Latest news with #ThorstenBecker
Forbes
27-04-2025
- Science
- Forbes
How Earth's Mantle Played A Role In Shaping Human Evolution
A sculptor's rendering of the hominid Australopithecus afarensis that lived 3.2 million years ago in ... More Africa. An international team of researchers investigated how Earth's mantle activity created an uplift between what is now the Arabian Peninsula and Anatolia about 35 to 20 million years ago. The resulting land bridge enabled the early ancestors of animals such as giraffes, elephants, rhinoceroses, cheetahs, and even humans, to leave Africa, ending a 75-million-year-long isolation of the continent. "This study has relevance to the question of 'How did our planet change, in general? What are the connections between life and tectonics?'" says Thorsten Becker, a study co-author and professor at the Jackson School's Department of Earth and Planetary Sciences and Institute for Geophysics, University of Texas. The full story begins 70 to 60 million years ago, when a slab of rock sliding into Earth's mantle melted, creating a plume that reached the surface some 30 million years later. The mantle plume pushing upwards, coupled with the collision of tectonic plates between Africa and Asia, created an uplift that contributed to closing the ancient Tethys Sea, splitting it into what is now the Mediterranean and Arabian Seas, and created a landmass that bridged Asia and Africa for the first time. In a similar way Iceland is today above sea level because it sits atop a mantle plume and between two tectonic plates. The study's lead author Eivind Straume analyzed the wide-ranging consequences of this geologic activity while he was a postdoctoral fellow at the Jackson School. He says the appearance of the land bridge and evolution of early hominids go hand in hand. "The shallow seaway closed several million years before it otherwise likely would have due to these specific processes—mantle convection and corresponding changes in dynamic topography," explains Straume, who is now a postdoctoral fellow at the Norwegian Research Center and The Bjerknes Center for Climate Research. "Without the plume, you could argue that the continental collision would have been different." Without the mantle plume, Africa and Asia may have remained isolated for much longer, and the animals that made their way into and out of Africa, including our ancestors, could have been much different. Several million years before the land bridge had completely closed, the primate ancestors of humans came to Africa from Asia. While those primates ended up going extinct in Asia, their lineages diversified in Africa. Then when the land bridge fully emerged, these primates re-colonized Asia and Europe. This uplift also had significant impacts on ocean circulation and Earth's climate. Without the Tethys Sea and oceanic currents redistributing energy to the north, the Indian Ocean got warmer and eastern Africa became more arid. Researchers believe this event was a final trigger in making the Sahara a desert, maybe even driving early hominids out of Africa as they followed the rain some 10 to 7 million years ago. The warmer ocean also enhanced evaporation and monsoon activity making southeast Asia wetter. This paper brings together existing research spanning plate tectonics, mantle convection, topography and paleogeography, evolutionary anthropology, mammal evolution, climate evolution, and ocean circulation, among other topics, to tell a cohesive story of the wide-ranging effects of these mantle dynamics. The study, "Collision, mantle convection and Tethyan closure in the Eastern Mediterranean," was published in the journal Nature Reviews Earth & Environment. Additional material and interviews provided by University of Texas at Austin.
Yahoo
05-04-2025
- Science
- Yahoo
North American continent slowly losing rock from its underside, discover scientists
Researchers have discovered that the North American continent is slowly losing rock from its underside in a process called "cratonic dripping." This is caused by the remnants of the Farallon Plate, an ancient tectonic plate, which is influencing the mantle and causing blobs of rock to detach and sink. The Midwest of the United States is where the dripping effect is most intense. But don't worry, the continent isn't about to collapse. These are incredibly slow geological processes, happening over millions of years. It provides valuable insights into how continents evolve over millions of years. The team at the University of Texas at Austin examined cratons, the ancient rock formations that make up Earth's continents. "We made the observation that there could be something beneath the craton. Luckily, we also got the new idea about what drives this thinning," said Junlin Hua, the study's lead author. Cratons are ancient, stable parts of continents that can last billions of years. However, they are not immune to change, and can experience alterations that disrupt their stability or lead to the loss of rock layers. One past example of craton change is the North China Craton, but the current discovery of cratonic dripping in North America is significant because it's presently happening. The researchers predict the dripping will halt once the tectonic plate remnants sink deeper, thus diminishing their impact on the craton. "This sort of thing is important if we want to understand how a planet has evolved over a long time. It helps us understand how do you make continents, how do you break them, and how do you recycle them [into Earth]," said Thorsten Becker, co-author, in the press release. So, what's causing this slow, subterranean drip? The remnants of the Farallon Plate. Researchers used advanced seismic imaging and computer models to see and simulate this process. The models showed that the dripping stopped when the Farallon Plate was removed, confirming its role. This project generated a detailed computer model of North America's subsurface utilizing EarthScope seismic data. It ultimately revealed previously unseen geological processes within the continent's crust and mantle. The new computer model allowed scientists to visualize the "dripping" phenomenon for the first time. Furthermore, it provided evidence linking the dripping to the Farallon Plate, an ancient oceanic plate that has been subducting under North America for last 200 millions of years. Researchers found the model's output closely aligned with observed data, suggesting its accuracy. "You look at a model and say, "Is it real, are we overinterpreting the data or is it telling us something new about Earth? But it does look like in many places that these blobs come and go, that it's [showing us] a real thing," added Becker. This discovery is essential for unraveling the mysteries of Earth's dynamic systems, particularly the formation and transformation of continents across immense timescales. The findings were published in the journal Nature Geoscience.
Yahoo
03-04-2025
- Science
- Yahoo
Earth's Crust Is Dripping Under Midwest US, Scientists Discover
Beneath the American Midwest, on the continent of North America, the underside of Earth's crust is dripping into the planetary interior. There, blobs of molten rock are coalescing in the upper mantle of the planet, eventually gaining enough mass to precipitate deeper, a slow, gradual mechanism revealed through seismic monitoring that shows the thinning lithosphere underlying the region. It's nothing to worry about. Only recently discovered, lithospheric dripping occurs in other parts of the world, too – but the revelation opens a new window onto our dynamic Earth's unique geological processes. "This sort of thing is important if we want to understand how a planet has evolved over a long time," explains geophysicist Thorsten Becker of the University of Texas at Austin. "It helps us understand how do you make continents, how do you break them, and how do you recycle them." The type of lithosphere here is a craton – a particularly large, stable section of Earth's crust that has been around, relatively unchanged, for a very long period of time. Because they are so stable, they are thought to be the nuclei around which continents form. We know of around 35 cratons lurking beneath our feet. Lithospheric dripping occurs when the underside of Earth's rocky crust is heated to a certain temperature. As the rock melts, a drop starts to form, eventually becoming weighty enough to break off and fall away deeper into the planet. It's a bit like an extreme version of a pitch drop experiment. In some cases, like in the Andes and Türkiye's Anatolian Plateau, this process can create wrinkles on the planet's surface that betray the activity occurring below. In this case, however, a team led by seismologist Junlin Hua, currently of the University of Science and Technology of China but at the University of Texas while undertaking this research, used seismic data to reconstruct the activity on the underside of Earth's crust. They used a computer model that builds a tomographic map of Earth's crust from seismic data collected by the EarthScope Consortium. It's like taking an X-ray of the crust, revealing where it is thickest and thinnest, and how its density varies. "Because of the use of this full-waveform method, we have a better representation of that important zone between the deep mantle and the shallower lithosphere where we would expect to get clues on what's happening with the lithosphere," Becker explains. The team's work reveals that the craton that sits under most of the North American continent is thinning, with the focal point beneath the Midwest of the US, and the probable cause is lithospheric dripping. What's even more intriguing is what's causing it. Some 600 kilometers (373 miles) from the craton, the ancient Farallon tectonic plate is sliding underneath the North American tectonic plate, a process known as subduction. This process has been playing out for hundreds of millions of years; by this point, the Farallon plate has been almost entirely subducted, with the bulk of it now sitting in the lower mantle, underneath the North American plate. The seismic data suggests that its presence is redirecting large-scale mantle flows that shear the bottom of the craton, weakening it. The dripping process could then be exacerbated by prior weakening of the lithosphere; an example of this would be through the release of volatiles from the remnants of the subducting Farallon slab. Together, these processes could soften and weaken the underside of the craton enough to facilitate lithospheric dripping, thinning the craton around which the continent is structured. Although the focal point is under the Midwest, the effects are widespread across the entire craton, the researchers found. But it's a process that has timescales of millions to billions of years, and is unlikely to affect anyone living on the North American continent for many generations to come. The research has been published in Nature Geoscience. Wild New Study Suggests Buttholes Once Had a Very Different Purpose Holes in Desert Rocks May Have Been Left by Microbe Unlike Any Known Orcas Are Terrorizing Sharks, And The Consequences Could Be Profound
