The Mawenzi : The Largest Tanzanite rough in the World
The Largest Tanzanite rough in the World
The world’s largest piece of rough tanzanite has been found at a mine in northern Tanzania in 2005, well over six pounds.
The discovery was made about 885 feet underground at Bravo Shaft of TanzaniteOne Ltd., the southernmost shaft of the world’s leading tanzanite miner and marketer. Weighing in at cts 16.839. (Well over six pounds) and measuring 8.6 inchesx 3.15 inchesx 2.8 inches, the rugged tanzanite piece is remarkable in size and shape and is the world’s largest single piece of tanzanite ever mined, said the company.
The company named the piece “The Mawenzi” after Kilimanjaro’s second highest peak. “We were reluctant to name it Uhuru, after Kilimanjaro’s highest peak, on the off chance that a larger piece is ever found,” said Ian Harebottle, TanzaniteOne’s president and COO
No value was put on stone. TanzaniteOne said it plans to examine and evaluate the piece before any final decision on the potential cutting and polishing from this crystal of individual tanzanite gems is made. The business is considering before cutting and polishing putting The Mawenzi on display.
Ami Mpungwe, TanzaniteOne’s deputy chairman said the find is comparable to what the Cullinan Diamond is to the diamond industry and that the stone will be cut and polished in Tanzania.
“It is only fitting that The Mawenzi is cut and polished here in Tanzania,” Mpungwe said. “We expect to produce some truly exquisite gems from it, some of which we will put on display at Tanzania’s National Museum.”
What is Tanzanite?
Tanzanite is the mineral zoisite (a calcium aluminum hydroxyl sorosilicate) blue and violet type caused by small amounts of vanadium belonging to the group of epidotes. Tanzanite is found only in Tanzania, in a very small mining area (about 7 km (4.3 mi) long and 2 km (1.2 mi) wide) close to the Mirerani Hills.
Tanzanite is known for its remarkably strong trichroism, appearing in turn blue, violet and burgundy depending on the orientation of the crystal. When viewed under different lighting conditions tanzanite can also appear differently. When exposed to fluorescent light the blues become more visible, and when viewed under incandescent lighting, the violet hues can be readily seen. A reddish brown to clear is colored in its rough state tanzanite, and it needs heat treatment to dissolve the brownish “veil” to bring out the stone’s blue violet.
The gemstone was given the name ‘tanzanite’ by Tiffany & Co. after Tanzania, the country in which it was discovered. The scientific name of “blue-violet zoisite” was not thought to be consumer friendly enough by Tiffany’s marketing department, who introduced it to the market in 1968. In 2002, the American Gem Trade Association chose tanzanite as a December birthstone, the first change to their birthstone list since 1912.
This mural was originally made for a recent Royal Ontario Museum exhibit about a fossil ankylosaur named Zuul crurivastator. That fossil is found within a couple of meters stratigraphically/temporally of the site described in this paper. The last author on the study, David Evans, is the dinosaur curator at the Royal Ontario Museum and was also involved in the description of Zuul and design of that exhibit. Credit: Danielle Dufault, Royal Ontario Museum.
A topic of considerable interest to paleontologists is how dinosaur-dominated ecosystems were structured, how dinosaurs and co-occurring animals were distributed across the landscape, how they interacted with one another, and how these systems compared to ecosystems today. In the Late Cretaceous (~100-66 million years ago), North America was bisected into western and eastern landmasses by a shallow inland sea. The western landmass (Laramidia) contained a relatively thin stretch of land running north-south, which was bordered by that inland sea to the east and the rising Rocky Mountains to the west. Along this ancient landscape of warm and wet coastal plains comes an extremely rich fossil record of dinosaurs and other extinct animals.
Yet, from this record, an unexpected pattern has been identified: Most individual basins preserve an abundant and diverse assemblage of dinosaur species, often with multiple groups of co-occurring large (moose- to elephant-sized) herbivorous species, yet few individual species occur across multiple putatively contemporaneous geological formations (despite them often being less than a few hundred kilometers apart). This is in fairly stark contrast to the pattern seen in modern terrestrial mammal communities, where large-bodied species often have very extensive, often continent-spanning ranges. It has therefore been suggested that dinosaurs (and specifically large herbivorous dinosaurs) were particularly sensitive to environmental differences over relatively small geographic distances (particularly with respect to distance from sea level), and may have even segregated their use of the landscape between more coastal and inland sub-habitats within their local ranges.
In their new study published in Geology, Thomas Cullen and colleagues sought to test some of these hypotheses as part of their broader research reconstructing the paleoecology of Late Cretaceous systems.
One of the methods they’re using to do that is stable isotope analysis. This process measures differences in the compositions of non-decaying (hence, “stable”) isotopes of various common elements, as the degree of difference in these compositions in animal tissues and in the environment have known relationships to various factors such as diet, habitat use, water source, and temperature. So the team applied these methods to fossilized teeth and scales from a range of animals, including dinosaurs, crocodilians, mammals, bony fish, and rays, all preserved together from a relatively small region over a geologically short period of time in sites called vertebrate microfossil bonebeds.
By analyzing the stable carbon and oxygen isotope compositions of these fossils they were able to reconstruct their isotopic distributions in this ecosystem — a proxy for their diets and habitat use. They found evidence of expected predator-prey dietary relationships among the carnivorous and herbivorous dinosaurs and among aquatic reptiles like crocodilians and co-occurring fish species.
Critically, says Cullen, “What we didn’t see was evidence for large herbivorous dinosaurs segregating their habitats, as the hadrosaurs, ceratopsians, and ankylosaurs we sample all had strongly overlapping stable carbon and oxygen ranges. If some of those groups were making near-exclusive use of certain parts of the broader landscape, such as ceratopsians sticking to coastal environments and hadrosaurs sticking to more inland areas, then we should see them grouping distinctly from each other. Since we didn’t see that, that suggests they weren’t segregating their resource use in this manner. It’s possible they were doing so in different ways though, such as by feeding height segregation, or shifting where in the landscape they go seasonally, and our ongoing research is investigating some of these possibilities.”
Another important part of their study was comparing the fossil results to an environmentally similar modern environment in order to examine how similar they are ecologically. For a modern comparison, they examined the animal communities of the Atchafalaya River Basin of Louisiana, the largest contiguous wetland area in the continental U.S. The landscape of this area is very similar to their Cretaceous system, as are many elements of the plant and animal communities (not including the non-avian dinosaurs, of course).
From their comparisons, the team found that the Cretaceous system was similar to the Louisiana one in having a very large amount of resource interchange between the aquatic and terrestrial components of the ecosystem, suggesting that fairly diverse/mixed diets were common, and food being obtained from both terrestrial and aquatic sources was the norm. They also found that habitat use differences among the herbivorous mammals in the Louisiana system was more distinct than among those large herbivorous dinosaurs in the Cretaceous system, lending further evidence to their results about their lack of strict habitat use preferences.
Lastly, the team used modified oxygen stable isotope temperature equations to estimate mean annual temperature ranges for both systems (with the Louisiana one being a test of the accuracy of the method, as they could compare their results to directly measured water and air temperatures). The team found that in their Late Cretaceous ecosystem in Alberta, mean annual temperature was about 16-20 degrees C, a bit cooler than modern day Louisiana, but much warmer than Alberta today, reflecting the hotter greenhouse climate that existed globally about 76 million years ago.
Characterizing how these ecosystems were structured during this time, and how these systems changed across time and space, particularly with respect to how they responded to changes in environmental conditions, may be of great importance for understanding and predicting future ecosystem responses under global climate change. The team’s research continues and should reveal much more about the food webs and ecology of the dinosaurs and other organisms that inhabited these ancient landscapes.
Reference:
D.C. Evans, M.J. Ryan, M.B. Goodwin, F. Fanti, L. Huang, U.G. Wortmann, F.J. Longstaffe, T.M. Cullen. Large-scale stable isotope characterization of a Late Cretaceous dinosaur-dominated ecosystem. Geology, 2020; DOI: 10.1130/G47399.1
Numerous specimens of Kateretidae in a piece of amber from the Institute of Geology and Palaeontology in Nanjing (China). Included are also pollen grains from primitive water lilies. Credit: Georg Oleschinski/Uni Bonn
Like a snapshot, amber preserves bygone worlds. An international team of paleontologists from the University of Bonn has now described four new beetle species in fossilized tree resin from Myanmar, which belong to the Kateretidae family. They still exist today, with only a few species. As well as the about 99 million years old insects, the amber also includes pollen. It seems that the beetles helped the flowering plants to victory, because they contributed to their propagation. In turn, the beetles benefited from the new food source. The results have now been published in the journal iScience.
The researchers have described the new beetle species using specimens in four amber pieces from Myanmar (previously known as Burma). The pieces are estimated to be 99 million years old and date from the Cretaceous period, when dinosaurs were a rich and diverse group. Two of the pieces are in the Museum of Natural Sciences of Barcelona (Spain), while the other two specimens are kept in the Institute of Geology and Palaeontology in Nanjing (China).
“Although Myanmar surprises us time and again with finds of great scientific importance, amber pieces containing numerous organisms are not often found there,” says project leader Dr. David Peris, who comes from Spain and is a postdoc at the Institute for Geosciences at the University of Bonn with an Alexander von Humboldt Foundation fellowship. He carried out the project with scientists from the USA, Spain, Germany, China and the Czech Republic.
Three of the examined amber pieces contained numerous beetles, while the fourth piece contained only one specimen of this family. Many pollen grains of different groups of seed plants, some of them long extinct, have been preserved with the beetles in the tree resin. Peris: “This close association suggests that the grains were distributed in the viscous lump of resin by the movement of the beetles.”
The beetle family still exists today
The Kateretidae are a small family of beetles with less than 100 described modern species that today live in South America and other temperate and subtropical regions. The species of this family feed on pollen and flower parts. Due to their dietary habits, they are nowadays regarded as pollinators of flowering plants (angiosperms). But in the middle Cretaceous period their rapid development had just begun. Previously, the Earth was colonized by gymnosperms, literally meaning “naked seeds”, which also includes our conifers. “The most important aspect of this study is that the pollen grains in three of the amber pieces do not belong to flowering plants,” says Peris. The pollen grains on the beetle of the fourth piece of amber, however, come from a water lily, a group of very primitive angiosperms that emerged at an early stage.
Living together for mutual benefit
There are other pollinating insects in amber, but almost all of them concern gymnosperms. When flowering plants (angiosperms) began their early development, they represented a new resource that was used by the Kateretidae. The beetles adapted quickly and formed a mutually beneficial symbiosis: The flowering plants served the beetles as a food source and these animals contributed to the propagation of the new angiosperms by pollination.
In earlier studies it was speculated that the beetles might belong to the insect groups that pollinated the earliest flowers. Some of these animals had developed the ability to pollinate gymnosperms well before the appearance of angiosperms. “Our study supports this hypothesis of significant host plant relocation, as there are no Kateretidae associated with gymnosperms today,” says Peris. Adapting to the new resource has proven to be an evolutionary advantage.
Reference:
David Peris et al, Generalist Pollen-Feeding Beetles During the Mid-Cretaceous, SSRN Electronic Journal (2019). DOI: 10.2139/ssrn.3492117
Geologists studying rock samples from Baffin Island find lost fragment of continent. Credit: istock
Sifting through diamond exploration samples from Baffin Island, Canadian scientists have identified a new remnant of the North Atlantic craton—an ancient part of Earth’s continental crust.
A chance discovery by geologists poring over diamond exploration samples has led to a major scientific payoff.
Kimberlite rock samples are a mainstay of diamond exploration. Formed millions of years ago at depths of 150 to 400 kilometers, kimberlites are brought to the surface by geological and chemical forces. Sometimes, the igneous rocks carry diamonds embedded within them.
“For researchers, kimberlites are subterranean rockets that pick up passengers on their way to the surface,” explains University of British Columbia geologist Maya Kopylova. “The passengers are solid chunks of wall rocks that carry a wealth of details on conditions far beneath the surface of our planet over time.”
But when Kopylova and colleagues began analyzing samples from a De Beers Chidliak Kimberlite Province property in southern Baffin Island, it became clear the wall rocks were very special. They bore a mineral signature that matched other portions of the North Atlantic craton—an ancient part of Earth’s continental crust that stretches from Scotland to Labrador.
“The mineral composition of other portions of the North Atlantic craton is so unique there was no mistaking it,” says Kopylova, lead author of a new paper in the Journal of Petrology that outlines the findings. “It was easy to tie the pieces together. Adjacent ancient cratons in Northern Canada—in Northern Quebec, Northern Ontario and in Nunavut—have completely different mineralogies.”
Cratons are billion-year old, stable fragments of continental crust—continental nuclei that anchor and gather other continental blocks around them. Some of these nuclei are still present at the center of existing continental plates like the North American plate, but other ancient continents have split into smaller fragments and been re-arranged by a long history of plate movements.
“Finding these ‘lost’ pieces is like finding a missing piece of a puzzle,” says Kopylova. “The scientific puzzle of the ancient Earth can’t be complete without all of the pieces.”
The continental plate of the North Atlantic craton rifted into fragments 150 million years ago, and currently stretches from northern Scotland, through the southern part of Greenland and continues southwest into Labrador.
The newly identified fragment covers the diamond bearing Chidliak kimberlite province in southern Baffin Island. It adds roughly 10 percent to the known expanse of the North Atlantic craton.
This is the first time geologists have been able to piece parts of the puzzle together at such depth—so called mantle correlation. Previous reconstructions of the size and location of Earth’s plates have been based on relatively shallow rock samples in the crust, formed at depths of one to 10 kilometers.
“With these samples we’re able to reconstruct the shapes of ancient continents based on deeper, mantle rocks,” says Kopylova. “We can now understand and map not only the uppermost skinny layer of Earth that makes up one percent of the planet’s volume, but our knowledge is literally and symbolically deeper. We can put together 200-kilometer deep fragments and contrast them based on the details of the deep mineralogy.”
The samples from the Chidliak Kimberlite Province in southern Baffin Island were initially provided by Peregrine Diamonds, a junior exploration company. Peregrine was acquired by the international diamond exploration company and retailer De Beers in 2018. The drill cores sample themselves are very valuable, and expensive to retrieve.
“Our partner companies demonstrate a lot of goodwill by providing research samples to UBC, which enables fundamental research and the training of many grad students,” says Kopylova. “In turn, UBC research provides the company with information about the deep diamondiferous mantle that is central to mapping the part of the craton with the higher changes to support a successful diamond mine.”
Reference:
M G Kopylova et al. The metasomatized mantle beneath the North Atlantic Craton: Insights from peridotite xenoliths of the Chidliak kimberlite province (NE Canada), Journal of Petrology (2019). DOI: 10.1093/petrology/egz061
Roughly 66 million years ago an asteroid slammed into the Yucatan peninsula. New research shows darkness, not cold, likely drove a mass extinction after the impact. Credit: NASA
New research finds soot from global fires ignited by an asteroid impact could have blocked sunlight long enough to drive the mass extinction that killed most life on Earth, including the dinosaurs, 66 million years ago.
The Cretaceous–Paleogene extinction event wiped out about 75 percent of all species on Earth. An asteroid impact at the tip of Mexico’s Yucatán Peninsula caused a period of prolonged cold and darkness, called an impact winter, that likely fueled a large part of the mass extinction. But scientists have had a hard time teasing out the details of the impact winter and what the exact mechanism was that killed life on Earth.
A new study in AGU’s journal Geophysical Research Letters simulates the contributions of the impact’s sulfur, dust, and soot emissions to the extreme darkness and cold of the impact winter. The results show the cold would have been severe but likely not devastating enough to drive a mass extinction. However, soot emissions from global forest fires darkened the sky enough to kill off photosynthesizers at the base of the food web for well over a year, according to the study.
“This low light seems to be a really big signal that would potentially be devastating to life,” said Clay Tabor, a geoscientist at the University of Connecticut and lead author of the new study. “It seems like these low light conditions are a probable explanation for a large part of the extinction.”
The results help scientists better understand this intriguing mass extinction that ultimately paved the way for humans and other mammals to evolve. But the study also provides insight into what might happen in a nuclear winter scenario, according to Tabor.
“The main driver of a nuclear winter is actually from soot in a similar type situation,” Tabor said. “What it really highlights is just how potentially impactful soot can be on the climate system.”
The impact and extinction
The Chicxulub asteroid impact spewed clouds of ejecta into the upper atmosphere that then rained back down to Earth. The returning particles would have had enough energy to broil Earth’s surface and ignite global forest fires. Soot from the fires, along with sulfur compounds and dust, blocked out sunlight, causing an impact winter lasting several years. Previous research estimates average global temperatures plummeted by at least 26 degrees Celsius (47 degrees Fahrenheit).
Scientists know the extreme darkness and cold were devastating to life on Earth but are still teasing apart which component was more harmful to life and whether the soot, sulfate, or dust particles were most disruptive to the climate.
In the new study, Tabor and his colleagues used a sophisticated climate model to simulate the climatic effects of soot, sulfates, and dust from the impact.
Their results suggest soot emissions from global fires absorbed the most sunlight for the longest amount of time. The model showed soot particles were so good at absorbing sunlight that photosynthesis levels dropped to below one percent of normal for well over a year.
“Based on the properties of soot and its ability to effectively absorb incoming sunlight, it did a very good job at blocking sunlight from reaching the surface,” Tabor said. “In comparison to the dust, which didn’t stay in the atmosphere for nearly as long, and the sulfur, which didn’t block as much light, the soot could actually block almost all light from reaching the surface for at least a year.”
A refuge for life
The darkness would have been devastating to photosynthesizers and could explain the mass extinction through a collapse of the food web, according to the researchers. All life on Earth depends on photosynthesizers like plants and algae that harvest energy from sunlight.
Interestingly, the temperature drop likely wasn’t as disturbing to life as the darkness, according to the study.
“It’s interesting that in their model, soot doesn’t necessarily cause a much larger cooling when compared other types of aerosol particles produced by the impact-but soot does cause surface sunlight to decline a lot more,” said Manoj Joshi, a climate dynamics professor at the University of East Anglia in the United Kingdom who was not connected to the new study.
In regions like the high latitudes, the results suggest oceans didn’t cool significantly more than they do during a normal cycle of the seasons.
“Even though the ocean cools by a decent amount, it doesn’t cool by that much everywhere, particularly in the higher latitude regions,” Tabor said. “In comparison to the almost two years without photosynthetic activity from soot, it seems to be a secondary importance.”
As a result, high latitude coastal regions may have been refuges for life in the months after the impact. Plants and animals living in the Arctic or Antarctic are already used to large temperature swings, extreme cold, and low light, so they may have had a better chance of surviving the impact winter, according to the researchers.
Reference:
Clay R. Tabor et al. Causes and Climatic Consequences of the Impact Winter at the Cretaceous‐Paleogene Boundary, Geophysical Research Letters (2020). DOI: 10.1029/2019GL085572
Julia Brugger et al. Baby, it’s cold outside: Climate model simulations of the effects of the asteroid impact at the end of the Cretaceous, Geophysical Research Letters (2016). DOI: 10.1002/2016GL072241
Quartz is a crystalline, strong mineral made up of silicon and oxygen atoms. The atoms are linked in a continuous SiO4 Silicon–oxygen tetrahedra structure, with each oxygen being shared between two tetrahedra, giving SiO2 an overall chemical formula. Quartz is the second most abundant of minerals in the continental crust of Earth, behind feldspar.
Quartz occurs in two types, normal α-quartz and high-temperature β-quartz, both chiral. The transformation from α-quartz to β-quartz occurs abruptly at 573 ° C (846 K; 1.063 ° F). Since the transformation is followed by a major volume change, it can easily trigger the fracturing of ceramics or rocks that pass this temperature threshold.
There are several different quartz types and some semi-precious gemstones. Quartz varieties have been the most widely used minerals in jewelry making and hardstone carvings since the antiquity, particularly in Eurasia.
Quartz belongs to the trigonal crystal system. The ideal crystal shape is a six-sided prism terminating with six-sided pyramids at each end. In nature quartz crystals are often twinned (with twin right-handed and left-handed quartz crystals), distorted, or so intergrown with adjacent crystals of quartz or other minerals as to only show part of this shape, or to lack obvious crystal faces altogether and appear massive. Well-formed crystals typically form in a ‘bed’ that has unconstrained growth into a void; usually the crystals are attached at the other end to a matrix and only one termination pyramid is present. However, doubly terminated crystals do occur where they develop freely without attachment, for instance within gypsum. A quartz geode is such a situation where the void is approximately spherical in shape, lined with a bed of crystals pointing inward.
What is Blue Quartz?
An opaque to translucent, blue quartz variety due to inclusions of its color, typically fibrous magnesioriebeckite or crocidolite, or tourmaline. The color can be caused by the color of the minerals used, or by microscopic inclusions of Rayleigh light scattering.
Blue quartz contains inclusions of fibrous magnesio-riebeckite or crocidolite.
How does Blue Quartz from?
Blue quartz formation may depend on the type of inclusion to which it relates. Within metamorphic rocks, the blue quartz with mineral inclusions typically crystallizes. Nevertheless, those where tourmaline inclusions predominate usually occur in igneous rocks and pegmatites. Coarse-grained blue quartz is often used to form the constituents of igneous rocks.
Where does Blue Quartz come from?
Quartz is a very common mineral throughout the world, having important deposits in the Americas, specifically in the United States, Colombia, Venezuela, and Brazil, in the European continent, this precious mineral can also be found in Spain, Switzerland, Italy and even in more remote areas such as the island of Madagascar.
How to identify Blue Quartz?
In the jewelry world one of the most common fakes is selling tinted glass as if it were blue quartz. In order to avoid anything like this from happening to us, you need to learn certain quartz physical characteristics this separate them from the rest.
While it sounds like a natural science lesson, identifying them in a very simple way is very useful knowledge. The first thing you should know about quartz is that it has a higher hardness than glass so you can do a simple test to verify whether you have an authentic piece.
A piece of quartz would be able to crack glass with a higher hardness, and you can try a glass bottle and if the stone scratches it is quartz with ease. In the other side, if it takes an enormous effort to create a crack in the bottle we can face a plain piece of glass.
The trick we’ve just discussed is a piece of homemade advice you can do at any time, but if you’d like anything more sophisticated you’ll need some jeweler loupes. Magnifying glasses are required to test whether or not there are bubbles in the composition of the rock.
Arial view of the Bungle Bungle range, May 2016. Credit: Creative Commons Attribution-Share Alike 4.0 International license. Nichollas Harrison
Their distinctive stripes made Purnululu world famous and have helped the striking sandstone formations survive for generations.
The story of the Bungle Bungles begins about 360 million years ago with a river not so different from the Ord River that flows nearby today.
That river flowed downhill towards the ocean until it hit a broad low basin. There, it spread out, slowed down and deposited its load of sediment before drying up.
Every wet season and every flood, the river left the sand and stone it carried behind, layer upon layer.
Strange and fantastic formations
After a few million years, the landscape shifted upwards. The plateau formed mountains and hills, and the river began to flow downstream again.
After megayears of adding new layers, the rivers began to take them away. In that time, the earliest layers buried kilometers below the surface had become sandstone.
But unlike regular sandstone, the Bungle Bungles are held together by nothing but pressure.
“If you reach out and touch them, you’ll feel sand coming away at your fingertips,” says Chris Done, Chairperson of the Purnululu World Heritage Committee.
“The grains of sand are held together by their own pressure on each other. There’s no cementing,” he explains.
(That’s the stuff between the grains that helps them stick together.)
“They’re just pressed down with enough weight above them that they’re forced together.”
There’s some debate among geologists about just how this happened. Some think that the rock formed with cementing and later lost it, while others think it never had cementing at all.
However it formed, once that soft sandstone was uncovered, wind and water carved through it easily. A surreal landscape reflecting the twisting paths of rivers and streams emerged, and the layers deposited years ago were exposed to the elements.
As Edward Hardman, the first European geologist to encounter the formation, described it: “The prevailing nature of the rock, however, is that of a yellow or reddish freestone, very soft in places, and susceptible to ‘weathering’, owing to which the rock-masses often assume strange and fantastic forms.”
The hills are alive
Once they were exposed, each layer reacted differently.
Layers slightly richer in iron developed a rust-colored red color, as the iron percolated through to the surface and oxidized.
Other layers, richer in clay, were able to hold onto more water. These became home to colonies of dark-colored cyanobacteria, sometimes called blue-green algae.
“Those algae are about some of the toughest lifeforms you can think of,” Chris says.
“They go dormant when it’s dry, and they thrive when it’s wet.
“If you go up there when it’s been raining, it’s a shiny deep green or black, whereas during the dry season, they’re more of a gray color.”
So while the layers run throughout the hills, the stripes are only visible on the surface. Underground, it’s pale sandstone all the way through.
Nothing but footprints
As well as giving the hills their striking colors, the protective crust of iron and bacteria slows erosion of the sandstone.
So without their distinctive appearance, the Bungle Bungles may not have endured the forces of nature for so long.
But are the stripes attracting a new force of erosion? As more and more tourists explore the spectacular site, could their feet crush the Bungle Bungles back to sand?
Humans have visited and lived in Purnululu for thousands of years. Aboriginal people hunted and traded in the area long before tourists arrived.
They recognised the range as a site of great significance long before it was World Heritage listed, and Rangers from their descendants still live in and care for the area.
They think an increase in tourists isn’t an immediate threat “as long as people do the right thing and stay on the trails”, says Chris.
So if you visit the Bungle Bungles, stick to the path and let the stripes do their job. With care, they’ll still be amazing us for megayears to come.
Note: The above post is reprinted from materials provided by Particle. The original article was written by Rockwell McGellin.
Fossil rudist bivalves (Vaccinites) from the Al-Hajar Mountains, United Arab Emirates. Credit: Wikipedia, Wilson44691 – Own work, Public Domain
Earth turned faster at the end of the time of the dinosaurs than it does today, rotating 372 times a year, compared to the current 365, according to a new study of fossil mollusk shells from the late Cretaceous. This means a day lasted only 23 and a half hours, according to the new study in AGU’s journal Paleoceanography and Paleoclimatology.
The ancient mollusk, from an extinct and wildly diverse group known as rudist clams, grew fast, laying down daily growth rings. The new study used lasers to sample minute slices of shell and count the growth rings more accurately than human researchers with microscopes.
The growth rings allowed the researchers to determine the number of days in a year and more accurately calculate the length of a day 70 million years ago. The new measurement informs models of how the Moon formed and how close to Earth it has been over the 4.5-billion-year history of the Earth-Moon gravitational dance.
The new study also found corroborating evidence that the mollusks harbored photosynthetic symbionts that may have fueled reef-building on the scale of modern-day corals.
The high resolution obtained in the new study combined with the fast growth rate of the ancient bivalves revealed unprecedented detail about how the animal lived and the water conditions it grew in, down to a fraction of a day.
“We have about four to five datapoints per day, and this is something that you almost never get in geological history. We can basically look at a day 70 million years ago. It’s pretty amazing,” said Niels de Winter, an analytical geochemist at Vrije Universiteit Brussel and the lead author of the new study.
Climate reconstructions of the deep past typically describe long term changes that occur on the scale of tens of thousands of years. Studies like this one give a glimpse of change on the timescale of living things and have the potential to bridge the gap between climate and weather models.
Chemical analysis of the shell indicates ocean temperatures were warmer in the Late Cretaceous than previously appreciated, reaching 40 degrees Celsius (104 degrees Fahrenheit) in summer and exceeding 30 degrees Celsius (86 degrees Fahrenheit) in winter. The summer high temperatures likely approached the physiological limits for mollusks, de Winter said.
“The high fidelity of this data-set has allowed the authors to draw two particularly interesting inferences that help to sharpen our understanding of both Cretaceous astrochronology and rudist palaeobiology,” said Peter Skelton, a retired lecturer of palaeobiology at The Open University and a rudist expert unaffiliated with the new study.
Ancient reef-builders
The new study analyzed a single individual that lived for over nine years in a shallow seabed in the tropics — a location which is now, 70-million-years later, dry land in the mountains of Oman.
Torreites sanchezi mollusks look like tall pint glasses with lids shaped like bear claw pastries. The ancient mollusks had two shells, or valves, that met in a hinge, like asymmetrical clams, and grew in dense reefs, like modern oysters. They thrived in water several degrees warmer worldwide than modern oceans.
In the late Cretaceous, rudists like T. sanchezi dominated the reef-building niche in tropical waters around the world, filling the role held by corals today. They disappeared in the same event that killed the non-avian dinosaurs 66 million years ago.
“Rudists are quite special bivalves. There’s nothing like it living today,” de Winter said. “In the late Cretaceous especially, worldwide most of the reef builders are these bivalves. So they really took on the ecosystem building role that the corals have nowadays.”
The new method focused a laser on small bits of shell, making holes 10 micrometers in diameter, or about as wide as a red blood cell. Trace elements in these tiny samples reveal information about the temperature and chemistry of the water at the time the shell formed. The analysis provided accurate measurements of the width and number of daily growth rings as well as seasonal patterns. The researchers used seasonal variations in the fossilized shell to identify years.
The new study found the composition of the shell changed more over the course of a day than over seasons, or with the cycles of ocean tides. The fine-scale resolution of the daily layers shows the shell grew much faster during the day than at night
“This bivalve had a very strong dependence on this daily cycle, which suggests that it had photosymbionts,” de Winter said. “You have the day-night rhythm of the light being recorded in the shell.”
This result suggests daylight was more important to the lifestyle of the ancient mollusk than might be expected if it fed itself primarily by filtering food from the water, like modern day clams and oysters, according to the authors. De Winter said the mollusks likely had a relationship with an indwelling symbiotic species that fed on sunlight, similar to living giant clams, which harbor symbiotic algae.
“Until now, all published arguments for photosymbiosis in rudists have been essentially speculative, based on merely suggestive morphological traits, and in some cases were demonstrably erroneous. This paper is the first to provide convincing evidence in favor of the hypothesis,” Skelton said, but cautioned that the new study’s conclusion was specific to Torreites and could not be generalized to other rudists.
Moon retreat
De Winter’s careful count of the number of daily layers found 372 for each yearly interval. This was not a surprise, because scientists know days were shorter in the past. The result is, however, the most accurate now available for the late Cretaceous, and has a surprising application to modeling the evolution of the Earth-Moon system.
The length of a year has been constant over Earth’s history, because Earth’s orbit around the Sun does not change. But the number of days within a year has been shortening over time because days have been growing longer. The length of a day has been growing steadily longer as friction from ocean tides, caused by the Moon’s gravity, slows Earth’s rotation.
The pull of the tides accelerates the Moon a little in its orbit, so as Earth’s spin slows, the Moon moves farther away. The moon is pulling away from Earth at 3.82 centimeters (1.5 inches) per year. Precise laser measurements of distance to the Moon from Earth have demonstrated this increasing distance since the Apollo program left helpful reflectors on the Moon’s surface.
But scientists conclude the Moon could not have been receding at this rate throughout its history, because projecting its progress linearly back in time would put the Moon inside the Earth only 1.4 billion years ago. Scientists know from other evidence that the Moon has been with us much longer, most likely coalescing in the wake of a massive collision early in Earth’s history, over 4.5 billion years ago. So the Moon’s rate of retreat has changed over time, and information from the past, like a year in the life of an ancient clam, helps researchers reconstruct that history and model of the formation of the moon.
Because in the history of the Moon, 70 million years is a blink in time, de Winter and his colleagues hope to apply their new method to older fossils and catch snapshots of days even deeper in time.
Reference:
Niels J. Winter, Steven Goderis, Stijn J.M. Van Malderen, Matthias Sinnesael, Stef Vansteenberge, Christophe Snoeck, Joke Belza, Frank Vanhaecke, Philippe Claeys. Subdaily‐Scale Chemical Variability in a Torreites Sanchezi Rudist Shell: Implications for Rudist Paleobiology and the Cretaceous Day‐Night Cycle. Paleoceanography and Paleoclimatology, 2020; 35 (2) DOI: 10.1029/2019PA003723
Scientists are finding that Earth’s mantle may have generated the planet’s early magnetic field. Credit: Naeblys
New research lends credence to an unorthodox retelling of the story of early Earth first proposed by a geophysicist at Scripps Institution of Oceanography at UC San Diego.
In a study appearing March 15 in the journal Earth and Planetary Science Letters, Scripps Oceanography researchers Dave Stegman, Leah Ziegler, and Nicolas Blanc provide new estimates for the thermodynamics of magnetic field generation within the liquid portion of the early Earth’s mantle and show how long that field was available.
The paper provides a “door-opening opportunity” to resolve inconsistencies in the narrative of the planet’s early days. Significantly, it coincides with two new studies from UCLA and Arizona State University geophysicists that expand on Stegman’s concept and apply it in new ways.
“Currently we have no grand unifying theory for how Earth has evolved thermally,” Stegman said. “We don’t have this conceptual framework for understanding the planet’s evolution. This is one viable hypothesis.”
The trio of studies are the latest developments in a paradigm shift that could change how Earth history is understood.
It has been a bedrock tenet of geophysics that Earth’s liquid outer core has always been the source of the dynamo that generates its magnetic field. Magnetic fields form on Earth and other planets that have liquid, metallic cores, rotate rapidly, and experience conditions that make the convection of heat possible.
In 2007, researchers in France proposed a radical departure from the long-held assumption that the Earth’s mantle has remained entirely solid since the very beginnings of the planet. They argued that during the first half of the planet’s 4.5-billion-year history, the bottom third of Earth’s mantle would have had to have been molten, which they call “the basal magma ocean.” Six years later, Stegman and Ziegler expanded upon that idea, publishing the first work showing how this once-liquid portion of the lower mantle, rather than the core, could have exceeded the thresholds needed to create Earth’s magnetic field during that time.
The Earth’s mantle is made of silicate material that is normally a very poor electrical conductor. Therefore, even if the lowermost mantle were liquid for billions of years, rapid fluid motions inside it wouldn’t produce large electrical currents needed for magnetic field generation, similar to how Earth’s dynamo currently works in the core. Stegman’s team asserted the liquid silicate might actually be more electrically conductive than what was generally believed.
“Ziegler and Stegman first proposed the idea of a silicate dynamo for the early Earth,” said UCLA geophysicist Lars Stixrude. The idea was met with skepticism because their early results “showed that a silicate dynamo was only possible if the electrical conductivity of silicate liquid was remarkably high, much higher than had been measured in silicate liquids at low pressure and temperature.”
A team led by Stixrude used quantum-mechanical computations to predict the conductivity of silicate liquid at basal magma ocean conditions for the first time.
According to Stixrude, “we found very large values of the electrical conductivity, large enough to sustain a silicate dynamo.” The UCLA study appeared in the Feb. 25 issue of Nature Communications.
In another paper, Arizona State geophysicist Joseph O’Rourke applied Stegman’s concept to consider whether it’s possible that Venus might have at one point generated a magnetic field within a molten mantle.
These new studies are signs that the premise is starting to take hold, but is still far from being widely accepted.
“No one is going to believe it until they do it themselves and now two other highly esteemed scientists have done it themselves,” said Stegman.
“The pioneering studies of Dave Stegman and his collaborators directly inspired my work on Venus,” said O’Rourke. “Their recent paper helps answer a question that vexed scientists for many years: How has Earth’s magnetic field survived for billions of years?”
If Stegman’s premise is correct, it would mean the mantle could have provided the young planet’s first magnetic shield against cosmic radiation. It could also underpin studies of how tectonics evolved on the planet later in history.
“If the magnetic field was generated in the molten lower mantle above the core, then Earth had protection from the very beginning and that might have made life on Earth possible sooner,” Stegman said.
“Ultimately, our papers are complementary because they demonstrate that basal magma oceans are important to the evolution of terrestrial planets,” said O’Rourke. “Earth’s basal magma ocean has solidified but was key to the longevity of our magnetic field.”
The Scripps Oceanography study was funded by the National Science Foundation, the U.S. Department of Energy, and a UC San Diego SEED Fellowship.
References:
Nicolas A. Blanc, Dave R. Stegman, Leah B. Ziegler. Thermal and magnetic evolution of a crystallizing basal magma ocean in Earth’s mantle. Earth and Planetary Science Letters, 2020; 534: 116085 DOI: 10.1016/j.epsl.2020.116085
J. G. O’Rourke. Venus: A Thick Basal Magma Ocean May Exist Today. Geophysical Research Letters, 2020; 47 (4) DOI: 10.1029/2019GL086126
Lars Stixrude, Roberto Scipioni, Michael P. Desjarlais. A silicate dynamo in the early Earth. Nature Communications, 2020; 11 (1) DOI: 10.1038/s41467-020-14773-4
The rocks the team analysed are the oldest preserved mantle rocks. They allow us to see into the early history of the Earth as if through a window. Credit: UNSW
Ancient rocks from Greenland have shown that the elements necessary for the evolution of life did not come to Earth until very late in the planet’s formation—much later than previously thought.
An international team of geologists—led by the University of Cologne and involving UNSW scientists—have published important new findings about the origin of oceans and life on Earth: they have found evidence that a large proportion of the elements that are essential to the formation of oceans and life—such as water, carbon and nitrogen—only came to Earth very late in its history.
Many scientists previously believed that these elements had already been there at the beginning of our planet’s formation. However, the geological investigations published in Nature today have shown that most of the water in fact only came to Earth when its formation was almost complete.
Volatile elements such as water originate from asteroids, the planetary building blocks that formed in the outer solar system. There has been a lot of discussion and controversy in the scientific community around when precisely these building blocks came to Earth.
Dr. Mario Fischer-Gödde from the Institute of Geology and Mineralogy at the University of Cologne, who led the work, says we are now able to narrow down the timeframe more precisely.
“The rocks we analyzed are the oldest preserved mantle rocks. They allow us to see into the early history of the Earth as if through a window.
“We compared the composition of the oldest, approximately 3.8 billion-year-old, mantle rocks from the Archean Eon with the composition of the asteroids from which they formed, and with the composition of the Earth’s mantle today.”
To understand the temporal process, the researchers determined the isotope abundances of a very rare platinum metal called ruthenium, which the Archean mantle of the Earth contained.
Like a genetic fingerprint, the rare platinum metal is an indicator for the late growth phase of the Earth.
“Platinum metals like ruthenium have an extremely high tendency to combine with iron. Therefore, when the Earth formed, ruthenium must have been completely discharged into the Earth’s metallic core,” says Professor Fischer-Gödde.
Professor Martin Van Kranendonk, the UNSW scientist who was part of the research, says the reason why this is of such interest relates directly to understanding the origins of life on Earth, how we humans came to be, and in fact, to whether we might be alone, or have neighbours in the universe.
“This is because the results show that Earth did not really become a habitable planet until relatively late in its accretionary history,” he says.
“If you combine this with the evidence for very ancient life on Earth, it reveals that life got started on our planet surprisingly quickly, within only a few hundred million years. Now this might sound like a lot of time, and it is, but it is far different from what we used to think, that life took half a billion, or even a billion years to get started.
“And this gives hope for finding life on other planets that had a shorter geological history and period of ‘warm and wet’ conditions than Earth, because if life could get started quickly here, then perhaps it got started quickly elsewhere.”
Professor Dr. Carsten Münker, also at the University of Cologne, added: “The fact that we are still finding traces of rare platinum metals in the Earth’s mantle means that we can assume they were only added after the formation of the core was completed—they were certainly the result of later collisions of the Earth with asteroids or smaller planetesimals.”
Scientists refer to the very late building blocks of Earth, which arrived through these collisions, as the ‘late veneer.”
“Our findings suggest that water and other volatile elements such as carbon and nitrogen did indeed arrive on Earth very late in the ‘late veneer’ phase,” Professor Fischer-Gödde says.
The new findings are the result of collaboration among scientists from Germany, Denmark, England, Australia and Japan. The scientists are planning further field trips to India, northwestern Australia, and Greenland to investigate more rock samples.
Reference:
Mario Fischer-Gödde et al. Ruthenium isotope vestige of Earth’s pre-late-veneer mantle preserved in Archaean rocks, Nature (2020). DOI: 10.1038/s41586-020-2069-3
The grey line in the rock, running from the foreground away under the boulder towards the mountains, is one of the shear zones from the study area. Credit: Lucy Campbell
A major international study has shed new light on the mechanisms through which earthquakes are triggered up to 40km beneath the earth’s surface.
While such earthquakes are unusual, because rocks at those depth are expected to creep slowly and aseismically, they account for around 30 per cent of intracontinental seismic activity. Recent examples include a significant proportion of seismicity in the Himalaya as well as aftershocks associated with the 2001 Bhuj earthquake in India.
However, very little is presently known about what causes them, in large part due to the fact that any effects are normally hidden deep underground.
The current study, published in Nature Communications and funded by the Natural Environment Research Council, sought to understand how such deep earthquakes may be generated.
They showed that earthquake ruptures may be encouraged by the interaction of different shear zones that are creeping slowly and aseismically. This interaction loads the adjacent blocks of stiff rocks in the deep crust, until they cannot sustain the rising stress anymore, and snap — generating earthquakes.
Emphasising observations of quite complex networks created by earthquake-generated faults, they suggest that this context is characterised by repeating cycles of deformation, with long-term slow creep on the shear zones punctuated by episodic earthquakes.
Although only a transient component of such deformation cycles, the earthquakes release a significant proportion of the accumulated stress across the region.
The research was led by the University of Plymouth (UK) and University of Oslo (Norway), with scientists conducting geological observations of seismic structures in exhumed lower crustal rocks on the Lofoten Islands.
The region is home to one of the few well-exposed large sections of exhumed continental lower crust in the world, exposed during the opening of the North Atlantic Ocean.
Scientists spent several months in the region, conducting a detailed analysis of the exposed rock and in particular pristine pseudotachylytes (solidified melt produced during seismic slip regarded as ‘fossil earthquakes’) which decorate fault sets linking adjacent or intersecting shear zones.
They also collected samples from the region which were then analysed using cutting edge technology in the University’s Plymouth Electron Microscopy Centre.
Lead author Dr Lucy Campbell, Post-Doctoral Research Fellow at the University of Plymouth, said: “The Lofoten Islands provide an almost unique location in which to examine the impact of earthquakes in the lower crust. But by looking at sections of exposed rock less than 15 metres wide, we were able to see examples of slow-forming rock deformation working to trigger earthquakes generated up to 30km beneath the surface. The model we have now developed provides a novel explanation of the causes and effects of such earthquakes that could be applied at many locations where they occur.”
Project lead Dr Luca Menegon, Associate Professor at the University of Plymouth and the University of Oslo, added: “Deep earthquakes can be as destructive as those nucleating closer to the Earth’s surface. They often occur in highly populated areas in the interior of the continents, like in Central Asia for example. But while a lot is known about what causes seismic activity in the upper crust, we know far less about those which occur lower. This study gives us a fascinating insight into what is happening deep below the Earth’s surface, and our challenge is now to take this research forward and see if we can use it to make at-risk communities more aware of the dangers posed by such activity.”
As part of the study, scientists also worked with University of Plymouth filmmaker Heidi Morstang to produce a 60-minute documentary film about their work. Pseudotachylyte premiered at the 2019 Bergen International Film Festival, and will be distributed internationally once it has screened at various other festivals globally.
Reference:
L. R. Campbell, L. Menegon, Å. Fagereng, G. Pennacchioni. Earthquake nucleation in the lower crust by local stress amplification. Nature Communications, 2020; 11 (1) DOI: 10.1038/s41467-020-15150-x
Galleria delle Stalattiti, Corchia Cave. Credit: Linda Tegg
New University of Melbourne research has revealed that ice ages over the last million years ended when the tilt angle of the Earth’s axis was approaching high values.
During these times, longer and stronger summers melted the large Northern Hemisphere ice sheets, propelling the Earth’s climate into a warm ‘interglacial’ state, like the one we’ve experienced over the last 11,000 years.
The study by PhD candidate, Petra Bajo, and colleagues also showed that summer energy levels at the time these ‘ice-age terminations’ were triggered controlled how long it took for the ice sheets to collapse, with higher energy levels producing fast collapse.
Researchers are still trying to understand how often these periods happen and how soon we can expect another one.
Since the mid 1800s, scientists have long suspected that changes in the geometry of Earth’s orbit are responsible for the coming and going of ice ages — the uncertainty has been over which orbital property is most important.
Petra Bajo’s paper “Persistent influence of obliquity on ice age terminations since the Middle Pleistocene transition,” published today in Science, moves closer to resolving some of the mystery of why ice ages end by establishing when they end.
The team combined data from Italian stalagmites with information from ocean sediments drilled off the coast of Portugal.
“Colleagues from the University of Cambridge and Portugal’s Instituto Português do Mar e da Atmosfera compiled detailed records of the North Atlantic’s response to ice-sheet collapse,” said Associate Professor Russell Drysdale, from the research team.
“We could identify in the stalagmite growth layers the same changes that were being recorded in the ocean sediments. This allowed us to apply the age information from the stalagmite to the ocean sediment record, which cannot be dated for this time period.”
Using the latest techniques in radiometric dating, the international team determined the age of two terminations that occurred about 960,000 and 875,000 years ago.
The ages suggest that the initiation of both terminations is more consistent with increases in Earth’s tilt angle. These increases produce warmer summers over the regions where the Northern Hemisphere ice sheets are situated, causing melting.
“Both terminations then progressed to completion at a time when Northern Hemisphere summer energy over the ice sheets approached peak values,” said Dr Drysdale. “A comparison of these findings with previously published data from younger terminations shows this pattern has been a recurring feature of the last million years.”
The team plan to have a closer look next at the Middle Pleistocene Transition when the average length of ice-age cycles suddenly doubled in length.
Reference:
Petra Bajo, Russell N. Drysdale, Jon D. Woodhead, John C. Hellstrom, David Hodell, Patrizia Ferretti, Antje H. L. Voelker, Giovanni Zanchetta, Teresa Rodrigues, Eric Wolff, Jonathan Tyler, Silvia Frisia, Christoph Spötl, Anthony E. Fallick. Persistent influence of obliquity on ice age terminations since the Middle Pleistocene transition. Science, 2020; 367 (6483): 1235 DOI: 10.1126/science.aaw1114
Scientists have discovered an extensive body of freshwater off the Canterbury coast between Timaru and Ashburton.
NIWA marine geologist Dr. Joshu Mountjoy says the discovery is one of the few times a significant offshore aquifer has been located around the world and may lead to a new freshwater resource for the region.
The aquifer lies just 20 metres below the seafloor, making the find one of the shallowest in the world. It extends up to 60 kilometres from the coastline and may contain as much as 2000 cubic kilometres of water which is equivalent to half the volume of groundwater across Canterbury.
Derived from rainfall, the aquifer is partly being replenished by groundwater flow from the coastline between Timaru and Ashburton. However, most of the freshwater became trapped offshore during the last three Ice Ages, when sea level was more than 100 metres lower than it is today.
First indications that the offshore groundwater was there was a chance find that arose when a scientific drilling project in 2012 found brackish water—or salt and freshwater mixed together—50km off the coast and about 50m below the seafloor.
Dr. Mountjoy says that discovery led to a 2017 voyage aboard NIWA research vessel Tangaroa to carry out further investigation in which scientists collected electromagnetic data. An electrical source was towed behind the ship and behind that was a line of receivers which record different signals depending on the electrical resistivity of the ground. Resistivity is strongly influenced by the amount of salt in the water locked up in sediments beneath the seafloor. This was then integrated with seismic reflection profiling and numerical modelling to determine the amount of freshwater beneath the seabed.
The findings have been published today in leading scientific journal Nature Communications.
“One of the most important aspects of this study is the improved understanding it offers to water management,” Dr. Mountjoy says.
“If you’re going to manage the groundwater on shore and near the coast, you need to understand what the downstream limits are.”
The project attracted funding from the European Research Council through the MARCAN project which is a five-year international programme investigating how offshore groundwater influences continental margins.
The structure of the aquifer has been mapped in 3-D and reveals complex variations in shape and salinity, according to paper lead-author Aaron Micallef of the University of Malta who also says the approach to characterising this aquifer could potentially be used to revise estimations of their number and volume globally.
Dr. Mountjoy says while there are other places where offshore groundwater is known about, this is only the second time such intensive surveying has been carried out to define the extent of the water body. “By defining how big it is we’re getting a handle on understanding it.”
The next step is to take samples for analysis. “At the moment we have used remote techniques, modelling and geophysics. We really need to go out there and ground-truth our findings and we are investigating options for that.”
Dr. Mountjoy says there are several places around New Zealand facing significant issues with their groundwater, such as Christchurch and Hawke’s Bay which are feeling the pressure of increasing populations and regular prolonged dry periods.
“Hawke’s Bay is an example of a region needing to manage what they’re dealing with onshore. They’ve only got half the picture if they don’t know how far out it goes, and how much is leaking into the ocean.
“We need to set the groundwork in place for the future. Our primary goal is to help people manage their onshore resources. Our groundwater systems are a critical resource for society, they are increasingly under pressure, and we need every bit of information we can get.”
Reference:
Aaron Micallef et al. 3-D characterisation and quantification of an offshore freshened groundwater system in the Canterbury Bight, Nature Communications (2020). DOI: 10.1038/s41467-020-14770-7
Japan’s risk of giant tsunamis may have grown when the angle of a down-going slab of ocean crust declined. Top: ocean crust (right) slides under continental crust at a steep angle, causing faulting (red lines) in seafloor sediments piled up behind. Bottom: as the angle shallows, stress is transferred to sediments piled onto the continental crust, and faults develop there. Blue dots indicate resulting earthquakes. At left in both images, the change in angle also shifts the region where magma fueling volcanoes is generated, pushing eruptions further inland. Credit: Adapted from Oryan and Buck, Nature Geoscience 2020
On March 11, 2011, a magnitude 9 earthquake struck under the seabed off Japan — the most powerful quake to hit the country in modern times, and the fourth most powerful in the world since modern record keeping began. It generated a series of tsunami waves that reached an extraordinary 125 to 130 feet high in places. The waves devastated much of Japan’s populous coastline, caused three nuclear reactors to melt down, and killed close to 20,000 people.
The tsunami’s obvious cause: the quake occurred in a subduction zone, where the tectonic plate underlying the Pacific Ocean was trying to slide under the adjoining continental plate holding up Japan and other landmasses. The plates had been largely stuck against each other for centuries, and pressure built up. Finally, something gave. Hundreds of square miles of seafloor suddenly lurched horizontally some 160 feet, and thrust upward by up to 33 feet. Scientists call this a megathrust. Like a hand waved vigorously underwater in a bathtub, the lurch propagated to the sea surface and translated into waves. As they approached shallow coastal waters, their energy concentrated, and they grew in height. The rest is history.
But scientists soon realized that something did not add up. Tsunami sizes tend to mirror earthquake magnitudes on a predictable scale; This one produced waves three or four times bigger than expected. Just months later, Japanese scientists identified another, highly unusual fault some 30 miles closer to shore that seemed to have moved in tandem with the megathrust. This fault, they reasoned, could have magnified the tsunami. But exactly how it came to develop there, they could not say. Now, a new study in the journal Nature Geoscience gives an answer, and possible insight into other areas at risk of outsize tsunamis.
The study’s authors, based at Columbia University’s Lamont-Doherty Earth Observatory, examined a wide variety of data collected by other researchers before the quake and after. This included seafloor topographic maps, sediments from underwater boreholes, and records of seismic shocks apart from the megathrust.
The unusual fault in question is a so-called extensional fault — one in which the Earth’s crust is pulled apart rather than being pushed together. Following the megathrust, the area around the extensional fault moved some 200 feet seaward, and a series of scarps 10 to 15 feet high could be seen there, indicating a sudden, powerful break. The area around the extensional fault was also warmer than the surrounding seabed, indicating friction from a very recent movement; that suggested the extensional fault had been jolted loose when the megathrust struck. This in turn would have added to the tsunami’s power.
Extensional faults are in fact common around subduction zones — but only in oceanic plates, not the overriding continental ones, where this one was found. How did it get there? And, might such dangerous features lurk in other parts of the world?
The authors of the new paper believe the answer is the angle at which the ocean plate dives under the continental; they say it has been gradually shallowing out over millions of years. “Most people would say it was the megathrust that caused the tsunami, but we and some others are saying there may have been something else at work on top of that,” said Lamont PhD. student Bar Oryan, the paper’s lead author. “What’s new here is we explain the mechanism of how the fault developed.”
The researchers say that long ago, the oceanic plate was moving down at a steeper angle, and could drop fairly easily, without disturbing the seafloor on the overriding continental plate. Any extensional faulting was probably confined to the oceanic plate behind the trench — the zone where the two plates meet. Then, starting maybe 4 million or 5 million years ago, it appears that angle of subduction began declining. As a result, the oceanic plate began exerting pressure on sediments atop the continental plate. This pushed the sediments into a huge, subtle hump between the trench and Japan’s shoreline. Once the hump got big and compressed enough, it was bound to break, and that was probably what happened when the megathrust quake shook things loose. The researchers used computer models to show how long-term changes in the dip of the plate could produce major changes in the short-term deformation during an earthquake.
There are multiple lines of evidence. For one, material taken from boreholes before the quake show that sediments had been squeezed upward about midway between the land and the trench, while those closer to both the land and the trench had been subsiding — similar to what might happen if one laid a piece of paper flat on a table and then slowly pushed in on it from opposite sides. Also, recordings of aftershocks in the six months after the big quake showed scores of extensional-fault-type earthquakes carpeting the seabed over the continental plate. This suggests that the big extensional fault is only the most obvious one; strain was being released everywhere in smaller, similar quakes in surrounding areas, as the hump relaxed.
Furthermore, on land, Japan hosts numerous volcanoes arranged in a neat north-south arc. These are fueled by magma generated 50 or 60 miles down, at the interface between the subducting slab and the continental plate. Over the same 4 million to 5 million years, this arc has been migrating westward, away from the trench. Since magma generation tends to take place at a fairly constant depth, this adds to the evidence that the angle of subduction has gradually been growing shallower, pushing the magma-generating zone further inland.
Lamont geophysicist and coauthor Roger Buck said that the study and the earlier ones it builds on have global implications. “If we can go and find out if the subduction angle is moving up or down, and see if sediments are undergoing this same kind of deformation, we might be better able to say where this kind of risk exists,” he said. Candidates for such investigation would include areas off Nicaragua, Alaska, Java and others in the earthquake zones of the Pacific Ring of Fire. “These are areas that matter to millions of people,” he said.
Reference:
Bar Oryan, W. Roger Buck. Larger tsunamis from megathrust earthquakes where slab dip is reduced. Nature Geoscience, 2020; DOI: 10.1038/s41561-020-0553-x
Note: The above post is reprinted from materials provided by Earth Institute at Columbia University. Original written by Kevin Krajick.
The discovery of a small, bird-like skull, described in an article published in Nature, reveals a new species, Oculudentavis khaungraae, that could represent the smallest known Mesozoic dinosaur in the fossil record.
While working on fossils from in northern Myanmar, Lars Schmitz, associate professor of biology at the W.M. Keck Science Department, and a team of international researchers discovered a seemingly mature skull specimen preserved in Burmese amber. The specimen’s size is on par with that of the bee hummingbird, the smallest living bird.
“Amber preservation of vertebrates is rare, and this provides us a window into the world of dinosaurs at the lowest end of the body-size spectrum,” Schmitz said. “Its unique anatomical features point to one of the smallest and most ancient birds ever found.”
The team studied the specimen’s distinct features with high-resolution synchrotron scans to determine how the skull of the Oculudentavis khaungraae differs from those of other bird-like dinosaur specimens of the era. They found that the shape and size of the eye bones suggested a diurnal lifestyle, but also revealed surprising similarities to the eyes of modern lizards. The skull also shows a unique pattern of fusion between different bone elements, as well as the presence of teeth. The researchers concluded that the specimen’s tiny size and unusual form suggests a never-before-seen combination of features.
The discovery represents a specimen previously missing from the fossil record and provides new implications for understanding the evolution of birds, demonstrating the extreme miniaturization of avian body sizes early in the evolutionary process. The specimen’s preservation also highlights amber deposits’ potential to reveal the lowest limits of vertebrate body size.
“No other group of living birds features species with similarly small crania in adults,” Schmitz said. “This discovery shows us that we have only a small glimpse of what tiny vertebrates looked like in the age of the dinosaurs.”
Reference:
Hummingbird-sized dinosaur from the Cretaceous period of Myanmar, Nature (2020). DOI: 10.1038/s41586-020-2068-4
Note: The above post is reprinted from materials provided by Scripps College.
Desert rose is the colloquial name given to rose-like formations of gypsum or baryte crystal clusters which contain abundant grains of sand. The ‘petals’ are crystals flattened on the c crystallographic axis, fanning open in radiating flattened crystal clusters.
The rosette crystal habit tends to occur when the crystals form under arid sandy conditions, such as a shallow salt basin becoming evaporated. The crystals form a circular series of flat plates that give the rock a similar shape to a rose blossom.
How Do Desert Rose Rock Form?
Gypsum roses tend to have sharper edges better defined than baryt roses. Celestine and other minerals bladed with evaporite may also form clusters of rosettes. These can either appear as a single rose-like bloom, or as bloom clusters, with most sizes ranging from pea size to 4 inches (10 cm) in diameter.
The ambient sand that is incorporated into the crystal structure, or otherwise encrusts the crystals, varies with the local environment. If iron oxides are present, the rosettes take on a rusty tone.
The desert rose may also be known by the names: sand rose, rose rock, selenite rose, gypsum rose and baryte (barite) rose.
Where to find desert rose rock ?
Rose rocks are found in Tunisia, Libya, Morocco, Algeria, Jordan, Saudi Arabia, Qatar, Egypt, the United Arab Emirates, Spain (Fuerteventura, Canary Islands; Canet de Mar, Catalonia; La Almarcha, Cuenca), Mongolia (Gobi), Germany (Rockenberg), the United States (central Oklahoma; Cochise County, Arizona; Texas), Mexico (Ciudad Juárez, Chihuahua), Australia, South Africa and Namibia.
Desert Rose Rock Size
he average size of rose rocks are anywhere from 0.5 inches (1.3 cm) to 4 inches (10 cm) in diameter. The largest recorded by the Oklahoma Geological Survey was 17 inches (43 cm) across and 10 inches (25 cm) high, weighing 125 pounds (57 kg). Clusters of rose rocks up to 39 inches (99 cm) tall and weighing more than 1,000 pounds (454 kg) have been found.
Collection of various fluorescent minerals under ultraviolet UV-A, UV-B and UV-C light. Chemicals in the rocks absorb the ultraviolet light and emit visible light of various colors, a process called fluorescence. Credit: Hannes Grobe/AWI
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation.
The most striking example of fluorescence happens when the absorbed radiation is in the ultraviolet region of the spectrum, and thus invisible to the human eye, whereas the light emitted is in the visible region, giving the fluorescent material a distinct color that can only be seen when exposed to UV light. Fluorescent materials almost immediately cease to glow when the source of radiation ceases, unlike phosphorescent materials that tend to emit light for some time.
Fluorescence has many practical applications, including mineralogy, gemology, medicine, chemical sensors (fluorescence spectroscopy), fluorescent marking, coloring biological detectors, and detection of cosmic rays. Its most common everyday use is in energy-saving fluorescent lamps and LED lamps, where fluorescent coatings are used to transform short-wavelength UV or blue light into longer-wavelength yellow light, thereby mimicking the warm light of energy-inefficient incandescent lamps. Fluorescence also occurs frequently in nature in some minerals and in various biological forms in many branches of the animal kingdom.
Fluorescent Minerals
Gemstones, minerals, may have a distinctive fluorescence or may fluoresce differently under short-wave ultraviolet, long-wave ultraviolet, visible light, or X-rays.
Many types of calcite and amber will fluoresce under shortwave UV, longwave UV and visible light. Rubies, emeralds, and diamonds exhibit red fluorescence under long-wave UV, blue and sometimes green light; diamonds also emit light under X-ray radiation.
Mineral fluorescence is caused by a wide array of activators. In some situations, the activator concentration must be restricted to below a certain level, to prevent the fluorescent emission from quenching. In addition, the mineral must be free of impurities such as iron or copper, in order to prevent possible fluorescence from quenching. Divalent manganese is present in concentrations up to several per cent. Hexavalent uranium, in the form of uranyl cation, fluoresces at all concentrations in a yellow color, causing the fluorescence of minerals such as autunite or andersonite, and causing the fluorescence of materials such as certain samples of hyalite opal at low concentrations. Trivalent, low-concentration chromium is the source of ruby red fluorescence. Divalent europium, when seen in the mineral fluorite, is the source of blue fluoresce. Trivalent lanthanides such as terbium and dysprosium are the primary activators of the creamy yellow fluorescence shown by the mineral fluorite yttrofluorite type, and contribute to the zircon’s orange fluorescence. Powellite (calcium molybdate) and scheelite (calcium tungstate) fluoresce intrinsically in yellow and blue, respectively. When present together in solid solution, energy is transferred from the higher-energy tungsten to the lower-energy molybdenum, such that fairly low levels of molybdenum are sufficient to cause a yellow emission for scheelite, instead of blue. Low-iron sphalerite (zinc sulfide), fluoresces and phosphoresces in a range of colors, influenced by the presence of various trace impurities.
Crude oil (petroleum) fluoresces in a range of colors, from dull-brown for heavy oils and tars through to bright-yellowish and bluish-white for very light oils and condensates. This phenomenon is used in oil exploration drilling to identify very small amounts of oil in drill cuttings and core samples.
Meganeura is a genus of extinct insects from the Carboniferous period (approximately 300 million years ago), which resembled and are related to the present-day dragonflies. Its wingspans from 65 cm (25.6 in) to more than 70 cm (28 in), M.Monyi is one of the largest known species of flying insects. Meganeura was predatory and their diet consisted mainly of other insects.
Fossils were discovered in the French Stephanian Coal Measures of Commentry in 1880. In 1885, French paleontologist Charles Brongniart described and named the fossil “Meganeura” (large-nerved), which refers to the network of veins on the insect’s wings. Another fine fossil specimen was found in 1979 at Bolsover in Derbyshire. The holotype is housed in the National Museum of Natural History, in Paris.
Meganeura Size
There was some controversy over how Carboniferous Period insects were able to grow so large.
Oxygen levels and atmospheric density
The way in which oxygen is diffused through the body of the insect through its tracheal respiration system puts an upper limit on body size, which ancient insects seem to have far surpassed. Harlé (1911) originally suggested that Meganeura could only fly because at that time the atmosphere provided more oxygen than the present 20 per cent. This theory was initially rejected by fellow scientists, but was more recently approved through further analysis of the relationship between the availability of gigantism and oxygen.
If this hypothesis is correct, these insects would have been vulnerable to declining oxygen levels and in our current atmosphere could probably not survive. Some research suggests that insects breathe with “rapid cycles of compression and expansion of trachea.” Recent analysis of modern insects and birds ‘ flight energetics suggests that both the oxygen levels and air density provide an upper bound on size.
In the case of the giant dragonflies, the presence of very large Meganeuridae with wing spans rivaling those of Meganeura during the Permian, when the atmospheric oxygen content was already much lower than in the Carboniferous, presented a problem for the oxygen-related explanations. However, despite the fact that Meganeurids had the largest known wing spans, their bodies were not very heavy, being less colossal than those of many living Coleoptera; therefore, they were not true giant insects, only giant in comparison with their living relatives.
Lack of predators
Other explanations for the large size of Meganeurids compared to living relatives are warranted. Bechly (2004) suggested that the lack of aerial vertebrate predators allowed pterygote insects to evolve to maximum sizes during the Carboniferous and Permian periods, perhaps accelerated by an evolutionary “arms race” for increase in body size between plant-feeding Palaeodictyoptera and Meganisoptera as their predators.
Aquatic larvae stadium
Another theory suggests that insects that developed in water before becoming terrestrial as adults grew bigger as a way to protect themselves against the high levels of oxygen.
A farmer has found the 20,000-year-old remains of four prehistoric armadillos that grew to the size of a car at the bottom of a dried-out riverbed.
Local media said that the farmer stumbled across the ‘four glyptodonts’, a heavily armoured mammal that lived during the Pleistocene epoch and were relatives of present-day armadillos.
They developed in South America around 20 million years ago and spread to southern regions of North America after the continents connected several million years ago.
The large fossils were discovered on a dried riverbed in the Argentine capital Buenos Aires and experts from the Institute of Archaeological and Palaeontological Investigations of the Pampa Quaternary (Incuapa-Conicet) will spend the next week extracting the remains.
Archaeologist Pablo Messineo told reporters that a man named Juan de Dios Sota was taking his cows to graze in a nearby field when he noticed the odd shapes on the dried riverbed as they did not appear to be the remains of horses or cows.
Messineo and a team of scientists arrived on the scene to dig out the prehistoric mega beast.
Messineo said: ‘We went there expecting to find two glyptodonts when the excavation started and then two more were found!
‘It is the first time there have been four animals like this in the same site. Most of them were facing the same direction like they were walking towards something.’
He added that the sizes indicate the group was comprised of two adults and two younglings.
The science team will require diggers to remove the shells as they can weigh up to one ton.
The fossils will then undergo further research to establish their age and sex and possibly cause of death.
At the moment, it is believed the four glyptodonts lived around 20,000 years ago.
Glyptodonts were a genus of large heavily armoured mammals with a rounded, bony shell and squat limbs similar to a turtle.
They are believed to have weighed around 1,000 kilogrammes (2,205 lbs) and could grow to the size of a Volkswagen Beetle.
The animal’s remains have been found in Brazil, Uruguay and Argentina and it is believed they became extinct 10,000 years ago.
Based on their jaw morphology, Glyptodons were herbivores and they were also hairy with very slow movements due to their size.
Note: The above post is reprinted from materials provided by Metro.
Aneuretopsychidae from Late Cretaceous Burmese amber. Credit: NIGPAS
An international research group led by Prof. Wang Bo from the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences (NIGPAS) has found a new genus, including two new aneuretopsychid species from early Late Cretaceous (99 million years ago) Burmese amber, which reveals new anatomically significant details of the elongate mouthpart elements.
Mesopsychoid scorpionflies are peculiar Mesozoic insects with a distinctly elongate mouthpart and are considered to be a critical group of pollinators prior to the rise of angiosperms.
A new genus found from 99-million-year-old Burmese amber reveals the origin of scorpionflies’ long mouthpart. This discovery was reported in Science Advances on March 4. Aneuretopsychidae is a family of mecopteran insects with a long siphonate mouthpart. In particular, this family is the key to understanding both the early evolution of highly modified mouthparts in Mesopsychoidea and arguably the origin of fleas.
Previously, all known aneuretopsychids were from compression fossils, and the detailed structure of their mouthparts was still unclear.
Now, however, an international research group led by Prof. Wang Bo from the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences (NIGPAS) has found a new genus, including two new aneuretopsychid species from early Late Cretaceous (99 million years ago) Burmese amber, which reveals new anatomically significant details of the elongate mouthpart elements.
The aneuretopsychid mouthpart in the new amber fossils consists of one pair of galeae and one unpaired central hypopharynx. During feeding, the galeae would come together temporarily and enclose the hypopharynx thus forming a functional tube.
The structures of the new three-dimensionally preserved fossils thus reveal that the aneuretopsychid mouthpart is not labial but maxillary in origin.
The phylogenetic results based on 38 taxa and 54 discrete characters support the monophyly of Mesopsychoidea and demonstrate that an elongate mouthpart is one of its key synapomorphies, challenging the view that the long-proboscid condition independently originated two or three times in this clade.
In addition, the mouthpart of Mesopsychoidea differs structurally from the highly modified piercing mouthparts of Siphonaptera. So, neither Aneuretopsychidae nor Mesopsychoidea is a sister group to Siphonaptera.
In the Burmese amber forest, at least five families of long-proboscid insects have been discovered, further revealing the variety and complexity of mid-Cretaceous pollinating insects.
This study provides new insights into the separate origin of the long mouthpart of Mesopsychoidea and fleas, and the evolution of Cretaceous pollinating insects.
Reference:
X. Zhao el al., “Mouthpart homologies and life habits of Mesozoic long-proboscid scorpionflies,” Science Advances (2020). DOI: 10.1126/sciadv.aay1259
