we find it complicated. One of us recently helped a relative enroll in Medicare for the first time. She’s healthy, has access to health insurance through her employer and doesn’t regularly take prescription drugs. Even in this straightforward scenario, the number of choices were overwhelming.
The stakes of these choices are even higher for people managing multiple chronic conditions. There is help available for beneficiaries, but we have found that there is considerable room for improvement – especially in making help available for everyone who needs it.
The choice is complex, especially when you are signing up for the first time and if you are eligible for both Medicare and Medicaid. Insurers often engage in aggressive and sometimes deceptive advertising and outreach through brokers and agents. Choose unbiased resources to guide you through the process, like www.shiphelp.org. Make sure to start before your 65th birthday for initial sign-up, look out for yearly plan changes, and start well before the Dec. 7 deadline for any plan changes.
2 paths with many decisions
Within Medicare, beneficiaries have a choice between two very different programs. They can enroll in either traditional Medicare, which is administered by the government, or one of the Medicare Advantage plans offered by private insurance companies.
Within each program are dozens of further choices.
Traditional Medicare is a nationally uniform cost-sharing plan for medical services that allows people to choose their providers for most types of medical care, usually without prior authorization. Deductibles for 2024 are US$1,632 for hospital costs and $240 for outpatient and medical costs. Patients also have to chip in starting on Day 61 for a hospital stay and Day 21 for a skilled nursing facility stay. This percentage is known as coinsurance. After the yearly deductible, Medicare pays 80% of outpatient and medical costs, leaving the person with a 20% copayment. Traditional Medicare’s basic plan, known as Part A and Part B, also has no out-of-pocket maximum.
Traditional Medicare starts with Medicare parts A and B.
People enrolled in traditional Medicare can also purchase supplemental coverage from a private insurance company, known as Part D, for drugs. And they can purchase supplemental coverage, known as Medigap, to lower or eliminate their deductibles, coinsurance and copayments, cap costs for Parts A and B, and add an emergency foreign travel benefit.
The Medicare Advantage program allows private insurers to bundle everything together and offers many enrollment options. Compared with traditional Medicare, Medicare Advantage plans typically offer lower out-of-pocket costs. They often bundle supplemental coverage for hearing, vision and dental, which is not part of traditional Medicare.
Different Medicare Advantage plans have varying and large impacts on enrollee health, including dramatic differences in mortality rates. Researchers found a 16% difference per year between the best and worst Medicare Advantage plans, meaning that for every 100 people in the worst plans who die within a year, they would expect only 84 people to die within that year if all had been enrolled in the best plans instead. They also found plans that cost more had lower mortality rates, but plans that had higher federal quality ratings – known as “star ratings” – did not necessarily have lower mortality rates.
While many Medicare Advantage plans boast about their supplemental benefits , such as vision and dental coverage, it’s often difficult to understand how generous this supplemental coverage is. For instance, while most Medicare Advantage plans offer supplemental dental benefits, cost-sharing and coverage can vary. Some plans don’t cover services such as extractions and endodontics, which includes root canals. Most plans that cover these more extensive dental services require some combination of coinsurance, copayments and annual limits.
Even when information is fully available, mistakes are likely.
At 65, when most beneficiaries first enroll in Medicare, federal regulations guarantee that anyone can get Medigap coverage. During this initial sign-up, beneficiaries can’t be charged a higher premium based on their health.
Older Americans who enroll in a Medicare Advantage plan but then want to switch back to traditional Medicare after more than a year has passed lose that guarantee. This can effectively lock them out of enrolling in supplemental Medigap insurance, making the initial decision a one-way street.
For the initial sign-up, Medigap plans are “guaranteed issue,” meaning the plan must cover preexisting health conditions without a waiting period and must allow anyone to enroll, regardless of health. They also must be “community rated,” meaning that the cost of a plan can’t rise because of age or illness, although it can go up due to other factors such as inflation.
People who enroll in traditional Medicare and a supplemental Medigap plan at 65 can expect to continue paying community-rated premiums as long as they remain enrolled, regardless of what happens to their health.
In most states, however, people who switch from Medicare Advantage to traditional Medicare don’t have as many protections. Most state regulations permit plans to deny coverage, impose waiting periods or charge higher Medigap premiums based on their expected health costs. Only Connecticut, Maine, Massachusetts and New York guarantee that people can get Medigap plans after the initial sign-up period.
Deceptive advertising
Information about Medicare coverage and assistance choosing a plan is available but varies in quality and completeness. Older Americans are bombarded with ads for Medicare Advantage plans that they may not be eligible for and that include misleading statements about benefits.
A November 2022 report from the U.S. Senate Committee on Finance found deceptive and aggressive sales and marketing tactics, including mailed brochures that implied government endorsement, telemarketers who called up to 20 times a day, and salespeople who approached older adults in the grocery store to ask about their insurance coverage.
The Department of Health and Human Services tightened rules for 2024, requiring third-party marketers to include federal resources about Medicare, including the website and toll-free phone number, and limiting the number of contacts from marketers.
Although the government has the authority to review marketing materials, enforcement is partially dependent on whether complaints are filed. Complaints can be filed with the federal government’s Senior Medicare Patrol, a federally funded program that prevents and addresses unethical Medicare activities.
Nearly one-third of Medicare beneficiaries seek information from an insurance broker. Brokers sell health insurance plans from multiple companies. However, because they receive payment from plans in exchange for sales, and because they are unlikely to sell every option, a plan recommended by a broker may not meet a person’s needs.
Help is out there − but falls short
An alternative source of information is the federal government. It offers three sources of information to assist people with choosing one of these plans: 1-800-Medicare, medicare.gov and the State Health Insurance Assistance Program, also known as SHIP.
Telephone SHIP services are available nationally, but one of us and our colleagues have found that in-person SHIP services are not available in some areas. We tabulated areas by ZIP code in 27 states and found that although more than half of the locations had a SHIP site within the county, areas without a SHIP site included a larger proportion of people with low incomes.
Virtual services are an option that’s particularly useful in rural areas and for people with limited mobility or little access to transportation, but they require online access. Virtual and in-person services, where both a beneficiary and a counselor can look at the same computer screen, are especially useful for looking through complex coverage options.
As one SHIP coordinator noted, many people are not aware of all their coverage options. For instance, one beneficiary told a coordinator, “I’ve been on Medicaid and I’m aging out of Medicaid. And I don’t have a lot of money. And now I have to pay for my insurance?” As it turned out, the beneficiary was eligible for both Medicaid and Medicare because of their income, and so had to pay less than they thought.
The interviews made clear that many people are not aware that Medicare Advantage ads and insurance brokers may be biased. One counselor said, “There’s a lot of backing (beneficiaries) off the ledge, if you will, thanks to those TV commercials.”
Many SHIP staff counselors said they would benefit from additional training on coverage options, including for people who are eligible for both Medicare and Medicaid. The SHIP program relies heavily on volunteers, and there is often greater demand for services than the available volunteers can offer. Additional counselors would help meet needs for complex coverage decisions.
The key to making a good Medicare coverage decision is to use the help available and weigh your costs, access to health providers, current health and medication needs, and also consider how your health and medication needs might change as time goes on.
This article is part of an occasional series examining the U.S. Medicare system.
This story has been updated to remove a graphic that contained incorrect information about SHIP locations, and to correct the date of the open enrollment period.
