Latest news with #mantleplumes
Yahoo
2 days ago
- Science
- Yahoo
Mysterious Blobs Deep Inside Earth May Fuel Deadly Volcanic Eruptions
Volcanic eruptions can destroy essential infrastructure, ground air traffic for days, wipe out entire cities, disrupt the climate for years, and even wipe out life on Earth, so it's important to know what causes them to blow. New research has revealed that specific features deep within Earth can be linked directly to such cataclysmic eruptions. Thousands of kilometers below Earth's surface, there is a solid layer of hot rock called the lower mantle. Textbook diagrams would have you believe this is a smooth layer, but the lower mantle actually contains a mountainous topography, with two continent-sized structures, possibly made of different materials than their surrounds. Related: These hidden structures feature craggy ranges that shift and buckle much like the tectonic plates far above them. Volcanologist Annalise Cucchiaro from the University of Wollongong in Australia and her colleagues have found these big lower-mantle basal structures – termed 'BLOBS' by the research team – have a direct influence on volcanic activity at Earth's surface. When scorching columns of rock, known as deep mantle plumes, first rise from depths of nearly 3,000 kilometers (almost 2,000 miles), we get the kinds of Earth-shattering volcanoes that wiped out most of life on Earth, and had a hand in the extinction of the dinosaurs. The BLOBS seemed a likely source of these subterranean plumes, and Cucchiaro's team has now confirmed this connection using three different datasets that provide extensive detail on large volcanic eruptions that happened around 300 million years ago. "This work highlights the importance of mantle plumes in acting as 'magma highways' to the surface, creating these giant eruptions," Cucchiaro says. "It also shows that these plumes move along with their source, the BLOBS." There are two BLOBS within the lower mantle. One is below the African hemisphere, and the other, under the Pacific. We still don't know if the BLOBS are ever fixed in place, or if they're always moving around via convection, but the new research suggests it's a dynamic system with direct repercussions for us surface dwellers. By simulating the movements of BLOBS 1 billion years ago, the team showed that they produced mantle plumes that were sometimes slightly tilted as they rose. This meant eruptions occurred either directly above the BLOBS, or close to it – and these locations matched that of known eruptions. "We used statistics to show that the locations of past giant volcanic eruptions are significantly related to the mantle plumes predicted by our models," Cucchiaro and her colleague, geoscientist Nicholas Flament, explained in The Conversation. "This is encouraging, as it suggests that the simulations predict mantle plumes in places and at times generally consistent with the geologic record." As much as they destroy, large eruptions also have the power to create, and knowing where they may occur – either historically or in the future – could also help us to find magmatic treasures like kimberlite and diamonds, and minerals that could be used in harnessing renewable energy. "This research cracks open one of the questions that has long plagued scientists – are the BLOBS stationary or mobile and how do they relate to giant volcanic explosions – so it is a thrill to finally [be able] to unravel these mysteries," says Flament. This research was published in Communications Earth & Environment. Atlantic Ocean's Nanoplastic Problem Revealed in Shocking New Study Scientists Discovered This Amazing Practical Use For Leftover Coffee Grounds Antarctica's Ocean Is Mysteriously Getting Saltier, Spelling End to Sea Ice
The Independent
6 days ago
- Science
- The Independent
Scientists discover the ‘missing link' that causes giant volcanic eruptions
Volcanic eruptions at Earth's surface have significant consequences. Smaller ones can scare tourists on Mount Etna or disrupt air traffic. Giant, large-scale eruptions can have more serious impacts. One such event contributed to the demise of the dinosaurs 66 million years ago. Giant volcanoes also triggered events that led to the largest mass dying on Earth, the Permian–Triassic extinction 252 million years ago But what fuels a giant eruption, and how does it make its way to the surface from deep within the planet? In a new study published in Communications Earth and Environment, we show that columns of hot rock, which rise some 3,000 kilometres through Earth's mantle and cause giant eruptions, are connected to continent-sized source regions we call BLOBS. Hidden blobs within Earth BLOBS are hot regions at the bottom of Earth's mantle (between about 2,000km and 3,000km in depth) which might be composed of different material compared with the surrounding mantle rocks. Scientists have long known about these two hot regions under the Pacific Ocean and Africa. Geologist David Evans from Yale University suggested the acronym BLOBS, which stands for Big LOwer-mantle Basal Structures. These BLOBS have possibly existed for hundreds of millions of years. It is unclear whether they're stationary or if they move around as part of mantle motion (called convection). Mantle plumes were the implicit link in previous studies relating BLOBS to giant volcanic eruptions. Their shape is a bit like a lollipop: the 'stick' is the plume tail and the 'candy' is the plume head. Mantle plumes rise very slowly through the mantle because they transport hot solid rock, not melt or lava. At lower pressures in the uppermost 200km of Earth's mantle, the solid rock melts, leading to eruptions. A long-sought relationship In our new study, we simulated mantle convection from one billion years ago and found that mantle plumes rise from moving BLOBS and can sometimes be gently tilted. Giant volcanic eruptions can be identified by the volume of volcanic rocks preserved at Earth's surface. The ocean floor preserves detailed fingerprints of mantle plumes for the past 120 million years or so (there is not much seafloor older than that). Oceanic plateaus, such as the Ontong Java-Manihiki-Hikurangi plateau currently in the southwest Pacific Ocean, are linked to plume heads. In contrast, a series of volcanoes such as the Hawaii -Emperor seamount chain and the Lord Howe seamount chain are linked to plume tails. We used statistics to show that the locations of past giant volcanic eruptions are significantly related to the mantle plumes predicted by our models. This is encouraging, as it suggests that the simulations predict mantle plumes in places and at times generally consistent with the geologic record. Are BLOBS fixed or mobile? We showed that the considered eruption locations fall either onto or close to the moving BLOBS predicted by our models. Eruption locations slightly outside moving BLOBS could be explained by plume tilting. We represented fixed BLOBS with 3D images of Earth's interior, created using seismic waves from distant earthquakes (a technique called seismic tomography). One out of the four seismic tomographic models that we considered matched the locations of past giant volcanic eruptions, implying that the fixed BLOBS scenario cannot be ruled out for geologically recent times – the past 300 million years. One of the next steps for this research is to explore the chemical nature of BLOBS and plume conduits. We can do so with simulations that track the evolution of their composition. Our results suggest the deep Earth is dynamic. BLOBS, which are some 2,000km below Earth's surface, move hundreds of kilometres over time, and are connected to Earth's surface by mantle plumes that create giant eruptions. To take a step back and keep things in perspective: while deep Earth motions are significant over tens of millions of years, they are generally in the order of 1 centimetre per year. This means BLOBS shift in a year at roughly the rate at which human hair grows each month. Nicolas Flament is an Associate Professor and ARC Future Fellow in Environmental Futures, School of Science at the University of Wollongong.
