Latest news with #plateTectonics
Gizmodo
20 hours ago
- Science
- Gizmodo
Weirdly Hot Rocks in New England Traced to 80-Million-Year-Old Greenland Rift
Roughly 124 miles (200 kilometers) beneath the Appalachian Mountains in New England lies the aptly named Northern Appalachian Anomaly (NAA), a mysterious 218-mile-wide (350-km) region of unusually hot rock. Researchers have long believed that the NAA resulted from the plate tectonic movement that broke North America off northwest Africa 180 million years ago. In a new study published Tuesday in the journal Geology, however, a team of international researchers argue that the hot, subsurface rocks are related to when North America and Greenland split near the Labrador Sea between 90 and 80 million years ago. The NAA 'lies beneath part of the continent that's been tectonically quiet for 180 million years, so the idea it was just a leftover from when the landmass broke apart never quite stacked up,' Tom Gernon, lead author of the study and an Earth scientist at the University of Southampton, said in a university statement. To reach this conclusion, the team used advanced computer simulations, seismic tomography data (like an ultrasound, but for Earth's interior), and tectonic plate reconstructions. According to the study, the NAA may have developed around 1,119 miles (1,800 km) from its current position and, at the rate of around 12 miles (20 km) per million years, slowly moved southwestward to where it sits now. 'Our research suggests it's part of a much larger, slow-moving process deep underground that could potentially help explain why mountain ranges like the Appalachians are still standing,' Gernon added. The slow-moving process is the team's previously proposed 'mantle wave' theory, which hypothesizes that hot, dense chunks of material detach from the base of tectonic plates after continents separate, like blobs in a lava lamp. 'Heat at the base of a continent can weaken and remove part of its dense root, making the continent lighter and more buoyant, like a hot air balloon rising after dropping its ballast,' Gernon explained. 'This would have caused the ancient mountains to be further uplifted over the past few million years.' As the blobs slowly 'drip' from the lithosphere—the layer including Earth's crust and upper part of the mantle—hotter mantle rocks rise to fill up the space, which creates a thermal anomaly. The same team's earlier work also revealed that these blobs can move over time. 'The feature we see beneath New England is very likely one of these drips, which originated far from where it now sits,' said Sascha Brune, study co-author and head of the Geodynamic Modelling Section at GFZ, Germany's national research center for Earth sciences. According to the team, the center of the NAA will likely move under New York in the next 15 million years. 'The idea that rifting of continents can cause drips and cells of circulating hot rock at depth that spread thousands of kilometres inland makes us rethink what we know about the edges of continents both today and in Earth's deep past,' admitted Derek Keir, another co-author of the study and a tectonics expert at the University of Southampton and the University of Florence. The researchers argue that their mantle wave theory could explain a similar anomalous hot zone under north-central Greenland—basically a reflection of the NAA on the other side of the Labrador Sea. The study is ultimately a reminder to never judge a book by its cover—or the Earth by its surface-level tectonic activity.
RNZ News
20-07-2025
- Science
- RNZ News
First video of Earth's surface lurching sideways in earthquake offers new insights
Analysis - During the devastating magnitude 7.7 Myanmar earthquake on March 28 this year, a CCTV camera captured the moment the plate boundary moved, providing the first direct visual evidence of plate tectonics in action. Tectonic plate boundaries are where chunks of Earth's crust slide past each other - not smoothly, but in sudden, violent ruptures. The footage shows Earth's surface lurching sideways, like a gigantic conveyor belt switched on for just a second, as the fault slips. What we're seeing is the propagation of a large earthquake rupture - the primary mechanism that accommodates plate boundary motion at Earth's surface. These shear fractures travel at several kilometres per second, making them notoriously difficult to observe. Workers wearing hazmat suit spray disinfectant to sterilise the rubble of a collapsed building in Mandalay on April 2, 2025, five days after a major earthquake struck central Myanmar. Photo: AFP These rare events, separated by centuries, have shaped our planet's surface over millions of years, creating features such as Aotearoa New Zealand's Alpine Fault and the Southern Alps. Until now, seismologists have relied on distant seismic instruments to infer how faults rupture during large earthquakes. This video sheds new light on the process that radiates seismic energy and causes the ground to shake. In our new study, we analysed the video frame by frame. We used a technique called pixel cross-correlation to reveal that the fault slipped 2.5 metres sideways over a duration of just 1.3 seconds, with a maximum speed of 3.2 metres per second. The total sideways movement in this earthquake is typical of strike-slip fault ruptures, which move the land sideways (in contrast to faults that move land up and down). But the short duration is a major discovery. The timing of when a fault starts and stops slipping is especially difficult to measure from distant recordings, because the seismic signal becomes smeared as it travels through Earth. In this case, the short duration of motion reveals a pulse-like rupture - a concentrated burst of slip that propagates along the fault like a ripple travels down a rug when it's flicked from one end. Capturing this kind of detail is fundamental to understanding how earthquakes work, and it helps us better anticipate the ground shaking likely to occur in future large events. Our analysis also revealed something more subtle about the way the fault moved. We found the slip didn't follow a straight path. Instead it curved. This subtle curvature mirrors patterns we've observed previously at fault outcrops. Called "slickenlines", these geological scratch marks on the fault record the direction of slip. Our work shows the slickenlines we see on outcrops are curved in a manner similar to the curvature seen in the CCTV footage. Based on our video analysis, we can be certain that curved slip occurs, giving credence to our interpretations based on geological observations. In our earlier research, we used computer models to show that curved slickenlines could emerge naturally when an earthquake propagates in a particular direction. The Myanmar rupture, which is known to have travelled north to south, matches the direction predicted by our models. This alignment is important. It gives us confidence in using geological evidence to determine the rupture direction of past earthquakes, such as the curved slickenlines left behind after the New Zealand Alpine Fault's 1717 earthquake. This first glimpse of a fault in motion shows the potential for video to become a powerful new tool in seismology. With more strategic deployments, future earthquakes could be documented with similar detail, offering further insight into the dynamics of fault rupture, potentially revolutionising our understanding of earthquake physics. This story originally appeared in The Conversation .
