Pulsing Magma in Earth's Mantle Drives Tectonic Plates Tearing Africa Apart
Scientists first proposed in the 1970s that a hot upsurge of material from Earth's mantle, known as a plume, was occurring below this spot. Since then researchers have debated whether a single plume, multiple smaller 'plumelets' or something else entirely is pushing the plates apart. Emma Watts, a geochemist at Swansea University in Wales, wanted to settle the question, so she and a team of geophysicists, geochemists and computational scientists put their heads together and came up with a likely answer.
'The more I look into it, the more I see that you've got to have all the pieces of the puzzle to see the big picture,' she says.
[Sign up for Today in Science, a free daily newsletter]
The team analyzed 130 rock samples from volcanoes in the Afar region. Chemical signatures from each sample helped the scientists piece together the movement of the molten rock below Earth's surface: The researchers calculated the ratios of concentrations of elements such as lead and cerium, which can indicate whether deep mantle material has surged upward, as well as the ratios of different isotopes that each originated from slightly varying reservoirs within the mantle.
After comparing their data to computational models of various permutations of mantle plumes, the researchers have found that the best explanation for their observations is a single plume that moves upward in pulses. The pulses appear to exert varying pressure that pushes on each rift zone differently, depending on the way the rift moves and the thickness of the crust on either side. The Afar Triangle's fast-spreading Red Sea Rift has pulses that move farther along the rift zone and that are more frequent than those of the slower-spreading Main Ethiopian Rift in the western part of the triangle.
'The rifting rates are really controlling what we're seeing in the plume,' Watts says. 'What we think is that [the Red Sea Rift is] spreading out faster..., so it has more space to move, and it's being stretched out easier.'
The relationship between the mantle movement and the geochemical fingerprints is 'exciting because it suggests geophysics and geochemistry can be married to infer large-scale geodynamic processes,' says Catherine Rychert, a geophysicist at the Woods Hole Oceanographic Institution, who was not involved in this research.
This is one of the first known examples of a dynamic mantle plume that responds to the tectonic plates above, so more research is needed to confirm the finding, Rychert says. Watts hopes this technique could be used in other rift systems and that more data from this system could give researchers a more precise view of what is happening deep below Earth's surface.
Hashtags
Try Our AI Features
Explore what Daily8 AI can do for you:
Comments
No comments yet...
Related Articles
Yahoo
6 hours ago
- Yahoo
Ethiopian fossils reveal new species in human evolutionary lineage
By Will Dunham (Reuters) -Researchers have unearthed tooth fossils in Ethiopia dating to about 2.65 million years ago of a previously unknown species in the human evolutionary lineage, one that lived in the same time and place as the earliest-known member of the genus Homo to which our own species belongs. The scientists discovered in the Ledi-Geraru research project area of northeastern Ethiopia's Afar Region 10 teeth - six molars, two incisors, one premolar and one canine - that they concluded belonged to a new Australopithecus species. The teeth came from two individuals. Until now, six species of the genus Australopithecus, an important early human ancestor that displayed a mix of ape-like and human-like traits, were known from fossils at various African sites. The researchers said the newly found teeth bore traits indicating they belonged to a seventh species. A genus is a group of closely related species that share similar characteristics. For example, lions and tigers are from the same genus but represent different species. The scientists also discovered three other teeth dating to 2.59 million years ago that had traits showing they belonged to the oldest-known species of Homo, one that was first revealed by a jawbone unearthed in the same vicinity in 2013. Scientists have not yet assigned names to the Australopithecus and Homo species represented by these 13 teeth because of the incomplete nature of the fossil remains. Our species Homo sapiens is the most recent member of the Homo genus, first appearing roughly 300,000 years ago in Africa before later spreading worldwide. The new dental fossils provide insight into a poorly understood period in human evolution. The close age of the teeth suggests that this newly identified Australopithecus species coexisted in this region with the early Homo species, raising questions about whether they competed for the same resources. The teeth also indicate that there were four hominins - as species in the human evolutionary lineage are known - that inhabited East Africa at the time. Previous fossils showed that another Australopithecus species and a species of Paranthropus, a hominin possessing a specialized skull adapted for heavy chewing, lived in East Africa during this time. An additional Australopithecus species also inhabited southern Africa, bringing the number of hominins then on the continent to five. The presence of these contemporaneous hominins illustrates the complicated nature of the human evolutionary process. "This reinforces the idea that the story of human evolution is not of a single lineage changing slowly through time," said University of Nevada, Las Vegas paleoanthropologist Brian Villmoare, lead author of the research published on Wednesday in the journal Nature. "Rather, the pattern of human evolution is similar to that of other organisms, repeatedly branching into multiple species throughout the fossil record, many of whom lived at the same time," Villmoare added. The researchers are seeking clues about the nature of any interaction between the Australopithecus and Homo species represented by the 13 teeth. "We are currently analyzing teeth to see if we can tell if they ate the same thing," said Arizona State University paleoecologist and project co-director Kaye Reed. If so, they may have fought over resources, Reed said. Crude stone tools dating to about the same time were previously discovered nearby, Reed said, probably made by the Homo species. The researchers determined the age of the teeth using a technique that dated feldspar crystals contained in volcanic ash in the sediments where they were discovered based on radioactive decay of the element argon. The Afar Region, one of Earth's hottest and lowest places, is an arid expanse of badlands. But at the time of these species, rivers flowed across a vegetated landscape into shallow lakes in a landscape populated by a splendid array of animals. These included giraffes, horses, pigs, elephants, hippos and antelopes as well as predators such as saber-toothed cats and hyenas. Homo is generally thought to have descended from a species of Australopithecus, though the exact species and the timing have been a matter of debate. Australopithecus eventually died out. Australopithecus includes the famous fossil Lucy, who was a member of the species Australopithecus afarensis who lived approximately 3.18 million years ago. Lucy's remains were discovered in 1974, also in the Afar Region. The newly discovered teeth had characteristics that showed they did not belong to Lucy's species, the researchers said. "This new Australopithecus species is in no way some 'missing link,' and we actually don't think that it was necessarily ancestral to any known species," Villmoare said. "Species arose and many went extinct," Reed said. "Each find is a piece of the puzzle that puts human evolution into a twiggy tree, rather than a linear graphic." Solve the daily Crossword
Yahoo
12 hours ago
- Yahoo
A meteorite crashed into a Georgia home. Scientists say it's older than the Earth itself
A meteorite that crashed into a Georgia home in June is older than the Earth itself, according to scientists who are studying the space rock. Onlookers in the Southeast were stunned when a fireball streaked across the sky on June 26. Fragments of the meteorite hurtled into the roof of a homeowner in McDonough, Henry County, just south of Atlanta, leaving behind a hole the size of a golf ball in the ceiling and a dent in the floor. Scott Harris, a researcher in the University of Georgia's Franklin College of Arts and Sciences' department of geology, has been studying the fragments and believes the meteorite formed 4.56 billion years ago. The Earth is thought to be 4.543 billion years old. 'This particular meteor that entered the atmosphere has a long history before it made it to the ground of McDonough, and in order to totally understand that, we actually have to examine what the rock is and determine what group of asteroids it belongs to,' Harris said in a university news release. Using optical and electron microscopy to analyze the fragments, Harris said he believes the meteorite to be a low metal ordinary Chondrite. 'It belongs to a group of asteroids in the main asteroid belt between Mars and Jupiter that we now think we can tie to a breakup of a much larger asteroid about 470 million years ago,' Harris said. 'But in that breakup, some pieces get into Earth-crossing orbits, and if given long enough, their orbit around the sun and Earth's orbit around the sun end up being at the same place, at the same moment in time.' The sound and vibration the meteor made was equivalent to a close-range gunshot. The homeowner told Harris he's still finding specks of space dust around his living room from the collision. 'I suspect that he heard three simultaneous things,' Harris said. 'One was the collision with his roof, one was a tiny cone of a sonic boom and a third was it impacting the floor all in the same moment. There was enough energy when it hit the floor that it pulverized part of the material down to literal dust fragments.' The meteorite, which has been named McDonough, is the 27th to be recovered in Georgia's history. 'This is something that used to be expected once every few decades and not multiple times within 20 years,' Harris said. 'Modern technology in addition to an attentive public is going to help us recover more and more meteorites.' Additional pieces of the meteorite that fell in the area will be displayed to the public at the Tellus Science Museum in Cartersville. Solve the daily Crossword
Yahoo
a day ago
- Yahoo
An icy supervolcano eruption on Pluto may have left a massive crater on the frozen world
When you buy through links on our articles, Future and its syndication partners may earn a commission. A landmark on Pluto that was previously designated as an impact crater may actually be the caldera of a supervolcano that has exploded in the past few million years, new research suggests. When NASA's New Horizons mission flew by Pluto in 2015, it revealed a geologically rich world, rather than the cold, dark landscape many had anticipated. Almost immediately, researchers identified two features, called Wright Mons and Piccard Mons, that were strongly suspected to be icy volcanoes, and further study confirmed their identity. But not every cryovolcano was easy to spot. The suspected supervolcano, Kiladze, was initially classified as an impact crater. However, now scientists suspect it's something else. "We evaluated the possibility of the depression as a cryovolcanic caldera versus having an impact crater origin," said Al Emran, a planetary scientist at the Jet Propulsion Laboratory in California. Emran presented his team's results in July at the Progress in Understanding the Pluto System: 10 Years After Flyby conference in Laurel, Maryland. "We think it's more like Yellowstone Caldera in Wyoming," Emran said. At least two of Yellowstone's eruptions, millions of years ago, reached supervolcano status. Impact crater or caldera? Kiladze remains listed as a crater. But the rich supply of water ice surrounding the bowl-shaped feature sparked Emran's curiosity, and he wondered if it might be a cryovolcano instead. At first glance, the elongated oval bears a strong similarity to an impact crater. It's large, with an average diameter of 2.5 miles (4 kilometers). Its walls are irregularly shaped, and the complex features it would require could easily have been eroded by Pluto's active surface processes. The landscape itself is marked by pits and other geological features, many of which have collapsed. If an incoming impactor broke through the surface and exposed veins of frozen lava beneath, it could have created the explosive distribution of water ice seen on the surface. But when Emran dug into the topography maps of Pluto created by the New Horizons team, he realized there was a problem: The crater was too deep. Across the solar system, crater depth scales with crater diameter in a predictable way, and the same law appeared to hold true for other craters on Pluto — but for not Kiladze. At best, estimates put an impact crater of its size at 1.7 miles (2.74 km) wide. But with the activity flowing across Pluto, material would have been more likely to fill in the crater over time, making it even shallower. Haze particles would have piled up, and melting or slumping ices would have fallen inward. However, Kiladze isn't shallower than projected; it's deeper. Parts of the basin reach 2.5 deep, and the entire site averages nearly 2 miles (3 km) in depth. For these reasons, Emran and his colleagues suspect that Kiladze is a caldera, a massive depression created by the eruption and subsequent collapse of a volcano. Magma — or cryomagma — spewing from the surface rapidly over a short period of time can weaken the supporting material, causing it to collapse inward on itself. Despite the supervolcano's collapse, the eruptive power of Kiladze would have been impressive. Emran and his colleagues calculated that the explosion could have ejected as much as 240 cubic miles (1,000 cubic kilometers) of icy cryomagma across the surrounding region, achieving the definition of a supervolcano. Although Yellowstone has erupted more than 80 times over its lifetime of more than 2 million years, only two explosions have been classified as supervolcanic. Kiladze may have blasted out its cryomagma in a single explosive event, or it may have spread its eruptions over time. Either way, its most recent event spewed water ice at least 60 miles (100 km). Emran suspects that estimate is low, however, as more water ice is likely visible at resolutions smaller than New Horizons could reach. "One or more cataclysmic explosive eruptions that resulted in the excavation and collapse of what is seen as the Kiladze caldera would be expected to scatter the water-ice cryomagma widely for a thousand or more kilometers, leaving exposures too small to be seen in the data at hand," the authors wrote in a paper recently published in The Planetary Science Journal. Clues in the ice Kiladze sits just north of Sputnik Planetia, the icy heart to Pluto. Although much of the dwarf planet's surface is covered with a variety of ices, very little of the surface matches what you might find in your freezer at home. Temperatures on Pluto are so cold that water ice serves as the bedrock for the dwarf planet, while other ices pile on top. But in the neighborhood surrounding Kiladze, water ice stretches across the surface. The ice has traces of an unidentified ammoniated compound. "It's difficult to determine the exact composition," Emran said. In fact, that particular signature of ammonia is not seen anywhere else on Pluto. Ammonia may be what allows the frigid ice to flow. Its addition lowers the freezing point of water, allowing it to remain liquid for longer periods. Beneath the surface, pockets of water and ammonia could have avoided freezing as Pluto's bedrock solidified. Eventually, tectonic pressure could have driven the icy magma to the surface, spewing it across the landscape around Kiladze, Emran explained. The mysterious traces of ammonia could also help to date the cryovolcano. Pure ammonia is quickly obliterated by the solar wind, ultraviolet particles and cosmic rays. Its faint presence suggests that the latest eruption occurred fairly recently in Pluto's history, Emran said. Pluto's haze can help to nail down geological activity. The light shroud covers the dwarf planet — a result of methane and other gases jumping from solid to gas. As the particles grow, they eventually fall back to the surface and spread all over the dwarf planet. Grounded haze particles would cover the water ice like a blanket, obscuring signs of the cryolava, Emran explained. If such a layer had formed, New Horizons would have seen nitrogen-rich ice instead of signs of water-rich volcanism. RELATED STORIES — Supervolcano eruption on Pluto hints at hidden ocean beneath the surface — Pluto's heart-shaped scar may offer clues to the frozen world's history — Pluto's atmosphere gets its blue haze from icy organic compounds, study suggests Burying the water ice requires at least 0.4 inches (10 millimeters) of haze particles falling to Pluto. That process takes at least 3 million years, Emran said. That could mean Pluto isn't as frozen as previously thought. "If Kiladze erupted as recently as 3 million years ago, it would indeed suggest that Pluto's interior may still retain some residual warmth today," Emran said. "This aligns with the idea that cryovolcanism on Pluto could be ongoing or episodic." Solve the daily Crossword
