LC7C. Stay Current—Earth’s Shifting Crust

2024-11-07. A New View of Deep Earth’s Carbon Emissions. By Saima May Sidik, Eos/AGU. Excerpt: From time to time, when Earth’s tectonic plates shift, the planet emits a long, slow belch of carbon dioxide. In a new modeling study, Müller et al. show how this gas released from deep Earth may have affected climate over the past billion years. …Scientists have often estimated the volume of such carbon emissions solely on the basis of the gas released by plate tectonics. But plate tectonics can also capture carbon by incorporating it into new crust formed at mid-ocean ridges. In the new work, researchers drew on two recent studies about the past billion years of plate movement to more precisely model how much carbon dioxide this process has generated. …Tectonic activity is a major determinant of Earth’s atmospheric composition over geologic time, the researchers conclude. https://doi.org/10.1029/2024GC011713, …. Full article at https://eos.org/research-spotlights/a-new-view-of-deEos/AGUearths-carbon-emissions.

2024-08-26. Near-Identical Dinosaur Tracks On Separate Continents Reveal Seismic Split 140 Million Years Ago. By Francesca Benson, IFLSCIENCE. Excerpt: racks of near-identical dinosaur prints have been found across two continents, demonstrating how the dinosaurs that made them 120 million years ago were among the last to be able to complete their journey. That’s because this was when the supercontinent Gondwana broke off from Pangea, severing the geological connection. The prints were discovered in Brazil and Cameroon, amounting to over 260 prints in total. When they were laid down in the mud and silt of ancient rivers and lakes, they left behind ichnological evidence of the very different lay of the land that existed during the Early Cretaceous. At that time, South America and Africa were so close together that terrestrial dinosaurs could walk freely between them. Now, such a journey would encompass a 6,000-kilometer (3,700-mile) swim across deep waters. “One of the youngest and narrowest geological connections between Africa and South America was the elbow of northeastern Brazil nestled against what is now the coast of Cameroon along the Gulf of Guinea,” Southern Methodist University paleontologist Louis Jacobs said in a statement. “The two continents were continuous along that narrow stretch, so that animals on either side of that connection could potentially move across it.”…. Full article at https://www.iflscience.com/dinosaur-tracks-on-two-separate-continents-reveal-seismic-split-140-million-years-ago-75694.

2023-11-08. Future Supercontinent Will Be Inhospitable for Mammals. [https://eos.org/articles/future-supercontinent-will-be-inhospitable-for-mammals] By Rebecca Owen, Eos/AGU. Excerpt: It sounds like something from an apocalyptic sci-fi movie: Continents collide and trigger volcanic turmoil. Toxic gases fill the air. The planet becomes a hot desert devoid of life…in the future as the continents regroup into one, Pangea Ultima. A new study published in Nature Geoscience projects that as this new supercontinent forms in around 250 million years, a hotter Sun, an absence of ocean coastline, and increased volcanic carbon dioxide (CO₂) emissions mean that temperatures, particularly in landlocked areas, will skyrocket. The study suggests that this distant future foretells a mass extinction for mammals. Alexander Farnsworth, a paleoclimatologist at the University of Bristol and one of the authors of the study, usually studies climates of the past (though he has also built models to assess the accuracy of the climate in fictional worlds, like Game of Thrones’ Westeros). During the pandemic, he began wondering if it was possible to predict climate conditions hundreds of millions of years from now on a supercontinent. …One thing is certain from the study’s models: Pangea Ultima is going to be very, very unpleasant for mammals. Most of the landmass will be far from an ocean, and the arid expanses in the supercontinent’s interior will be between 50°C and 65°C during an average summer—too hot even for most plants to grow. …Two Hundred Fifty Million Years Is a Long Way Off…Although Pangea Ultima sounds bleak, the timescales of such tectonic upheavals mean the future presented in this study is not exactly imminent….

2020-05-08. Are We Seeing a New Ocean Starting to Form in Africa? By Erik Klemetti, Eos/AGU. Excerpt: …The entire Afar region in eastern Africa finds itself in the middle of changes that could split the continent, forming a new ocean basin. The magmatism at Erta Ale might be offering signs of this switch by mimicking the characteristics of a mid-ocean ridge. … What we will be able to see standing on top of Erta Ale will change dramatically in 5 million, 50 million, or 100 million years. The question is whether Erta Ale and the Afar region will become a new ocean, or whether ongoing tectonic collisions to Africa’s north and east will prevent this transition from occurring…. [https://eos.org/articles/are-we-seeing-a-new-ocean-starting-to-form-in-africa] 

2017-02-17. Zealandia: Is there an eighth continent under New Zealand? By BBC News. Excerpt: Say hello to Zealandia, a huge landmass almost entirely submerged in the southwest Pacific. .you might have heard of its highest mountains, the only bits showing above water: New Zealand. Scientists say it qualifies as a continent and have now made a renewed push for it to be recognised as such. In a paper published in the Geological Society of America’s Journal, researchers explain that Zealandia measures five million sq km (1.9m sq miles) which is about two thirds of neighbouring Australia. Some 94% of that area is underwater with only a few islands and three major landmasses sticking out above the surface: New Zealand’s North and South Islands and New Caledonia. You might think being above water is crucial to making the cut as a continent, but the researchers looked at a different set of criteria, all of which are met by the new kid in town. …elevation above the surrounding area …distinctive geology …a well-defined area …a crust thicker than the regular ocean floor….  http://www.bbc.com/news/world-asia-39000936

2012 Feb 8.  Next Supercontinent Will Form in Arctic, Geologists Say.  By Sindya N. Bhanoo, The NY Times.  Excerpt: Geologists have long predicted that North and South America will eventually fuse together and merge with Asia, forming a new supercontinent along the lines of the ancient Pangea — the precursor to today’s great land masses, which separated about 200 million years ago.
In the past, researchers had guessed that the new continent, often called Amasia, would form either in the same location as Pangea, closing over the Atlantic near present-day Africa, or 180 degrees away, on the other side of the world.
But a new study predicts that Amasia will form over the Arctic Ocean….

2010 Feb 27. Underwater Plate Cuts 400-Mile Gash. By HENRY FOUNTAIN, NY Times. Excerpt: The magnitude 8.8 earthquake that struck off the coast of Chile early Saturday morning occurred along the same fault responsible for the biggest quake ever measured, a 1960 tremor that killed nearly 2,000 people in Chile and hundreds more across the Pacific.
Both earthquakes took place along a fault zone where the Nazca tectonic plate, the section of the earth’s crust that lies under the Eastern Pacific Ocean south of the Equator, is sliding beneath another section, the South American plate. The two are converging at a rate of about three and a half inches a year.
Earthquake experts said the strains built up by that movement, plus the stresses added along the fault zone by the 1960 quake, led to the rupture on Saturday along what is estimated to be about 400 miles of the zone, at a depth of about 22 miles under the sea floor. The quake generated a tsunami, with small surges hitting the West Coast of the United States and slightly larger ones in Hawaii and other parts of the Pacific. A 7.7-foot surge was recorded in Talcahuano, Chile.
Jian Lin, a geophysicist with the Woods Hole Oceanographic Institution, said the quake occurred just north of the site of the 1960 earthquake, with very little overlap. “Most of the rupture today picked up where the 1960 rupture stopped,” said Mr. Lin, who has studied the 1960 event, which occurred along about 600 miles of the fault zone and was measured at magnitude 9.5….

2008 May.The Living Story of Sulawesi. by Kathleen M. Wong, ScienceMatters@Berkeley.Excerpt: The Indonesian island of Sulawesi is a 12,000-square-mile jigsaw puzzle. During the past 25 million years, drifting tectonic plates tore four separate paleo-islands from the far corners of the South Pacific and smashed them together in a steamy corner of Southeast Asia.
This turbulent history has turned Sulawesi into a complex biological cipher. Today, it houses a mélange of species with confusing origins: some may have been passengers on the original islands, some may have arrived afterward, and some may have evolved from the mix.
…Jim McGuire, curator of herpetology at Berkeley’s Museum of Vertebrate Zoology and a professor of integrative biology, is studying how these species evolved and came to be distributed on Sulawesi today.
..”It was as if they were cut off from each other at some point. But in many cases we don’t know what the underlying mechanism would be,” McGuire says.
…Based on these data, he uses computer simulations to reconstruct the evolutionary history of these animal groups. He then plans to go back and study contact zones between species more closely to try to identify any environmental or ecological barriers, such as past flooding or the presence of a predator, that are enforcing species isolation….

28 August 2007. A Daddy Longlegs Tells the Story of the Continents’ Big Shifts. By CARL ZIMMER, NY Times. Excerpt: Few people have heard of the mite harvestman, …. The animal is a relative of the far more familiar daddy longlegs. But its legs are stubby rather than long, and its body is only as big as a sesame seed. … “They look like grains of dirt,” said Gonzalo Giribet, an invertebrate biologist at Harvard. … Dr. Giribet and his colleagues have spent six years searching for them on five continents. The animals have an extraordinary story to tell: they carry a record of hundreds of millions of years of geological history, chronicling the journeys that continents have made around the Earth.
The Earth’s land masses have slowly collided and broken apart again several times, carrying animals and plants with them. These species have provided clues to the continents’ paths.
The notion of continent drift originally came from such clues. In 1911, the German scientist Alfred Wegner was struck by the fact that fossils of similar animals and plants could be found on either side of the Atlantic. The ocean was too far for the species to have traveled themselves. Wegner speculated – correctly, as it turned out – that the surrounding continents had originally been welded together in a single landmass, which he called Pangea.
Continental drift, or plate tectonics as it is scientifically known, helped move species around the world. Armadillos and their relatives are found in South America and Africa today because their ancestors evolved when the continents were joined. …The 5,000 or so mite harvestmen species can be found on every continent except Antarctica. Unlike animals found around the world like cockroaches, mite harvestmen cannot disperse well. The typical harvestman species has a range of less than 50 miles. Harvestman are not found on young islands like Hawaii.
“It’s really hard to find a group of species that is distributed all over the world but that also don’t disperse very far,” said Sarah Boyer, a former student of Dr. Giribet, now an assistant professor at Macalester College in St. Paul….