How deep-ocean vents fuel massive phytoplankton blooms

June 9, 2019

Researchers at Stanford University say they have found an aquatic highway that lets nutrients from Earth’s belly sweep up to surface waters off the coast of Antarctica and stimulate explosive growth of microscopic ocean algae.

Their study, published June 5 in the journal Nature Communications, suggests that hydrothermal vents — openings in the seafloor that gush scorching hot streams of mineral-rich fluid — may affect life near the ocean’s surface and the global carbon cycle more than previously thought.

Mathieu Ardyna, a postdoctoral scholar and the study’s lead author, said the research provides the first observed evidence of iron from the Southern Ocean’s depths turning normally anemic surface waters into hotspots for phytoplankton — the tiny algae that sustain the marine food web, pull heat-trapping carbon dioxide out of the air and produce a huge amount of the oxygen we breathe. “Our study shows that iron from hydrothermal vents can well up, travel across hundreds of miles of open ocean and allow phytoplankton to thrive in some very unexpected places,” he said.

Kevin Arrigo, a professor of Earth system science and senior author of the paper, called the findings “important because they show how intimately linked the deep ocean and surface ocean can be.”

Mysterious blooms

Phytoplankton need iron to thrive, and that limits their abundance in vast swaths of the ocean where concentrations of the nutrient are low. But when conditions are right, phytoplankton can also grow explosively, blooming across thousands of square miles in a matter of days.

That’s what Ardyna noticed recently as he looked at data recorded in 2014 and 2015 by a fleet of floating robots outfitted with optical sensors in the Southern Ocean. More than 1,300 miles off the coast of Antarctica and 1,400 miles from the African continent, two unexpectedly large blooms cropped up in an area known for severe iron shortages and low concentrations of chlorophyll, an indicator of phytoplankton populations.

Massive blooms in this region could only be possible with an influx of iron. Ardyna and Arrigo quickly ruled out the ocean’s most common sources, including continental shelves, melting sea ice and atmospheric dust, which were simply too far away to have much influence.

That led them to suspect that the nutrient must be welling up from below, possibly from a string of hydrothermal vents that dot a mid-ocean ridge 750 miles from where the massive blooms had inexplicably appeared. To help test their hypothesis, they recruited an international team of collaborators specialized in various aspects of oceanography and modeling.

“It has long been known that hydrothermal vents create unique and profound oases of life,” Ardyna said. Until recently, scientists generally believed those nourishing effects remained fairly local. But a growing amount of evidence from computer simulations of ocean dynamics has hinted that iron and other life-sustaining elements spewed from hydrothermal vents may in fact fuel planktonic blooms over much wider areas.

However, direct measurements have been lacking.

In the Southern Ocean, that’s partly due to the remote location, extreme cold and rough seas, which make it difficult to study up close or collect accurate data. “Your sensors have to be in the right place at the right time to see these blooms,” Ardyna said. “Satellites can underestimate intensity or miss them altogether because of bad coverage or strong mixing of the water column, which pushes phytoplankton down too deep for satellites to see.”

Clues from space, floating robots

To track the flow of particles from the vents on the mid-ocean ridge, the scientists analyzed data from satellites measuring chlorophyll and from autonomous, sensor-laden buoys known as Argo floats. As they dive and drift along ocean currents, some of these buoys detect chlorophyll and other proxies for phytoplankton biomass. “The floats give us precious and unique data, covering a large section of the water column down to 1,000 meters deep during an entire annual cycle,” Ardyna said.

The scientists couldn’t directly measure iron in the water, but instead analyzed measurements of helium collected by scientific cruises in the 1990s. The presence of helium signals waters influenced by hydrothermal vents, which funnel large amounts of primordial helium from beneath Earth’s crust.

The chlorophyll, phytoplankton and helium data suggest that a powerful current circling Antarctica grabs nutrients rising up from vents. Two turbulent, fast-moving branches of the current then shuttle the nutrients eastward for a month or two before serving them like a banquet to undernourished phytoplankton. Together with the arrival of spring sunshine that phytoplankton need for photosynthesis, the delivery triggers a massive bloom that can likely absorb and store significant amounts of carbon from the atmosphere, said Arrigo, who is also the Donald and Donald M. Steel Professor in Earth Sciences.

Over time, the blooms drift eastward toward the current racing around Antarctica and fade as sea creatures devour them. “We suspect these hotspots are either consumed or exported to deep waters,” Ardyna said.

Each bloom lasts little more than a month, but the mechanisms that trigger them are likely to be more common in the global ocean than scientists previously suspected.

“Hydrothermal vents are scattered all over the ocean floor,” Ardyna said. Knowing about the pathways that bring their nutrients up to surface waters will help researchers make more accurate calculations about the flow of carbon in the world’s oceans. “Much remains to be done to reveal other potential hotspots and quantify how this mechanism is altering the carbon cycle.”

Reference:
Mathieu Ardyna, Léo Lacour, Sara Sergi, Francesco d’Ovidio, Jean-Baptiste Sallée, Mathieu Rembauville, Stéphane Blain, Alessandro Tagliabue, Reiner Schlitzer, Catherine Jeandel, Kevin Robert Arrigo, Hervé Claustre. Hydrothermal vents trigger massive phytoplankton blooms in the Southern Ocean. Nature Communications, June 5, 2019; DOI: 10.1038/s41467-019-09973-6

Note: The above post is reprinted from materials provided by Stanford’s School of Earth, Energy & Environmental Sciences. Original written by Josie Garthwaite.

New findings on Earth’s magnetic field

June 9, 2019

This is what the Earth inside looks like: Deep down lies the core of the Earth, followed by the Earth’s mantle. The Earth’s crust begins 35 kilometres below the surface. Credit: Peter Eggermann / Adobe Stock

The huge magnetic field which surrounds the Earth, protecting it from radiation and charged particles from space — and which many animals even use for orientation purposes — is changing constantly, which is why geoscientists keep it constantly under surveillance. The old well-known sources of the Earth’s magnetic field are the Earth’s core — down to 6,000 kilometres deep down inside the Earth — and the Earth’s crust: in other words, the ground we stand on. The Earth’s mantle, on the other hand, stretching from 35 to 2,900 kilometres below the Earth’s surface, has so far largely been regarded as “magnetically dead.” An international team of researchers from Germany, France, Denmark and the USA has now demonstrated that a form of iron oxide, hematite, can retain its magnetic properties even deep down in the Earth’s mantle. This occurs in relatively cold tectonic plates, called slabs, which are found especially beneath the western Pacific Ocean.

“This new knowledge about the Earth’s mantle and the strongly magnetic region in the western Pacific could throw new light on any observations of the Earth’s magnetic field,” says mineral physicist and first author Dr. Ilya Kupenko from the University of Münster (Germany). The new findings could, for example, be relevant for any future observations of the magnetic anomalies on the Earth and on other planets such as Mars. This is because Mars has no longer a dynamo and thus no source enabling a strong magnetic field originating from the core to be built up such as that on Earth. It might, therefore, now be worth taking a more detailed look on its mantle. The study has been published in the “Nature” journal.

Background and methods used:

Deep in the metallic core of the Earth, it is liquid iron alloy that triggers electrical flows. In the outermost crust of the Earth, rocks cause magnetic signal. In the deeper regions of the Earth’s interior, however, it was believed that the rocks lose their magnetic properties due to the very high temperatures and pressures.

The researchers now took a closer look at the main potential sources for magnetism in the Earth’s mantle: iron oxides, which have a high critical temperature — i.e. the temperature above which material is no longer magnetic. In the Earth’s mantle, iron oxides occur in slabs that are buried from the Earth’s crust further into the mantle, as a result of tectonic shifts, a process called subduction. They can reach a depth within the Earth’s interior of between 410 and 660 kilometres — the so-called transition zone between the upper and the lower mantle of the Earth. Previously, however, no one had succeeded in measuring the magnetic properties of the iron oxides at the extreme conditions of pressure and temperature found in this region.

Now the scientists combined two methods. Using a so-called diamond anvil cell, they squeezed micrometric-sized samples of iron oxide hematite between two diamonds, and heated them with lasers to reach pressures of up to 90 gigapascal and temperatures of over 1,000 °C (1,300 K). The researchers combined this method with so-called Mössbauer spectroscopy to probe the magnetic state of the samples by means of synchrotron radiation. This part of the study was carried out at the ESRF synchrotron facility in Grenoble, France, and this made it possible to observe the changes of the magnetic order in iron oxide.

The surprising result was that the hematite remained magnetic up to a temperature of around 925 °C (1,200 K) — the temperature prevailing in the subducted slabs beneath the western part of Pacific Ocean at the Earth’s transition zone depth. “As a result, we are able to demonstrate that the Earth’s mantle is not nearly as magnetically ‘dead’ as has so far been assumed,” says Prof. Carmen Sanchez-Valle from the Institute of Mineralogy at Münster University. “These findings might justify other conclusions relating to the Earth’s entire magnetic field,” she adds.

Relevance for investigations of the Earth’s magnetic field and the movement of the poles

By using satellites and studying rocks, researchers observe the Earth’s magnetic field, as well as the local and regional changes in magnetic strength. Background: The geomagnetic poles of the Earth — not to be confused with the geographic poles — are constantly moving. As a result of this movement they have actually changed positions with each other every 200,000 to 300,000 years in the recent history of the Earth. The last poles flip happened 780,000 years ago, and last decades scientists report acceleration in the movement of the Earth magnetic poles. Flip of magnetic poles would have profound effect on modern human civilisation. Factors which control movements and flip of the magnetic poles, as well as directions they follow during overturn are not understood yet.

One of the poles’ routes observed during the flips runs over the western Pacific, corresponding very noticeably to the proposed electromagnetic sources in the Earth’s mantle. The researchers are therefore considering the possibility that the magnetic fields observed in the Pacific with the aid of rock records do not represent the migration route of the poles measured on the Earth’s surface, but originate from the hitherto unknown electromagnetic source of hematite-containing rocks in the Earth’s mantle beneath the West Pacific.

“What we now know — that there are magnetically ordered materials down there in the Earth’s mantle — should be taken into account in any future analysis of the Earth’s magnetic field and of the movement of the poles,” says co-author Prof. Leonid Dubrovinsky at the Bavarian Research Institute of Experimental Geochemistry and Geophysics at Bayreuth University.

Reference:
I. Kupenko, G. Aprilis, D. M. Vasiukov, C. McCammon, S. Chariton, V. Cerantola, I. Kantor, A. I. Chumakov, R. Rüffer, L. Dubrovinsky, C. Sanchez-Valle. Magnetism in cold subducting slabs at mantle transition zone depths. Nature, 2019; 570 (7759): 102 DOI: 10.1038/s41586-019-1254-8

Note: The above post is reprinted from materials provided by University of Münster.

Study provides new insight into origin of Canadian Rockies

June 9, 2019

The Canadian Rocky Mountains were formed when the North American continent was dragged westward during the closure of an ocean basin off the west coast and collided with a microcontinent over 100 million years ago, according to a new study by University of Alberta scientists.

The research, based on high resolution data of Earth’s subsurface at the Alberta-British Columbia (BC) border, favours an interpretation different from the traditional theory of how the Canadian Rocky Mountains formed. The traditional theory, known as the accretion model, suggests that a gradual accumulation of additional matter eventually formed the Canadian Rockies — unlike the sudden collision event proposed by this research.

“This research provides new evidence that the Canadian section of this mountain range was formed by two continents colliding,” said Jeffrey Gu, professor in the Department of Physics and co-author on the study. “The proposed mechanism for mountain building may not apply to other parts of the Rocky Mountains due to highly variable boundary geometries and characteristics from north to south.”

The study involved seismic data collected from a dense network of seismic stations in western Alberta and eastern BC, combined with geodynamic calculations and geological observations. The results suggest that an ocean basin off North America’s west coast descended beneath the ribbon-shaped microcontinent, dragging North America westward, where it collided with the microcontinent.

“This study highlights how deep Earth images from geophysical methods can help us to understand the evolution of mountains, one of the most magnificent processes of plate tectonics observed at the Earth’s surface,” said Yunfeng Chen, who conducted this research during his PhD studies under the supervision of Gu. Chen received the Faculty of Science Doctoral Dissertation Award in 2018.

“There are other mountain belts around the world where a similar model may apply,” said Claire Currie, associate professor of physics and co-author on the study. “Our data could be important for understanding mountain belts elsewhere, as well as building our understanding of the evolution of western North America.”

Alberta and British Columbia communities supported these research efforts by hosting seismic stations on their land. This research is also supported by the Alberta Energy Regulator.

Reference:
Yunfeng Chen, Yu Jeffrey Gu, Claire A. Currie, Stephen T. Johnston, Shu-Huei Hung, Andrew J. Schaeffer, Pascal Audet. Seismic evidence for a mantle suture and implications for the origin of the Canadian Cordillera. Nature Communications, 2019; 10 (1) DOI: 10.1038/s41467-019-09804-8

Note: The above post is reprinted from materials provided by University of Alberta. Original written by Katie Willis.

Pterosaur : What Is a Pterosaur?

June 6, 2019

Pterosaur

Pterosaurs were flying reptiles of the extinct clade or order Pterosauria. For most of the Mesozoic, they persisted: from the early Triassic to the end of the Cretaceous (228 to 66 million years old). Pterosaurs are the oldest vertebrate flight recognized to have developed. Their wings were created by a skin, muscle, and other tissue membrane that stretched from the knees to a fourth finger dramatically extended.

Early species had long, completely dented jaws and lengthy bodies, while subsequent types had a sharply decreased tail and teeth were missing from some. Many sported furry coats consisting of hair-like filaments known as pycnofibers that coated their heads and wing components. Pterosaurs ranged from the very tiny anurognathides to the biggest recognized flying animals of all time, including Quetzalcoatlus and Hatzegopteryx, to a broad spectrum of adult dimensions.

Pterosaurs are often referred to in the famous press and by the general public as ‘ flying animals, ‘ but the word ‘ homo ‘ is limited to those reptiles that came from the last common ancestor of the communities Saurischia and Ornithischia (clad Dinosaur, which contains animals), and the current scientific consensus is that this category excludes pterosaurs as well as the multiple types of ex-patriarchs.

However, pterosaurs, unlike these other reptiles, are closer to birds and dinosaurs than to crocodiles or any other living reptiles. Also known informally as pterodactyls are pterosaurs, especially in fiction and reporters. However, technically, pterodactyl only refers to members of the genus Pterodactylus, and more broadly to members of the suborder Pterodactyloidea of the pterosaurs.

When was pterosaur fossil Discovered?

In 1784, the Italian naturalist Cosimo Alessandro Collini defined the first pterosaur fossil. Collini misunderstood his sample as a seagoing animal that used as paddles its lengthy front legs. Even until 1830, when German zoologist Johann Georg Wagler proposed that Pterodactylus use its legs as flippers, a few researchers persisted to promote aquatic interpretation. In 1801, Georges Cuvier first proposed that pterosaurs were floating beasts and created the word “Ptero-dactyle” for the sample retrieved in Germany in 1809.

However, the formal title for this genus became Pterodactylus owing to the standardization of scientific names, although the word “pterodactyl” continued to be given popularly and wrongly to all Pterosaurian representatives. Now, palaeontologists prevent using “pterodactyl” and prefer “pterosaur.” They relegate the word “pterodactyl” specifically for Pterodactylus genus representatives or more widely for Pterodactyloidea suborder representatives.

Pterosaur Evolution

Scientists have long discussed where the evolutionary tree is fitted with pterosaurs. Today’s major hypothesis is that pterosaurs, reptiles, and crocodiles are strongly linked to each other and belong to a community called archosaurs.

Pterosaurs have been an incredibly effective reptile community. Throughout the dinosaur era they flourished, a span of over 150 million years. The oldest pterosaurs, relatively tiny flying reptiles with sturdy bodies and lengthy tails, evolved over moment into a wide range of species. Some had long, slim jaws, sophisticated head crests, or customized teeth, and some were extremely big.

Pterosaur Extinction

It was once believed that rivalry with early bird species could have brought many of the pterosaurs to extinction. Part of this is because it was believed that only big species of pterosaurs were present by the end of the Cretaceous (not correct anymore; see below). It was believed that the lower species had become extinct, their niche filled with birds. However, the decrease of pterosaurs (if current) tends to be irrelevant to the variety of birds, as the ecological overlap between the two communities seems minimal.

In reality, pterosaurs had recovered at least some avian niches before the KT case. The Cretaceous–Paleogene extinction incident, which also wiped out all non-avian dinosaurs and most avian species, and many other creatures, appears to have hit the pterosaurs at the end of the Cretaceous Period.

In the early 2010s, several new pterosaur taxa, such as the ornithocheirids Piksi and “Ornithocheirus,” possible pteranodontides and nyctosaurides, several tapejarids and indeterminate non-azhdarchid Navajodactylus, have been discovered dating to the Campanian / Maastrichtian. In the Campanian there were also small azhdarchoid pterosaurs. This indicates that late Cretaceous pterosaur faunas have been much more varied than earlier assumed, potentially not even substantially declining from the early Cretaceous. Piksi, however, is no longer regarded as a pterosaur.

Apparently there were small size pterosaur species in the Csehbánya Formation, suggesting a greater variety of Late Cretaceous pterosaur ##s than earlier reported. The latest results of a tiny cat-sized adult azhdarchid further show that tiny pterosaurs from the Late Cretaceous may, in reality, have been scarcely maintained in the fossil record, assisted by the reality that there is a powerful bias against tiny terrestrial vertebrates such as juvenile animals, and that their variety may effectively have been much greater than earlier assumed.

Late Cretaceous maintained at least some non-pterodactylod pterosaurs, postulating a rock taxa scenario for late Cretaceous pterosaur faunas.

How Did Pterosaurs Fly?

Flight enabled pterosaurs to move lengthy distances, utilize fresh environments, evade predators, and take their prey from above. They distributed throughout the globe and branched out into a huge variety of species, including the largest animals ever to wing.

Built to Fly

Pterosaurs produced lift with their wings like other flying animals. They required the same types of movements as birds and bats, but their wings developed separately and developed their own separate aerodynamic framework.

With their forelimbs, Pterosaurs moved. Their lengthy wings developed from the same portion of the body as our arms. As the arm and leg bones of pterosaurs developed for floating, they lengthened, and one finger’s bones— our ring finger’s equal — became extraordinarily lengthy. These bones, like the mast on a boat, backed the top of the wing, a slim skin flap formed like a flag.

Wing Bones

Although there are many creatures that can glide through the air, pterosaurs, birds, and bats are the only vertebrates that have developed to move through their bones. All three organizations came down from creatures living on the floor, and their wings developed in a comparable manner: their forelimbs gradually became lengthy, bladelike, and aerodynamic.

In order to get off the floor, large pterosaurs required powerful limbs, but dense bones would have rendered them too heavy. The answer? The wing bones of a pterosaur were hollow pipes, with no bigger walls than a play board. They were versatile and lightweight like bird bones, while reinforced by inner struts.

Inside the Wings

Recent findings indicate that wing membranes of pterosaurs were more than just skin flaps. Long strands stretched from the front to the back of the bones forming a sequence of stabilizing bases so that the membranes could be spread tight or folded as a fan. Separate muscle fibers assisted pterosaurs to change their wings ‘ strain and shape, and veins and arteries maintained blood-fed wings.

The exhibition includes a remarkable Rhamphorhynchus muensteri fossil, discovered in Germany in 2001, featuring wing tissues so well preserved that scientists could see fine details in their structure. Researchers identified skin cells lined with blood vessels, muscles, and lengthy fibers that strengthened the wing under ultraviolet light. Paleontologists call this fossil Dark Wing due to the shadowy shape of the wing membrane.

Reference:
Pterosaur
What Is a Pterosaur?
How Did Pterosaurs Fly?

Rare fossils provide more detailed picture of biodiversity during Middle Ordovician

June 6, 2019

The sluglike mollusk Wiwaxia was among the trove of fossils dating back to the Middle Ordovician. Credit: Julien Kimmig.

A clutch of marine fossil specimens unearthed in northern Portugal that lived between 470 and 459 million years ago is filling a gap in understanding evolution during the Middle Ordovician period.

The discovery, explained in a new paper just published in The Science of Nature, details three fossils found in a new “Burgess Shale-type deposit.” (The Burgess Shale is a deposit in Canada renowned among evolutionary biologists for excellent preservation of soft-bodied organisms that don’t have a biomineralized exoskeleton.)

“The paper describes the first soft-body fossils preserved as carbonaceous films from Portugal,” said lead author Julien Kimmig, collections manager at the University of Kansas Biodiversity Institute and Natural History Museum. “But what makes this even more important is that it’s one of the few deposits that are actually from the Ordovician period — and even more importantly, they’re from the Middle Ordovician, a time were very few soft-bodied fossils are known.”

Kimmig and his KU Biodiversity Institute colleagues, undergraduate researcher Wade Leibach and senior curator Bruce Lieberman, along with Helena Couto of the University of Porto in Portugal (who discovered the fossils), describe three marine fossil specimens: a medusoid (jellyfish), possible wiwaxiid sclerites and an arthropod carapace.

“Before this, there had been nothing found on the Iberian Peninsula in the Ordovician that even resembled these,” Kimmig said. “They close a gap in time and space. And what’s very interesting is the kind of fossils. We find Medusozoa — a jellyfish — as well as animals which appear to be wiwaxiids, which are sluglike armored mollusks that have big spines. We found these lateral sclerites of animals which were actually thought to have gone extinct in the late Cambrian. There might have been some that survived into the Ordovician in a Morocco deposit, but nothing concrete has been ever published on those. And here we have evidence for the first ones actually in the middle of the Ordovician, so it extends the range of these animals incredibly.”

Kimmig said the discovery of uncommon wiwaxiids fossils in this time frame suggests the animals lived on Earth for a far greater span of time than previously understood.

“Especially with animals that are fairly rare that we don’t have nowadays like wiwaxiids, it’s quite nice to see they lived longer than we ever thought,” he said. “Closely after this deposit, in the Upper Ordovician, we actually get a big extinction event. So, it’s likely the wiwaxiids survived up to that big extinction event and didn’t go extinct earlier due to other circumstances. But it might have been whatever caused the big Ordovician extinction event killed them off, too.”

According to the researchers, the soft-bodied specimens fill a gap in the fossil record for the Middle Ordovician and suggest “many soft-bodied fossils in the Ordovician remain to be discovered, and a new look at deep-water shales and slates of this time period is warranted.”

“It’s a very interesting thing with these discoveries — we’re actually getting a lot of information about the distribution of animals chronologically and geographically,” Kimmig said. “Also, this gives us a lot of information on how animals adapted to different environments and where they actually managed to live. With these soft-body deposits, we get a much better idea of how many animals there were and how their environment changed over time. It’s something that applies to modern days, with changing climate and changing water temperatures, because we can see how animals over longer periods of time in the geologic record have actually adapted to these things.”

Co-author Couto discovered the fossils in the Valongo Formation in northern Portugal, an area famed for containing trilobites. When the animals were alive, the Valongo Formation was part of a shallow sea on the margin of northern Gondwana, the primeval supercontinent.

“Based on the shelly fossils, the deposit looks like it was a fairly common Ordovician community,” Kimmig said. “And now we know that in addition to those common fossils jellyfish were floating around, we had sluglike mollusks roaming on the ground, too, and we had bigger arthropods, which might have been predatory animals. So, in that regard, we’re getting a far better image with these soft-bodied fossils of what these communities actually looked like.”

According to the KU researcher, scientists didn’t grasp until recently that deposits from this period could preserve soft-bodied specimens.

“For a long time, it was just not known that these kinds of deposits survived in to the Ordovician,” Kimmig said. “So, it is likely these deposits are more common in the Ordovician than we know of, it’s just that people were never looking for them.”

Kimmig led analysis of the fossils at KU’s Microscopy and Analytical Imaging Laboratory to ensure the fossils were made of organic material. Leibach, the KU undergraduate researcher, conducted much of the lab work.

“We analyzed the material and looked at the composition because sometimes you can get pseudo fossils — minerals that create something that looks like a fossil,” Kimmig said. “We had to make sure that these fossils actually had an organic origin. And what we found is that they contain carbon, which was the big indication they would actually be organic.”

Reference:
Julien Kimmig, Helena Couto, Wade W. Leibach, Bruce S. Lieberman. Soft-bodied fossils from the upper Valongo Formation (Middle Ordovician: Dapingian-Darriwilian) of northern Portugal. The Science of Nature, 2019; 106 (5-6) DOI: 10.1007/s00114-019-1623-z

Note: The above post is reprinted from materials provided by University of Kansas.

Feathers came first, then birds

June 6, 2019

Reconstruction of the studied pterosaur, with four different feather types over its head, neck, body, and wings, and a generally ginger-brown colour. Credit: Reconstruction by Yuan Zhang.

New research, led by the University of Bristol, suggests that feathers arose 100 million years before birds — changing how we look at dinosaurs, birds, and pterosaurs, the flying reptiles.

It also changes our understanding of feathers themselves, their functions and their role in some of the largest events in evolution.

The new work, published in the journal Trends in Ecology & Evolution combines new information from palaeontology and molecular developmental biology.

The key discovery came earlier in 2019, when feathers were reported in pterosaurs — if the pterosaurs really carried feathers, then it means these structures arose deep in the evolutionary tree, much deeper than at the point when birds originated.

Lead author, Professor Mike Benton, from the University of Bristol’s School of Earth Sciences, said: “The oldest bird is still Archaeopteryx first found in the Late Jurassic of southern Germany in 1861, although some species from China are a little older.

“Those fossils all show a diversity of feathers — down feathers over the body and long, vaned feathers on the wings. But, since 1994, palaeontologists have been contending with the perturbing discovery, based on hundreds of amazing specimens from China, that many dinosaurs also had feathers.”

Co-author, Baoyu Jiang from the University of Nanjing, added: “At first, the dinosaurs with feathers were close to the origin of birds in the evolutionary tree.

“This was not so hard to believe. So, the origin of feathers was pushed back at least to the origin of those bird-like dinosaurs, maybe 200 million years ago.”

Dr Maria McNamara, co-author from University College Cork, said: “Then, we had the good fortune to work on a new dinosaur from Russia, Kulindadromeus.

“This dinosaur showed amazingly well-preserved skin covered with scales on the legs and tail, and strange whiskery feathers all over its body.

“What surprised people was that this was a dinosaur that was as far from birds in the evolutionary tree as could be imagined. Perhaps feathers were present in the very first dinosaurs.”

Danielle Dhouailly from the University of Grenoble, also a co-author, works on the development of feathers in baby birds, especially their genomic control. She said: “Modern birds like chickens often have scales on their legs or necks, and we showed these were reversals: what had once been feathers had reversed to be scales.

“In fact, we have shown that the same genome regulatory network drives the development of reptile scales, bird feathers, and mammal hairs. Feathers could have evolved very early.”

Baoyu Jiang continued: “The breakthrough came when we were studying two new pterosaurs from China.

“We saw that many of their whiskers were branched. We expected single strands — monofilaments — but what we saw were tufts and down feathers. Pterosaurs had feathers.”

Professor Benton added: “This drives the origin of feathers back to 250 million years ago at least.

“The point of origin of pterosaurs, dinosaurs and their relatives. The Early Triassic world then was recovering from the most devastating mass extinction ever, and life on land had come back from near-total wipe-out.

“Palaeontologists had already noted that the new reptiles walked upright instead of sprawling, that their bone structure suggested fast growth and maybe even warm-bloodedness, and the mammal ancestors probably had hair by then.

“So, the dinosaurs, pterosaurs and their ancestors had feathers too. Feathers then probably arose to aid this speeding up of physiology and ecology, purely for insulation. The other functions of feathers, for display and of course for flight, came much later.”

Reference:
Michael J. Benton, Danielle Dhouailly, Baoyu Jiang, Maria McNamara. The Early Origin of Feathers. Trends in Ecology & Evolution, 2019; DOI: 10.1016/j.tree.2019.04.018

Note: The above post is reprinted from materials provided by University of Bristol.

Glacial sediments greased the gears of plate tectonics

June 6, 2019

This view of the Grand Canyon shows the Great Unconformity, a boundary where as much as a billion years’ worth of sedimentary deposits are missing from the geologic record. The boundary can be seen at roughly the middle of this image, separating the older, lumpy and angular rocks below from the younger horizontal layers above. New research suggests that the missing sediments, likely scrubbed away by glaciers during the global “snowball Earth” that ended roughly 635 million years ago, washed away to the oceans, where they lubricated subduction faults and kick-started the modern age of plate tectonics. Image credit: USGS/Alex Demas

Earth’s outer layer is composed of giant plates that grind together, sliding past or dipping beneath one another, giving rise to earthquakes and volcanoes. These plates also separate at undersea mountain ridges, where molten rock spreads from the centers of ocean basins.

But this was not always the case. Early in Earth’s history, the planet was covered by a single shell dotted with volcanoes — much like the surface of Venus today. As Earth cooled, this shell began to fold and crack, eventually creating Earth’s system of plate tectonics.

According to new research, the transition to plate tectonics started with the help of lubricating sediments, scraped by glaciers from the slopes of Earth’s first continents. As these sediments collected along the world’s young coastlines, they helped to accelerate the motion of newly formed subduction faults, where a thinner oceanic plate dips beneath a thicker continental plate.

The new study, published June 6, 2019 in the journal Nature, is the first to suggest a role for sediments in the emergence and evolution of global plate tectonics. Michael Brown, a professor of geology at the University of Maryland, co-authored the research paper with Stephan Sobolev, a professor of geodynamics at the GFZ German Research Centre for Geosciences in Potsdam.

The findings suggest that sediment lubrication controls the rate at which Earth’s crust grinds and churns. Sobolev and Brown found that two major periods of worldwide glaciation, which resulted in massive deposits of glacier-scrubbed sediment, each likely caused a subsequent boost in the global rate of plate tectonics.

The most recent such episode followed the “snowball Earth” that ended sometime around 635 million years ago, resulting in Earth’s modern plate tectonic system.

“Earth hasn’t always had plate tectonics and it hasn’t always progressed at the same pace,” Brown said. “It’s gone through at least two periods of acceleration. There’s evidence to suggest that tectonics also slowed to a relative crawl for nearly a billion years. In each case, we found a connection with the relative abundance — or scarcity — of glacial sediments.”

Just as a machine needs grease to keep its parts moving freely, plate tectonics operates more efficiently with lubrication. While it may be hard to confuse the gritty consistency of clay, silt, sand and gravel with a slippery grease, the effect is largely the same at the continental scale, in the ocean trenches where tectonic plates meet.

“The same dynamic exists when drilling Earth’s crust. You have to use mud — a very fine clay mixed with water or oil — because water or oil alone won’t work as well,” Brown said. “The mud particles help reduce friction on the drill bit. Our results suggest that tectonic plates also need this type of lubrication to keep moving.”

Previous research on the western coast of South America was the first to identify a relationship between sediment lubrication and friction along a subduction fault. Off the coast of northern Chile, a relative lack of sediment in the fault trench creates high friction as the oceanic Nazca plate dips beneath the continental South America plate. This friction helped to push the highest peaks of the central Andes Mountains skyward as the continental plate squashed and deformed.

In contrast, further south there is a higher sediment load in the trench, resulting in less friction. This caused less deformation of the continental plate and, consequently, created smaller mountain peaks. But these findings were limited to one geographic area.

For their study, Sobolev and Brown used a geodynamic model of plate tectonics to simulate the effect of sediment lubrication on the rate of subduction. To verify their hypothesis, they checked for correlations between known periods of widespread glaciation and previously published data that indicate the presence of continental sediment in the oceans and trenches. For this step, Sobolev and Brown relied on two primary lines of evidence: the chemical signature of the influence of continental sediments on the chemistry of the oceans and indicators of sediment contamination in subduction-related volcanoes, much like those that make up today’s “ring of fire” around the Pacific Ocean.

According to Sobolev and Brown’s analysis, plate tectonics likely emerged on Earth between 3 and 2.5 billion years ago, around the time when Earth’s first continents began to form. This time frame also coincides with the planet’s first continental glaciation.

A major boost in plate tectonics then occurred between 2.2 to 1.8 billion years ago, following another global ice age that scrubbed massive amounts of sediments into the fault trenches at the edges of the continents.

The next billion years, from 1.75 billion to 750 million years ago, saw a global reduction in the rate of plate tectonics. This stage of Earth’s history was so sedate, comparatively speaking, that it earned the nickname “the boring billion” among geologists.

Later, following the global “snowball Earth” glaciation that ended roughly 635 million years ago, the largest surface erosion event in Earth’s history may have scrubbed more than a vertical mile of thickness from the surface of the continents. According to Sobolev and Brown, when these sediments reached the oceans, they kick-started the modern phase of active plate tectonics.

Reference:
Stephan V. Sobolev, Michael Brown. Surface erosion events controlled the evolution of plate tectonics on Earth. Nature, 2019; 570 (7759): 52 DOI: 10.1038/s41586-019-1258-4

Note: The above post is reprinted from materials provided by University of Maryland.

In hot pursuit of dinosaurs: Tracking extinct species on ancient Earth via biogeography

June 6, 2019

During the Early Cretaceous period (145-100 million years ago), nonavian dinosaurs likely migrated between Africa and Europe. Image adapted from research figure originally published in Systematic Biology, DOI: 10.1093/sysbio/syz024, CC-BY

One researcher at the University of Tokyo is in hot pursuit of dinosaurs, tracking extinct species around ancient Earth. Identifying the movements of extinct species from millions of years ago can provide insights into ancient migration routes, interaction between species, and the movement of continents.

“If we find fossils on different continents from closely related species, then we can guess that at some point there must have been a connection between those continents,” said Tai Kubo, Ph.D., a postdoctoral researcher affiliated with the University Museum at the University of Tokyo.

A map of life — biogeography

Previous studies in biogeography — the geographic distribution of plants and animals — had not considered the evolutionary relationships between ancient species. The new method that Kubo designed, called biogeographical network analysis, converts evolutionary relationships into geographical relationships.

For example, cats and dogs are more closely related to each other than to kangaroos. Therefore, a geographical barrier must have separated the ancestors of kangaroos from the ancestors of cats and dogs well before cats and dogs became separate species.

Most fossils are found in just a few hot-spot locations around the world and many ancient species with backbones (vertebrates) are known from just one fossil of that species. These limitations mean that a species’ fossils cannot reveal the full area of where it was distributed around the world.

“Including evolutionary relationships allows us to make higher resolution maps for where species may have migrated,” said Kubo.

The analysis used details from evolutionary studies, the location of fossil dig sites, and the age of the fossils. Computer simulations calculated the most likely scenarios for the migration of species between continents on the Cretaceous-era Earth, 145 to 66 million years ago.

North and south divide

This new analysis verified what earlier studies suggested: nonavian dinosaurs were divided into a group that lived in the Northern Hemisphere and another that lived in the Southern Hemisphere, and that those two groups could still move back and forth between Europe and Africa during the Early Cretaceous period (145 to 100 million years ago), but became isolated in the Late Cretaceous period (100 to 66 million years ago).

During the Early Cretaceous period, there were three major supercontinents: North America-Europe-Asia, South America-Africa, and Antarctica-India-Australia.

By the Late Cretaceous period, only the North America-Europe-Asia supercontinent remained. The other supercontinents had separated into the continents we know today, although they had not yet drifted to their current locations.

“During the Late Cretaceous period, high sea levels meant that Europe was a series of isolated islands. It makes sense that nonavian dinosaur species differentiated between Africa and Europe during that time,” said Kubo.

Kubo plans to complete additional biogeographical analyses for different time periods to continue tracking extinct species around the world and through time.

Reference:
Tai Kubo. Biogeographical Network Analysis of Cretaceous Terrestrial Tetrapods: A Phylogeny-Based Approach. Systematic Biology, 2019; DOI: 10.1093/sysbio/syz024

Note: The above post is reprinted from materials provided by University of Tokyo.

Download Google Earth For Free

June 4, 2019

Google Earth

Google Earth is a free program from Google that allows you to “fly” over a virtual globe and view the Earth through high-resolution graphics and satellite images.

Google Earth is a computer program based mainly on satellite imagery that makes a 3D representation of Earth. By superimposing satellite images, aerial photography, and GIS data onto a 3D globe, the program maps the Earth, enabling users to see towns and landscapes from different perspectives. By entering addresses and coordinates, or using a keyboard or mouse, users can explore the globe.

The program can also be downloaded using a touch screen or stylus to navigate on a smartphone or tablet. Users can use the program to use Keyhole Markup Language to add their own information and upload it through multiple sources, such as forums or blogs. Google Earth can display multiple types of overlaid pictures on the Earth’s surface and is also a Web Map Service customer.

In relation to Earth navigation, through the desktop application, It offers a number of other instruments. There are additional globes accessible for the Moon and Mars, as well as a night sky viewing instrument. It also includes a flight simulator match. Other characteristics enable consumers to view pictures uploaded to Panoramio from multiple locations, data given on some locations by Wikipedia, and graphics from Street View. Google Earth’s web-based edition also involves Voyager, a function that brings in-program trips on a regular basis, often provided by researchers and documentaries.

Versions

On macOS, Linux, iOS, and Android, Google Earth has been published. The Linux variant started with Google Earth’s version 4 beta, using the Qt toolkit as a indigenous port. The Free Software Foundation considers it a high priority free software project to develop a free compliant client for Google Earth. Google Earth came out on February 22, 2010 for Android, and on October 27, 2008 for iOS. Google Earth’s portable variants can use multi-touch controls to shift, zoom, or spin the perspective around the globe, allowing the present place to be selected.

Click Here to Download Your Free Version

New mineral classification system captures Earth’s complex past

June 4, 2019

Currently 32 different mineral species of the “tourmaline group” are delineated by the distribution of the major elements of which they are comprised. So, a single shard of tourmaline with slight variations in chemistry often contains multiple species of the mineral, even if they all formed in the same geologic event. Credit: Public domain

The first minerals to form in the universe were nanocrystalline diamonds, which condensed from gases ejected when the first generation of stars exploded. Diamonds that crystallize under the extreme pressure and temperature conditions deep inside of Earth are more typically encountered by humanity. What opportunities for knowledge are lost when mineralogists categorize both the cosmic travelers and the denizens of deep Earth as being simply “diamond“?

Could a new classification system that accounts for minerals’ distinct journeys help us better understand mineralogy as a process of universal and planetary evolution?

The current system for classifying minerals—developed by James Dwight Dana in the 1850s—categorizes more than 5,400 mineral “species” based on their dominant chemical compositions and crystalline structures. This is an unambiguous, robust, and reproducible designation scheme.

Carnegie’s Robert Hazen suggests an additional classification system, which could amplify existing knowledge of how minerals evolve over time without superseding the existing designations. In American Mineralogist’s Roebling Medal Paper, Hazen argues for categories that reflect a deeper, more-modern understanding of planetary scale transformation over time.

A system grouping minerals and non-crystalline natural solids—which are not currently classified by the existing system—into what Hazen calls “natural kind clusters” would better reflect the inherent messiness of planetary evolution, he explains.

“For maximum efficacy, scientific classification systems must not just organize and define, but also reflect current theory, and allow it to expand and guide us to new conclusions,” Hazen says.

He pioneered the concept of mineral evolution—linking an explosion in mineral diversity to the rise of life on Earth and the resulting oxygen-rich atmosphere. Hazen then added another layer to his vision by introducing mineral ecology—which analyzes the spatial distribution of Earth’s minerals to predict which ones remain undiscovered and to assert our planet’s mineralogical uniqueness.

A system of categorization that reflects not just a mineral’s chemistry and crystalline structure, but also the physical, chemical, or biological processes by which it formed, would be capable of recognizing that nanodiamonds from space are fundamentally different to diamonds formed in Earth’s depths.

The existing classification system groups some minerals with disparate formation histories together in one category, while splitting others with similar origin stories into separate mineral species.

Another example: currently 32 different mineral species of the “tourmaline group” are delineated by the distribution of the major elements of which they are comprised. So, a single shard of tourmaline with slight variations in chemistry often contains multiple species of the mineral, even if they all formed in the same geologic event.

A natural kind classification system would rectify that problem, and allow for the inclusion of non-crystalline materials, such as volcanic glass, amber, and coal, which currently aren’t counted as minerals, but can offer knowledge about our evolving planet.

“Earth’s mineralogy tells vivid stories, revealing how eons of geologic activity and the rise of life facilitated novel combinations of elements,” Hazen argues. “But to glean every nuance of this mineralogical text, we must embrace a new language for describing the creation of minerals that reflects the passage of time.”

Reference:
Robert M. Hazen. American Mineralogist (2017) 102 (5): 1134-1135. doi.org/10.2138/am-2017-AP10252

Note: The above post is reprinted from materials provided by Carnegie Institution for Science.

Earthquakes that talk to each other

June 3, 2019

The location of the two largest earthquakes are shown with place markers along with their magnitudes determined in this study. Credit: University of Melbourne

On 19th June 2012 at 8:53 pm local time, a moment magnitude-4.9 earthquake rattled the residents in and around the small town of Thorpdale in eastern Victoria. Moment magnitude measures the size or strength of an earthquake based on how much energy is released, which differs from the better known Richter scale.

The quake was felt more than 100 kilometers away in Melbourne’s CBD and in other parts of the state.

Then, nearly a month later, on 20th July at 7:11 pm, another magnitude-4.3 seismic shock jolted the region.

A second earthquake like this is normal because, usually, the release of residue stress on a fault produces smaller aftershocks in the days following a mainshock.

But, in fact, our new research suggests that these earthquakes broke not one, but two adjacent faults. And it’s likely that the seismic slip on the first fault activated the second one; which means that the first earthquake communicated with the second one in a language that only the Earth understands.

A quake conversation

Two days after the first quake, the University of Melbourne seismology group deployed 13 temporary seismic stations on a rolling basis in Thorpdale.

These stations are designed to pick up any distinct signals of seismic waves emanating from tiny aftershocks following the first earthquake.

But the stations then picked up signals from the second earthquake that people felt along with the aftershocks.

Because the first earthquake was of reasonable size, permanent—more distant seismic stations maintained by the University of Melbourne along with other agencies like Geoscience Australia and the Seismology Research Centre—picked up its seismic signals.

These signals consist of three main types:

Primary (or P) waves are the fastest seismic waves and will be picked up by a station first

The Secondary (S) waves travel at a slower speed than the P waves. Both these wave types are called body waves because they travel inside the Earth. In Victoria, P and S waves travel at speeds, respectively, of about 20,000 kilometers an hour and 12,600 kilometers an hour
Surface waves, on the other hand, travel along the surface of the Earth and are the slowest, traveling at around 10,000 kilometers per hour but produce the most shaking.

To give you an idea of how fast this is, the speed of sound sits at around 1200 kilometers per hour.

Using these P waveforms, our research team accurately estimated the first earthquake as 4.9 magnitude and the second July one to be 4.3.

The energy released in the first earthquake was about 27 petajoules (PJ) and it released eight times more energy than the second one. In terms of strength, 27 PJ could power the state of Victoria for an entire week.

By accurately timing the arrival of P and S waves at the stations, our team then worked to precisely triangulate the locations of the earthquakes in Thorpdale.

And this is when things got interesting.

More than a single fault

If these earthquakes (including aftershocks) occurred on a single fault, all the earthquakes should have clustered in one place.

But, the two earthquakes had their own separate clusters, and the second earthquake was located roughly seven kilometers to the northwest of the first one. So, it became clear that these earthquakes were two separate mainshocks—which was confirmed by additional projections of fault plane analysis.

There were forty-four aftershocks in the first 24 hours following the first mainshock.

A week later, the aftershock rate diminished to about one a day, and after 18 days, none were recorded. Then, five days before the second mainshock, that aftershock rate picked up.

Three days prior to the second main event, four aftershocks were recorded, and a day after that, another twelve occurred.

A day before the second mainshock, six aftershocks were detected. It appears that the aftershocks—or the geologic conditions that produce them—were gradually moving towards the location of the second, magnitude 4.3 earthquake.

And on the day of the second mainshock, forty-one aftershocks occurred.

Stress transfer

One way that an earthquake can trigger another is as a result of a mechanism known as Coulomb stress transfer. That is, an earthquake can change stress conditions in the surrounding Earth’s crust in a way that could bring nearby faults either closer to or away from failure.

Testing this condition showed us that the first mainshock slightly relieved stress at the location of the second mainshock. This may have contributed to the nearly 30-day delay in the second mainshock.

In addition, any water trapped in the crust’s pores under high compression near the second mainshock may have played a role. It’s possible that this water seeped into the fault plane, triggering the second mainshock, as a result of shaking and aftershocks from the first quake.

Seeping water can act as a lubricant for an otherwise locked fault interface, reducing the frictional strength that holds a fault together.

This process is similar to the way in which man-made earthquakes (known as induced seismicity) are triggered from reservoir impoundment and waste water injections.

Victoria’s Thomson Reservoir, which sits about 200 kilometers east of Melbourne, is one example of seeping fluid triggering an earthquake.

In this instance, a swarm of earthquakes occurred, that included one in 1996 with a local magnitude of five.

Predicting quakes?

One of the most famous examples of “communicating earthquakes” are the ones that occurred along the 1500-kilometer-long North Anatolian Fault, which sits in modern-day Turkey.

This fault separates two tectonic plates—the Eurasian plate to the north and the Anatolian plate to the south. From 1939 until around 1999, twelve earthquakes with magnitudes exceeding 6.7 have marched westward along the fault line.

So, does this information help us predict earthquakes? Does it help us foretell the size, location and the time of an earthquake?

The short answer is no.

Professor Charles Richter, who developed the Richter magnitude scale which quantifies the size of earthquakes, once famously said: “Journalists and the general public rush to any suggestion of earthquake prediction like hogs toward a full trough, [prediction] provides a happy hunting ground for amateurs, cranks, and outright-publicity seeking fakers.”

All that is possible is an earthquake forecast that gives a probability of occurrence of an earthquake with a certain size in a region over decadal time-scales.

Even this process has large uncertainties especially in places like Australia where our historical earthquake record is poor.

But what these two earthquakes talking to each other does tell us, is that earthquakes are not isolated events. Instead, they can interact with each other and increase damage by prolonging earthquake activity in a region.

Note: The above post is reprinted from materials provided by University of Melbourne.

Mapping groundwater’s influence on the world’s oceans

June 3, 2019

Researchers at The Ohio State University have created high-resolution maps of points around the globe where groundwater meets the oceans—the first such analysis of its kind, giving important data points to communities and conservationists to help protect both drinking water and the seas.

In a study published June 3 in the journal Geophysical Research Letters, the team showed that nearly half of fresh submarine groundwater discharge flows into the ocean near the tropics. They also found that regions near active fault lines—the area around the San Andreas Fault in California, for example—send greater volumes of groundwater into the ocean than regions that are tectonically stable. And, they found that dry, arid regions have very little groundwater discharge, opening the limited groundwater supplies in those parts of the world to saltwater intrusion.

The Ohio State team worked with researchers at NASA’s Jet Propulsion Laboratory and the University of Saskatchewan to combine topographical data from satellites and climate models to show the flow of groundwater around the world’s coasts.

The findings could help coastal communities better protect and manage their drinking water.

“Freshwater-groundwater discharge is a natural line of defense against saltwater intrusion,” said Audrey Sawyer, assistant professor of earth sciences at Ohio State and a co-author of the study. “And saltwater intrusion is a concern in places like Miami, Georgia, Cape Cod—it’s up and down the coast. It’s a problem that dry regions have as little groundwater discharge as they do because these are also the places where people are going to tend to look for groundwater to meet their freshwater needs.”

Their work, the first near-global and spatially distributed high-resolution map of fresh groundwater flow to the coast, could give scientists better clues about where to monitor groundwater discharge. Such monitoring is more challenging than monitoring the water quality of a river or stream, because groundwater, by its nature, enters oceans and lakes under water—people can’t see it from land.

When researchers think about coastal water quality and the way water affects the biochemical makeup of the world’s lakes and oceans, they typically think about rivers and streams—and for good reason. Most of the water that gets to lakes and oceans comes from surface water sources. But groundwater plays and important role, too, carrying minerals and, in some cases, pollutants, to surface bodies of water.

“If you’ve ever been swimming in a lake or in the ocean in the summertime and you go through a cold patch, that is probably a place where groundwater is coming out,” Sawyer said. “And that’s just one way that groundwater affects surface water—in that case, it’s affecting temperature, but it also affects the chemistry of the water. These effects can be hard to measure over large scales.”

That’s why Sawyer’s team started building these images: The research group focuses on groundwater, and realized that there was limited information showing—in detail—where groundwater was most likely to flow into the oceans.

The study found that in some parts of the world, groundwater could be polluting oceans and lakes with nutrients and other chemicals.

Groundwater, for example, can carry higher concentrations of nitrates—a key contributor of the types of harmful algal blooms that have caused problems for both fish and drinking water in Lake Erie, the Chesapeake Bay and the Gulf of Mexico—as well as high concentrations of mercury. Understanding how and where groundwater gets to surface water could help policymakers create better plans to improve those bodies of water.

The study also found that climate heavily influences groundwater flow, and that cities in dry areas are especially vulnerable to saltwater contamination of aquifers.

“This study draws attention to the idea that surface water and groundwater are all connected, and if you start to extract groundwater, you’re affecting that connection to our surface water bodies, and that can affect surface water quality, too,” Sawyer said. “There is competition between the outward push of groundwater towards the coast and the saltwater that wants to come in, and if we don’t have as much of an outward push because we’re taking that fresh groundwater out of the ground instead of letting it flow to the coast, it puts us in a more vulnerable position. It’s not that we can’t use groundwater, but we need to monitor our impact and remember that groundwater is not an inexhaustible resource.”

Note: The above post is reprinted from materials provided by The Ohio State University.

A 49 kilometers high volcanic ash column rose up over the Mayan civilization

June 3, 2019

Deposits of medium flows. The flows of Unit F are covered by the deposits of the subsequent eruption of the San Salvador Volcano. Credit: Dario Pedrazzi

The Ilopango’s volcano eruption (also known as Tierra Blanca Joven or TBJ) occurred approximately 1,500 years ago. Pyroclastics currents were dispersed over much of the present territory of El Salvador and a volcanic ash column reached a height of 49 km, according to a new research published recently in Journal of Volcanology and Geothermal Research.

Dario Pedrazzi, researcher at the Institute of Earth Sciences Jaume Almera of the CSIC (ICTJA-CSIC) is the lead author of a research that, by means of analysing the TBJ ash (tephra) deposits, has reconstructed the eruptive process of what is thought to be the largest explosive eruption occurred in Central America in the Holocene (last 10,000 years).

“The TBJ eruption was initially studied several years ago, but such a complete stratigraphic study hadn’t yet been carried out and the physical parameters were not defined. The volcanic products dispersion was neither determined”, said Dario Pedrazzi.

This new study presents a complete stratigraphic description and the extent of the pyroclastic deposits of TBJ eruption, which are still present all over El Salvador and in some neighbouring countries. The study also describes the physical parameters of the different phases of the eruption that generated the surveyed deposits.

This research was carried out with the collaboration of researchers from the Centro de Geociencias of the Universidad Autónoma de México (UNAM) and the División de Geociencias aplicadas del IPICYT, Mexico; the Istituto Nazionale di Geofisica e Vulcanologia (INGV), Italy; the Oxford University, UK; the Oregon State University, USA and the Ministerio de Medio Ambiente y Recursos Naturales de El Salvador (MARN).

The authors of the study conducted a detailed field mapping of an area of about 200.000 km2 during three field campaigns in order to reconstruct the stratigraphy of the TBJ deposits and the relationship with other eruptive deposits.

“What called our attention was the thickness of the pyroclastic deposits. Some of them were up to 70m thick and reached distances of at least 40-50 km from the vent. We shouldn’t forget that San Salvador City and its metropolitan area were built over the pyroclastic deposits originated during TBJ eruption”, explains Dario Pedrazzi.

Researchers measured 82 stratigraphic sections all over El Salvador Country, but they finally focused on 21 outcrops. They collected nearly 200 samples from all the outcrops that were analysed afterwards in the MARN and UNAM laboratories to obtain the parameters needed to develop numerical simulations.

With all this data available, the authors of the study were able to reconstruct the TBJ eruption dynamics. They could identify a total of 8 units in the deposits that correspond to the different phases of the eruption.

“It was an eruption that started with pyroclastic surges in a very specific area. Then, there was a shift in the eruptive dynamics, characterized by ash fallout, and then it shifted again to another phase driven mainly by pyroclastic flows”, said Pedrazzi.

According to the researcher, “the eruption reached its climax with a series of pyroclastic flows probably linked to a caldera collapse. In the last phase, all the materials ejected previously were deposited by fallout mechanisms”. Some of these materials were transported and spread by the dominating winds and they reached distances as large as 100 km from the vent, especially fine grain ashes.

Thanks to the numerical simulations conducted, the authors of the study were able to estimate that during the final phase of the eruption, the column of volcanic ashes and gases (co-ignimbrite plume) reached a height of 49 km. Moreover, they calculated that the total bulk volume of ejected material was about 60 km3 of magma (30 km3 dense rock equivalent, which is the original volume of erupted magma), corresponding to a 6.8 magnitude eruption.
The study notes that the” Mayan populations living in the region would have been considerably affected “ and that the communities living in the territory within 50 km from the Ilopango Caldera were the ones who suffered a more direct impact. However, indirect effects on the social, economic and political systems derived from the eruption “probably affected a much wider area of Central America”.

According to the researchers, this study “represents the first and necessary step towards improved volcanic hazard assessment for the region” to mitigate volcanic risk for the large number of communities living around Ilopango Caldera, an active volcano whose last eruption was in 1879. It was then when some domes (Islas Quemadas) were formed inside the caldera. About 3 million people live currently within 30 kilometres of the caldera.
“The previous eruption occurred 8,000 years before TBJ eruption. The returning time of the last eruptions are shorter if we compare them with the first ones, occurred about 1.5 million years ago, although the volume of material ejected during the most recent eruptions is smaller”, said Dario Pedrazzi.

The Ilopango Caldera is located less than 10 km from San Salvador City, the capital of El Salvador, and it forms part of Volcanic Arc of El Salvador which includes a total of 21 active volcanoes, being one of the most active segments of the Central America Volcanic Arc.

This work is part of a project founded by CONACYT and lead by Dr.Gerardo Aguírre Díaz, UNAM researcher. The project is focused in the study of the Ilopango Caldera and its goal is to determine the potential hazard of volcanic supereruptions in Central America.

Reference:
Pedrazzi, D., Sunye-Puchol, I., Aguirre-Díaz, G., Costa, A., Smith, V., Poret, M., Dávila-Harris, P., Miggins,D., Hernández, W., Gutiérrez, E. (2019) “The Ilopango Tierra Blanca Joven (TBJ) eruption, El Salvador: Volcano-Stratigraphy and physical characterization of the major Holocene event of Central America”. Journal of Volcanology and Geothermal Research, 377, 81-102. DOI: 10.1016/j.jvolgeores.2019.03.0060377-0273

Note: The above post is reprinted from materials provided by ICTJA-CSIC. The original article was written by Jordi Cortés.

Garnet Color : What is Garnet’s Color?

June 3, 2019

What is Garnet?

Garnets are a group of minerals of silicate that have been used as gemstones and abrasives since the Bronze Age.

All garnet species have similar physical characteristics and crystal shapes, but differ in chemical composition. The various species are pyrope, almandine, spessartine, gross (hessonite or cinnamon-stone and tsavorite varieties), uvarovite and and andradite. Two solid solution series are made up of garnets: pyrope-almandine-spessartine and uvarovite-grossular-andradite.

Garnet is not a single mineral, but it describes a group of several minerals that are closely related. Garnets are available in a variety of colors and have many varieties. However, Garnet gemstones’ most widely known color is dark red. When using the term “Garnet,” the dark red form is usually connotative; more descriptive gemstone terms are usually given to other color garnets.

Garnet Color

Uvarovite: dark green.
Grossular: colorless, white, gray, yellow, green, green (various shades: pale green apple, medium green apple, dark green), brown, pink, reddish, black.
Andradite: Yellow-green, green, brown green, yellow orange, brown, black and black grayish. The color is associated with Ti and Mn’s content. The color is light if there is little of either element, and it may look grossly.
Pyrope: Purple red, pink red, orange red, raspberry, dark red. Note: Colorless pure pyrope ; red colors are derived from Fe + Cr.
Almandine: red, brownish red, brownish black, violet red.
Spessartine: red, reddish orange, orange, yellow-brown, reddish brown, blackish brown.
Malaia: various shades of orange, red-orange, peach, and pink.
Rhodolite: usually has a distinctive purplish color.

Is Garnet Rare?

It depends on Garnet’s type and color. Peach, green and clear are the rarest garnets. More common are the red garnets.

How much does a Garnet Cost?

It depends on the gemstone’s size and color. A 2ct stone can range from $ 10 per carat to $ 5,000 per carat, for example.

How many Garnets types?

There are two different groups and six different types. The two groups are Garnets of Calcium and Garnets of Magnesium.

Almandine
Pyrope
Spessartite
Grossular
Andradite
Uvarovite

How Hard is Garnet?

It depends on the Garnet type, but it varies between 6.5 and 7.5 ” Mohs Hardness Scale ”

Uses Garnet

Gemstones

Pure garnet crystals are still being used as gemstones. The varieties of gemstones occur in green, red, yellow, and orange shades. It is known as the January birthstone in the US. It is Connecticut’s state mineral, New York’s gemstone, and Idaho’s state gemstone is the star garnet (garnet with rutile asterisms).

Industrial uses

Garnet sand is a good abrasive and a common substitute in sand blasting for silica sand. For such blasting treatments, alluvial rounder garnet grains are more suitable. In water jets, the garnet is mixed with very high pressure water to cut steel and other materials. Grenets extracted from hard rock are suitable for water jet cutting as they are more angular in shape, hence more efficient in cutting.

Unconformity : What Is Unconformity? What are Types of Unconformity?

June 3, 2019

Siccar Point is a rocky promontory in the county of Berwickshire on the east coast of Scotland. It is famous in the history of geology for Hutton’s Unconformity found in 1788, which James Hutton regarded as conclusive proof of his uniformitarian theory of geological development.

Unconformity

An unconformity is a buried erosional or non-depositional surface that separates two different-age rock masses or strata, indicating that the deposition of sediments was not continuous. The older layer was generally exposed to erosion for an interval of time before the younger layer was deposed, but the term is used to describe any break in the sedimentary geological record.

How is an unconformity formed?

Unconformities are gaps in the geologic record that may indicate episodes of crustal deformation, erosion, and sea level variations. They are a characteristic of stratified rocks and are thus usually found in sediments (but can also be found in stratified volcanics). They are surfaces that form a substantial break (hiatus) in the geological record between two rock bodies (sometimes people say inaccurately that “time” is missing). Unconformities represent times when deposition stopped, some of the previously deposited rock was removed by an erosion interval and finally resumed deposition.

What are Types of Unconformity?

Disconformity

A disconformity is an unconformity between parallel layers of sedimentary rocks which is a period of erosion or non-deposition. Disconformities are characterized by subaerial erosion features. This type of erosion may leave in the rock record channels and paleosols. A paraconformity is a type of disconformity where separation is a simple bedding plane with no apparent buried erosional surface.

Nonconformity

A nonconformity exists between sedimentary rocks and metamorphic or igneous rocks when the sedimentary rock lies above and was deposited on the pre-existing and eroded metamorphic or igneous rock. Namely, if the rock below the break is igneous or has lost its bedding due to metamorphism, the plane of juncture is a nonconformity.

Angular unconformity

An angular unconformity is an unconformity in which horizontally parallel strata of sedimentary rock are deposited on tilted and eroded layers, resulting in angular discordance with the horizontal layers above. Further orogenic activity can deform and tilt the entire sequence later.

Paraconformity

A paraconformity is a type of unconformity in which strata are parallel ; no apparent erosion occurs and the surface of the unconformity resembles a simple bedding plane. It is also called pseudoconformity or nondepositional unconformity. Short paraconformities are called diastems.

Buttress unconformity

When younger bedding is deposited against older strata, an unconformity of the buttress occurs, thus influencing its bedding structure.

Blended unconformity

A blended unconformity is a type of disconformity or nonconformity that has no distinct plane or contact separation, sometimes consisting of soils, paleosols, or pebble beds derived from the rock.

What is the difference between Disconformity and nonconformity?

A nonconformity is what its called when sedimentary rock strata are over crystalline (metamorphic or igneous) strata. A disconformity is when the sedimentary strata is over another sedimentary strata.

Earth recycles ocean floor into diamonds

May 31, 2019

The diamond on your finger is most likely made of recycled seabed cooked deep in the Earth.

Traces of salt trapped in many diamonds show the stones are formed from ancient seabeds that became buried deep beneath the Earth’s crust, according to new research led by Macquarie University geoscientists in Sydney, Australia.

Most diamonds found at the Earth’s surface are formed this way; others are created by crystallization of melts deep in the mantle.

In experiments recreating the extreme pressures and temperatures found 200 kilometres underground, Dr Michael Förster, Professor Stephen Foley, Dr Olivier Alard, and colleagues at Goethe Universität and Johannes Gutenberg Universität in Germany, have demonstrated that seawater in sediment from the bottom of the ocean reacts in the right way to produce the balance of salts found in diamond.

The study, published in Science Advances, settles a long-standing question about the formation of diamonds. “There was a theory that the salts trapped inside diamonds came from marine seawater, but couldn’t be tested,” says lead author Michael. “Our research showed that they came from marine sediment.”

Diamonds are crystals of carbon that form beneath the Earth’s crust in very old parts of the mantle. They are brought to the surface in volcanic eruptions of a special kind of magma called kimberlite.

While gem diamonds are usually made of pure carbon, so-called fibrous diamonds, which are cloudy and less appealing to jewellers, often include small traces of sodium, potassium and other minerals that reveal information about the environment where they formed.

These fibrous diamonds are commonly ground down and used in technical applications like drill bits.

Fibrous diamonds grow more quickly than gem diamonds, which means they trap tiny samples of fluids around them while they form.

“We knew that some sort of salty fluid must be around while the diamonds are growing, and now we have confirmed that marine sediment fits the bill,” says Michael.

For this process to occur, a large slab of sea floor would have to slip down to a depth of more than 200 kilometres below the surface quite rapidly, in a process known as subduction in which one tectonic plate slides beneath another.

The rapid descent is required because the sediment must be compressed to more than four gigapascals (40,000 times atmospheric pressure) before it begins to melt in the temperatures of more than 800°C found in the ancient mantle.

To test the idea, team members at the Johannes Gutenberg Universität Mainz and Goethe Universität Frankfurt in Germany carried out a series of high-pressure, high-temperature experiments.

They placed marine sediment samples in a vessel with a rock called peridotite that is the most common kind of rock found in the part of the mantle where diamonds form. Then they turned up the pressure and the heat, giving the samples time to react with one another in conditions like those found at different places in the mantle.

At pressures between four and six gigapascals and temperatures between 800°C and 1100°C, corresponding to depths of between 120 and 180 kilometres below the surface, they found salts formed with a balance of sodium and potassium that closely matches the small traces found in diamonds.

“We demonstrated that the processes that lead to diamond growth are driven by the recycling of oceanic sediments in subduction zones,” says Michael.

“The products of our experiments also resulted in the formation of minerals that are necessary ingredients for the formation of kimberlite magmas, which transport diamonds to the Earth’s surface.”

Reference:
Michael W. Förster, Stephen F. Foley, Horst R. Marschall, Olivier Alard, Stephan Buhre. Melting of sediments in the deep mantle produces saline fluid inclusions in diamonds. Science Advances, 2019; 5 (5): eaau2620 DOI: 10.1126/sciadv.aau2620

Note: The above post is reprinted from materials provided by Macquarie University.

Scientists find telling early moment that indicates a coming megaquake

May 31, 2019

Scientists have found in GPS data a telling window that begins 10 seconds into an earthquake. In four sample events (colored lines), the acceleration of peak ground displacement (measurements shown at right) just five seconds later suggests whether a megaquake, such as a magnitude 9 (red X) or a sub-7 magnitude quake is in progress. Real time monitoring, the researchers say, could enhance earthquake early warning. Credit: University of Oregon

Scientists combing through databases of earthquakes since the early 1990s have discovered a possible defining moment 10-15 seconds into an event that could signal a magnitude 7 or larger megaquake.

Likewise, that moment — gleaned from GPS data on the peak rate of acceleration of ground displacement — can indicate a smaller event. GPS picks up an initial signal of movement along a fault similar to a seismometer detecting the smallest first moments of an earthquake.

Such GPS-based information potentially could enhance the value of earthquake early warning systems, such as the West Coast’s ShakeAlert, said Diego Melgar, a professor in the Department of Earth Sciences at the University of Oregon.

The physics-heavy analyses of two databases maintained by co-author Gavin P. Hayes of the U.S. Geological Survey’s National Earthquake Information Center in Colorado detected a point in time where a newly initiated earthquake transitions into a slip pulse where mechanical properties point to magnitude.

Melgar and Hayes also were able to identify similar trends in European and Chinese databases. Their study was detailed in the May 29 issue of the online journal Science Advances.

“To me, the surprise was that the pattern was so consistent, Melgar said. “These databases are made different ways, so it was really nice to see similar patterns across them.”

Overall, the databases contain data from more than 3,000 earthquakes. Consistent indicators of displacement acceleration that surface between 10-20 seconds into events were seen for 12 major earthquakes occurring in 2003-2016.

GPS monitors exist along many land-based faults, including at ground locations near the 620-mile-long Cascadia subduction zone off the U.S. Pacific Northwest coast, but their use is not yet common in real time hazard monitoring. GPS data shows initial movement in centimeters, Melgar said.

“We can do a lot with GPS stations on land along the coasts of Oregon and Washington, but it comes with a delay,” Melgar said. “As an earthquake starts to move, it would take some time for information about the motion of the fault to reach coastal stations. That delay would impact when a warning could be issued. People on the coast would get no warning because they are in a blind zone.”

This delay, he added, would only be ameliorated by sensors on the seafloor to record this early acceleration behavior.

Having these capabilities on the seafloor and monitoring data in real time, he said, could strengthen the accuracy of early warning systems. In 2016, Melgar, as a research scientist at Berkeley Seismological Laboratory in Berkeley, California, led a study published in Geophysical Research Letters that found real time GPS data could provide an additional 20 minutes of warning of a possible tsunami.

Japan already is laying fiber optic cable off its shores to boost its early warning capabilities, but such work is expensive and would be more so for installing the technology on the seafloor above the Cascadia fault zone, Meglar noted.

Melgar and Hayes came across the slip-pulse timing while scouring USGS databases for components that they could code into simulations to forecast what a magnitude 9 rupture of the Cascadia subduction zone would look like.

The subduction zone, which hasn’t had a massive lengthwise earthquake since 1700, is where the Juan de Fuca ocean plate dips under the North American continental plate. The fault stretches just offshore of northern Vancouver Island to Cape Mendocino in northern California.

Reference:
Diego Melgar and Gavin P. Hayes. Characterizing large earthquakes before rupture is complete. Science Advances, 2019 DOI: 10.1126/sciadv.aav2032

Note: The above post is reprinted from materials provided by University of Oregon.

A family of comets reopens the debate about the origin of Earth’s water

May 31, 2019

The comet 46P/Wirtanen on January 3, 2019. Credit: © Nicolas Biver

Where did the Earth’s water come from? Although comets, with their icy nuclei, seem like ideal candidates, analyses have so far shown that their water differs from that in our oceans.

Now, however, an international team, bringing together CNRS researchers at the Laboratory for Studies of Radiation and Matter in Astrophysics and Atmospheres (Paris Observatory — PSL/CNRS/ Sorbonne University/University of Cergy-Pontoise) and the Laboratory of Space Studies and Instrumentation in Astrophysics (Paris Observatory — PSL/CNRS/Sorbonne University/University of Paris), has found that one family of comets, the hyperactive comets, contains water similar to terrestrial water. The study, published in the journal Astronomy & Astrophysics on May 20, 2019, is based in particular on measurements of comet 46P/Wirtanen carried out by SOFIA, NASA’s Stratospheric Observatory for Infrared Astronomy.

According to the standard theory, the Earth is thought to have formed from the collision of small celestial bodies known as planetesimals. Since such bodies were poor in water, Earth’s water must have been delivered either by a larger planetesimal or by a shower of smaller objects such as asteroids or comets.

To trace the source of terrestrial water, researchers study isotopic ratios (1), and in particular the ratio in water of deuterium to hydrogen, known as the D/H ratio (deuterium is a heavier form of hydrogen). As a comet approaches the Sun, its ice sublimes (2), forming an atmosphere of water vapour that can be analysed remotely. However, the D/H ratios of comets measured so far have generally been twice to three times that of ocean water, which implies that comets only delivered around 10% of the Earth’s water.

When comet 46P/Wirtanen approached the Earth in December 2018 it was analysed using the SOFIA airborne observatory, carried aboard a Boeing aircraft. This was the third comet found to exhibit the same D/H ratio as terrestrial water. Like the two previous comets, it belongs to the category of hyperactive comets which, as they approach the Sun, release more water than the surface area of their nucleus should allow. The excess is produced by ice-rich particles present in their atmosphere.

Intrigued, the researchers determined the active fraction (i.e. the fraction of the nucleus surface area required to produce the amount of water present in their atmosphere) of all comets with a known D/H ratio. They found that there was an inverse correlation between the active fraction and the D/H ratio of the water vapour: the more a comet tends towards hyperactivity (i.e. an active fraction exceeding 1), the more its D/H ratio decreases and approaches that of the Earth.

Hyperactive comets, whose water vapour is partially derived from icy grains expelled into their atmosphere, thus have a D/H ratio similar to that of terrestrial water, unlike comets whose gas halo is produced only by surface ice. The researchers suggest that the D/H ratios measured in the atmosphere of the latter are not necessarily indicative of the ice present in their nucleus. If this hypothesis is correct, the water in all cometary nuclei may in fact be very similar to terrestrial water, reopening the debate on the origin of Earth’s oceans.

Notes:

The isotopic ratio is the ratio, within the same sample, between two isotopes (two forms with a different mass) of a chemical element. This can be used both to date a sample and determine its source.
Sublimation is the direct transition from a solid (in this case, ice) to a gas (water vapour).

Reference:
Dariusz C. Lis, Dominique Bockelée-Morvan, Rolf Güsten, Nicolas Biver, Jürgen Stutzki, Yan Delorme, Carlos Durán, Helmut Wiesemeyer, Yoko Okada. Terrestrial deuterium-to-hydrogen ratio in water in hyperactive comets. Astronomy & Astrophysics, 2019; 625: L5 DOI: 10.1051/0004-6361/201935554

Note: The above post is reprinted from materials provided by CNRS.

‘Fettuccine’ may be most obvious sign of life on Mars, researchers report

May 31, 2019

New research focuses on filamentous microbes that make their living in hot springs and catalyze the formation of travertine rock. Credit: Bruce W. Fouke

A rover scanning the surface of Mars for evidence of life might want to check for rocks that look like pasta, researchers report in the journal Astrobiology.

The bacterium that controls the formation of such rocks on Earth is ancient and thrives in harsh environments that are similar to conditions on Mars, said University of Illinois geology professor Bruce Fouke, who led the new, NASA-funded study.

“It has an unusual name, Sulfurihydrogenibium yellowstonense,” he said. “We just call it ‘Sulfuri.'”

The bacterium belongs to a lineage that evolved prior to the oxygenation of Earth roughly 2.35 billion years ago, Fouke said. It can survive in extremely hot, fast-flowing water bubbling up from underground hot springs. It can withstand exposure to ultraviolet light and survives only in environments with extremely low oxygen levels, using sulfur and carbon dioxide as energy sources.

“Taken together, these traits make it a prime candidate for colonizing Mars and other planets,” Fouke said.

And because it catalyzes the formation of crystalline rock formations that look like layers of pasta, it would be a relatively easy life form to detect on other planets, he said.

The unique shape and structure of rocks associated with Sulfuri result from its unusual lifestyle, Fouke said. In fast-flowing water, Sulfuri bacteria latch on to one another “and hang on for dear life,” he said.

“They form tightly wound cables that wave like a flag that is fixed on one end,” he said. The waving cables keep other microbes from attaching. Sulfuri also defends itself by oozing a slippery mucus.

“These Sulfuri cables look amazingly like fettuccine pasta, while further downstream they look more like capellini pasta,” Fouke said. The researchers used sterilized pasta forks to collect their samples from Mammoth Hot Springs in Yellowstone National Park.

The team analyzed the microbial genomes, evaluated which genes were being actively translated into proteins and deciphered the organism’s metabolic needs, Fouke said.

The team also looked at Sulfuri’s rock-building capabilities, finding that proteins on the bacterial surface speed up the rate at which calcium carbonate — also called travertine — crystallizes in and around the cables “1 billion times faster than in any other natural environment on Earth,” Fouke said. The result is the deposition of broad swaths of hardened rock with an undulating, filamentous texture.

“This should be an easy form of fossilized life for a rover to detect on other planets,” Fouke said.

“If we see the deposition of this kind of extensive filamentous rock on other planets, we would know it’s a fingerprint of life,” Fouke said. “It’s big and it’s unique. No other rocks look like this. It would be definitive evidence of the presences of alien microbes.”

Fouke also is an affiliate professor of microbiology and of the Carl R. Woese Institute for Genomic Biology at the U. of I.

Reference:
Yiran Dong, Robert A. Sanford, William P. Inskeep, Vaibhav Srivastava, Vincent Bulone, Christopher J. Fields, Peter M. Yau, Mayandi Sivaguru, Dag Ahrén, Kyle W. Fouke, Joseph Weber, Charles R. Werth, Isaac K. Cann, Kathleen M. Keating, Radhika S. Khetani, Alvaro G. Hernandez, Chris Wright, Mark Band, Brian S. Imai, Glenn A. Fried, Bruce W. Fouke. Physiology, Metabolism, and Fossilization of Hot-Spring Filamentous Microbial Mats. Astrobiology, 2019; DOI: 10.1089/ast.2018.1965

Note: The above post is reprinted from materials provided by University of Illinois at Urbana-Champaign, News Bureau. Original written by Diana Yates.

Contact Metamorphism Vs. Regional Metamorphism

May 28, 2019

Contact Metamorphism Vs. Regional Metamorphism

Metamorphism is the solid change in minerals and textures in a pre-existing rock (country rock) due to changing pressure / temperature conditions. Fluids like H2O also have a very important role to play.

Regional metamorphism occurs as a result of convergent tectonic activity and is usually characterised by low temperature and high pressure conditions. Thus this type of metamorphism is often associated with orogenic events and over a large area causes metamorphism. Under regional metamorphic conditions, Barrovian zone sequences and structures such as folds are formed.

Conversely, contact metamorphism usually occurs under higher temperature conditions associated with ignorant intrusions on a smaller scale. The high temperatures ‘ bake’ the surrounding country rock as the magma intrudes into the country rock and a metamorphic aureole is formed. The formed rocks are usually called hornfels.

The three types of metamorphism

Contact Metamorphism

Contact Metamorphism occurs when magma comes into contact with an existing rock body. When this happens, the temperature of the existing rocks rises and is also infiltrated with the magma fluid. The area affected by magma contact is usually small, ranging from 1 km to 10 km. Contact metamorphism produces rocks like marble, quartzite, and horns that are non-foliated(rocks without any cleavage).

Regional Metamorphism

Regional metamorphism takes place over a much wider area. This metamorphism creates rocks like gneiss and schist. Large geological processes such as mountain-building cause regional metamorphism. When exposed to the surface, these rocks show the incredible pressure that causes the mountain building process to bend and break the rocks. Regional metamorphism usually produces gneiss and schist-like foliated rocks.

Dynamic Metamorphism

There is also dynamic metamorphism due to mountain building. These enormous heat and pressure forces bend, fold, crush, flatten, and shear the rocks.

Mysterious blooms

Clues from space, floating robots

Background and methods used:

Relevance for investigations of the Earth’s magnetic field and the movement of the poles

Pterosaur

When was pterosaur fossil Discovered?

Pterosaur Evolution

Pterosaur Extinction

How Did Pterosaurs Fly?

Built to Fly

Wing Bones

Inside the Wings

A map of life — biogeography

North and south divide

Google Earth

Versions

A quake conversation

More than a single fault

Stress transfer

Predicting quakes?

What is Garnet?

Garnet Color

Is Garnet Rare?

How much does a Garnet Cost?

How many Garnets types?

How Hard is Garnet?

Uses Garnet

Gemstones

Industrial uses

Unconformity

How is an unconformity formed?

What are Types of Unconformity?

Disconformity

Nonconformity

Angular unconformity

Paraconformity

Buttress unconformity

Blended unconformity

What is the difference between Disconformity and nonconformity?

Contact Metamorphism Vs. Regional Metamorphism

The three types of metamorphism

Contact Metamorphism

Regional Metamorphism

Dynamic Metamorphism

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