New isotopic evidence supporting moon formation via Earth collision with planet-sized body

June 7, 2014

The moon. A new series of measurements of oxygen isotopes provides increasing evidence that the moon formed from the collision of the Earth with another large, planet-sized astronomical body, around 4.5 billion years ago. Credit: NASA/JPL

A new series of measurements of oxygen isotopes provides increasing evidence that the Moon formed from the collision of Earth with another large, planet-sized astronomical body, around 4.5 billion years ago.
This work will be published in Science on 6th June, and will be presented to the Goldschmidt geochemistry conference in California on 11th June.

Most planetary scientists believe that the Moon formed from an impact between Earth and a planet-sized body, which has been given the name Theia. Efforts to confirm that the impact had taken place had centred on measuring the ratios between the isotopes of oxygen, titanium, silicon and others. These ratios are known to vary throughout the solar system, but their close similarity between Earth and Moon conflicted with theoretical models of the collision that indicated that the Moon would form mostly from Theia, and thus would be expected to be compositionally different from Earth.

Now a group of German researchers, led by Dr. Daniel Herwartz, have used more refined techniques to compare the ratios of 17O/16O in lunar samples, with those from Earth. The team initially used lunar samples which had arrived on Earth via meteorites, but as these samples had exchanged their isotopes with water from Earth, fresher samples were sought. These were provided by NASA from the Apollo 11, 12 and 16 missions; they were found to contain significantly higher levels of 17O/16O than their Earthly counterparts.

Dr Herwartz said “The differences are small and difficult to detect, but they are there. This means two things; firstly we can now be reasonably sure that the Giant collision took place. Secondly, it gives us an idea of the geochemistry of Theia. Theia seems to have been similar to what we call E-type chondrites.If this is true, we can now predict the geochemical and isotopic composition of the Moon, because the present Moon is a mixture of Theia and the early Earth. The next goal is to find out how much material of Theia is in the Moon.”

Most models estimate that the Moon it is composed of around 70% to 90% material from Theia, with the remaining 10% to 30% coming from the early Earth. However, some models argue for as little as 8% Theia in the Moon. Dr Herwartz said that the new data indicate that a 50:50 mixture seems possible, but this needs to be confirmed.

The team used an advanced sample preparation technique before measuring the samples via stable isotope ratio mass spectrometry, which showed a 12 parts per million (± 3 ppm) difference in 17O/16O ratio between Earth and Moon.

Note : The above story is based on materials provided by European Association of Geochemistry.

Asymmetric continental margins and the slow birth of an ocean

June 7, 2014

A newborn ocean. Only few tenths of kilometres separate the massive rift shoulders of the Sinai-Peninsula from the African continent on the far side of the Gulf of Suez. 130 Million years ago, the young South Atlantic ocean has likely looked similar. Credit: Christian Heine, University of Sydney, under Creative Commons

When South America split from Africa 150 to 120 million years ago, the South Atlantic formed and separated Brazil from Angola. The continental margins formed through this separation are surprisingly different. Along offshore Angola 200 km wide, very thin slivers of continental crust have been detected, whereas the Brazilian counterpart margin features an abrupt transition between continental and oceanic crust.
For decades, geoscientists have struggled to explain not only why the amount of thinning and the geometries of opposite rifted continental margin are not symmetric, but also why wide margins are often underlain by highly thinned continental crust. Now geoscientists from the German Research Centre for Geosciences (GFZ), the University of Sydney and the University of London have found an explanation, published in the current issue of Nature Communications. Using high-resolution computer models and geological data from the South Atlantic margins, they discovered that the centre of the rift, where the continental crust gets actively thinned through faulting, does not stay fixed during continental break-up, but migrates laterally.

“We could show that rifts are capable of moving sideways over hundreds of kilometres”, says Dr Sascha Brune of the GFZ. “During rift migration, the crust on one side of the rift is weakened by hot upwelling material in Earth’s mantle, whereas the other side is slightly stronger as the crust there is colder. New faults form only on the warm, weak rift side, while those of the strong side become inactive.” This leads to a sideways motion of the rift system, which is equivalent with conveying crustal material from the South American plate to the African plate. These transferred crustal blocks are strongly extended by the rift and finally constitute the enigmatic thin crustal slivers of the African margin.

Asymmetry of the South Atlantic continental margins. Shown is a model cross section for the South Atlantic, shortly after the separation of Africa and South America 120 million years ago. Credit: Sascha Brune, German Research Centre for Geosciences GFZ

Such a relocation of a rift takes its time: during the formation of the present-day Angolan and Brazilian margins, the rift centre migrated more than 200 km westward. This delayed continental break-up and the generation of oceanic crust by up to 20 million years. The new models reveal that extension velocity plays a crucial role in understanding the widths of South Atlantic margins: faster crustal extension leads to longer rift migration and hence to more pronounced asymmetry of the generated continental margins.

Rifts constitute an important tectonic element of our planet. They are responsible for the shape of today’s continents, and their activity still continues at present.

Illustrating a new aspect of plate tectonic theory, this study shows that during continental break-up, large amounts of material can be conveyed from one side of the plate boundary to the other, a process that has not been yet accounted for. The new models and analyses provide an important stepping-stone toward a comprehensive understanding of rift processes and continental margin formation.

More information:
Brune, S./Heine, C./Marta Pérez-Gussinyé, M./Sobolev, S.: “Rift migration explains continental margin asymmetry and crustal hyper-extension”, Nature Communications. 5:4014 DOI: 10.1038/ncomms5014 (2014)

Note : The above story is based on materials provided by Helmholtz Association of German Research Centres

Microcline

June 7, 2014

Chemical Formula: KAlSi₃O₈
Locality: Common world wide occurrences.
Name Origin: From the Greek mikron – “little” and klinein – “to stoop.”

Microcline (KAlSi₃O₈) is an important igneous rock-forming tectosilicate mineral. It is a potassium-rich alkali feldspar. Microcline typically contains minor amounts of sodium. It is common in granite and pegmatites. Microcline forms during slow cooling of orthoclase; it is more stable at lower temperatures than orthoclase. Sanidine is a polymorph of alkali feldspar stable at yet higher temperature. Microcline may be clear, white, pale-yellow, brick-red, or green; it is generally characterized by cross-hatch twinning that forms as a result of the transformation of monoclinic orthoclase into triclinic microcline.

Microcline may be chemically the same as monoclinic orthoclase, but because it belongs to the triclinic crystal system, the prism angle is slightly less than right angles; hence the name “microcline” from the Greek “small slope.” It is a fully ordered triclinic modification of potassium feldspar and is dimorphous with orthoclase. Microcline is identical to orthoclase in many physical properties; it can be distinguished by x-ray or optical examination; viewed under a polarizing microscope, microcline exhibits a minute multiple twinning which forms a grating-like structure that is unmistakable.

Table of Contents

History

Discovery date : 1830
Town of Origin : FREDRIKSVARN
Country of Origin : NORVEGE

Optical properties

Optical and misc. Properties : Translucent to transparent
Refractive Index : from 1,51 to 1,53
Axial angle 2V : 66-103°

Physical Properties

Cleavage: {001} Perfect, {010} Good
Color: Bluish green, Green, Gray, Grayish yellow, Yellowish.
Density: 2.56
Diaphaneity: Translucent to transparent
Fracture: Uneven – Flat surfaces (not cleavage) fractured in an uneven pattern.
Hardness: 6 – Orthoclase
Luminescence: Fluorescent, Short UV=cherry red.
Luster: Vitreous (Glassy)
Streak: white

Photos :

Microcline (amazonite) “Whitecap” Pikes Peak, El Paso County, Colorado USA (±1964) Specimen size: 8.1 × 5.9 × 3.3 cm = 3.2” × 2.3” × 1.3” © Fabre Minerals

Microcline set ex. Art Montgomery Pikes Peak Area, Colorado, USA Miniature, 4.5 x 3.8 x 2.3 cm © irocks

Microcline (amazonite) Park County Claims, Tarryall, Park County, Colorado USA (±1990) Specimen size: 9 × 7 × 4.5 cm = 3.5” × 2.8” × 1.8” Main crystal size: 7 × 2.5 cm = 2.8” × 1.0” © Fabre Minerals

Scientists solve mystery of ancient American lakes

June 7, 2014

During the Last Glacial Maximum, large lakes (light blue) covered many of the now dry desert basins of Nevada, Oregon and California. Credit: Daniel Ibarra

A new study by Stanford scientists solves a longstanding mystery of how ancient lakes in the western United States grew to such colossal sizes.

The research, published in the journal Geological Society of America Bulletin, found that the lakes were able to grow large – rivaling the Great Lakes – during the peak of the last Ice Age 21,000 years ago, a period known as the “Last Glacial Maximum,” because evaporation rates were significantly lower than today.

“It was previously thought that the lakes grew because there was more rain and snowfall during this period of the Earth’s history,” said Daniel Ibarra, a graduate student in Stanford’s Department of Environmental Earth System Science and the first author of the study.

More quantitative studies of past climate could help refine the computer models used by the Intergovernmental Panel on Climate Change (IPCC) to simulate Earth’s atmospheric conditions under changing atmospheric conditions, said Kate Maher, assistant professor of geological and environmental sciences, who headed the project.

“The IPCC uses climate models to simulate past and future climate, so knowing that some of the models do a better job of simulating past changes gives us more confidence that we understand the physics involved,” Maher said. “That can give us more confidence in the models we use to simulate future climate change.”

During the Last Glacial Maximum (LGM), giant lakes covered large sections of California, Nevada, Oregon and Utah, including where Salt Lake City is today. Earth scientists have long been puzzled by how these ancient lakes, now completely dry, grew so large. The prevailing theory was there was more rain and snowfall during this time period. But recent evidence from paleoecology and climate model simulations indicates that precipitation rates were actually relatively low compared to later periods.

To resolve the discrepancy between computer models and the interpretation of geologic evidence, Ibarra collected more than 80 samples of tufa – a limestone created by the evaporation of mineralized water – from different locations around the edges of Lake Surprise, a moderate-sized fossil lake in Surprise Valley, California.

“The smaller lakes can tell you about the regional climate and can serve as a water gauge for the bigger lakes,” Maher said.

By measuring the decay of radioactive carbon-14 and uranium in tufa samples, the team reconstructed the ancient shorelines of Lake Surprise at different times in the past. Their findings showed that at the height of the LGM, Lake Surprise had a surface area of about 390 square miles, roughly the size of San Francisco Bay.

With support from other laboratories at Stanford, Ibarra also used a mass spectrometer to precisely measure the amounts of two slightly different forms of oxygen in the tufa samples: oxygen-16 and the slightly heavier oxygen-18. Both isotopes of oxygen are present in water, but oxygen-18 water evaporates at a slower rate than oxygen-16 water. By knowing the ratio of oxygen-16 to oxygen-18 in the tufa samples, the scientists were able to calculate Lake Surprise’s water balance through time.

Cooler temperatures

Their analyses revealed that 21,000 years ago, the evaporation rate at Lake Surprise was nearly 40 percent lower than today, with precipitation rates similar to the modern era. These results are consistent with previously run climate simulations that show Earth’s climate was cooler during the LGM.

The cooler global temperatures would have reduced evaporation rates, allowing the lakes to gradually grow over time through inflows from streams and rivers.

“Lake Surprise is located in a closed basin. All streams flow into the lake, but there is no outflow. The only way for water to escape is through evaporation,” Ibarra said.

The team’s dating and isotope measurements also show that precipitation rates in the region increased for a brief period after the LGM. The tufa measurements indicated that Lake Surprise reached its largest size – around 530 square miles – 15,000 years ago.

Thus, the enormous lakes that once dotted the western United States initially grew large during the peak of the LGM due to reduced evaporation, but didn’t reach their maximum sizes until several thousand years later, when rain and snowfall increased.

Knowledge about the past precipitation patterns of the region could be used to test the accuracy of the differing climate models scientists currently use to simulate global climate conditions.

“We can actually rank the models now,” Ibarra said. “Our findings have implications for evaluating the models, and deciding which models successfully reproduced the past precipitation patterns we observe.”

More information:
“Rise and fall of late Pleistocene pluvial lakes in response to reduced evaporation and precipitation: Evidence from Lake Surprise, California,” Geological Society of America Bulletin, B31014.1, first published on June 2, 2014, DOI: 10.1130/B31014.1

Note : The above story is based on materials provided by Stanford University

New species of ancient chirping giant pill-millipedes from Madagascar already threatened

June 7, 2014

Upper left to Lower right: This image shows different color morphs, genetically found to be identical, of the chirping giant pill-millipede (Sphaeromimus musicus), and a similar-looking species (lower left) of a different genus (Zoosphaerium blandum). Credit: Wesener 2007

An international team of researchers comprised of Thomas Wesener, Museum Koenig, Bonn, Daniel Le, Field Museum, Chicago and Stephanie Loria, American Museum of Natural History, New York, discovered seven new species of chirping giant pill-millipedes on Madagascar. The study was published in the open access journal ZooKeys.
The species discovered all belong to the genus Sphaeromimus, which is Latin for ‘small ball animal’. However, the designation ‘small’ is not always true for the members of the genus as one of the newly discovered species surprises with a size larger than a ping-pong ball. Another special characteristic of the genus is that its species have the largest chirping organs of any millipede, which are most probably used during mating.

Despite sometimes sharing a habitat with Madagascar’s ‘large’ pill-millipedes, which can reach the size of a baseball, the new species are more closely related to millipedes found in India than their Malagasy neighbours. This relationship dates back more than 80 million years to at least as early as the Cretaceous period, when dinosaurs walked the Earth and India and Madagascar were connected.

One of the new species Sphaeromimus andrahomana offers clues to Madagascar’s ecosystems thousands of years ago. Although the species was found in a cave in Madagascar’s southern dry spiny forest region, genetically, it is a rainforest taxon. The lemur skeletons found inside the same cave are also evidence that a rainforest existed in the now desert-like area until 3000-5000 years ago. The species, sheltered by the humid cave, is probably a living witness to this ancient rainforest.

The discovery is particularly exciting as some of species are microendemics, meaning they are only found in one tiny forest fragment, a few hundred meters long and wide.

S. lavasoa, for example, is restricted to the Lavasoa Mountain, which is covered by an isolated, slightly larger than 100 hectare, rainforest remnant, which is famous for the recent discovery of a large scorpion as well as a dwarf lemur species. This discovery further highlights the importance of the area as a Center of Endemism.

Another new species (S. saintelucei) is probably the most endangered millipede on Madagascar. It was found in a fragment of the Sainte Luce littoral rainforest characterized by its laterite soil that is now so small that no lemur or other large vertebrate species can survive in it.

The nearby Sainte Luce forest fragment with sandy ground harbours a different species (S. splendidus) also believed to be a microendemic. “Despite their close proximity, both species are not even closely related. Both the fragments where they were found are currently threatened by a huge, billion-dollar titanium ore strip mining project. Although there are intentions to designate and manage conservation zones, the plan is to protect only one large fragment may result in the extinction of some of the species if additional conservation measures aren’t undertaken.” explains the lead author Dr. Thomas Wesener from the Research Museum Alexander Koenig in Bonn, Germany.

Original source:

Wesener T, Le DM-T, Loria SF (2014) Integrative revision of the giant pill-millipede genus Sphaeromimus from Madagascar, with the description of seven new species (Diplopoda, Sphaerotheriida, Arthrosphaeridae). ZooKeys 414: 67. doi: 10.3897/zookeys.414.7730

Note : The above story is based on materials provided by Pensoft Publishers

Miargyrite

June 6, 2014

Chemical Formula: AgSbS₂
Locality: Braunsdorf, Freiberg, Sachsen (Saxony), Germany.
Name Origin: From the Greek, meyon, “smaller” and argyros, “silver.” in allusion to the lessor silver content of the mineral.

Miargyrite is a mineral, a sulfide of silver and antimony with the formula AgSbS₂. It is a dimorph of cuboargyrite. Originally discovered in the Freiberg district of Germany in 1824, it has subsequently been found in many places where silver is mined. It usually occurs in low temperature hydrothermal deposits. and forms black metallic crystals which may show a dark red internal reflection. The streak is also red.

Miargyrite is named from the Greek meyon, “smaller” and argyros, “silver,” as its silver content is lower than most silver sulfides.

Table of Contents

History

Discovery date : 1829
Town of Origin : BRAUNSDORF, FREIBERG, SAXE
Country of Origin : ALLEMAGNE

Optical properties

Optical and misc. Properties : Translucent to Subopaque
Reflective Power: 26,3-38,7% (580)
Refractive Index : from 2,72 to 2,73

Physical Properties

Cleavage: {010} Imperfect
Color: Steel gray, Lead gray, Blackish red, Reddish gray.
Density: 5.1 – 5.3, Average = 5.19
Diaphaneity: Translucent to Subopaque
Fracture: Brittle – Generally displayed by glasses and most non-metallic minerals.
Hardness: 2-2.5 – Gypsum-Finger Nail
Luminescence: Non-fluorescent.
Luster: Sub Metallic
Streak: cherry red

Photos :

Miargyrite, Pyrargyrite 5.7×4.8×5.2 cm San Genaro Mine Castrovirreyna, Huancavelica Peru Copyright © David K. Joyce Minerals

Miargyrite micro cm Van Silver Mine nr. Whistler British Columbia, Canada Copyright © David K. Joyce Minerals

Neue Hoffnung Gottes Mine, Bräunsdorf, Freiberg District, Erzgebirge, Saxony, Germany © Stephan Wolfsried

Thermal monitoring of volcanic activity from space

June 6, 2014

The Nyiragongo lava lake at night. Credit: INVOLCAN

Data from the Meteosat satellite 36,000 km from Earth, has been used to measure the temperature of lava at the Nyiragongo lava lake in the Democratic Republic of Congo. An international team compared data from the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) on board Meteosat with data collected at the lava lake with thermal cameras. Researchers say the technique could be used to help monitor volcanoes in remote places all over the world, and may help with the difficult task of anticipating eruptions.
Data from the Meteosat satellite has been used to measure the temperature of lava at a remote volcano in Africa.

The scientists compared data from the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) on board Meteosat with ground data from a thermal camera, to show the temperature of the lava lake at Nyiragongo, in the Democratic Republic of Congo.

The technique was pioneered in Europe, and the researchers say it could be used to help monitor volcanoes in remote places all over the world.

“I first used the technique during a lava fountain at Mt Etna in August 2011,” says Dr. Gaetana Ganci, who worked on the study with colleagues Letizia Spampinato, Sonia Calvari and Ciro Del Negro from the Istituto Nazionale di Geofisica e Vulcanologia (INGV) in Italy.

“The first time I saw both signals I was really surprised. We found a very similar radiant heat flux curve — that’s the measurement of heat energy being given out — from the ground-based thermal camera placed a few kilometres from Etna and from SEVIRI at 36,000km above the Earth.”

Transferring the technique to Nyiragongo was important — partly because the exposed lava lake can yield data important for modelling shallow volcanic systems in general, but more importantly because advance warning of eruptions is necessary for the rapidly expanding city of Goma nearby.

The research, published in the Journal of Geophysical Research: Solid Earth is the first time in which Nyiragongo’s lake has been studied using ground-based thermal images in addition to satellite data to monitor the volcano’s radiative power record.

Dr. Ganci and her colleagues developed an algorithm they call HOTSAT to detect thermal anomalies in the Earth’s surface temperature linked to volcanoes. They calculate the amount of heat energy being given out in a target area based on analysis of SEVIRI images.

Combining the frequent SEVIRI images with the more detailed but less frequent images from NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS), they showed that temperature anomalies could be observed from space before an eruption is underway. They believe that space-based observations can be a significant help in the difficult task of predicting volcanic eruptions, but that providing advance warning will never be easy.

“Satellite data are a precious means to improve the understanding of volcanic processes. There are cases of thermal anomalies being observed in volcanic areas just before an eruption,” says Ganci. “Combining different kinds of data from the ground and from space would be the optimal condition — including infra-red, radar interferometry, seismic measurements etc. But even in well-monitored volcanoes like Mt. Etna, predicting eruptions is not a trivial thing.”

The team developed HOTSAT with a view to making an automatic system for monitoring volcanic activity. They are now developing a new version of HOTSAT. This should allow the processing of all the volcanic areas that can be monitored by SEVIRI in near-real time.Continuing ground-based observations will be needed for validation.

“For remote volcanoes, such as Nyiragongo, providing reliability to satellite data analysis is even more important than in Europe. Thanks to ground-based measurements made by Pedro Hernández, David Calvo, Nemesio Pérez (ITER, INVOLCAN Spain), Dario Tedesco (University of Naples, Italy) and Mathieu Yalire (Goma Volcanological Observatory), we could make a step in this direction,” says Ganci.

“This study shows the range of science that can be done with Meteosat,” says Dr. Marianne Koenig, EUMETSAT’s atmospheric and imagery applications manager for the Meteosat Second Generation satellites, “And opens up the possibility of monitoring isolated volcanoes.”

Note : The above story is based on materials provided by European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT).

First 3-D pterosaur eggs found with their parents

June 6, 2014

This image depicts ecological reconstructions of Hamipterus. Credit: Chuang Zhao

Researchers have discovered the first three-dimensionally preserved pterosaur eggs in China. The eggs were found among dozens, if not hundreds, of pterosaur fossils, representing a new genus and species (Hamipterus tianshanensis). The discovery, described in the Cell Press journal Current Biology on June 5, reveals that the pterosaurs — flying reptiles with wingspans ranging from 25 cm to 12 m — lived together in gregarious colonies.
Xiaolin Wang of the Chinese Academy of Sciences’ Institute of Vertebrate Paleontology and Paleoanthropology says it was most exciting to find many male and female pterosaurs and their eggs preserved together. “Five eggs are three-dimensionally preserved, and some are really complete,” he says.

The fossil record of the pterosaurs has generally been poor, with little information about their populations, the researchers say. Prior to this latest find, only four isolated and flattened pterosaur eggs were known to science.

The resting place of the pterosaurs now described was first uncovered in 2005 in the Turpan-Hami Basin, south of the Tian Shan Mountains in Xinjiang, northwestern China. The fossil-rich area may harbor thousands of bones, including three-dimensional male and female skulls and the first three-dimensional eggs. Wang says that sediments in the area suggest that the pterosaurs died in a large storm about 120 million years ago in the Early Cretaceous period.

The researchers examined the largely intact pterosaur egg specimens to find that they were pliable, with a thin, calcareous eggshell outside and a soft, thick membrane inside, similar to the eggs of some modern-day snakes. The researchers’ observations of 40 male and female individuals suggest differences between the sexes in the size, shape, and robustness of their head crests.

The combination of many pterosaurs and eggs strongly indicates the presence of a nesting site nearby and indicates that this species developed gregarious behavior, the researchers say. Hamipterus most likely buried their eggs in sand along the shore of an ancient lake to prevent them from drying out. While the new fossils shed light on the reproductive strategy, development, and behavior of pterosaurs, there is still plenty left to learn about them.

“Sites like the one reported here provide further evidence regarding the behavior and biology of this amazing group of flying reptiles that has no parallel in modern time,” the researchers write.

Note : The above story is based on materials provided by Cell Press.

Metatorbernite

June 6, 2014

Chemical Formula: Cu(UO₂)₂(PO₄)₂·8H₂O
Locality: Schneeberg, Sachsen (Saxony), Germany
Name Origin: Named as the lower hydrate of tobernite.

Metatorbernite (or meta-torbernite) is a radioactive phosphate mineral, and is a dehydration pseudomorph of torbernite. Chemically, it is a copper uranyl phosphate and usually occurs in the form of green platy deposits. It can form by direct deposition from a supersaturated solution, which produces true crystalline metatorbernite, with a dark green colour, translucent diaphaneity, and vitreous lustre. However, more commonly, it is formed by the dehydration of torbernite, which causes internal stress and breakage within the crystal lattice, resulting in crystals composed of microscopic powder held together using electrostatic force, and having a lighter green colour, opaque diaphaneity, and a relatively dull lustre. As with torbernite, it is named after the Swedish chemist Tornbern Bergmann. It is especially closely associated with torbernite, but is also found amongside autunite, meta-autunite and uraninite.

Table of Contents

History

Discovery date : 1786
Town of Origin: SCHNEEBERG, SAXE
Country of Origin : ALLEMAGNE

Optical properties

Optical and misc. Properties : Transparent to Translucent
Refractive Index: 1,62

Physical Properties

Cleavage: {001} Perfect
Color: Light green, Dark green.
Density: 3.7 – 3.8, Average = 3.75
Diaphaneity: Transparent to Translucent
Fracture: Brittle – Generally displayed by glasses and most non-metallic minerals.
Hardness: 2.5 – Finger Nail
Luster: Vitreous – Adamantine
Streak: light green

Photos :

Metatorbernite from the National Mineral Collection Photo by Chip Clark

Metatorbernite Locality: Les Montmins Mine (Ste Barbe vein), Échassières, Ébreuil, Allier, Auvergne, France Field of view 1m X 1mm Michel poullaouec

La Commanderie mine, Le Temple, Deux-Sèvres, Poitou-Charentes, France © JM. Johannet

What a 66-million-year old forest fire reveals about the last days of the dinosaurs

June 6, 2014

McGill field crew collecting fossils as part of a field course in Grasslands National. Credit: Larsson/Bamforth

As far back as the time of the dinosaurs, 66 million years ago, forests recovered from fires in the same manner they do today, according to a team of researchers from McGill University and the Royal Saskatchewan Museum.

During an expedition in southern Saskatchewan, Canada, the team discovered the first fossil-record evidence of forest fire ecology — the regrowth of plants after a fire — revealing a snapshot of the ecology on earth just before the mass extinction of the dinosaurs. The researchers also found evidence that the region’s climate was much warmer and wetter than it is today.

“Excavating plant fossils preserved in rocks deposited during the last days of the dinosaurs, we found some preserved with abundant fossilized charcoal and others without it. From this, we were able to reconstruct what the Cretaceous forests looked like with and without fire disturbance,” says Hans Larsson, Canada Research Chair in Macroevolution at McGill University.

The researchers’ discovery revealed that at the forest fire site, the plants are dominated by flora quite similar to the kind that begin forest recovery after a fire today. Ancient forests recovered much like current ones, with plants like alder, birch, and sassafras present in early stages, and sequoia and ginkgo present in mature forests.

“We were looking at the direct result of a 66-million-year old forest fire, preserved in stone,” says Emily Bamforth, of the Royal Saskatchewan Museum and the study’s first author. “Moreover, we now have evidence that the mean annual temperature in southern Saskatchewan was 10-12 degrees Celsius warmer than today, with almost six times as much precipitation.”

“The abundant plant fossils also allowed us for the first time to estimate climate conditions for the closing period of the dinosaurs in southwestern Canada, and provides one more clue to reveal what the ecology was like just before they went extinct,” says Larsson, who is also an Associate Professor at the Redpath Museum.

Forest fires can affect both plant and animal biodiversity. The team’s finding of ancient ecological recovery from a forest fire will help broaden scientists’ understanding of biodiversity immediately before the mass extinction of dinosaurs. “We won’t be able to fully understand the extinction dynamics until we understand what normal ecological processes were going on in the background.” says Larsson.

Note : The above story is based on materials provided by McGill University.

Cave temperature study could improve climate change predictions

June 6, 2014

Dr Mark Cuthbert inspects a speleothem in Wellington Caves. Credit: Martin S. Andersen

Researchers studying the hydrology of Wellington Caves in central NSW have made a discovery that challenges a key assumption used to reconstruct past climates from cave deposits.

Published in Nature’s open access journal Scientific Reports, the research found that there can be a 1.5 degree Celsius difference between the temperature of the air in the cave and the drip water that forms the stalactite.

Stalactites and other cave formations – collectively known as speleothems – form when rainwater drips from the surface into the cave system, picking up minerals along the way that solidify once exposed to the cave air.

Scientists had previously assumed that speleothems formed at a temperature equal to the average temperature outside the cave and used this assumption to construct records of past climate variations, says lead author Dr Mark Cuthbert, holder of a European Community-funded Marie Curie Research Fellowship at UNSW’s Connected Waters Initiative.

“However that assumption had never been tested,” he says. “The 1.5 degree difference is very significant if you’re looking at past climate change. It is similar to the kind of change in temperature that we’ve had in the last 12,000 years naturally during the Holocene.”

The difference in temperature is attributed to evaporative cooling, which occurs as the water moves along the cave wall before reaching the point at which it drips and forms the speleothem.

“If you were looking at a speleothem formed in that environment and didn’t know this process of evaporative cooling was happening, you might jump to the wrong conclusions, in either direction, about what the climate outside the cave was like at the time the speleothem formed,” says co-author Monika Markowska, a Research Scientist at the Institute for Environmental Research at the Australian Nuclear Science and Technology Organisation (ANSTO).

ANSTO researchers have developed expertise in modelling climate change using nuclear techniques such as neutron activation soil analysis and carbon 14 dating.

The research team also includes Professor Andy Baker, Director of the Connected Waters Initiative (CWI) and other CWI researchers.

The same researchers recently found that other important evaporative effects occur between the soil and the cave that also need to be taken into account when interpreting speleothems as records of climate change.

“Further experimental work is underway to investigate the influence of the geometry, orientation, the thermal properties of a particular formation, and the water film thicknesses, on the relative cooling rate,” the researchers say in their paper.

Dr Cuthbert hopes that ongoing research will lead to numerical models that take into account all the different variables in a cave system that might influence climate change calculations.

Speleothem chemistry is one of several methods used to reconstruct past climates alongside other techniques including sediments, ice cores, trees and corals. Caves can yield particularly high-resolution records going back several hundred thousand years.

More information: “Evaporative cooling of speleothem drip water.” M. O. Cuthbert et al. Scientific Reports 4, Article number: 5162. DOI: 10.1038/srep05162. Received 28 March 2014 Accepted 07 May 2014 Published 04 June 2014

Note : The above story is based on materials provided by University of New South Wales

Meta-autunite

June 5, 2014

Chemical Formula: Ca(UO₂)₂(PO₄)₂· 6-8H₂O
Locality: Daybreak mine, Mt Spokane, Washington, USA
Name Origin: Named as the lower hydrate of autunite.

Meta-autunite is a dehydration product of its close cousin, autunite, hence the name. When the mineral autunite loses water and converts to meta-autunite, it becomes what is known as a pseudomorph. A pseudomorph is generally an atom by atom replacement of one mineral’s chemistry in place of another mineral’s chemistry, while the original crystal’s outward shape remains largely unchanged. The process leaves the crystal shape of the original mineral intact, but the original mineral is no longer there. Pseudomorph translated from latin means false shape (pseudo=false; morph=shape).

The structure of meta-autunite is composed of phosphate tetrahedrons linked to uranium-oxygen groups that form distorted octahedrons. The phosphate and uranium groups form sheets that are weakly held together by water molecules. This structure produces the tabular habit, the one perfect direction of cleavage, and the relative softness. It is an analogous structure to that of the phyllosilicates.

Meta-autunite is a highly fluorescent mineral. It is said to fluoresce with a brightness comparable to some of the brightest fluorescing minerals in the world. The bright green fluorescence of meta-autunite is similar to other green fluorescing minerals such as autunite, adamite, green fluorescing opal and of course the spectacular willemites from Franklin, New Jersey, USA. The uranium is the fluorescent activator in meta-autunite and autunite. Trace amounts of uranium are responsible for the green fluorescence in opal and adamite as well. Remember because of the uranium, meta-autunite is a radioactive mineral and should be stored away from other minerals that are affected by radioactivity and human exposure should always be limited.

Table of Contents

History

Discovery date : 1904

Optical properties

Optical and misc. Properties : Translucent to Opaque
Refractive Index: from 1,58 to 1,60
Axial angle 2V : 0-20°

Physical Properties

Color: Yellow, Greenish yellow, Yellowish green.
Density: 3.45 – 3.55, Average = 3.5
Diaphaneity: Translucent to Opaque
Hardness: 1 – Talc
Luminescence: Fluorescent, Short UV=pale yellow green, Long UV=pale yellow green.
Luster: Pearly

Photos:

Meta-autunite Location: Carretona, Spain. Copyright: © Lou Perloff / Photo Atlas of Minerals

Meta-autunite Locality: Daybreak Mine, near Mount Spokane, Spokane County, Washington Overall Size: 35x20x8 mm Crystals: 3-8 mm © JohnBetts-FineMinerals

Climate not to blame for the disappearance of large mammals

June 5, 2014

Skeleton of a giant ground sloth at the Los Angeles County Museum of Natural History, circa 1920. Wikimedia

Was it humankind or climate change that caused the extinction of a considerable number of large mammals about the time of the last Ice Age? Researchers at Aarhus University have carried out the first global analysis of the extinction of the large animals, and the conclusion is clear — humans are to blame. A new study unequivocally points to humans as the cause of the mass extinction of large animals all over the world during the course of the last 100,000 years.
“Our results strongly underline the fact that human expansion throughout the world has meant an enormous loss of large animals,” says Postdoctoral Fellow Søren Faurby, Aarhus University.

Table of Contents

Was it due to climate change?

For almost 50 years, scientists have been discussing what led to the mass extinction of large animals (also known as megafauna) during and immediately after the last Ice Age.

One of two leading theories states that the large animals became extinct as a result of climate change. There were significant climate changes, especially towards the end of the last Ice Age — just as there had been during previous Ice Ages — and this meant that many species no longer had the potential to find suitable habitats and they died out as a result. However, because the last Ice Age was just one in a long series of Ice Ages, it is puzzling that a corresponding extinction of large animals did not take place during the earlier ones.

Theory of overkill

The other theory concerning the extinction of the animals is ‘overkill’. Modern man spread from Africa to all parts of the world during the course of a little more than the last 100,000 years. In simple terms, the overkill hypothesis states that modern man exterminated many of the large animal species on arrival in the new continents. This was either because their populations could not withstand human hunting, or for indirect reasons such as the loss of their prey, which were also hunted by humans.

First global mapping

In their study, the researchers produced the first global analysis and relatively fine-grained mapping of all the large mammals (with a body weight of at least 10 kg) that existed during the period 132,000-1,000 years ago — the period during which the extinction in question took place. They were thus able to study the geographical variation in the percentage of large species that became extinct on a much finer scale than previously achieved.

The researchers found that a total of 177 species of large mammals disappeared during this period — a massive loss. Africa ‘only’ lost 18 species and Europe 19, while Asia lost 38 species, Australia and the surrounding area 26, North America 43 and South America a total of 62 species of large mammals.

The extinction of the large animals took place in virtually all climate zones and affected cold-adapted species such as woolly mammoths, temperate species such as forest elephants and giant deer, and tropical species such as giant cape buffalo and some giant sloths. It was observed on virtually every continent, although a particularly large number of animals became extinct in North and South America, where species including sabre-toothed cats, mastodons, giant sloths and giant armadillos disappeared, and in Australia, which lost animals such as giant kangaroos, giant wombats and marsupial lions. There were also fairly large losses in Europe and Asia, including a number of elephants, rhinoceroses and giant deer.

Weak climate effect

The results show that the correlation between climate change — i.e. the variation in temperature and precipitation between glacials and interglacials — and the loss of megafauna is weak, and can only be seen in one sub-region, namely Eurasia (Europe and Asia). “The significant loss of megafauna all over the world can therefore not be explained by climate change, even though it has definitely played a role as a driving force in changing the distribution of some species of animals. Reindeer and polar foxes were found in Central Europe during the Ice Age, for example, but they withdrew northwards as the climate became warmer,” says Postdoctoral Fellow Christopher Sandom, Aarhus University.

Extinction linked to humans

On the other hand, the results show a very strong correlation between the extinction and the history of human expansion. “We consistently find very large rates of extinction in areas where there had been no contact between wildlife and primitive human races, and which were suddenly confronted by fully developed modern humans (Homo sapiens). In general, at least 30% of the large species of animals disappeared from all such areas,” says Professor Jens-Christian Svenning, Aarhus University.

The researchers’ geographical analysis thereby points very strongly at humans as the cause of the loss of most of the large animals.

The results also draw a straight line from the prehistoric extinction of large animals via the historical regional or global extermination due to hunting (American bison, European bison, quagga, Eurasian wild horse or tarpan, and many others) to the current critical situation for a considerable number of large animals as a result of poaching and hunting (e.g. the rhino poaching epidemic).

Note : The above story is based on materials provided by Aarhus University.

Scientist uses fossils to prove historic Ohio millstones have French origins

June 5, 2014

Millstone made of French buhr at the site of Clover Hill Mill, Trumbull County, Ohio. Credit: © SEPM

A geologist studied fossils to confirm that stones used in 19th century Ohio grain mills originated from France. Fossils embedded in these millstones were analyzed to determine that stones known as French buhr were imported from regions near Paris, France, to Ohio in the United States. Dr. Joseph Hannibal, curator of invertebrate paleontology at The Cleveland Museum of Natural History, was lead author on research published in the Society for Sedimentary Geology journal PALAIOS.
The study documents a technique that uses fossils to definitively distinguish French buhr from similar-looking Ohio chert (also known as flint). The most revealing fossil is a one-millimeter wide reproductive structure of a charophyte (a type of algae also known as a stonewort) that occurs in the rocks of the Paris Basin, a geological province centered around Paris, France.

Millstones made of Ohio chert were found to contain typical saltwater marine fossils that are much older than the fossils found in French buhr. These include brachiopods and small oval fossils called fusulinids and brachiopods. These Ohio rocks date from the latter part of the Paleozoic era (about 300 million years ago). Alternatively, the French stone is made from rock derived from freshwater deposits. The fossils found in this stone include freshwater snails and algae. The French stone dates from the Tertiary Period (from 65 to 2.6 million years ago), which is geologically younger than the Ohio stone.

“The story of the importation of this stone from France is not widely known,” said Dr. Joseph Hannibal, curator of invertebrate paleontology at The Cleveland Museum of Natural History. “They are not always correctly identified as being from France. Based on the stones we have examined, it is clear that the French stone was more popular. Examples of millstones made of this stone are widespread in North America and throughout the world. So the use of fossils for their identification is a broadly applicable concept.”

During the late 18th and 19th century, large amounts of stone known as French buhr were imported from France to Ohio and other states in North America for the manufacture of millstones. The French stone was preferred by grain millers over locally found stone because it was considered superior in cutting grain that sifted more easily to produce white flour. The Ohio cities of Cleveland and Cincinnati were major centers for manufacture of millstones made of this French stone. However, local Ohio stone, some of it similar in color and texture to the French stone, was quarried in eastern and southeastern Ohio at localities including the famous locality of Flint Ridge.

“Many millstones have been identified as being made of French stone or Ohio stone,” said Hannibal. “But since the stones used are generally similar in color and other properties, I questioned how these stones had been identified as originating from France or Ohio. When visiting the remains of an old mill in Trumbull County, Ohio, we first noticed that there were charophytes in some millstones. Our study progressed from there.”

The study was done over a period of five years. The research team searched 60 millstone sites, looking at several hundred millstones. A total of 16 millstones containing fossils were included in the study. The research team, which included college students and high school students, analyzed wafer thin samples of rock under microscopes. The team also applied liquid rubber latex to stone surfaces to obtain impressions of fossils such as snails for investigation. Four college students, two from Kent State University, one from Heidelberg University, and one from Oberlin College, are coauthors of this study.

The study is ongoing and is part of a broader research project on the geology of millstones and the trans-Atlantic stone trade. Millstones in about 30 Ohio counties have been studied to date as part of this larger project.

Note : The above story is based on materials provided by Cleveland Museum of Natural History.

Mesolite

June 5, 2014

Chemical Formula: Na₂Ca₂Si₉Al₆O₃₀·8H₂O
Locality: Cyclopean Islands northeast of Catania, Sicily.
Name Origin: From the Greek mesos – “middle.”
Mesolite is a tectosilicate mineral with formula Na₂Ca₂Si₉Al₆O₃₀·8H₂O. It is a member of the zeolite group and is closely related to natrolite which it also resembles in appearance.

Mesolite crystallizes in the orthorhombic system and typically forms fibrous, acicular prismatic crystals or masses. Radiating sprays of needlelike crystals are not uncommon. It is vitreous in luster and clear to white in color. It has a Mohs hardness of 5 to 5.5 and a low specific gravity of 2.2 to 2.4. The refractive indices are nα=1.505 nβ=1.505 nγ=1.506.

Table of Contents

Occurrence

It was first described in 1816 for an occurrence in the Cyclopean Islands near Catania, Sicily.From the Greek mesos, “middle”, as its composition lies between natrolite and scolecite.Like other zeolites, mesolite occurs as void fillings in amygdaloidal basalt also in andesites and hydrothermal veins.

History

Discovery date: 1816
Town of Origin : LNS
Country of Origin : ISLANDE; ILES FAROE

Optical properties

Optical and misc. Properties: Transparent to translucent
Refractive Index : 1,50
Axial angle 2V : ~80°

Physical Properties

Cleavage: {101} Perfect, {001} Perfect
Color: White, Gray, Pale yellow.
Density: 2.2 – 2.4, Average = 2.29
Diaphaneity: Transparent to translucent
Fracture: Uneven – Flat surfaces (not cleavage) fractured in an uneven pattern.
Hardness: 5 – Apatite
Luminescence: Non-fluorescent.
Luster: Vitreous – Silky
Streak: white

Photos :

Mesolite Ritter Hot Springs, Grant Co., Oregon, USA Size: 5.5 x 4.0 x 3.0 cm (small cabinet) © danweinrich

Mesolite and chabazite Rupe di Aci Castello – Aci Castello – Etna Volcanic Complex – Catania prov. – Sicily – Italy Specimen weight:145 gr. Crystal size:mm. 7 Overall size: 97mm x 45 mm x 37 mm © minservice

Volcanic ash can threaten air traffic

June 5, 2014

Santiaguito volcano, Guatemala. Credit: David Damby

The presence of volcanic ash in the upper atmosphere presents multiple threats to aviation. It not only reduces visibility and abrades the exposed areas of the aircraft, the fine particles can also endanger the operation of aircraft engines. Recent experiments undertaken by volcanologists, led by Professor Donald Dingwell, Director of the Department of Earth and Environmental Science at LMU Munich, have shown that reheated ash becomes molten and begins to flow at temperatures around 1050°C.
The resulting viscous droplets can adhere to surfaces, and could thus damage jet-engine turbines more severely than is generally assumed. The new work is described in two papers that appear in the Journal of Applied Volcanology and Geophysical Research Letters.

The studies were carried out on ash samples obtained from two sources: Eyjafjallajökull volcano, in Iceland, and Santiaguito, in Guatemala. With the aid of a special microscope equipped with a heating stage, the researchers observed the change in morphology of ash pellets when subjected to a stepwise increase in temperature over the range 50 to 1600°C. This range encompasses the prevailing temperatures in the different parts of the turbines used in jet engines.

“At high temperatures, volcanic ash particles behave like sticky droplets of grease, which could potentially coat vital components of the engines,” says Dr. Wenjia Song. This could lead to alterations in the airflow within the turbines and compromise the cooling of the engines.

The ash particles used in the experiments began to soften at around 600 degrees, and fused to form porous agglomerates at 1050°C. “Our studies show that volcanic ash melts and can stick to surfaces at lower temperatures than anticipated. This means that they are potentially more hazardous to air traffic than currently believed,” says Dr. Ulrich Kueppers.

The researchers compared this behavior to that of the quartz sand conventionally used by engine manufacturers to test the durability of turbines. This material turned out to behave differently in the same range of temperature than the ash particles. “Crystalline sand is not an appropriate material with which to simulate the effects of volcanic ash on aircraft engines,” Kueppers concludes. For this reason, the authors of the new studies argue that the threat to jet-engine turbines posed by volcanic ash needs further assessment. “Moreover, such tests should evaluate the effects of varying ash particle concentrations both by weight and by number,” says Kueppers.

More information:
Song, W., K.-U. Hess, D. E. Damby, F. B. Wadsworth, Y. Lavallée, C. Cimarelli, and D. B. Dingwell (2014), Fusion characteristics of volcanic ash relevant to aviation hazards, Geophys. Res. Lett., 41, 2326–2333, DOI: 10.1002/2013GL059182.

Note : The above story is based on materials provided by Ludwig Maximilian University of Munich

Peace River

June 5, 2014

The Peace River is a river in Canada that originates in the Rocky Mountains of northern British Columbia and flows to the northeast through northern Alberta. The Peace River flows into the Slave River, a tributary of the Mackenzie River. The Mackenzie is the 12th longest river in the world, preceded by the Mekong and followed by the Niger River. The Finlay River, the main headwater of the Peace River, is regarded as the ultimate source of the Mackenzie River.

Table of Contents

History

The regions along the river are the traditional home of the Danezaa people, called the Beaver by the Europeans. The fur trader Peter Pond is believed to have visited the river in 1785. In 1788 Charles Boyer of the North West Company established a fur trading post at the river’s junction with the Boyer River.

In 1792 and 1793, the explorer Alexander Mackenzie travelled up the river to the Continental Divide. Mackenzie referred to the river as Unjegah, from a native word meaning “large river”.

The decades of hostilities between the Danezaa and the Cree, (in which the Cree dominated the Danezaa), ended in 1781 when a smallpox epidemic decimated the Cree. The Treaty of the Peace was celebrated by the smoking of a peace pipe. The treaty made the Peace River a border, with the Danezaa to the North and the Cree to the South.

In 1794, a fur trading post was built on the Peace River at Fort St. John; it was the first non-native settlement on the British Columbia mainland.

Post-Settlement

The rich soils of the Peace River valley in Alberta have been producing wheat crops since the late 19th century. The Peace River region is also an important centre of oil and natural gas production. There are also pulp and paper plants along the river in British Columbia.

The Peace River has two navigable sections, separated by the Vermilion Chutes, near Fort Vermilion. The first steam-powered vessel to navigate the Peace River was the Grahame, a Hudson’s Bay Company vessel built at Fort Chipewyan, on Lake Athabasca. Brothers of the Oblate Order of Mary Immaculate, built the St. Charles, to navigate the upper reaches of the River, from Fort Vermilion to Hudson’s Hope. Approximately a dozen vessels were to navigate the river. Most of the early vessels were wood-burning steamships, fueled by wood cut from the river’s shore. The last cargo vessel was the Watson’s Lake, retired in 1952.

Geography

Course

This river is 1,923 km long (from the head of Finlay River to Lake Athabasca). It drains an area of approximately 302,500 km2. At Peace Point, where it drains in the Slave River, it has an annual discharge of 2161 m3/s or 68,200,000 dam3/a.

A large man-made lake, Williston Lake, has been formed on the upper river by the construction of the W. A. C. Bennett Dam for hydroelectric power generation. The river then flows into Dinosaur Lake, which serves as a reservoir for the Peace Canyon Dam. After the dams, the river flows east into Alberta and then continues north and east into the Peace-Athabasca Delta in Wood Buffalo National Park, at the western end of Lake Athabasca. Water from the delta flows into the Slave River east of Peace Point and reaches the Arctic Ocean via the Great Slave Lake and Mackenzie River.

Note : The above story is based on materials provided by Wikipedia

Merwinite

June 3, 2014

Chemical Formula: Ca₃Mg(SiO₄)₂
Locality: Crestmore quarry, 5 miles NW of Riverside, Riverside Co., California.
Name Origin: Herbert Eugene Merwin (1878-1963), American mineralogist and petrologist, Carnegie Institute, Washington, D.C., USA.

Table of Contents

History

Discovery date : 1921
Town of Origin : CARRIERE WET WEATHER, CRESTMORE, RIVERSIDE, CALIFORNIE
Country of Origin : USA

Optical properties

Optical and misc. Properties: Transparent to translucent
Refractive Index: from 1,70 to 1,72
Axial angle 2V : 66-76°

Physical Properties

Cleavage: {010} Perfect
Color: Colorless, Gray, Pale green.
Density: 3.15
Diaphaneity: Transparent to translucent
Fracture: Brittle – Generally displayed by glasses and most non-metallic minerals.
Hardness: 6 – Orthoclase
Luminescence: Non-fluorescent.
Luster: Vitreous (Glassy)
Magnetism: Nonmagnetic
Streak: white

Photos :

Mineral: Merwinite in Monticellite-Spurrite Locality: Crestmore Quarry, Riverside County, California (Type Locality for Merwinite) Overall Size: 6x4x3 cm Crystals: 1-3 mm © JohnBetts-FineMinerals

Mineral: Merwinite and Plombièrite Locality: Crestmore Quarry, Riverside County, California (Type Locality for Merwinite) Overall Size: 9.5×8.5×4 cm Crystals: 1-3 mm © JohnBetts-FineMinerals

Modern Ocean Acidification Is Outpacing Ancient Upheaval, Study Suggests

June 3, 2014

Ocean acidification in the modern ocean may already be affecting some marine life, as shown by the partly dissolved shell of this planktic snail, or pteropod, caught off the Pacific Northwest. Credit: Nina Bednaršedk/NOAA

Some 56 million years ago, a massive pulse of carbon dioxide into the atmosphere sent global temperatures soaring. In the oceans, carbonate sediments dissolved, some organisms went extinct and others evolved.

Scientists have long suspected that ocean acidification caused the crisis — similar to today, as humanmade CO2 combines with seawater to change its chemistry. Now, for the first time, scientists have quantified the extent of surface acidification from those ancient days, and the news is not good: the oceans are on track to acidify at least as much as they did then, only at a much faster rate.

In a study published in the latest issue of Paleoceanography, the scientists estimate that ocean acidity increased by about 100 percent in a few thousand years or more, and stayed that way for the next 70,000 years. In this radically changed environment, some creatures died out while others adapted and evolved. The study is the first to use the chemical composition of fossils to reconstruct surface ocean acidity at the Paleocene-Eocene Thermal Maximum (PETM), a period of intense warming on land and throughout the oceans due to high CO2.

“This could be the closest geological analog to modern ocean acidification,” said study coauthor Bärbel Hönisch, a paleoceanographer at Columbia University’s Lamont-Doherty Earth Observatory. “As massive as it was, it still happened about 10 times more slowly than what we are doing today.”

The oceans have absorbed about a third of the carbon humans have pumped into the air since industrialization, helping to keep earth’s thermostat lower than it would be otherwise. But that uptake of carbon has come at a price. Chemical reactions caused by that excess CO2 have made seawater grow more acidic, depleting it of the carbonate ions that corals, mollusks and calcifying plankton need to build their shells and skeletons.

In the last 150 years or so, the pH of the oceans has dropped substantially, from 8.2 to 8.1–equivalent to a 25 percent increase in acidity. By the end of the century, ocean pH is projected to fall another 0.3 pH units, to 7.8. While the researchers found a comparable pH drop during the PETM–0.3 units–the shift happened over a few thousand years.

“We are dumping carbon in the atmosphere and ocean at a much higher rate today — within centuries,” said study coauthor Richard Zeebe, a paleoceanographer at the University of Hawaii. “If we continue on the emissions path we are on right now, acidification of the surface ocean will be way more dramatic than during the PETM.”

The study confirms that the acidified conditions lasted for 70,000 years or more, consistent with previous model-based estimates. “It didn’t bounce back right away,” said Timothy Bralower, a researcher at Penn State who was not involved in the study. “It took tens of thousands of years to recover.”

From seafloor sediments drilled off Japan, the researchers analyzed the shells of plankton that lived at the surface of the ocean during the PETM. Two different methods for measuring ocean chemistry at the time — the ratio of boron isotopes in their shells, and the amount of boron –arrived at similar estimates of acidification. “It’s really showing us clear evidence of a change in pH for the first time,” said Bralower.

What caused the burst of carbon at the PETM is still unclear. One popular explanation is that an overall warming trend may have sent a pulse of methane from the seafloor into the air, setting off events that released more earth-warming gases into the air and oceans. Up to half of the tiny animals that live in mud on the seafloor — benthic foraminifera — died out during the PETM, possibly along with life further up the food chain.

Other species thrived in this changed environment and new ones evolved. In the oceans, dinoflagellates extended their range from the tropics to the Arctic, while on land, hoofed animals and primates appeared for the first time. Eventually, the oceans and atmosphere recovered as elements from eroded rocks washed into the sea and neutralized the acid.

Today, signs are already emerging that some marine life may be in trouble. In a recent study led by Nina Bednaršedk at the U.S. National Oceanic and Atmospheric Administration, more than half of the tiny planktic snails, or pteropods, that she and her team studied off the coast of Washington, Oregon and California showed badly dissolved shells. Ocean acidification has been linked to the widespread death of baby oysters off Washington and Oregon since 2005, and may also pose a threat to coral reefs, which are under additional pressure from pollution and warming ocean temperatures.

“Seawater carbonate chemistry is complex but the mechanism underlying ocean acidification is very simple,” said study lead author Donald Penman, a graduate student at University of California at Santa Cruz. “We can make accurate predictions about how carbonate chemistry will respond to increasing carbon dioxide levels. The real unknown is how individual organisms will respond and how that cascades through ecosystems.”

Other authors of the study, which was funded by the U.S. National Science Foundation: Ellen Thomas, Yale University; and James Zachos, UC Santa Cruz.

Note : The above story is based on materials provided by The Earth Institute at Columbia University.

Ancient reefs preserved tropical marine biodiversity

June 3, 2014

View of reef biodiversity in the Indo-Pacific. Credit: Copyright David R. Bellwood

Habitat refugia in which coral reefs have remained stable over time played a key role in preserving tropical marine fish biodiversity, a study highlights. Researchers at the Laboratoire Ecologie des Systèmes Marins Côtiers (CNRS/IRD/Universités Montpellier 1 and 2/IFREMER) and the Laboratoire CoRéUs 2 (IRD) have shown that the current distribution of tropical marine biodiversity is mainly due to the persistence of such refugia during glacial periods in the Quaternary.
This imprint left by history thus has a greater impact on tropical fish biodiversity than contemporary environmental factors such as water temperature and reef area. The study, carried out in collaboration with several international teams, demonstrates the need to protect certain irreplaceable habitats that allow species to persist during periods of climate change.

Scientists have long been intrigued by the marine biodiversity peak located around Indonesia and the Philippines, in the so-called Coral Triangle, which hosts approximately three thousand coral reef fish species, i.e. ten times more than in the eastern Pacific and Atlantic at the same latitude and in similar habitats. This biodiversity gradient is still poorly understood. Although many hypotheses have been put forward, most of them focus on the impact of current variables such as reef area and water temperature.

Coral reef habitats develop under highly specific temperature and light conditions. On the basis of reconstructed Quaternary sea temperatures, the authors of the study were able to map the reefs and observe their evolution over 2.6 million years. By comparing the contemporary global distribution of tropical marine fish1 with that of the paleo-reefs, the researchers were for the first time able to test the key role of habitats that persisted over many glacial periods and thus served as biodiversity refugia.

The researchers showed that the degree of isolation of contemporary reefs from Quaternary refugia is the most significant factor explaining the distribution of tropical marine fish observed today. The closer a reef is to one of these regions that are stable over time, the greater its biodiversity today. These findings point to the persistence of species in these regions, massive extinction rates outside them, and the ability of habitat refugia to act as sources for the colonization of new coral reefs that appeared in warmer periods.

If fish did leave refugia to occupy new regions, contemporary biodiversity should also depend on the recolonization ability of each species. To test this hypothesis, the researchers investigated three families of fish that are characteristic of coral reef habitats and have different dispersal capacities. Damselfish are less effective colonizers than butterflyfish and wrasse. As a result, with increasing distance from refugia, species diversity in damselfish falls significantly faster than for the other two families. The very old history of reefs therefore has a crucial effect not only on contemporary biodiversity distribution but also on the species and phylogenetic lineage2 composition of tropical fish communities.

By studying the ages of the various species in these three families of fish, the researchers also observed that both the oldest species and the most recent ones occur only in coral habitats near refugia. These reefs that have persisted over time have thus played a dual role as museum and cradle: they have preserved old species and led to the emergence of new ones (speciation). Quaternary climate fluctuations have therefore left a lasting imprint on the global distribution of coral reef biodiversity. This message from the past highlights the need to protect habitat refugia, since it is these stable regions, associated with corridors favorable to recolonization, that ensure the large-scale preservation of biodiversity. In today’s context of global change leading to extreme climate events impacting habitats, this message is more important than ever.

(1) Distribution established thanks to the GASPAR project headed by Michel Kulbicki and funded by the Fondation pour la Recherche sur la Biodiversité (FRB) via the Centre de Synthèse et d’Analyse sur la Biodiversité (CESAB).

(2) Species belong to lineages based on their degree of kinship. Such lineages make it possible to understand the evolutionary history of species.

Note : The above story is based on materials provided by CNRS.

History

Optical properties

Physical Properties

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Cooler temperatures

History

Optical properties

Physical Properties

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History

Optical properties

Physical Properties

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History

Optical properties

Physical Properties

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Was it due to climate change?

Theory of overkill

First global mapping

Weak climate effect

Extinction linked to humans

Occurrence

History

Optical properties

Physical Properties

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History

Post-Settlement

Geography

Course

History

Optical properties

Physical Properties

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