On October 1st, 2017 we learned about

An emptied Mediterranean Sea enabled an increase in volcanic eruptions

Earthquakes can be bad. Earthquakes blocking off a key water source are likely worse. Earthquakes blocking water that eventually trigger volcanic eruptions would be… ridiculous? It may sound like a script to a summer blockbuster from the 1990s, but this story actually took place in the Miocene Epoch, around seven million years ago, leaving the Mediterranean Sea dry enough to walk across. The ground, and water levels, have obviously moved again since that time, but layers of earth all around the Mediterranean still tell the story the Messinian salinity crisis, when the sea was walkable and apparently lined by unusually active volcanoes.

Sediment layers under the sea

In cliffs along the Mediterranean, you can see layers of salt and gypsum crystals that were deposited thanks to evaporating seawater. It’s not surprising to see those sediment patterns in cliffs now exposed to the Sun, giving evidence to higher water levels long ago. The plot thickened in 1961, when researchers drilling under the Mediterranean Sea found the same patterns under water. For evaporation to have laid down salt and gypsum there, the only explanation was that what’s now the bottom of the sea was temporarily exposed to the Sun, although more than sunshine would have been required to dry up 965,300 square miles of water.

The loss of water was thanks to some major earthquakes near the strait of Gibraltar. As the European and African tectonic plates ground into each other, land was pushed up, blocking up the flow of water between the Atlantic ocean and the Mediterranean Sea. Without a regular supply of new water, the Mediterranean Sea was more susceptible to evaporation, drying up up enough to loose a half-mile of depth in places where water remained. The Sea started to look more like lakes, and which a new study suggests is what started to make some local mountains look more like volcanoes.

Water goes down, magma comes up

As much as we associate magma with being hot water with being cool, the big issue here was actually weight. Water is heavy enough to simply weigh down the ground, demonstrated recently by the 0.8 inches Houston, Texas was measured to have dropped under the weight of Hurricane Harvey’s rainfall. The dried Mediterranean greatly reduced the pressure on the ground below it, which allowed magma to more easily rise to the Earth’s surface. As a result of the magma’s freed movement, the rate of volcanic eruptions in the area more than doubled, with at least 13 eruptions taking place around 5.9 to 5.4 million years ago. To put it in a nutshell, blocking up the water effectively unblocked the magma.

Since the Mediterranean doesn’t currently look like Mordor, it’s easy to surmise that these changes were all reversed at some point. Another series of earthquakes reopened the strait of Gibraltar bit by bit, allowing the Atlantic to come rushing back in. Sediment layers suggest that these floods occurred more than once, although it’s unknown if that would have made for another disaster movie, or just welcome relief from the salty land and extra eruptions.

My kids asked: What about animals that got stuck out there when the water was gone and came back?

These transitions were probably difficult for most organisms. Even as water slowly dried up, the increased salinity would have giving many marine species a run for their money in whatever water remained. At least a few animals probably wandered out when the water was low, only to be isolated on newly defined islands when sea levels returned to normal. Once trapped on an island, it’s likely that some species underwent island dwarfism or gigantism thanks to the environmental pressures of living in a very different space than their ancestors did.

Source: Disappearance of Mediterranean Sea Seven Million Years Ago Triggered Widespread Volcanic Activity by David Bressan, Forbes

On September 19th, 2017 we learned about

Speculation about why the ancient Greeks repeatedly rebuilt on earthquake fault lines

Despite what housing prices in the San Francisco Bay area may suggest, most people have an understanding of how dangerous living on an earthquake fault-line can be. It helps that since San Francisco’s historic quake in 1906, a lot of research has been done on what causes earthquakes, leading to more safely engineered buildings that can survive a tremblor. Of course, before people even considered the notion of plate tectonics, seismically active locations have been surprisingly active real estate markets. In fact, there’s a chance that the occasional shake-up actually attracted people, since they interpreted earthquakes as being divine in origin.

Guessing why the ground shakes

Geologist Iain Stewart from the University of Plymouth noticed an odd trend in building locations in ancient Greece, as many cities, temples and monuments were built directly on active fault lines. On it’s own that’s not that odd, but the fact that ancient people’s repeatedly rebuilt ruined structures at these locations indicates that there was a strong motivation to do so. Without scientific explanations and predictions to help shape people’s reactions, Stewart suspects that the ground’s spontaneous movement was likely understood to be an expression of the gods’ will. Even if a building was shaken to dust, knowing that a deity had taken an interest in a particular plot of land boosted its prestige as a sort of ‘holy’ site.

In some cases, the intersection of geology and faith is fairly clear. The famed Oracle of Delphi described visions that foretold the future and explained the actions of the gods. While the accuracy of those interpretations may be up for debate, a biochemical component has been found for the seer’s visions, as ethylene gas was likely produced underground, and released with each bit of seismic activity. The priestess was then probably subject to hallucinations, and would share the her descriptions of these sights as guidance for her visitors. Similarly, an oracle at Perachora Heraion may have lost their divine gift after a quake blocked off a water supply to vision-inducing hot springs in 300 BC.

Picking fault lines on purpose?

Even ignoring these more mind-altering interactions with fissures in the rock, Stewart believes that the ancient Greeks weren’t rebuilding on fault lines at random. It’s hard to move a city to avoid seismic activity, but it should have been possible to a least move a broken temple off a fault. Instead, Stewart things the Greeks rebuilt at the same locations on purpose, possibly to harness the inexplicable energy of that spot. While Stewart has a list of at least four more cities that seem conspicuously located along active fault lines, he admits that he’s looking at this from a geologist’s perspective. He’s hoping that archaeologists will look for evidence of people’s intent to build where the ground shook, helping answer how they rationalized living in such a risk-prone place.

As for the Bay Area… the weather really is lovely most of the year, and the local produce is hard to beat, plate tectonics be damned.

Source: Ancient Greeks May Have Deliberately Built Sacred Sites on Earthquake Faults by John Dyer, Seeker

On July 24th, 2017 we learned about

Meteorites may have delivered the metals we find on Earth and Mars

Even if you’ve visited a mine, you still might not appreciate where metals come from. Humans have been digging metals out of the ground for thousands of years, but we’ve only been digging that metal out of the planet’s crust. This is weird, because when the Earth was forming billions of years ago, most of the precious metals like gold and platinum sank to the planet’s core with the iron that now dominates that space. That should have made those metals inaccessible to anyone on the surface, and yet we happily make use of these metals on a daily basis. It’s quite possible that the metal we find in the Earth’s crust actually came from space.

Assuming that our “native” gold, platinum, copper and more are all buried in the center of the planet, the shiny stuff we do dig up would have started on a meteorite. Billions of years ago, its hypothesized that a barrage of meteorites covered the Earth with a fresh supply of metals. Some of those metals were simply buried in the planet’s crust, while others may have been absorbed as deep as the mantle where they could have been churned and moved to new locations. Over time, some of these metals could have been pushed closer to the surface thanks to seismic activity, leaving us with situations like ancient Cyprus, where copper was found in such abundance we named the metal after the island.

Massive impacts on Mars

A twist on this model has also been proposed for other planets. Mars currently lacks the tectonic activity that could have moved and brought metals to its surface, and yet the Red Planet’s southern hemisphere seems to have plenty of metals that shouldn’t be there. That region also has a lot of scars from ancient impact craters, which helps support the idea that the metals on the surface of Mars were also delivered via meteorite billions of years ago.

In the proposed model, a huge meteor hit the planet, not only loading it with a new supply of metals, but also kicking up debris that would eventually coalesce into at least one of Mars’ two moons. It’s a tidy hypothesis, and it fits well with everything from concepts surrounding how planets are formed to why the surface of Mars’ northern hemisphere appears to be a different age than the southern hemisphere.

Source: Where does all Earth's gold come from? Precious metals the result of meteorite bombardment, rock analysis finds, Science Daily

On July 11th, 2017 we learned about

Study links subtle, subterranean vibrations to future volcanic activity

Volcanoes would be a lot easier to deal with if they were a bit more predictable. People live in the shadow of volcanoes around the world, often hoping that the richness of the soil created by the magma-spewing structures will outweigh the potential risk of fiery, toxic annihilation. Fortunately, volcanoes like Kīlauea in Hawaii are actually pretty consistent and thus relatively easy to work with. Kīlauea has been erupting since January 3, 1983, and that constant activity has made a great place to test technologies that might help us predict the eruptions of more volatile volcanoes elsewhere.

Two ways to monitor magma

Researchers from the University of Cambridge have been looking at two potential signals that, when taken together, may act as an early warning for eruptions. The first line of data concerned vibrations in the ground around the volcano. There’s often a fair amount of energy pulsing through rock and dirt from a variety of sources, many of which have nothing to do with moving lava. But over the course of four years, patterns could be detected in the speed of the vibrations shifting through the ground. To help make better sense of this low-intensity activity, two sensors were compared, looking for vibrations that started close to one and then moved to the other. This would help filter out seismic activity that originated elsewhere, and thus wasn’t directly tied to Kīlauea.

The second line of data concerned larger changes in the shape of Kīlauea itself. As magma moves through different layers of earth, heat and pressure changes create deformities in the volcano itself, particularly in the main magma chamber below that feeds the volcano. These can sometimes lead to bigger movement, such as when Kīlauea opened up a new ‘waterfall’ of lava into the ocean after a large hunk of mountain fell away.

Anticipating eruptions

Putting these data together, researchers are looking at the intersection of all this activity. As the magma chamber fills up, the overall mountain bulges and shrinks. This helps speed up local vibrations in the ground that sensors can detect. Once the magma chamber fill more, pressure underground increases, which we now know further boosts the speed of the seismic vibrations in the ground. This suggests that future detectors will be able to look for these more subtle changes in vibration speeds, rather than waiting for more obvious earthquakes. This should help catch more eruptions before it’s too late for people nearby to react.

Source: 'Bulges' in volcanoes could be used to predict eruptions by University of Cambridge, EurekAlert!

On July 5th, 2017 we learned about

Crystals laced with lithium suggest that most of a volcano’s magma isn’t liquefied

As we’ve all been taught, when a volcano erupts it spews ash, noxious fumes, and molten lava— lava of course being a term to describe the melted rocks that were forced to the Earth’s surface. However, zircon crystals, which also get pushed to the surface in a good eruptions, are rewriting this a bit. Formed deep underground, variations in these crystals indicate that there’s more of a distinction between lava and magma than its location. Most of the world’s magma isn’t really a liquid at all, a fact that may help us make sense of how, and more importantly, when, volcanoes erupt in the first place.

Digging miles into the Earth to sample magma “in the wild” isn’t terribly practical, which is part of why understanding the exact state of magma under the Earth’s crust has eluded us for so long. Fortunately, zircon crystals essentially record the condition of the magma they sit in allowing us to get an idea of how hot things were before they were brought to the surface. When a crystal is heated over 1,382° Fahrenheit, it softens and absorbs lithium from it’s local environment. Scientists can then look at how much lithium has been absorbed into a crystal to determine how hot, or cool, the surrounding magma was. Based on samples from New Zealand, most magma isn’t as squishy as we’re often led to believe.

Few signs of flowing stone

This batch of crystals was brought to the Earth’s surface in an eruption 700 years ago. Before that, they’d been buried underground for over 50,000 years, giving them plenty of opportunities to be exposed to hotter or cooler magma in the region. As it turns out, very as few as 40 of those years were spent in truly liquefied rock—  most of the crystals’ time seems to have been in magma as soft as a sort of rocky slurry at best. If anything, it seems that most of the time in truly molten magma was just before the actual eruption that carried the crystals to the surface.

Researchers know that there were more eruptions before that time though, which tells them more about the composition of the buried magma. If some parts of the Taupo Volcanic Zone were hot and pressurized enough to erupt without cooking these particular crystals, it seems that the larger supply of magma is fairly compartmentalized. Hot, liquid rock can apparently form before an eruption, but doesn’t mean that the entire region is floating over a sea of molten magma. Alternatively, eruptions may occur when molten material arrives from even deeper underground, melting a path to the surface. In either case, it seems that the lava we see is very likely very freshly made, at least on geologic timescale.

Source: Magma stored under volcanoes is mostly solid by Maria Temming, Science News

On June 1st, 2017 we learned about

When changes in climate made Antarctica one of the most comfortable continents

Antarctica is getting green again. For the last 50 years, moss has been making inroads along the Antarctic Peninsula thanks to global climate change, although it’s certainly not the first time this continent has seen non-winterized flora and fauna. In fact, Antarctica’s milder periods may have made it a haven for species having a hard time when the rest of the world’s climate was being a bit less hospitable. That’s not to say that it’s a place to buy real estate though, since for starters, Antarctica used to be in a different location altogether.

600 million years ago, before creatures like dinosaurs were even close to being a thing, Antarctica was part of the single super-continent, Gondwana. Life at that point would have been happy in a petri dish, and so nothing was going to discriminate against Antarctica or it’s neighbors Australia and India. The fact that all the world’s continents were sort of centered along the equator meant that no place was especially colder than another, and the six-month winter that helps keep modern Antarctica frosty wasn’t an issue.

From the Great Dying to dinosaurs

At the end of the Permian Period, around 250 million years ago, Antarctica got to differentiate itself a bit. A lack of oxygen in the Earth’s oceans and spike in carbon dioxide levels was wreaked havoc across ecosystems, wiping out an estimated 96 percent of life forms on the planet. Average global temperatures also rose, which turned most of Gondwana into a harsh, parched wasteland, except in Antarctica. Being on the cooler end of the global climate, even just a bit, helped the southern end of the super-continent remain a bit more habitable, and home to various plants, reptiles, synapsids and more. By the Jurassic Period, Antarctica was in full bloom, complete with conifer trees, cycads, pterosaurs and some decently-sized dinosaurs.

One such dinosaur was a theropod named Cryolophosaurus ellioti. Walking on two tall legs with arms long enough to make a T. rex jealous, this predator also sported a pretty neat head crest, probably used in either species or sex identification. In the large scheme of things, at around 21 feet long, Cryolophosaurus was a larger theropod than many of its contemporaries on other continents. It’s not clear why this larger size evolved early but these species didn’t really keep pace. A herbivorous sauropod found in Antarctica was notably shorter, or “wimpier,” than it’s long-necked kin elsewhere, but by the Cretaceous period it was becoming clear that this southern continent’s role as a habitat was being pushed to the margins.

Around 145 million years ago, the Cretaceous period began, marking the birth of a modern Antarctica. The super-continent of Gondwana was breaking apart, and continents were migrating to their modern positions on the globe. For Antarctica, this of course meant heading to the Earth’s south pole, and being geographically isolated from other land masses. For a time, Australia stayed with Antarctica, but that union would eventually end as well. Dinosaurs stuck things out at long as they could, although even the south pole wasn’t safe from the asteroid impact that famously caused the extinction of non-avian dinosaurs, pterosaurs and marine reptiles around the world.

Warming as a warning?

As Antarctica warms once again, we will likely be able to uncover more of its history that’s been hidden beneath layers of ice and snow. Unfortunately, it looks like other parts of our planet’s history may also be repeating, with more northern climates heating up faster than life can adapt. As great as it would be to find more fossils in Antarctica, nobody wants life to have to retreat to this elusive continent all over again.

Source: The Mysterious World of Prehistoric Antarctica by Charles Owen-Jackson, Earthly Universe

On May 16th, 2017 we learned about

Smooth streaks surrounding Martian craters suggests violent vortexes were created during impacts

What’s cooler than a huge asteroid impact on another planet like Mars? How about an asteroid hitting Mars hard enough to produce giant tornadoes that scoured the surrounding area with 500 mile-per-hour winds? This dramatic scenario may sound like a set-piece for an upcoming Michael Bay movie, but it was actually put together in a simulation based on thermal infrared images taken by the Mars Odyssey orbiter. Beyond scrubbing the red planet’s surface, these winds may have also left clues about the nature of the asteroids that caused them in the first place.

Detected in the dark

As impressive as these tornadoes must have been when they occurred, nobody has observed any of these tornadoes directly, and even the trace evidence of them has only seen at night. As the orbiter passed over the dark side of Mars, it still took infrared images that captured how much heat was being emitted by the planet’s surface. While you’re not going to see what color a feature is, the amount of heat emitted at night can describe what the texture of that area looks like, with blocky objects shedding more heat than rough powders or debris. So these night-time heat images can be used to build a sort map of all the different surfaces and textures, some of which turned out to make some very interesting patterns near impact craters.

Large streaks of smoothed ground were detected radiating out from impact craters, which is what caught researchers’ eyes. They looked a bit like patterns that projectiles create in the air when being fired out of a cannon, which isn’t a bad analog for an asteroid hitting a planet. The patterns weren’t always perfectly consistent though, which, with the help of computer simulations, was partially explained by the topography near the craters.

Whipping up wind

According to simulations, the asteroids or comets likely hit the ground and were instantly vaporized, taking the material at the point of impact with it. Huge, powerful vapor traveled outwards (again, think Michael Bay explosions here,) skirting along over the surface of the planet at supersonic speeds. All that heat and motion would drum up winds in the Martian atmosphere, which would stir things up but not actually scour the ground like a tornado. For that, the winds and vapor plumes would need to run into slightly elevated features which would disrupt their movement and lead to a vortex that would scrape along the ground like an F8 tornado.

The need for specific elevations helps explain the frequency of these tornado streaks to a certain extent, but they’re still not as common as they might be if bumpy terrain were the only required ingredient (beyond the asteroid or comet, of course.) This suggests that the material that makes up the ground or the asteroid itself may be a competent to this phenomenon, with something like ice behaving differently than iron, for instance. If this can be pieced together, it may offer a new way to build the history of what’s been hitting Mars, or what Mars looked like, back when these impacts took place ages ago.

Source: Ancient Mars impacts created tornado-like winds that scoured surface, Scienmag

On May 15th, 2017 we learned about

What California zoos can do for their animals during fires, earthquakes and tsunamis

How do you move an elephant through a city that’s on fire? If people are supposed to hide under a solid surface like a table in an earthquake, what should a giraffe at the zoo do? As we’ve been teaching our kids some basic earthquake safety, they’ve of course been thinking beyond the patterns and scenarios that most adults limit themselves to, and answering this question caught me flat-footed, even though I’ve experienced both earthquakes and giant wildfires. It turns out there are a lot of layers to protecting captive animals in a disaster, largely thanks to how different these disasters can be.

Wildfires and captive animals

Unless you’re in the fire department, the way people are supposed to respond to encroaching wildfires is to evacuate. History has shown that getting people to cooperate with these orders isn’t easy, so it’s not a huge surprise that zoos can’t really attempt to relocate every gazelle, zebra or rhino. Zookeepers generally try to move animals to their off-exhibit barns so they’ll be somewhat shielded from the smoke and chaos of sirens and helicopters, as panicking animals can be a safety hazard even if the fire never touches the zoo itself. If an animal isn’t cooperative, zookeepers can’t spend too much time convincing them, as they’re often under evacuation orders themselves and the zoo doesn’t want to loose any humans to a fire either. Fortunately, grazing herbivores do a good job of removing fuel from their environment, so a fire at a fence might not find a lot to burn inside a paddock.

Some animals might be transported away from an obvious threat like a fire. Small, non-venomous reptiles and mammals that can be more easily handled might be packed up. Zoos with special conservation projects, such as the California condors and their eggs at the San Diego Zoo, will be captured and moved away from dangerous locations, as they’re about as irreplaceable as an animal comes while being more portable than an agitated lion. Otherwise, zoos run emergency drills to help make the best of a tough situation.

The aftermath of animals in an earthquake

In California, those emergency drills have to also include plans for earthquakes. Unlike a fire, an earthquake gives you no real warnings to react to, and so zoos instead have to focus on making the fallout as painless as possible. Teams plan for resecuring animals, coordinating with city fire departments and police if necessary. The Oakland Zoo, which sits at the top of a hill along the Hayward fault in Oakland, is included in city disaster response plans, so that that coordination doesn’t have to be figured out after the fact.

Otherwise, zoos have to deal with earthquakes a lot like any other resident who’s been shaken. They have at least three days of extra food, water and fuel to run generators, which would hopefully be enough time for roads to be reopened for fresh supplies to be delivered. While parks would ideally be evacuated after an earthquake, there’s the chance that visitors would be stuck at the zoo for a while too, adding an additional layer of complication to tending to the animals, structures, etc.

Coping and clean-up after a tsunami

While the Oakland Zoo has to be ready for an earthquake, their high ground away from any water at least clears them of tsunami problems. The San Francisco Zoo, on the other hand, is a stone’s throw from the ocean, meaning that tsunami plans are one of their biggest concerns. Thanks to being triggered by an earthquake, there’s not a lot of time to react to a wave before it hits. Plans are in place to help coordinate evacuations and tend to casualties, but there’s only so much that can be done against a surge of water big enough to carry a building.

It may sound grim, but these events are considered to be disasters for a reason. In the wild, some animals may manage themselves fairly well, but we also have evidence of fires and floods claiming animals lives for millions of years.

Source: No foolproof zoo disaster plan by Carla Hall, Los Angeles Times

On April 16th, 2017 we learned about

Ash and poop reveals the perseverance of penguins amid repeated volcanic eruptions

Gentoo penguins grow to around two-and-a-half feet tall, weighing no more than 12 pounds. Like many penguins, they live off the oceans just north of Antarctica, catching fish, squid and krill. They are quite adept swimmers, staying underwater for up to seven minutes, diving as deep as 655 feet and moving at a record-setting 22 miles-per-hour. They are not, however, fireproof. They do require fresh air to breath. And they require food to eat. For these reasons, it seems fair to say that their choice of nesting grounds on Ardley Island off the Antarctic peninsula may not have been the best place to start a nursery.

Rough real estate

Actually, Ardley Island isn’t all that bad, as far as Antarctic nesting grounds go. There isn’t a lot of scenic flora exactly, but there’s open space and plenty of pebbles to construct nests. The adults don’t have to worry about any predators (outside of human hunters) on Ardley, and thus have used it during mating season for around 7,000 years, according to bone and guano layers in sediment cores from the area.

However, those same sediment samples also reveal that Ardley Island has a very destructive neighbor. Deception Island may look benign from the outside, but it that appearance is deceptive, as it hides the fact that the island is basically the caldera of a volcano. The volcano’s last major eruption was in 1970, but that was small compared to what likely took place 3,000, 4,300 and 5,300 years ago. Layers of thick, toxic ash indicate that those eruptions were large and explosive, akin to the Mount Saint Helens eruption in 1980.

Penguin parents (barely) persist

Judging by the amount of penguin poop laid down after the ash, the penguins didn’t fair too well during each eruption. Populations were probably decimated, taking four to eight hundred years to recover each time. The sediment cores can’t fill in every detail, but it’s likely that only well-fed adults would have survived these eruptions, particularly if they could have swam away from Ardley Island in a hurry. The fact that gentoo penguins generally share nest building, incubation and parenting duties pretty equally, any volcanic activity during mating season would have been devastating to these colonies.

However, you could argue that the penguins have actually won this battle, at least in the long run. Deception Island isn’t completely dormant, but it has been a lot quieter for the last 2000 years, and the penguins haven’t given up nesting on Ardley Island. Further eruptions are of course possible, but humans have followed the penguins lead to a degree, setting up harbors, whaling outposts and now science and tourism facilities inside the caldera itself. There aren’t, however, any new nurseries at this point, so human populations aren’t incurring a major risk in the case of future eruptions.

Source: Oddly, Penguins Keep Coming Back to Erupting Volcano by Laura Geggel, Live Science

On March 15th, 2017 we learned about

Seismic modeling finds new reasons for more movement in the Earth’s mantel

An earthquake, as we normally experience it, is the sum of a variety of different vibrations pulsing through the ground. Most of what we notice are P, S and surface waves, shifting the ground in vertical, shearing and undulating motions respectively. While this activity is apparent at the time of an earthquake, seismologists have also detected vibrations coming from deeper in the Earth’s mantle, even when things are the surface seem nice and stable. They’re of great interest though, since they may be precursors to much more violent activity sometime in the future.

These particular vibrations, called Episodic Tremor and Slip (ETS) are technically caused by seismic tremors. As one tectonic plate is gradually forced under another at a fault, it faces plenty of resistance and friction from it’s neighbor. There is movement, although it’s generally deep and gradual that the ETS waves are hard to monitor on the surface. As such, there’s concern that the pressure and energies at work may surprise us someday with a huge, sudden release, complete with destructive shaking on the surface.

Slipping and sliding

To try to fill in some of these holes, researchers are looking at new modeling techniques to better simulate the forces at work where tectonic plates are squeezing each other. Drawing on various types of data, a point of interest has become the water that can also accumulate where oceanic plates meet. As one plate moves down, water understandably follows, running through small cracks and crevices between the rocks and dirt. The water can also clog up channels with eroded sediment, accumulating between the plates enough to act as a lubricant.

The slightly lubricated plates can then move more easily, which may be a good thing, at least temporarily. The movement deep down likely causes movement above it, but overall this reduces some energy buildup on the plate as a whole. It may even leave pockets and gaps in the rock, which would almost “insulate” some areas from the pressure and stress from ETS waves deeper down, since the wave needs rock and dirt as a medium to move through the ground. This doesn’t mean that the deep, slower seismic tremors can’t lead to built up pressure that could result in a devastating earthquake, but that the process may be more complicated and varied than previously thought.

My second grader asked: So the water letting the plate move is a good thing?

At the risk of oversimplifying things, it seems like it’s more good than bad. Since dangerous earthquakes are the sudden release of built-up energy, it’s probably better for everyone on the surface if that energy is doled out in many smaller events that can create those hard-to-detect ETS waves.

Source: The bangs, crackles and hums of Earth's seismic orchestra by Dr Stephen Hicks, The Guardian