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
Bastnaesite (the reddish parts) in Carbonatite. Bastnaesite is an important ore for rare earth elements, one of the mineral commodities identified as most at-risk of supply disruption by the USGS in a new methodology. Credit: Scott Horvath, USGS
Policymakers and the U.S. manufacturing sector now have a powerful tool to help them identify which mineral commodities they rely on that are most at risk to supply disruptions, thanks to a new methodology by the U.S. Geological Survey and its partners.
“This methodology is an important part of how we’re meeting our goals in the President Trump’s Strategy to ensure a reliable supply of critical minerals,” said USGS director Jim Reilly. “It provides information supporting American manufacturers’ planning and sound supply-chain management decisions.”
The methodology evaluated the global supply of and U.S. demand for 52 mineral commodities for the years 2007 to 2016. It identified 23 mineral commodities, including some rare earth elements, cobalt, niobium and tungsten, as posing the greatest supply risk for the U.S. manufacturing sector. These commodities are vital for mobile devices, renewable energy, aerospace and defense applications, among others.
“Manufacturers of new and emerging technologies depend on mineral commodities that are currently sourced largely from other countries,” said USGS scientist Nedal Nassar, lead author of the methodology. “It’s important to understand which commodities pose the greatest risks for which industries within the manufacturing sector.”
The supply risk of mineral commodities to U.S. manufacturers is greatest under the following three circumstances: U.S. manufacturers rely primarily on foreign countries for the commodities, the countries in question might be unable or unwilling to continue to supply U.S. manufacturers with the minerals; and U.S. manufacturers are less able to handle a price shock or from a disruption in supply.
“Supply chains can be interrupted for any number of reasons,” said Nassar. “International trade tensions and conflict are well-known reasons, but there are many other possibilities. Disease outbreaks, natural disasters, and even domestic civil strife can affect a country’s mineral industry and its ability to export mineral commodities to the U.S.”
Risk is not set in stone; it changes based on global market conditions that are specific to each individual mineral commodity and to the industries that use them. However, the analysis indicates that risk typically does not change drastically over short periods, but instead remains relatively constant or changes steadily.
“One thing that struck us as we were evaluating the results was how consistent the mineral commodities with the highest risk of supply disruption have been over the past decade,” said Nassar. “This is important for policymakers and industries whose plans extend beyond year-to-year changes.”
For instance, between 2007 and 2016, the risk for rare earth elements peaked in 2011 and 2012 when China halted exports during a dispute with Japan. However, the supply of rare earth elements consistently remained among the highest risk commodities throughout the entire study period.
In 2019, the U.S. Department of Commerce, in coordination with the Department of the Interior and other federal agencies, published the interagency report entitled “A Federal Strategy to Ensure a Reliable Supply of Critical Minerals,” in response to President Trump’s Executive Order 13817. Among other things, the strategy commits the U.S. Department of the Interior to improve the geophysical, geologic, and topographic mapping of the U.S.; make the resulting data and metadata electronically accessible; support private mineral exploration of critical minerals; make recommendations to streamline permitting and review processes enhancing access to critical mineral resources.
The methodology is entitled “Evaluating the Mineral Commodity Supply Risk of the U.S. Manufacturing Sector,” and is published in Science Advances.
Reference:
Evaluating the mineral commodity supply risk of the U.S. manufacturing sector, Science Advances 21 Feb 2020: Vol. 6, no. 8, eaay8647, DOI: 10.1126/sciadv.aay8647
The rising Earth from the perspective of the moon. Credit: NASA Goddard
Sometimes, you need to leave home to understand it. For Stanford planetary geologist Mathieu Lapôtre, “home” encompasses the entire Earth.
“We don’t only look at other planets to know what’s out there. It’s also a way for us to learn things about the planet that’s under our own feet,” said Lapôtre, an assistant professor of geological sciences in the School of Earth, Energy, & Environmental Sciences (Stanford Earth).
Scientists since Galileo have sought to understand other planetary bodies through an earthly lens. More recently, researchers have recognized planetary exploration as a two-way street. Studies of space have helped to explain aspects of climate and the physics of nuclear winter, for example. Yet revelations have not permeated all geoscience fields equally. Efforts to explain processes closer to the ground—at Earth’s surface and deep in its belly—are only beginning to benefit from knowledge gathered in space.
Now, as telescopes acquire more power, exoplanet studies grow more sophisticated and planetary missions produce new data, there’s potential for much broader impacts across Earth sciences, as Lapôtre and co-authors from Arizona State University, Harvard University, Rice University, Stanford and Yale University argue in the journal Nature Reviews Earth & Environment.
“The multitude and variety of planetary bodies within and beyond our solar system,” they write in a paper published March 2, “might be key to resolving fundamental mysteries about the Earth.”
In the coming years, studies of these bodies may well alter the way we think about our place in the universe.
Alien forms
Observations from Mars have already changed the way scientists think about the physics of sedimentary processes on Earth. One example got underway when NASA’s Curiosity Rover crossed a dune field on the red planet in 2015.
“We saw that there were big sand dunes and small, decimeter-scale ripples like the ones we see on Earth,” said Lapôtre, who worked on the mission as a Ph.D. student at Caltech in Pasadena, Calif. “But there was also a third type of bedform, or ripple, that does not exist on Earth. We couldn’t explain how or why this shape existed on Mars.”
The strange patterns prompted scientists to revise their models and invent new ones, which ultimately led to the discovery of a relationship between the size of a ripple and the density of the water or other fluid that created it. “Using these models developed for the environment of Mars, we can now look at an old rock on Earth, measure ripples in it and then draw conclusions about how cold or salty the water was at the time the rock formed,” Lapôtre said, “because both temperature and salt affect fluid density.”
This approach is applicable across the geosciences. “Sometimes when exploring another planet, you make an observation that challenges your understanding of geological processes, and that leads you to revise your models,” Lapôtre explained.
Planets as experiments
Other planetary bodies can also help to show how frequent Earth-like bodies are in the universe and what, exactly, makes Earth so different from the average planet.
“By studying the variety of outcomes that we see on other planetary bodies and understanding the variables that shape each planet, we can learn more about how things might have happened on Earth in the past,” explained co-author Sonia Tikoo-Schantz, a geophysics professor at Stanford Earth whose research centers on paleomagnetism.
Consider, she suggested, how studies of Venus and Earth have helped scientists better understand plate tectonics. “Venus and Earth are about the same size, and they probably formed under fairly similar conditions,” Tikoo-Schantz said. But while Earth has tectonic plates moving around and abundant water, Venus has a mostly solid lid, no water on its surface and a very dry atmosphere.
“From time to time, Venus has some kind of catastrophic disruption and a resurfacing of much of the world,” Tikoo-Schantz said, “but we don’t see this continuous steady state tectonic environment that we have on Earth.”
Scientists are increasingly convinced that water may explain much of the difference. “We know that subduction of tectonic plates brings water down into the Earth,” Tikoo-Schantz said. “That water helps lubricate the upper mantle, and helps convection happen, which helps drive plate tectonics.”
This approach—using planetary bodies as grand experiments—can be applied to answer more questions about how Earth works. “Imagine you want to see how gravity might affect certain processes,” Lapôtre said. “Going to other planets can let you run an experiment where you can observe what happens with a lower or higher gravity—something that’s impossible to do on Earth.”
Core paradox
Studies measuring magnetism in ancient rocks suggest that Earth’s magnetic field has been active for at least 3.5 billion years. But the cooling and crystallization of the inner core that scientists believe sustains Earth’s magnetic field today started less than 1.5 billion years ago. This 2-billion-year gap, known as the new core paradox, has left researchers puzzling over how Earth’s dynamo could have started so early, and persisted for so long.
Answers may lie in other worlds.
“In our circle of close neighbors—the Moon, Mars, Venus—we’re the only planet with a magnetic field that’s been going strong since the beginning and remains active today,” Lapôtre said. But Jupiter-sized exoplanets orbiting close to their star have been identified with magnetic fields, and it may soon be technically feasible to detect similar fields on smaller, rocky, Earth-like worlds. Such discoveries would help clarify whether Earth’s long-lived dynamo is a statistical anomaly in the universe whose startup required some special circumstance.
Ultimately, the mystery around the origin and engine behind Earth’s dynamo is a mystery about what creates and sustains the conditions for life. Earth’s magnetic field is essential to its habitability, protecting it against dangerous solar winds that can strip a planet of water and atmosphere. “That’s part of why Mars is such a dry desert compared to Earth,” Tikoo-Schantz said. “Mars started to dehydrate when its magnetic field died.”
Earth everchanging
Much of the impetus to look far beyond Earth when trying to decode its inner workings has to do with our planet’s restless nature. At many points in its 4.5 billion-year existence, Earth looked nothing like the blue-green marble it is today.
“We’re trying to get to the point where we can characterize planets that are like the Earth, and hopefully, someday find life on one of them,” said co-author Laura Schaefer, a planetary scientist at Stanford Earth who studies exoplanets. Chances are it will be something more like bacteria than E.T., she said.
“Just having another example of life anywhere would be amazing,” Schaefer said. It would also help to illuminate what happened on Earth during the billions of years before oxygen became abundant and, through processes and feedback loops that remain opaque, complex life burst forth.
“We’re missing information from different environments that existed on the surface of the Earth during that time period,” Schaefer explained. Plate tectonics constantly recycles rocks from the surface, plunging them into the planet’s fiery innards, while water sloshing around oceans, pelting down from rainclouds, hanging in the air, and slipping in rivers and streams tends to alter the geochemistry of rocks and minerals that remain near the surface.
Earth’s very liveliness makes it a poor archive for evidence of life and its impacts. Other planetary bodies—some of them dead still and bone dry, others somehow akin to the ancient Earth—may prove better suited to the task.
That’s part of why scientists were so excited to find, in 2019, that a rock sample collected by the Apollo 14 astronauts in 1971 may in fact hold minerals that rocketed off of Earth as a meteorite billions of years ago. “On the Moon, there is no plate tectonics or aqueous weathering,” Lapôtre said. “So this piece of rock has been sitting there intact for the last few billion years just waiting for us to find it.”
To be sure, planetary scientists do not expect to find many ancient Earth time capsules preserved in space. But continued exploration of other worlds in our solar system and beyond could eventually yield a small statistical sample of planets with life on them—not carbon copies of Earth’s systems, but systems nonetheless where interactions between life and atmosphere can come into sharper focus.
“They’re not going to be at the same stage of life as we have today on Earth, and so we’ll be able to learn about how planets and life evolve together,” Schaefer said. “That would be pretty revolutionary.”
Reference:
Mathieu G. A. Lapôtre et al. Probing space to understand Earth, Nature Reviews Earth & Environment (2020). DOI: 10.1038/s43017-020-0029-y
Fossilised threads – some as long as four metres – connecting organisms known as rangeomorphs, which dominated Earth’s oceans half a billion years ago. Credit: Alex Liu
Some of the first animals on Earth were connected by networks of thread-like filaments, the earliest evidence yet found of life being connected in this way.
Scientists from the Universities of Cambridge and Oxford discovered the fossilised threads—some as long as four metres—connecting organisms known as rangeomorphs, which dominated Earth’s oceans half a billion years ago.
The team found these filament networks—which may have been used for nutrition, communication or reproduction -in seven species across nearly 40 different fossil sites in Newfoundland, Canada. Their results are reported in the journal Current Biology.
Towards the end of the Ediacaran period, between 571 and 541 million years ago, the first diverse communities of large and complex organisms began to appear: prior to this, almost all life on Earth had been microscopic in size.
Fern-like rangeomorphs were some of the most successful life forms during this period, growing up to two metres in height and colonising large areas of the sea floor. Rangeomorphs may have been some of the first animals to exist, although their strange anatomies have puzzled palaeontologists for years; these organisms do not appear to have had mouths, organs or means of moving. One suggestion is that they absorbed nutrients from the water around them.
Since rangeomorphs could not move and are preserved where they lived, it is possible to analyse whole populations from the fossil record. Earlier studies of rangeomorphs have looked at how these organisms managed to reproduce and be so successful in their time.
“These organisms seem to have been able to quickly colonise the sea floor, and we often see one dominant species on these fossil beds,” said Dr. Alex Liu from Cambridge’s Department of Earth Sciences, and the paper’s first author. “How this happens ecologically has been a longstanding question—these filaments may explain how they were able to do that.”
Most of the filaments were between two and 40 centimetres in length, although some were as long as four metres. Since they are so thin however, the filaments are only visible in places where the fossil preservation is exceptionally good, which is one of the reasons they were not identified sooner. The fossils for this study were found on five sites in eastern Newfoundland, one of the world’s richest sources of Ediacaran fossils.
It’s possible that the filaments were used as a form of clonal reproduction, like modern strawberries, but since the organisms in the network were the same size, the filaments may have had other functions. For example, the filaments may have provided stability against strong ocean currents. Another possibility is that they enabled organisms to share nutrients, a prehistoric version of the ‘wood wide web’ observed in modern-day trees. What is known however, is that some reconsideration of how Ediacaran organisms lived may be in order.
“We’ve always looked at these organisms as individuals, but we’ve now found that several individual members of the same species can be linked by these filaments, like a real-life social network,” said Liu. “We may now need to reassess earlier studies into how these organisms interacted, and particularly how they competed for space and resources on the ocean floor. The most unexpected thing for me is the realisation that these things are connected. I’ve been looking at them for over a decade, and this has been a real surprise.”
“It’s incredible the level of detail that can be preserved on these ancient sea floors; some of these filaments are only a tenth of a millimetre wide,” said co-author Dr. Frankie Dunn from the Oxford University Museum of Natural History. “Just like if you went down the beach today, with these fossils, it’s a case of the more you look, the more you see.”
The SHIRE project, which contributed resources to this research, is investigating seamounts within the Hikurangi Trench, to learn how they generate or dampen earthquakes at different stages of subduction. This seismic image shows a seamount known as Puke Seamount, colliding with New Zealand. Image: SHIRE/Andrew Gase.
Subduction zones — places where one tectonic plate dives beneath another — are where the world’s largest and most damaging earthquakes occur. A new study has found that when underwater mountains — also known as seamounts — are pulled into subduction zones, not only do they set the stage for these powerful quakes, but also create conditions that end up dampening them.
The findings mean that scientists should more carefully monitor particular areas around a subducting seamount, researchers said. The practice could help scientists better understand and predict where future earthquakes are most likely to occur.
“The Earth ahead of the subducting seamount becomes brittle, favoring powerful earthquakes while the material behind it remains soft and weak, allowing stress to be released more gently,” said co-author Demian Saffer, director of the University of Texas Institute for Geophysics (UTIG), a research unit of The University of Texas at Austin Jackson School of Geosciences.
The study was published on March 2 in Nature Geoscience and was led by Tian Sun, who is currently a research scientist at the Geological Survey of Canada. Other co-authors include Susan Ellis, a scientist at the New Zealand research institute GNS Science. Saffer supervised the project and was Sun’s postdoctoral advisor at Penn State when they began the study.
The researchers used a computer model to simulate what happens when seamounts enter ocean trenches created by subduction zones. According to the model, when a seamount sinks into a trench, the ground ahead of it becomes brittle, as its slow advance squeezes out water and compacts the Earth. But in its wake, the seamount leaves a trail of softer wet sediment. The hard, brittle rock can be a source for powerful earthquakes, as forces generated by the subducting plate build up in it — but the weakened, wet material behind the seamount creates an opposite, dampening effect on these quakes and tremors.
Although seamounts are found all over the ocean floor, the extraordinary depths at which subduction occurs means that studying or imaging a subducting seamount is extremely difficult. This is why until now, scientists were not sure whether seamounts could affect the style and magnitude of subduction zone earthquakes.
The current research tackled the problem by creating a realistic computer simulation of a subducting seamount and measuring the effects on the surrounding rock and sediment, including the complex interactions between stresses in the Earth and fluid pressure in the surrounding material. Getting realistic data for the model involved conducting experiments on rock samples collected from subduction zones by scientific ocean drilling offshore Japan.
The scientists said the model’s results took them completely by surprise. They had expected water pressure and stress to break up material at the head of the seamount and thus weaken the rocks, not strengthen them.
“The seamount creates a feedback loop in the way fluids get squeezed out and the mechanical response of the rock to changes fluid pressure,” said Ellis, who co-developed the numerical code at the heart of the study.
The scientists are satisfied their model is robust because the earthquake behavior it predicts consistently matches the behavior of real earthquakes.
While the weakened rock left in the wake of seamounts may dampen large earthquakes, the researchers believe that it could be an important factor in a type of earthquake known as a slow slip event. These slow-motion quakes are unique because they can take days, weeks and even months to unfold.
Laura Wallace, a research scientist at UTIG and GNS Science, who was the first to document New Zealand slow slip events, said that the research was a demonstration of how geological structures in the Earth’s crust, such as seamounts, could influence a whole spectrum of seismic activity.
“The predictions from the model agree very nicely with what we are seeing in New Zealand in terms of where small earthquakes and tremors are happening relative to the seamount,” said Wallace, who was not part of the current study.
Sun believes that their investigations have helped address a knowledge gap about seamounts, but that research will benefit from more measurements.
“We still need high resolution geophysical imaging and offshore earthquake monitoring to better understand patterns of seismic activity,” said Sun.
The research was funded by the Seismogenesis at Hikurangi Integrated Research Experiment (SHIRE), an international project co-led by UT Austin to investigate the origin of earthquakes in subduction zones.
The study was also supported by the National Science Foundation, the New Zealand Ministry of Business, Innovation and Employment, and GNS Science.
Reference:
Tianhaozhe Sun, Demian Saffer, Susan Ellis. Mechanical and hydrological effects of seamount subduction on megathrust stress and slip. Nature Geoscience, 2020; DOI: 10.1038/s41561-020-0542-0
Research suggest that rocks colliding inside fault zones, like this one in Maine, may contribute to damaging high-frequency earthquake vibrations. Credit: Julia Carr
Earthquakes produce seismic waves with a range of frequencies, from the long, rolling motions that make skyscrapers sway, to the jerky, high-frequency vibrations that cause tremendous damage to houses and other smaller structures. A pair of Brown University geophysicists has a new explanation for how those high-frequency vibrations may be produced.
In a paper published in Geophysical Research Letters, Brown faculty members Victor Tsai and Greg Hirth propose that rocks colliding inside a fault zone as an earthquake happens are the main generators of high-frequency vibrations. That’s a very different explanation than the traditional one, the researchers say, and it could help explain puzzling seismic patterns made by some earthquakes. It could also help scientists predict which faults are likely to produce the more damaging quakes.
“The way we normally think of earthquakes is that stress builds up on a fault until it eventually fails, the two sides slip against each other, and that slip alone is what causes all the ground motions we observe,” said Tsai, an associate professor in Brown’s Department of Earth, Environmental and Planetary Sciences. “The idea of this paper is to evaluate whether there’s something other than just slip. The basic question is: If you have objects colliding inside the fault zone as it slips, what physics could result from that?”
Drawing from mathematical models that describe the collisions of rocks during landslides and other debris flows, Tsai and Hirth developed a model that predicts the potential effects of rock collisions in fault zones. The model suggested the collisions could indeed be the principal driver of high-frequency vibrations. And combining the collision model with more traditional frictional slip models offers reasonable explanations for earthquake observations that don’t quite fit the traditional model alone, the researchers say.
For example, the combined model helps explain repeating earthquakes — quakes that happen at the same place in a fault and have nearly identical seismic wave forms. The odd thing about these quakes is that they often have very different magnitudes, yet still produce ground motions that are nearly identical. That’s difficult to explain by slip alone, but makes more sense with the collision model added, the researchers say.
“If you have two earthquakes in the same fault zone, it’s the same rocks that are banging together — or at least rocks of basically the same size,” Tsai said. “So if collisions are producing these high-frequency vibrations, it’s not surprising that you’d get the same ground motions at those frequencies regardless of the amount of slip that occurs.”
The collision model also may help explain why quakes at more mature fault zones — ones that have had lots of quakes over a long period of time — tend to produce less damage compared to quakes of the same magnitude at more immature faults. Over time, repeated quakes tend to grind down the rocks in a fault, making the faults smoother. The collision model predicts that smoother faults with less jagged rocks colliding would produce weaker high-frequency vibrations.
Tsai says that more work needs to be done to fully validate the model, but this initial work suggests the idea is promising. If the model does indeed prove valid, it could be helpful in classifying which faults are likely to produce more or less damaging quakes.
“People have made some observations that particular types of faults seem to generate more or less high-frequency motion than others, but it has not been clear why faults fall into one category or the other,” he said. “What we’re providing is a potential framework for understanding that, and we could potentially generalize this to all faults around the world. Smoother faults with rounded internal structures may generally produce less high-frequency motions, while rougher faults would tend to produce more.”
The research also suggests that some long-held ideas about how earthquakes work might need revising.
“In some sense it might mean that we know less about certain aspects of earthquakes than we thought,” Tsai said. “If fault slip isn’t the whole story, then we need a better understanding of fault zone structure.”
Reference:
Victor C. Tsai, Greg Hirth. Elastic Impact Consequences for High‐Frequency Earthquake Ground Motion. Geophysical Research Letters, 2020; DOI: 10.1029/2019GL086302
Representative Image : Scientists used the model to calculate seismic risk in the L.A. Basin. Credit: Juan Vargas, Jean-Philippe Avouac, Chris Rollins / Caltech
Devastating historical earthquakes and tsunamis in Indonesia can be traced to a recently discovered submarine extensional fault system, where sediment slumping along the fault zone triggers the tsunamis, according to a study published in Nature Geoscience. These findings provide a new theory for earthquake and tsunami hazard in this highly tectonically active region.
A number of destructive events in the Banda Sea have been documented from the seventeenth century onwards, including detailed reports of the large 1852 Banda earthquake and tsunami in Indonesia. This event, along with the others, had been assumed to have been caused by compressional faults in the subduction zone—where one tectonic plate plunges below another—that underlies the Banda Sea. However, there is geological evidence of submarine extensional faulting that suggests this region has recently been experiencing stretching rather than compression.
Phil Cummins and colleagues combined existing geological information with GPS observations of crustal motion and an analysis of historical earthquakes and tsunamis in the region, with a particular focus on the 1852 event. They found that the 1852 Banda earthquake and four other historical earthquakes that devastated the Banda Islands were triggered by the shallowly dipping extensional fault system, rather than a deeper source related to subduction. Furthermore, the authors found that slumping of marine sediment destabilized by the earthquakes along the fault zone triggered the tsunamis, rather than the tsunamis being directly triggered by the earthquakes themselves.
The authors conclude that their findings demonstrate that earthquake-induced sediment slumping can trigger large tsunamis, and that—in the Banda Sea—seismic activity in a region of extensional tectonics is a source of large earthquake and tsunami hazard for Indonesia.
Reference:
Phil R. Cummins et al. Earthquakes and tsunamis caused by low-angle normal faulting in the Banda Sea, Indonesia, Nature Geoscience (2020). DOI: 10.1038/s41561-020-0545-x
Note: The above post is reprinted from materials provided by Springer Nature .
Benjamin Johnson of Iowa State University woks at an outcrop in remote Western Australia where geologists are studying 3.2-billion-year-old ocean crust. Photo by Jana Meixnerova. Photos provided by Benjamin Johnson.
The Earth of 3.2 billion years ago was a “water world” of submerged continents, geologists say after analyzing oxygen isotope data from ancient ocean crust that’s now exposed on land in Australia.
And that could have major implications on the origin of life.
“An early Earth without emergent continents may have resembled a ‘water world,’ providing an important environmental constraint on the origin and evolution of life on Earth as well as its possible existence elsewhere,” geologists Benjamin Johnson and Boswell Wing wrote in a paper just published online by the journal Nature Geoscience.
Johnson is an assistant professor of geological and atmospheric sciences at Iowa State University and a recent postdoctoral research associate at the University of Colorado Boulder. Wing is an associate professor of geological sciences at Colorado. Grants from the National Science Foundation supported their study and a Lewis and Clark Grant from the American Philosophical Society supported Johnson’s fieldwork in Australia.
Johnson said his work on the project started when he talked with Wing at conferences and learned about the well-preserved, 3.2-billion-year-old ocean crust from the Archaean eon (4 billion to 2.5 billion years ago) in a remote part of the state of Western Australia. Previous studies meant there was already a big library of geochemical data from the site.
Johnson joined Wing’s research group and went to see ocean crust for himself — a 2018 trip involving a flight to Perth and a 17-hour drive north to the coastal region near Port Hedland.
After taking his own rock samples and digging into the library of existing data, Johnson created a cross-section grid of the oxygen isotope and temperature values found in the rock.
(Isotopes are atoms of a chemical element with the same number of protons within the nucleus, but differing numbers of neutrons. In this case, differences in oxygen isotopes preserved with the ancient rock provide clues about the interaction of rock and water billions of years ago.)
Once he had two-dimensional grids based on whole-rock data, Johnson created an inverse model to come up with estimates of the oxygen isotopes within the ancient oceans. The result: Ancient seawater was enriched with about 4 parts per thousand more of a heavy isotope of oxygen (oxygen with eight protons and 10 neutrons, written as 18O) than an ice-free ocean of today.
How to explain that decrease in heavy isotopes over time?
Johnson and Wing suggest two possible ways: Water cycling through the ancient ocean crust was different than today’s seawater with a lot more high-temperature interactions that could have enriched the ocean with the heavy isotopes of oxygen. Or, water cycling from continental rock could have reduced the percentage of heavy isotopes in ocean water.
“Our preferred hypothesis — and in some ways the simplest — is that continental weathering from land began sometime after 3.2 billion years ago and began to draw down the amount of heavy isotopes in the ocean,” Johnson said.
The idea that water cycling through ocean crust in a way distinct from how it happens today, causing the difference in isotope composition “is not supported by the rocks,” Johnson said. “The 3.2-billion-year-old section of ocean crust we studied looks exactly like much, much younger ocean crust.”
Johnson said the study demonstrates that geologists can build models and find new, quantitative ways to solve a problem — even when that problem involves seawater from 3.2 billion years ago that they’ll never see or sample.
And, Johnson said these models inform us about the environment where life originated and evolved: “Without continents and land above sea level, the only place for the very first ecosystems to evolve would have been in the ocean.”
Reference:
Benjamin W. Johnson & Boswell A. Wing. Limited Archaean continental emergence reflected in an early Archaean 18O-enriched ocean. Nature Geoscience, 2020 DOI: 10.1038/s41561-020-0538-9
In a New Jersey mine spanning 2,670 vertical feet—more than twice as deep as the Empire State Building is tall—visitors might notice a little glow. The Sterling Hill Mining Museum is well known to have the largest collection of fluorescent rocks publicly exhibited in the world— one that shines bright neon colors under certain types of light.
The museum is an old zinc mine— one of the country’s oldest, opened in 1739 and in operation until 1986, when it was an important site for zinc removal, as well as iron and manganese removal. The abandoned mine was bought in 1989 and turned into a museum in 1990, and now attracts about 40,000 visitors each year. The museum itself includes both outdoor and indoor mining exhibits, rock and fossil discovery centers, an observatory, an underground mine tour and the Thomas S. Warren Museum of Fluorescence, devoted to the glowing minerals.
The Museum of Fluorescence occupies the old mill of the mine, a building dating back to 1916. There are approximately 1,800 square feet of rooms, with more than two dozen exhibits— some of which you can view and experience alone. Even the entrance is impressive; over 100 large fluorescent mineral specimens cover a whole wall that is illuminated by various types of ultraviolet light, showing the sparkling capabilities of each mineral type. For kids, there’s a “cave,” complete with a fluorescent volcano, a castle and some glowing wildlife. And there’s an exhibit comprised solely of fluorescent rocks and minerals from Greenland. All told, more than 700 objects are on display in the museum.
Approximately 15 percent of minerals fluoresce under black light and usually do not glow during the day. Essentially, ultraviolet light reflecting on these minerals is absorbed into the rock, where it interacts with the material’s chemicals and excites the mineral’s electrons, releasing its energy as an outward glow. Different types of ultraviolet light— longwave and shortwave — can produce different colors from the same rock, and some rocks can glow multiple colors that have other materials within them (called activators).
“A mineral could pick up different activators depending on where it is made, so a specimen from Mexico could fluoresce a different color than one from Arizona, even though it’s the same mineral,” Jill Pasteris, a professor of earth and planetary sciences at Washington University, told the newspaper at the college. “A few rocks, on the other hand, are just fine fluorescents. Of example, calcite will shine in just about any fluorescent colour. Yet interestingly enough, having too much of an activator can also prevent fluorescence. So an excess of a generic activator such as manganese will keep from lighting up a good fluorescer like calcite.
Among the most exciting aspects of the Sterling Hill mine tour is the walk through the Rainbow Tunnel culminating in a whole fluoresced room called the Rainbow Room. Much of the route is illuminated by ultraviolet light which causes the exposed zinc ore in the walls to burst with flashing, neon reds and greens. The green color stands for another form of zinc ore called willemite. The color of the mineral can vary wildly at daylight — all from the usual reddish-brown pieces to crystallized and gem-like blues and greens — but all variations fluoresce bright neon green. When the mine was active, the ore covered the walls throughout, so anyone shining ultraviolet light would have had a similar experience to what occurs in the tunnel today.
A tiny lizard forefoot of the genus Anolis is trapped in amber that is about 15 to 20 million years old. Credit: Jonas Barthel
The tiny forefoot of a lizard of the genus Anolis was trapped in amber about 15 to 20 million years ago. Every detail of this rare fossil is visible under the microscope. But the seemingly very good condition is deceptive: The bone is largely decomposed and chemically transformed, very little of the original structure remains. The results, which are now presented in the journal PLOS ONE, provide important clues as to what exactly happens during fossilization.
How do fossils stay preserved for millions of years? Rapid embedding is an important prerequisite for protecting the organisms from access by scavengers, for example. Decomposition by microorganisms can for instance be prevented by extreme aridity. In addition, the original substance is gradually replaced by minerals. The pressure from the sediment on top of the fossil ensures that the fossil is solidified. “That’s the theory,” says Jonas Barthel, a doctoral student at the Institute for Geosciences at the University of Bonn. “How exactly fossilization proceeds is currently the subject of intensive scientific investigation.”
Amber is considered an excellent preservative. Small animals can be enclosed in a drop of tree resin that hardens over time. A team of geoscientists from the University of Bonn has now examined an unusual find from the Dominican Republic: The tiny forefoot of a lizard of the genus Anolis is enclosed in a piece of amber only about two cubic centimeters in size. Anolis species still exist today.
Vertebrate inclusions in amber are very rare
The Stuttgart State Museum of Natural History has entrusted the exhibit to the paleontologists of the University of Bonn for examination. “Vertebrate inclusions in amber are very rare, the majority are insect fossils,” says Barthel. The scientists used the opportunity to investigate the fossilization of the seemingly very well preserved vertebrate fragment. Since 2018 there is a joint research project of the University of Bonn with the German Research Foundation, which contributes to the understanding of fossilization using experimental and analytical approaches. The present study was also conducted within the framework of this project.
The researchers had thin sections prepared for microscopy at the Institute for Evolutionary Biology at the University of Bonn. The claws and toes are very clearly visible in the honey-brown amber mass, almost as if the tree resin had only recently dripped onto them — yet the tiny foot is about 15 to 20 million years old.
Scans in the micro-computer tomograph of the Institute for Geosciences revealed that the forefoot was broken in two places. One of the fractures is surrounded by a slight swelling. “This is an indication that the lizard had perhaps been injured by a predator,” says Barthel. The other fracture happened after the fossil was embedded — exactly at the place where a small crack runs through the amber.
Amber did not protect from environmental influences
The analysis of a thin section of bone tissue using Raman spectroscopy revealed the state of the bone tissue. The mineral hydroxyapatite in the bone had been transformed into fluoroapatite by the penetration of fluorine. Barthel: “This is surprising, because we assumed that the surrounding amber largely protects the fossil from environmental influences.” However, the small crack may have encouraged chemical transformation by allowing mineral-rich solutions to find their way in. In addition, Raman spectroscopy shows that collagen, the bone’s elastic component, had largely degraded. Despite the seemingly very good state of preservation, there was actually very little left of the original tissue structure.
“We have to expect that at least in amber from the Dominican Republic, macromolecules are no longer detectable,” says the supervisor of the study, Prof. Dr. Jes Rust from the Institute for Geosciences. It was not possible to detect more complex molecules such as proteins, but final analyses are still pending. The degradation processes in this amber deposit are therefore very advanced, and there is very little left of the original substance.
Acids in tree resin attack bone
Amber is normally considered an ideal preservative: Due to the tree resin, we have important insights into the insect world of millions of years. But in the lizard’s bone tissue, the resin might even have accelerated the degradation processes: Acids in the tree secretion have probably attacked the apatite in the bone — similar to tooth decay.
Reference:
H. Jonas Barthel, Denis Fougerouse, Thorsten Geisler, Jes Rust. Fluoridation of a lizard bone embedded in Dominican amber suggests open-system behavior. PLOS ONE, 2020; 15 (2): e0228843 DOI: 10.1371/journal.pone.0228843
Maculaferrum blaisi, described in a study published in Acta Palaeontologica Polonica, is the first hemipteran insect (true bug) to be discovered at the Redmond Formation, a fossil site from the Cretaceous period near Schefferville, Labrador. Credit: Alexandre V. Demers-Potvin
A fossilised insect wing discovered in an abandoned mine in Labrador has led palaeontologists from McGill University and the University of Gdańsk to identify a new hairy cicada species that lived around 100 million years ago.
Maculaferrum blaisi, described in a study published in Acta Palaeontologica Polonica, is the first hemipteran insect (true bug) to be discovered at the Redmond Formation, a fossil site from the Cretaceous period near Schefferville, Labrador.
Alexandre Demers-Potvin, a Master’s student under the supervision of Professor Hans Larsson, Director of the Redpath Museum at McGill, said that a single wing was sufficient to identify the family to which the insect belonged.
“We were easily able to demonstrate that the insect belonged to the Tettigarctidae family thanks to the pattern of the veins we observed on its wing,” said Demers-Potvin, who is also a 2018 National Geographic Explorer.
The genus name (Maculaferrum) is derived from the Latin words macula — spot — because of the spotted pattern found on parts of the wing and ferrum — iron — due to the high iron content of the red rocks found at the Redmond site. The species name — blaisi — is in honour of Roger A. Blais, who conducted the first survey of the Redmond Formation and of its fossils in 1957 while working for the Iron Ore Company of Canada.
“This gives us a better understanding of the site’s insect biodiversity during the Cretaceous, a time before the dinosaurs were wiped out,” Demers-Potvin added. “The finding also illustrates that rare species can be found at the Redmond mine and that it deserves the attention from the palaeontological community.”
“The find is exciting because it represents the oldest, diverse insect locality in Canada. It’s also from an exciting time during an evolutionary explosion of flowering plants and pollinating insects, that evolved into the terrestrial ecosystems of today,” said Larsson.
Reference:
Alexandre Demers-Potvin, Jacek Szwedo, Cassia Paragnani, Hans Larsson. First North American occurrence of hairy cicadas discovered in a Late Cretaceous (Cenomanian) exposure from Labrador, Canada. Acta Palaeontologica Polonica, 2020; 65 DOI: 10.4202/app.00669.2019
Mystery has long surrounded the evolution of Facivermis, a worm-like creature that lived approximately 518 million years ago in the Cambrian period. Credit: Franz Anthony
Scientists have discovered the earliest known example of an animal evolving to lose body parts it no longer needed.
Mystery has long surrounded the evolution of Facivermis, a worm-like creature that lived approximately 518 million years ago in the Cambrian period.
It had a long body and five pairs of spiny arms near its head, leading to suggestions it might be a “missing link” between legless cycloneuralian worms and a group of fossil animals called “lobopodians,” which had paired limbs all along their bodies.
But the new study — by the University of Exeter, Yunnan University and the Natural History Museum — reveals Facivermis was itself a lobopodian that lived a tube-dwelling lifestyle anchored on the sea floor, and so evolved to lose its lower limbs.
“A key piece of evidence was a fossil in which the lower portion of a Facivermis was surrounded by a tube,” said lead author Richard Howard.
“We don’t know the nature of the tube itself, but it shows the lower portion of the worm was anchored inside by a swollen rear end.
“Living like this, its lower limbs would not have been useful, and over time the species ceased to have them.
“Most of its relatives had three to nine sets of lower legs for walking, but our findings suggest Facivermis remained in place and used its upper limbs to filter food from the water.
“This is the earliest known example of ‘secondary loss’ — seen today in cases such as the loss of legs in snakes.”
The Cambrian period is seen as the dawn of animal life, and the researchers were fascinated to find a species evolving to be “more primitive” even at this early stage of evolution.
“We generally view organisms evolving from simple to more complex body plans, but occasionally we see the opposite occurring,” said senior author Dr Xiaoya Ma.
“What excited us in this study is that even at this early stage of animal evolution, secondary-loss modifications — and in this case, reverting ‘back’ to lose some of its legs — had already occurred.
“We’ve known about this species for about 30 years, but it’s only now that we’ve got a confident grasp of where it fits in the evolutionary tree.
“Studies like this help us understand the shape of the tree of life and figure out where the adaptations and body parts we now see have come from.”
Co-author Greg Edgecombe, of the Natural History Museum, said: “For several years we and others have been finding lobopodians from the Cambrian period with pairs of appendages along the length of the body — long, grasping ones in the front, and shorter, clawed ones in the back.
“But Facivermis takes this to the extreme, by completely reducing the posterior batch.”
The Chengjiang Biota in Yunnan Province, south-west China has been a source of well-preserved Facivermis fossils.
Using these fossils, the study placed Facivermis in the Cambrian lobopodian group, which gave rise to three modern animal groups (phyla): Arthropoda (including insects, shrimps and spiders), Tardigrada (water bears) and Onychophora (velvet worms).
The research was funded by the Natural History Museum and the Natural Environment Research Council (NERC).
Reference:
Richard J. Howard, Xianguang Hou, Gregory D. Edgecombe, Tobias Salge, Xiaomei Shi, Xiaoya Ma. A Tube-Dwelling Early Cambrian Lobopodian. Current Biology, 2020; DOI: 10.1016/j.cub.2020.01.075
Alaska Centennial Nugget : Largest Gold Nugget Ever Found in Alaska
The largest gold nugget ever found in Alaska is named the Alaska Centennial Nugget. It weighs a whopping 294.10 troy ounces, and was found near the town of Ruby, Alaska in 1998.
A number of big nuggets have been discovered in Alaska. Yes, Alaska is probably the best state in the U.S. to look for gold, especially if you’re looking for a BIG nugget.
Miners have been looking for gold in Alaska for more than 100 years now, and some spectacular nuggets have been found. Of all the gold found in Alaska, the Centennial Nugget in Alaska is the most spectacular of all the discoveries made here.
Barry Clay was a placer mining region that was known for producing big nuggets along Swift Creek. He was driving dirt with his bulldozer when his eye spotted something odd. He jumped out of the dozer, catching the ring. He knew immediately by weight that a huge gold nugget had been found. He buried the nugget under a nearby tree afterwards, until he could find out what to do with it.
As he finally took it to town for further study, it was determined he had discovered the largest nugget ever found in Alaska, and the second largest nugget ever found in the western hemisphere behind the Cortez nugget found in Mexico.
It was named the Centennial nugget because it was discovered on the Klondike Gold Rush’s 100th anniversary which took thousands of men north to Alaska in search of gold. His finding in 1998 indicates that a number of huge gold nuggets are still left to be found. They haven’t all been discovered, not by a long shot!
With the record high gold prices in recent years and the renewed interest in gold mining, there is a very good chance in the very near future that more large gold nuggets will be discovered.
There were also many other big nuggets found in the Ruby Mining District, including several nuggets that weighed over a pound.
Alaska has by far the most commercial mining operations compared to other states, mainly due to its miner friendly regulations in comparison to other states. Alaska has a reputation for large nuggets as well. Overall gold produced here is not as high as other states like California and Nevada, but if you want to find a huge gold nugget in the United States, Alaska is the best place to look.
This beautiful nugget wasn’t alone. It may be the largest to be found here, but several whoppers have been found around Ruby. Nearly all the waters in this area, including Ruby Creek, Long Creek, Poorman Creek, Moose Creek and Bear Gulch, have produced gold. Such drainages have also created some of the most valuable nuggets in Alaska.
Ruby is in this region the primary center for the mines. The city is located on the Yukon River and is the main supply source for the placer mines operating in this region. Some of Alaska’s richest placers were working in the areas around Ruby from 1910 to 1920. There are only a handful of commercial mining operations here today, but it is very probable that good nuggets are still unearthed here.
