Home Blog Page 2

Scientists discover one of the Earth’s earliest animals in Australian outback

contact.geology
-
0
Scientists discover one of the Earth’s earliest animals in Australian outback

In the shadow of South Australia’s largest mountain range beneath the outback soil lies a fossil record that reveals a rich history of life on Earth. Fossils found at Nilpena Ediacara National Park preserve a pivotal moment in the history of evolution: the crucial period during which single-celled organisms began to evolve into the planet’s first complex, visible animals.

A new discovery in the area by Scott Evans, assistant professor of geology in the Florida State University Department of Earth, Ocean and Atmospheric Science, and a multi-institution team of paleontologists has identified an early marine animal from around 555 million years ago. The discovery helps answer how life evolved on Earth.

Quaestio simpsonorum is the first animal to show a definitive left-right asymmetry, an important sign of evolutionary development. The team’s findings appear in Evolution & Development.

“The animal is a little smaller than the size of your palm and has a question-mark shape in the middle of its body that distinguishes between the left and right side,” Evans said. “There aren’t other fossils from this time that have shown this type of organization so definitively. This is especially interesting as this is also one of the first animals that was capable of moving on its own.”

Researchers said Quaestio, pronounced “kways-tee-oh,” behaved like a small marine Roomba vacuum, consuming nutrients from microscopic algae, bacteria and other organisms as it moved along the seafloor. The collection of microbes formed an organic mat, like a layer of slime filled with nutrients on the seafloor, which formed a particular texture preserved in the rock slabs that make up the park’s fossil beds. Researchers discovered distinct Quaestio impressions along with evidence of its trails—known as trace fossils—in this fossilized mat texture.

“One of the most exciting moments when excavating the bed where we found many Quaestio was when we flipped over a rock, brushed it off, and spotted what was obviously a trace fossil behind a Quaestio specimen—a clear sign that the organism was motile; it could move,” said Ian Hughes, a Harvard University organismic and evolutionary biology graduate student and one of the team’s researchers.

The team also includes researchers from the University of California, Riverside, the South Australian Museum and the University of Adelaide, Australia.

Mary Droser, Nilpena’s lead scientist, distinguished professor of geology at UC Riverside and Evans’ former doctoral adviser, has guided this team on digs in the outback for more than 20 years.

“It’s incredibly insightful in terms of telling us about the unfolding of animal life on Earth,” Droser said. “We’re the only planet that we know of with life, so as we look to find life on other planets, we can go back in time on Earth to see how life evolved on this planet. Studying the history of life through fossils tells us how animals evolve and what processes cause their extinction, be it climate change or low oxygen.”

Nilpena Ediacara National Park opened to the public in early 2023 and is part of a bid to be recognized as a UNESCO World Heritage Site. UNESCO World Heritage Sites are natural or cultural sites considered to be of outstanding universal value and are protected by an international convention.

Researchers said this effort is due in large part to the work and generosity of Mary Lou Simpson, founder and chairwoman of the Flinders Ranges Ediacara Foundation, and her husband Antony Simpson for whom Quaestio simpsonorum is named.

“As the oldest fossil animals, the Ediacara biota, can tell us a great deal about early developmental processes,” Evans said. “Determining the gene expressions needed to build these forms provides a new method for evaluating the mechanisms responsible for the beginnings of complex life on this planet.

“Because animals today use the same basic genetic programming to form distinct left and right sides, we can be reasonably confident those same genes were operating to produce these features in Quaestio, an animal that has been extinct for more than half-a-billion years.”

Though the team has been excavating at this location for decades—in fossil beds and rock slabs ranging from the size of a fingernail to a several-hundred-pound slab—Quaestio was only recently discovered at one of the newest excavation sites in the park in a collaborative effort with volunteers at the South Australia Museum. The research team hopes to continue reexamining sites throughout the park’s nearly 150,000 acres.

“We’re still finding new things every time we dig,” Hughes said. “Even though these were some of the first animal ecosystems in the world, they were already very diverse. We see an explosion of life really early on in the history of animal evolution.”

More information: Scott D. Evans et al, A new motile animal with implications for the evolution of axial polarity from the Ediacaran of South Australia, Evolution & Development (2024). DOI: 10.1111/ede.12491

Provided by Florida State University 

Fossil unearthed in Brazil is 237-million-year-old sister-group to Dinosauria

contact.geology
-
0
Fossil unearthed in Brazil is 237-million-year-old sister-group to Dinosauria

Paleontologist Rodrigo Temp Muller with Universidade Federal de Santa Maria, working with colleagues in Brazil, has confirmed the finding of one of the oldest dinosauromorph fossils ever uncovered in South America.

In his paper published in the journal Gondwana Research, Muller describes where the fossil was found, its condition, and where it fits in with a group of extinct Triassic reptiles that were related to dinosaurs.

Muller found the fossil in 2015, near the town of Paraiso do Sul, in the southern part of Brazil. But it was only recently that he and his colleagues began to study it. Dating showed the creature had lived approximately 237 million years ago, during the Middle-Upper-Triassic, and that it was not a dinosaur, but a member of a sister-group called Silesauridae, which are in turn part of a group of non-dinosaur dinosauriforms.

Most members of the group were four-legged and had long necks and legs and short tails. Evidence suggests some members of the group walked upright part of the time. Silesaurids are thought to have existed for approximately 30 million years, and paleontologists have suggested they may have been a precursor to archosaurs.

The fossil consisted of most of the skeletal remains of the ancient creature, enough to prove that it was a distinct species, which Muller has named Gondwanax paraisensis. The remains were also complete enough to show that the find represents one of the oldest dinosauromorphs ever unearthed in South America and one of the oldest silesaurids found anywhere.

Muller determined that the creature’s unique combination of physical attributes, such as its incipient fourth trochanter of the femur and three sacral vertebrae, suggest a high diversity of locomotor strategies, which meant it was likely able to traverse any terrain it may have encountered. It also likely differentiated the species from others with similar features, giving it a possible niche.

Muller suggests the fossil is important because it could help us better understand how the creatures that lived during the Triassic co-existed and because it might help us to better understand the early evolution of bird-line archosaurs.

More information: Rodrigo Temp Müller, A new “silesaurid” from the oldest dinosauromorph-bearing beds of South America provides insights into the early evolution of bird-line archosaurs, Gondwana Research (2024). DOI: 10.1016/j.gr.2024.09.007

Journal information: Gondwana Research 

© 2024 Science X Network

Easter Island’s volcanic history suggests Earth’s mantle behaves quite differently than previously assumed

contact.geology
-
0
Easter Island’s volcanic history suggests Earth’s mantle behaves quite differently than previously assumed

Geography textbooks describe the Earth’s mantle beneath its plates as a well-mixed viscous rock that moves along with those plates like a conveyor belt. But that idea, first set out some 100 years ago, is surprisingly difficult to prove. A mysterious find on Easter Island, investigated by Cuban, Colombian and Utrecht geologists among others, suggests that the Earth’s mantle seems to behave quite differently.

Easter Island consists of several extinct volcanoes. The oldest lava deposits formed some 2.5 million years ago on top of an oceanic plate not much older than the volcanoes themselves. In 2019, a team of Cuban and Colombian geologists left for Easter Island to accurately date the volcanic island.

To do so, they resorted to a tried-and-tested recipe: dating zircon minerals. When magma cools, these minerals crystallize. They contain a bit of uranium, which “turns” into lead through radioactive decay. Their findings are available as a preprint in ESS Open Archive.

Because we know how fast that process happens, we can measure how long ago those minerals formed. The team from Colombia’s Universidad de Los Andes, led by Cuban geologist Yamirka Rojas-Agramonte, therefore went in search of those minerals. Rojas-Agramonte, now at the Christian Albrechts-University Kiel, found hundreds of them. But surprisingly, not only from 2.5 million years old, but also from much further back in time, up to 165 million years ago. How could that be?

Chemical analysis of the zircons showed that their composition was more or less the same in all cases. So, they all had to have come from magma of the same composition as that of today’s volcanoes. Yet those volcanoes cannot have been active for 165 million years, because the plate below them is not even that old. The only explanation then is that the ancient minerals originated at the source of volcanism, in the Earth’s mantle beneath the plate, long before the formation of today’s volcanoes. But that presented the team with yet another conundrum.

Hotspot volcanoes and their origins

Volcanoes like those on Easter Island are so-called “hotspot volcanoes.” These are common in the Pacific Ocean; Hawai’i is a famous example. They form from large blobs of rock that slowly rise from the deep Earth’s mantle—so-called mantle plumes. When they get close to the base of the Earth’s plates, the rocks of the plume as well as from the surrounding mantle melt and form volcanoes.

Scientists have known since the 1960s that mantle plumes stay in place for a very long time while the Earth’s plates move over them. Every time the plate shifts a bit, the mantle plume produces a new volcano. This explains the rows of extinct underwater volcanoes in the Pacific Ocean, with one or a few active ones at the end. Had the team found evidence that the mantle plume under Easter Island has been active for 165 million years?

Echoes from the past: a geological mystery unravelled on Easter Island
Statues on Easter Island. Credit: Douwe van Hinsbergen

Subduction zones

To answer that question, Rojas-Agramonte needed evidence from the geology of the “Ring of Fire,” an area around the ocean with many earthquakes and volcanism, where oceanic plates dip (“subduct”) into the Earth’s mantle. So she contacted Utrecht geologist Douwe van Hinsbergen.

“The difficulty is that the plates from 165 million years ago have long since disappeared in those subduction zones,” says Van Hinsbergen, who had reconstructed the vanished pieces in detail. When he added a large volcanic plateau to those reconstructions at the site of present-day Easter Island 165 million years ago, it turned out that that plateau must have disappeared under the Antarctic Peninsula some 110 million years ago.

“And that just so happened to coincide with a poorly understood phase of mountain building and crust deformation in that exact spot. That mountain range, whose traces are still clearly visible, could well be the effect of subduction of a volcanic plateau that formed 165 million years ago,” he adds.

His reconstruction therefore showed that the Easter Island mantle plume could very well have been active for that long. This would solve the geological mystery of Easter Island: the ancient zircon minerals would be remnants of earlier magmas that were brought to the surface from deep inside the earth, along with younger magmas in volcanic eruptions.

Inconsistencies

But then another problem presents itself. The classical “conveyor belt theory” was already difficult to reconcile with the observation that mantle plumes stay in place while everything around them continues to move. Van Hinsbergen says, “People explained this by saying that plumes rise so fast that they are not affected by a mantle that was moving with the plates. And that new plume material is constantly being supplied under the plate to form new volcanoes.”

But in that case, old bits of the plume, with the old zircons, should have been carried off by those mantle currents, away from the location of Easter Island, and could not now be there at the surface.

“From that, we draw the conclusion that those ancient minerals could have been preserved only if the mantle surrounding the plume is basically as stationary as the plume itself,” he adds.

The discovery of the ancient minerals on Easter Island therefore suggests that the Earth’s mantle behaves fundamentally differently and moves much slower than has always been assumed; a possibility that both Rojas-Agramonte and Van Hinsbergen and their teams raised a few years ago in studies on the Galapagos Islands and New Guinea, and for which Easter Island now provides new clues.

More information: Yamirka Rojas-Agramonte et al, Zircon xenocrysts from Easter Island (Rapa Nui) reveal hotspot activity since the middle Jurassic, ESS Open Archive (2023). DOI: 10.22541/au.170129661.17646127/v1

Provided by Utrecht University 

Scientists date moon’s oldest impact basin to over 4.32 billion years ago

contact.geology
-
0
Scientists date moon’s oldest impact basin to over 4.32 billion years ago

Scientists believe they could have pinpointed the age of the largest and oldest impact basin on the moon to more than 4.32 billion years ago.

The moon, like the Earth, has been bombarded by asteroids and comets since its formation, leaving behind craters and basins. However, the exact timing and intensity of most of these events, notably the oldest and largest basin on the moon, have remained unclear to scientists—until now.

By analyzing a lunar meteorite known as Northwest Africa 2995, a team led by scientists at The University of Manchester have investigated the age of the formation of the massive South Pole-Aitken (SPA) basin—the moon’s oldest confirmed impact site, which is located on the far side of the moon and stretches more than 2,000 kilometers.

The proposed date is around 120 million years earlier than what is believed to be the most intense period of impact bombardment on the moon.

The finding, published today in Nature Astronomy, provides a clearer picture of the moon’s early impact history.

Dr. Joshua Snape, Royal Society University Research Fellow at The University of Manchester, said, “Over many years, scientists across the globe have been studying rocks collected during the Apollo, Luna, and Chang’e 5 missions, as well as lunar meteorites, and have built up a picture of when these impact events occurred.

“For several decades there has been general agreement that the most intense period of impact bombardment was concentrated between 4.2 and 3.8 billion years ago—in the first half a billion years of the moon’s history.

“But now, constraining the age of the South-Pole Aitken basin to 120 million years earlier weakens the argument for this narrow period of impact bombardment on the moon and instead indicates there was a more gradual process of impacts over a longer period.”

The Northwest Africa 2995 meteorite was found in Algeria in 2005 and is what geologists refer to as a regolith breccia, which means it contains fragments of different rock types that were once a lunar soil and have been fused together by the heat and pressure involved in an impact event.

By analyzing the amount of uranium and lead found in a range of mineral and rock fragments within the meteorite, the researchers were able to determine the materials dated back to between 4.32 and 4.33 billion years ago.

The team, which included The University of Manchester, the Institute of Geology and Geophysics–Chinese Academy of Sciences in Beijing, the Swedish Museum of Natural History in Stockholm, and the University of Portsmouth, then compared these results to data collected by NASA’s Lunar Prospector mission, which orbited the moon studying its surface composition between 1998 and 1999.

The comparison revealed many chemical similarities between the meteorite and the rocks within the SPA basin, confirming their link and enabling the new age estimate.

Dr. Romain Tartese, Senior Lecturer at The University of Manchester, said, “The implications of our findings reach far beyond the moon. We know that the Earth and the moon likely experienced similar impacts during their early history, but rock records from the Earth have been lost. We can use what we have learned about the moon to provide us with clues about the conditions on Earth during the same period of time.”

This new understanding opens new avenues for future lunar exploration.

Professor Katherine Joy from The University of Manchester, said, “The proposed ancient 4.32 billion year old age of the South Pole-Aiken basin now needs to be tested by sample return missions collecting rocks from known localities within the crater itself.”

More information: K. H. Joy et al, Evidence of a 4.33 billion year age for the Moon’s South Pole–Aitken basin, Nature Astronomy (2024). DOI: 10.1038/s41550-024-02380-y

Journal information: Nature Astronomy 

Provided by University of Manchester 

5.9 magnitude quake hits eastern Türkiye, authorities assess damage

contact.geology
-
0
5.9 magnitude quake hits eastern Türkiye, authorities assess damage

A 5.9 magnitude earthquake struck Türkiye’s eastern Malatya province at 10:46 a.m. local time, with the epicenter located in the Kale district, the country’s disaster management agency, Disaster and Emergency Management Authority (AFAD), reported on Wednesday.

There were no immediate reports of casualties or significant damage, though authorities are continuing to assess the situation. Emergency response teams have been dispatched to the area to provide assistance, and residents have been advised to remain cautious due to the possibility of aftershocks.

Türkiye lies on major fault lines and is frequently shaken by earthquakes.

The earthquake was also felt strongly in the provinces of Adıyaman, Şanlıurfa and Kahramanmaraş.

The Kahramanmaraş Governor’s Office said in a statement that immediately after the earthquake, teams from the AFAD and related organizations began field assessments without delay.

“As of now, there have been no reports of significant issues. Developments are being closely monitored. We extend our best wishes to citizens affected by the earthquake,” the statement read.

Adıyaman Governor Osman Varol also reported that there were no negative developments received from any sources following the earthquake.

Varol noted that the tremor was strongly felt in the city center and surrounding districts. “So far, we have not received any reports of serious issues from the police, gendarmerie or emergency services. There have only been a few calls reporting citizens feeling faint or unwell due to panic. No damage or destruction has been reported,” Varol said.

A magnitude 6.2 earthquake strikes off Costa Rica’s Pacific coast

contact.geology
-
0
A magnitude 6.2 earthquake strikes off Costa Rica’s Pacific coast

A magnitude-6.2 earthquake occurred off the northwestern coast of Costa Rica at around 12:43 Oct. 12. The epicenter was about 42 km (26 miles) northwest of Tamarindo, Guanacaste Province.

The tremor occurred at a depth of about 18 km (12 miles), and moderate shaking was probably felt in western coastal areas of Guanacaste Province, as well as light shaking throughout parts of northwestern Costa Rica and southwestern Nicaragua.

There have been no initial reports of damage or casualties as a result of the earthquake, and significant damage is unlikely.

It could take several hours until authorities can conduct comprehensive damage assessments, especially in remote areas. Light-to-moderate aftershocks are likely over the coming days. The event has not prompted any tsunami advisories.

Officials may temporarily shut down transportation infrastructure in the tremor zone to check for damage. Minor disruptions could occur during shutdowns, but service will likely resume quickly if no damage is found. Utility outages are possible, particularly near the earthquake’s epicenter.

How did the building blocks of life arrive on Earth? Zinc fingerprints in meteorites offer clues

contact.geology
-
0
How did the building blocks of life arrive on Earth? Zinc fingerprints in meteorites offer clues

Researchers have used the chemical fingerprints of zinc contained in meteorites to determine the origin of volatile elements on Earth. The results suggest that without ‘unmelted’ asteroids, there may not have been enough of these compounds on Earth for life to emerge.

Volatiles are elements or compounds that change into vapor at relatively low temperatures. They include the six most common elements found in living organisms, as well as water. The zinc found in meteorites has a unique composition, which can be used to identify the sources of Earth’s volatiles.

The researchers, from the University of Cambridge and Imperial College London, have previously found that Earth’s zinc came from different parts of our solar system: about half came from beyond Jupiter and half originated closer to Earth.

“One of the most fundamental questions on the origin of life is where the materials we need for life to evolve came from,” said Dr. Rayssa Martins from Cambridge’s Department of Earth Sciences. “If we can understand how these materials came to be on Earth, it might give us clues to how life originated here, and how it might emerge elsewhere.”

Planetesimals are the main building blocks of rocky planets, such as Earth. These small bodies are formed through a process called accretion, where particles around a young star start to stick together, and form progressively larger bodies.

But not all planetesimals are made equal. The earliest planetesimals that formed in the solar system were exposed to high levels of radioactivity, which caused them to melt and lose their volatiles. But some planetesimals formed after these sources of radioactivity were mostly extinct, which helped them survive the melting process and preserved more of their volatiles.

How did the building blocks of life arrive on Earth?
An iron meteorite from the core of a melted planetesimal (left) and a chondrite meteorite, derived from a ‘primitive’, unmelted planetesimal (right). Credit: Sedgwick Museum of Earth Sciences, University of Cambridge.

In a study published in the journal Science Advances, Martins and her colleagues looked at the different forms of zinc that arrived on Earth from these planetesimals.

The researchers measured the zinc from a large sample of meteorites originating from different planetesimals and used this data to model how Earth got its zinc, by tracing the entire period of the Earth’s accretion, which took tens of millions of years.

Their results show that while these ‘melted’ planetesimals contributed about 70% of Earth’s overall mass, they only provided around 10% of its zinc.

According to the model, the rest of Earth’s zinc came from materials that didn’t melt and lose their volatile elements. Their findings suggest that unmelted, or ‘primitive’ materials were an essential source of volatiles for Earth.

“We know that the distance between a planet and its star is a determining a factor in establishing the necessary conditions for that planet to sustain liquid water on its surface,” said Martins, the study’s lead author. “But our results show that there’s no guarantee that planets incorporate the right materials to have enough water and other volatiles in the first place – regardless of their physical state.”

The ability to trace elements through millions or even billions of years of evolution could be a vital tool in the search for life elsewhere, such as on Mars, or on planets outside our solar system.

“Similar conditions and processes are also likely in other young planetary systems,” said Martins. “The roles these different materials play in supplying volatiles is something we should keep in mind when looking for habitable planets elsewhere.”

More information: Rayssa Martins et al, Primitive asteroids as a major source of terrestrial volatiles, Science Advances (2024). DOI: 10.1126/sciadv.ado4121. www.science.org/doi/10.1126/sciadv.ado4121

Journal information: Science Advances 

Provided by University of Cambridge 

Asteroid mining: A potential trillion-dollar industry

contact.geology
-
0
Asteroid mining: A potential trillion-dollar industry

Earth’s newest celestial neighbor has finally arrived. Astronomers using a powerful telescope in Sutherland, South Africa, first detected the 33-foot-long asteroid in August, reporting their discovery in Research Notes of the American Astronomical Society.

There are bigger space rocks, to be sure. But what makes 2024 PT5 so fascinating is that it now orbits Earth as a “mini moon” caught in our planet’s gravitational pull.

Earth’s “second moon,” however, won’t be sticking around for long. It is following a horseshoe path around our world before returning to a heliocentric orbit (an orbit around the sun) in late November.

Such near-Earth objects “offer a glimpse into the processes that formed our solar system,” said Nico Cappelluti, an associate professor of astrophysics in the University of Miami College of Arts and Sciences. “Most of the asteroids in our solar system are rocky remnants left over from the formation of our solar system.”

Asteroid 2024 PT5 is part of Arjuna, an asteroid belt consisting of space rocks that follow orbits around the sun very similar to that of Earth.

“And for that reason, sometimes they remain briefly trapped in our gravitational field,” Cappelluti said. “Having them so close is a captivating opportunity.”

While the school bus-sized asteroid is too dim and too small to be seen with the naked eye or with amateur telescopes, its two-month sojourn around Earth is helping to maintain our keen interest in space rocks. NASA has sent several robotic spacecraft to explore asteroids. Two years ago, in what was called the first test of a planetary defense system, NASA even crashed a spacecraft into a giant space rock, Dimorphos, proving that it is possible to redirect an asteroid should one ever be on a collision course with Earth.

Private companies also want to send spacecraft to asteroids, hoping to mine the celestial objects for the precious metals they contain.

“Asteroids are classified based on their orbit and also based on their content,” said Bertrand Dano, an assistant professor of practice in the College of Engineering’s Department of Mechanical and Aerospace Engineering. “Some are just made of stone, while others have high concentrations of rare metals—platinum and gold for electronics, nickel and cobalt for catalyst and fuel-cell technology, and, of course, iron.”

Asteroid mining is not a far-flung idea, Dano believes. “There are currently millions of asteroids in our solar system, and about 2 million of them are larger than 1 kilometer. The resources contained inside them are the new dream of El Dorado, and there is currently a handful of companies banking on it,” he said, noting that recent missions to rendezvous with and to orbit and land on asteroids have demonstrated that space mining could be just a matter of time.

But pursuing asteroid mining will require a massive investment—from the mining equipment, which would need to run in a vacuum, to the technology needed to transport extracted minerals to Earth, Dano pointed out.

And then, there is the spacecraft itself. A ship dedicated to traveling to an asteroid for the purpose of extracting minerals from it would likely be a robotic craft.

“A trip to Mars takes approximately eight months in the best conditions. The space and equipment required to sustain life is better used for spare equipment and resource storage,” Dano explained. “Leaving Earth’s gravity requires a lot of energy, so mining missions would be better launched from space or from low gravity bodies such as the moon, Mars, or Titan, one of Saturn’s natural satellites.

“Returning to Earth is relatively easy,” he continued, “but it is hazardous for the materials. It would be unfortunate to see the whole prize go up in smoke. Refining could be done in space and periodically ship the refined product. To my knowledge, nobody is thinking that far.”

Still, asteroid mining has the potential payback of a hundredfold or more, according to Dano. “Mining and returning platinum or gold from asteroids could make a person a trillionaire overnight, with the potential to flip our entire economy, trade, and market,” he said. “As astrophysicist Neil deGrasse Tyson once said, ‘The first trillionaire there will ever be is the person who exploits the natural resources on asteroids.'”

Provided by University of Miami 

LA’s quake mystery: 2024 brings the most seismic activity in decades. Why now?

contact.geology
-
0
LA’s quake mystery: 2024 brings the most seismic activity in decades. Why now?

The ground beneath Southern California has been particularly unsteady as of late, with the region experiencing more moderate-sized earthquakes this year than it has in decades.

What precisely is fueling the sequence of shakers is not entirely clear, and officials warn that prior seismic activity does not necessarily mean more powerful temblors are imminent. But the series of modest shakers have many wondering what is going on.

“Earthquakes pop off around the state, and it’s a little bit like popcorn that they hit—sometimes they bunch up for reasons that we don’t understand,” said Susan Hough, seismologist for the U.S. Geological Survey.

Where the quakes are

By the count of seismologist Lucy Jones, a Caltech research associate, Southern California has felt 15 independent seismic sequences this year, with at least one magnitude 4 or higher earthquake. That’s the highest annual total in the last 65 years, surpassing the 13 seen in 1988.

The most recent—a magnitude 4—struck before dawn Sunday near Ontario International Airport. Just in Ontario, one of the most populous cities in San Bernardino County, there have been five earthquakes of magnitude 3 or higher over the past month.

The Malibu area has been another hot spot. There was a magnitude 4.6 earthquake on Feb. 9, strong enough to toss items off a counter; and a magnitude 4.7 on Sept. 12—startling enough that the city’s mayor and his wife dove under their kitchen table.

Eastside L.A. was rattled by a magnitude 4.4 earthquake centered in El Sereno on Aug. 12 and a magnitude 3.4 on June 2.

A magnitude 5.2 earthquake, the strongest to strike the region in three years, shook Southern California on Aug. 6, with an epicenter northwest of the Grapevine. Another widely felt quake, magnitude 4.9, struck on July 29 about 13 miles northeast of Barstow.

Little help reading the tea leaves

The series of seismic disturbances has shaken the nerves of some Southern Californians—serving as an unpleasant reminder of the omnipresent threat of the Big One.

But experts caution that the latest quakes don’t provide any additional clarity on the potential timing of such a cataclysm.

“Seismologists have spent decades trying to read the tea leaves to look for patterns. The seismic network was installed in Southern California 100 years ago because scientists thought that small earthquakes would show patterns before the big earthquakes happened. And that just didn’t work out,” Hough said.

One thing has been clear: “Nobody has found patterns that are statistically meaningful before big earthquakes happen,” she said.

However, the recent spate of quakes should reinforce the threat posed by the state’s notoriously active seismic landscape, experts say, and serve as a reminder of just how many Californians live in a danger zone.

The summer’s Eastside L.A earthquakes, for instance, were centered on faults associated with the Puente Hills thrust fault system, which is underneath downtown L.A. and swaths of southeast L.A. County, the San Gabriel Valley and northern Orange County.

A moment to reflect on past seismic destruction

All of this comes as the state prepares for the annual Great California ShakeOut earthquake drill on Oct. 17. People can sign up to participate in the drill, which starts at 10:17 a.m., at shakeout.org.

This year’s drill happens to fall on the 35th anniversary of the Loma Prieta earthquake.

The 1989 temblor was a magnitude 6.9 and centered in the Santa Cruz Mountains. It rocked Northern California, resulting in 63 deaths.

That earthquake changed Northern California forever—causing heavy damage to downtown Santa Cruz, parts of San Francisco, and causing the collapse of sections of Interstate 880 in Oakland and the San Francisco-Oakland Bay Bridge.

This year also marked the 30th anniversary of Los Angeles’ last destructive earthquake: the magnitude 6.7 Northridge temblor.

At least 57 people died in that 1994 earthquake, which caused the collapse of part of the Santa Monica Freeway and the interchange between Interstate 5 and Highway 14.

Many buildings collapsed or were heavily damaged, from wooden apartments with flimsy ground stories—known as soft-story buildings—to concrete medical offices and a department store, to a steel-frame building housing the Automobile Club of Southern California.

The USGS is asking Californians who remember feeling the 1989 or 1994 earthquakes to fill out a quick survey to recall what they felt at their location. Both earthquakes occurred before the era of widespread internet service, and scientists are hopeful that more responses will help refine their understanding of the events.

“Every bit of data is valuable,” Hough said.

The USGS’ online “Did You Feel It” crowdsourcing maps for the Loma Prieta and Northridge earthquakes will be updated with new responses.

“There’s just so many different ways that we can look at the data,” Hough said. “We can look at how the ground shook. We can look at the variation of shaking across different areas.”

This is also a way to be a part of history.

“Human memories are fleeting,” Hough said. “The people who experienced that earthquake—we’re not going to be around forever. So it’s a chance to capture people’s experiences in a way that contributes to science.”

Preparations make a difference

The ShakeOut drill is a good time to prepare for an earthquake, such as by checking your emergency supply kit and downloading the free earthquake early warning smartphone app, available at myshake.berkeley.edu. The app, powered by the USGS ShakeAlert system, can enable many users to get seconds of warning of incoming shaking before it arrives at their location.

The Google-powered Android operating system also has a built-in earthquake early warning app.

MyShake will send out a test alert on Oct. 17 at 10:17 a.m.

“That’s a way to know whether or not, if you have MyShake, it’s set up correctly,” said Robert de Groot, a ShakeAlert operations team leader.

People can also get earthquake early warnings without downloading an app through an Amber Alert-style text message called a Wireless Emergency Alert. But officials widely urge people to download the MyShake app as a good way to get these warnings.

To get the fastest, most relevant warnings wherever you are, you can set the app’s settings to allow MyShake to access your location “always.” The alerts are calculated to warn you based on your location when the earthquake hits.

Apple also suggests changing a setting on your iPhone—turning on “Local Awareness” to facilitate more timely or accurate earthquake early warnings. To do so, go to “settings,” then “notifications,” and scroll all the way down to select “emergency alerts,” and press the “local awareness” switch to turn it on by making it green.

2024 Los Angeles Times. Distributed by Tribune Content Agency, LLC.

How did magma oceans evolve on early Earth and Mars? Iron chemistry and primordial atmospheres offer clues

contact.geology
-
0
How did magma oceans evolve on early Earth and Mars? Iron chemistry and primordial atmospheres offer clues

Before Earth became the blue planet, it was engulfed by a very different kind of ocean: a vast, deep magma ocean reaching down hundreds or perhaps even thousands of kilometers.

As early Earth’s magma ocean cooled and solidified, different types of minerals crystallized at different rates, so the chemical makeup of the molten rock changed over time. And as the magma released gases into early Earth’s atmosphere, the chemical makeup of the atmosphere changed as well.

During their formation, Mars and many other rocky planets went through similar magma ocean stages. However, because this all occurred in the distant past for Earth and Mars—and in distant space for younger rocky planets—it is very difficult to know exactly how it all happened. However, information about the chemical makeup of rocky planets’ early atmospheres is preserved in unreactive noble gases.

Now, Schaefer and team present novel models simulating how Earth’s and Mars’s magma oceans might have changed over time as they crystallized, using these atmospheric clues and information about iron chemistry. The research is published in the Journal of Geophysical Research: Planets.

The models incorporate new calculations that capture how ferrous (reduced) and ferric (oxidized) iron behave as magma crystallizes in the mantle. The research team tested the model with different initial magma ocean depths and chemical makeups to see which combination would create the atmospheres they know existed around early Earth and Mars.

The researchers found that for Earth, models that start with a shallow magma ocean outperform models that start with a fully molten mantle. A shallow magma ocean could indicate either a mantle that was only partially melted or a fully melted mantle that began solidifying from its middle, with the innermost and outermost layers remaining molten for some time.

For Mars, none of the models successfully aligned with prior research findings about the red planet’s early atmosphere, unless the initial magma composition had lower levels of ferric iron than it is thought to have contained.

These findings lead toward a deeper understanding of how rocky planets such as Earth and Mars form while also highlighting the need for more experimental research on the behavior of iron in molten rock.

More information: Laura Schaefer et al, Ferric Iron Evolution During Crystallization of the Earth and Mars, Journal of Geophysical Research: Planets (2024). DOI: 10.1029/2023JE008262

Journal information: Journal of Geophysical Research: Planets 

Provided by American Geophysical Union 

This story is republished courtesy of Eos, hosted by the American Geophysical Union. Read the original story here.

123...206Page 2 of 206

© Geology Science 2021