back to top
27.8 C
New York
Wednesday, April 2, 2025
Home Blog Page 280

New understanding of ocean passageway could aid climate change forecasts

The passageway that links the Pacific Ocean to the Indian Ocean

The passageway that links the Pacific Ocean to the Indian Ocean is acting differently because of climate change, and now its new behavior could, in turn, affect climate in both ocean basins in new ways.
UH Mānoa physical oceanographer James Potemra is co-author of a study led by Janet Sprintall of Scripps Institution of Oceanography at UC San Diego. The scientists have found that the flow of water in the Indonesian Throughflow – the network of straits that pass Indonesia’s islands – has changed since the late 2000s under the influence of dominant La Niña conditions. The flow has become more shallow and intense in the manner that water flows through a hose that has become kinked. The study suggests that human-caused climate change might make this characteristic a more dominant feature of the throughflow, even when El Niño conditions return.

Sprintall and colleagues have spent more than a decade understanding the dynamics of the throughflow, an ocean region that acts like a cable sending information between two electronic devices. The Indonesian seas are the only tropical location in the world where two oceans interact in this manner. The throughflow has an effect on the climate well beyond its boundaries, playing a role in everything from Indian monsoons to the El Niño phenomena experienced by California.

“This is a seminal paper on a key oceanographic feature that may have great utility in climate research in this century,” said Eric Lindstrom, a physical oceanography program scientist who co-chairs the Global Ocean Observing System Steering Committee at NASA, which funded Sprintall’s portion of the study. “The connection of the Pacific and Indian oceans through the Indonesian Seas is modulated by a complex circulation, climate variations, and sensitive ocean-atmosphere feedbacks. It’s a great place for us to sustain ocean observations to monitor potential changes in the ocean’s general circulation under a changing climate.”

Sprintall, a physical oceanographer at Scripps Oceanography, said this new research starts a new chapter in the history of the throughflow, one characterized by the changed variables created by global warming.

“Now that we have a better understanding of how the Indonesian Throughflow responds to El Niño and La Niña variability, we can begin to understand how this current behaves in response to changes in the trade wind system that are brought on through anthropogenic climate change,” Sprintall said. “Changes in the amount of warm water that is carried by the throughflow will have a subsequent impact on the sea surface temperature and so shift the patterns of rainfall in the whole Asian region.”

The study, “The Indonesian seas and their role in the coupled ocean-climate system,” appeared in the June 22 advance online publication of the journal Nature Geoscience.

In previous work over the past decade, Sprintall and colleagues from several countries have revised earlier thinking that most of the action in the throughflow was just at the surface where winds and waves interact. In fact, the flow often runs as much as 100 meters (328 feet) below the surface and features upwellings and other strong vertical flows of water. Model simulations have suggested that without this flow, the Indian Ocean would be generally colder at the surface as the Pacific would not be able to route warm water to it as efficiently.

These computer-generated scenarios have helped researchers forecast what could be happening as a consequence of human-caused climate change. Since the mid-twentieth century, scientists have noticed that Pacific Ocean tradewinds are weakening. The tradewinds help push Pacific Ocean water toward the throughflow and ultimately to the Indian Ocean. This corresponds to a predicted general slowdown of global thermohaline circulation – the flow of heat and salt around the world’s oceans.

The researchers found that as a strong El Niño regime begun in the late 1990s slowly yielded to La Niña conditions in the middle of the following decade, the nature of the throughflow changed. The strongest currents became shallower and faster through the main component of the throughflow, the Makassar Strait that runs between the Indonesian islands of Kalimantan and Sulawesi.

La Niña and El Niño are characterized in part by the location of a warm pool of surface water in the Pacific Ocean. Warm water in the western Pacific near Indonesia is usually associated with La Niña and warm water in the eastern equatorial Pacific with El Niño.

The researchers said the study provides an important consideration that should guide the intense marine conservation efforts that are underway in Indonesia and neighboring countries. The nature of the throughflow has a direct influence on what nutrients get delivered to marine organisms in the region and in what quantity. The work also suggests that ongoing regular observations of what is happening in the throughflow are a necessity going forward.

More information: 
“The Indonesian seas and their role in the coupled ocean–climate system.” Janet Sprintall, et al. Nature Geoscience (2014) DOI: 10.1038/ngeo2188. Received 02 January 2014 Accepted 21 May 2014 Published online 22 June 2014

Note : The above story is based on materials provided by University of Hawaii at Manoa

Parisite

Parisite-(Ce) Locality: East Kemptville Tin mine, East Kemptville, Argyle, Yarmouth Co., Nova Scotia, Canada Source: Donald Doell

Chemical Formula: Ca(Ce,La)2(CO3)3F2
Locality: Emerald mines, Muso, columbia.
Name Origin: Named for J. J. Paris, mine proprietor at Muzo, north of Bogota, Columbia.

Parisite is a rare mineral consisting of cerium, lanthanum and calcium fluoro-carbonate, Ca(Ce,La)2(CO3)3F2. Parisite is mostly parisite-(Ce), but when neodymium is present in the structure the mineral becomes parisite-(Nd).
It is found only as crystals, which belong to the trigonal or monoclinic pseudo-hexagonal system and usually have the form of acute double pyramids terminated by the basal planes; the faces of the hexagonal pyramids are striated horizontally, and parallel to the basal plane there is a perfect cleavage. The crystals are hair-brown in color and are translucent. The hardness is 4.5 and the specific gravity is 4.36. Light which has traversed a crystal of parisite exhibits a characteristic absorption spectrum.

At first, the only known occurrence of this mineral was in the famous emerald mine at Muzo in Colombia, South America, where it was found by J.J. Paris, who rediscovered and worked the mine in the early part of the 19th century; here it is associated with emerald in a bituminous limestone of Cretaceous age.

Closely allied to parisite, and indeed first described as such, is a mineral from the nepheline-syenite district of Julianehaab in south Greenland. To this the name synchysite has been given. The crystals are rhombohedral (as distinct from hexagonal; they have the composition CeFCa(CO3)2, and specific gravity of 2.90. At the same locality there is also found a barium-parisite, which differs from the Colombian parisite in containing barium in place of calcium, the formula being (CeF)2Ba(CO3)3: this is named cordylite on account of the club-shaped form of its hexagonal crystals. Bastnasite is a cerium lanthanum and neodymium fluoro-carbonate (CeF)CO3, from Bastnas, near Riddarhyttan, in Vestmanland, Sweden, and the Pikes Peak region in Colorado, U.S.A.

History

Discovery date : 1845
Town of Origin: DISTRICT DE MUZO, BOGOTA
Country of Origin : COLOMBIE

Physical properties

Hardnes : 4,50
Density : 4,36
Color : brownish yellow; brown; yellow; grayish yellow
Luster: vitreous; resinous; nacreous
Streak : white
Break : sub-conchoidal; splintery
Cleavage : Yes

Photos :

Parisite-(Ce) Muzo Mine, Boyaca Department, Colombia (TYPE LOCALITY) Small Cabinet, 6.3 x 5.0 x 3.5 cm “Courtesy of Rob Lavinsky, The Arkenstone, www.iRocks.com”

Hottest lava eruption linked to growth of first continents

A collaborative research team has discovered an important link between the eruption of Earth’s hottest lavas, the location of some of the largest ore deposits and the emergence of the first land masses on the planet – the continents – more than 2500 million years ago.

The research team includes researchers from the Centre for Exploration Targeting at The University of Western Australia and Curtin University, which are key nodes of the ARC Centre of Excellence for Core to Crust Fluid Systems, in collaboration with colleagues from CSIRO and the Geological Survey of Western Australia.

The generation and evolution of the Earth’s continental crust has played a fundamental role in the development of the planet. Its formation modified the composition of the Earth’s interior, contributed to the establishment of the atmosphere and led to the creation of ecological niches, essential for early life.

The study, published today in the prestigious international journal Proceedings of the National Academy of Sciences, used a combination of different radiogenic isotopes to show that in the early evolutionary stages of our planet, the formation and stabilisation of continents also controlled the location and extent of major komatiite volcanic eruptions.

Study co-author Professor Marco Fiorentini said komatiites were ultra-high temperature lavas that erupted in large volumes more than 2500 million years ago (Archean eon), but only very rarely since.

“They are the signature rock type of a hotter Earth in the primordial stages of its evolution, and provide the most direct link between the Earth’s interior and the Earth’s surface,” Professor Fiorentini said.

“They locally contain some of the largest known deposits of metals such as nickel, cobalt and platinum. Due to the unique geological processes that led to the formation of komatiites, they represent a rare window into the development of the innermost parts of our planet, notably the deep and inaccessible mantle and core.”

Focusing on the Yilgarn Craton of Western Australia as a natural laboratory, the research team combined sophisticated geochemical and isotopic techniques to unveil the progressive development of an Archean micro-continent.

Results from this study show that in the ancient Earth, relatively small crustal ‘blocks’, not unlike modern micro-plates, progressively developed and coalesced to form larger continental masses, called cratons, Professor Fiorentini said.

“This ‘cratonisation’ process formed deep roots to the continental land masses, extending more than 200km deep into the Earth,” he said. “The roots drove the hottest and most voluminous komatiite eruptions to the edge of established continental blocks. The ability to map these continental blocks through time points to the location where major metal deposits formed in these lavas.”

As a result, the dynamic evolution of the early continents directly influenced where deep mantle material was added to the Archean crust, oceans and atmosphere.

The complex interaction between the eruptions of some of the hottest lavas that ever existed on the planet, with the emergence of the first continents, provided a fundamental control on the distribution of major ore deposits. It also had an irreversible impact on the nature of the terrestrial biosphere-hydrosphere-atmosphere.

Reference: 
David R. Mole, Marco L. Fiorentini, Nicolas Thebaud, Kevin F. Cassidy, T. Campbell McCuaig, Christopher L. Kirkland, Sandra S. Romano, Michael P. Doublier, Elena A. Belousova, Stephen J. Barnes, and John Miller. “Archean komatiite volcanism controlled by the evolution of early continents.” PNAS 2014 ; published ahead of print June 23, 2014, DOI: 10.1073/pnas.1400273111

Note : The above story is based on materials provided by  University of Western Australia

Darling River

The Darling is a major tributary of the Murray-Darling system

The Darling River is the third longest river in Australia, measuring 1,472 kilometres (915 mi) from its source in northern New South Wales to its confluence with the Murray River at Wentworth, New South Wales. Including its longest contiguous tributaries it is 2,844 km (1,767 mi) long, making it the longest river system in Australia.

The Darling River is the outback’s most famous waterway. The Darling has been in poor health, suffering from overuse of its waters, pollution from pesticide runoff and prolonged drought. In some years it has barely flowed at all. The river has a high salt content and declining water quality. Increased rainfall in its catchment in 2010 has improved flow, but the health of the river will depend on long-term management.

The Division of Darling, Division of Riverina-Darling, Electoral district of Darling and Electoral district of Lachlan and Lower Darling were named after the river.

History

The Queensland headwaters of the Darling (the area now known as the Darling Downs) were gradually colonised from 1815 onward. In 1828 the explorer Charles Sturt and Hamilton Hume were sent by the Governor of New South Wales, Sir Ralph Darling, to investigate the course of the Macquarie River. He discovered the Bogan River and then, early in 1829, the upper Darling, which he named after the Governor. In 1835, Major Thomas Mitchell travelled a 483 km portion of the Darling River. Although his party never reached the junction with the Murray River he correctly assumed the rivers joined.

In 1856, the Blandowski Expedition set off for the junction of the Darling and Murray Rivers to discover and collect fish species for the National Museum. The expedition was a success with 17,400 specimens arriving in Adelaide the next year.

Although its flow is extraordinarily irregular (the river dried up on no fewer than forty-five occasions between 1885 and 1960), in the later 19th century the Darling became a major transportation route, the pastoralists of western New South Wales using it to send their wool by shallow-draft paddle steamer from busy river ports such as Bourke and Wilcannia to the South Australian railheads at Morgan and Murray Bridge. But over the past century the river’s importance as a transportation route has declined.

In 1992, the Darling River suffered from severe cyanobacterial bloom that stretched the length of the river.The presence of phosphorus was essential for the toxic algae to flourish. Flow rates, turbulence, turbidity and temperature were other contributing factors.

In 2008, the Federal government spent $23 million to buy Toorale Station in northern New South Wales, which allowed for the return of eleven gigalitres of environmental flows.

Course

The whole Murray-Darling river system, one of the largest in the world, drains all of New South Wales west of the Great Dividing Range, much of northern Victoria and southern Queensland and parts of South Australia. Its meandering course is three times longer than the direct distance it traverses.

Much of the land that the Darling flows through are plains and is therefore relatively flat, having an average gradient of just 16 mm per kilometre. Officially the Darling begins between Brewarrina and Bourke at the confluence of the Culgoa and Barwon rivers; streams whose tributaries rise in the ranges of southern Queensland and northern New South Wales west of the Great Dividing Range. These tributaries include the Balonne River (of which the Culgoa is one of three main branches) and its tributaries; the Macintyre River and its tributaries such as the Dumaresq River and the Severn Rivers (there are two – one either side or the state border); the Gwydir River; the Namoi River; the Castlereagh River; and the Macquarie River. Other rivers join the Darling near Bourke or below – the Bogan River, the Warrego River and Paroo River.
Darling River at Louth

South east of Broken Hill, the Menindee Lakes are a series of lakes that were once connected to the Darling River by short creeks. The Menindee Lake Scheme has reduced the frequency of flooding in the Menindee Lakes. As a result about 13,800 hectares of lignum and 8,700 hectares of Black box have been destroyed. Weirs and constant low flows have fragmented the river system and blocked fish passage.

The Darling River runs south-south-west, leaving the Far West region of New South Wales, to join the Murray River on the New South Wales – Victoria border at Wentworth, New South Wales.

The Barrier Highway at Wilcania, the Silver City Highway at Wentworth and the Broken Hill railway line at Medindee, all cross the Darling River. Part of the river north of Menindee marks the border of Kinchega National Park. In response to the 1956 Murray River flood a weir was constructed at Menindee to mitigate flows from the Darling River.

The north of the Darling River is in the Southeast Australia temperate savanna ecoregion and the south west of the Darling is part of the Murray Darling Depression ecoregion.

Population centres

Major settlements along the river include Brewarrina, Bourke, Louth, Tilpa, Wilcannia, Menindee, Pooncarie and Wentworth. Wentworth was Australia’s busiest inland port in the late 1880s.

Navigation by steam boat to Brewarrina was first achieved in 1859. Brewarrina was also the location of inter-tribal meetings for Indigenous Australians who speak Darling and live in the river basin. Ancient fish traps in the river provided food for feasts. These heritage listed rock formations have been estimated at more than 40,000 years old making them the oldest man-made structure on the planet.

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

Paravauxite

Paravauxite Siglo XX Mine, Llallagua, Bolivia Small Cabinet, 8.3 x 5.7 x 3.0 cm © irocks

Chemical Formula: Fe2+Al2(PO4)2(OH)2·8H2O
Locality: Llallagua, Potosi, Bolivia.
Name Origin: Named for the chemical similarity to vauxite. Polymorph of metavauxite.

History

Discovery date : 1922
Town of Origin: LLALLAGUA, POTOSI
Country of Origin : BOLIVIE

Optical properties

Optical and misc. Properties : Transparent  –   Translucide  –   Fragile, cassant
Refractive Index : from 1,55 to 1,57
Axial angle 2V: 72°

Physical properties

Hardness: 3,00
Density : 2,36
Color : colorless; greenish white
Luster : vitreous; nacreous
Streak: white
Break: conchoidal
Cleavage : Yes

Photos :

Paravauxite 10.0×8.1×2.9 cm Siglo XX Mine Llallagua, Bustillo Province Bolivia Copyright © David K. Joyce Minerals
Paravauxite Siglo Veinte Mine, Llallagua, Bolivia Thumbnail, 1.6 x 1.1 x 1.1 cm © irocks
Paravauxite Siglo Veinte Mine (Siglo XX Mine; Llallagua Mine), Llallagua, Potosí Department, Bolivia (TYPE LOCALITY) Cabinet, 23.7 x 18.0 x 5.0 cm © irocks

Getting ready for the next big one : The North Anatolian Fault is roughly 1300km long

Earthquake progression with time along the North Anatolian Fault.

Is one of the world’s great cities due to be struck by a serious earthquake? Ekbal Hussain describes how scientists are working to make sure Istanbul is prepared for the dangers that may be on the way.
Straddling the European and Asian borders Istanbul is an ancient and beautiful city. Once known as Constantinople, it has been at the centre of major empires including the Roman, Byzantine, Latin and Ottoman. This great city is inundated with rich culture and history, and with nearly 14 million inhabitants it is also one of the largest cities in the world.

But this thriving metropolis sits on the edge of one of the fastest moving faults in the world: the North Anatolian Fault. This is a system of large fractures within the Earth on which energy, from the motion of the tectonic plates, is stored and released in earthquakes.

The North Anatolian Fault is roughly 1300km long, running along the entire length of northern Turkey from the Aegean Sea in the west to Lake Van in the east. It slips such that central and southern Turkey are moving west relative to northern Turkey at speeds of 20-30mm a year. It is the most active and destructive earthquake-prone fault system in Turkey.

It has been known for a while now that earthquakes on the fault tend to follow a regular sequence. That is, an earthquake will often occur on the section of the fault adjacent to the last rupture. Starting with the 1939 magnitude 7.9 Erzincan earthquake and culminating in the 1999 magnitude 7.4 and 7.2 earthquakes, there have been 12 events with magnitudes greater than 6.4 that together have ruptured almost the entire length of the fault.

The map shows this westward progression of seismic activity. The 1999 Izmit (magnitude 7.4) and Duzce (magnitude 7.2) earthquakes killed about 18,000 people, mostly in the city of Izmit. These events occurred less than 100km east of Istanbul, leading some researchers to predict the next quake will strike Istanbul itself.

Seismologists calculate the chance of an earthquake greater than magnitude 7 occurring near Istanbul in the next 30 years at somewhere between 35 and 70 per cent. And with almost a million people moving to the metropolis every year it is no surprise that Istanbul is a major candidate for the so called ‘million-death quake.’

We need to improve our ability to forecast such quakes by creating realistic models of the fault’s behaviour, and to do this we need to know more about the fault itself.

The NERC-funded FaultLab project based at the University of Leeds is helping address these problems, with support from the University’s Climate and Geohazard Services group. The investigators use data from a multitude of sources including satellite radar and geological observations, as well as data from the densest network of seismic stations ever deployed across a fault.

The project scientists aim to use the seismic data to investigate the deep structure of the fault and to see if there are differences in the crust either side of the fracture. The geologists will be looking at an old fault zone to probe the microscopic structure of minerals inside these large fracture zones. Together, these observations will enable us to better understand what the fault is doing deep in the ground and how this has affected the crust adjacent to it. The geodesy group (earth observation scientists) will use satellite radar to make accurate maps of how the ground surface is moving and relate that to the amount of energy being stored on the fault. Finally, the modelling team will link these observations together to produce an accurate picture of the behaviour of the fault. These results can then feed into models to make a more realistic forecast of the hazard Istanbul faces.
A resilient city

Professor Nicholas Ambraseys, a leading expert in the field, famously said: ‘Earthquakes don’t kill people, buildings do.’

We technically don’t need to know when the earthquake will occur to save lives. Death and injury can be prevented through simple engineering works to reinforce vulnerable buildings and by ensuring new structures are built to earthquake-resilient standards. It’s estimated to cost only 10 per cent more to build a house that is earthquake resistant compared to one that isn’t.

The Turkish government has not been idle. The new Sabiha Gökçen International Airport terminal, which opened in October 2009, is designed to withstand shaking from a magnitude 8 earthquake and, importantly, keep working afterwards – this will be an important entry point for foreign aid after a disaster.

The Marmaray rail tunnel, opened in October 2013, runs beneath the Bosphorus Straits and links the European and Asian sides of the country. The rail tunnel was built to withstand a magnitude 9 earthquake.

In May 2012 a new Urban Transformation Law was passed, stating that all buildings that do not meet current earthquake hazard criteria will be demolished. This means nearly 6.5 million buildings throughout Turkey could be demolished over the next two decades, and will pave the way for more resilient cities.

Ambitions on this scale need strong governance and management, but they also need good science – to help the Turkish government prioritise its engineering projects and work on effective evacuation and mitigation plans. The results from the FaultLab project will help develop and refine their forecast models, so those plans can be put in action the moment there’s a sign that a deadly earthquake is imminent.

Note : The above story is based on materials provided by Ekbal Hussain is a PhD student in the School of Earth and Environment at the University of Leeds. ” © Natural Environment Research Council “

Q&A: Will the fossil record preserve your computer?

Last week, scientists reported finding rocks made of plastic on a Hawaiian beach. Some researchers have speculated that these and other humanmade objects could become part of the fossil record, defining a human-dominated period of Earth’s history called the Anthropocene. Science chatted with Jan Zalasiewicz, a paleontologist at the University of Leicester in the United Kingdom and a leading scholar on the Anthropocene, about the kinds of things humans are leaving behind—and what they’ll look like millions of years hence.
This interview has been edited for clarity and brevity.

Q: You have called these humanmade fossils “technofossils.” What are they, and how are they different from normal fossils?

A: Technofossils are basically all the things we manufacture, large and small. Because most of them are preservable, they can potentially become fossils—particularly since, unlike nature, we’re so poor at recycling the things we make. They can survive for thousands, millions, perhaps billions of years in rock strata [rock or sediment layers] in the future. We think they deserve a separate category because there’s so much about them that is distinct.

Q: What kinds of things can we expect to survive in the fossil record for millions of years, and what will they look like after all that time?

A: Looking around at my room, I’m struggling to see anything that is not fossilizable. So let’s take my desk—wood can fossilize really quite well. We’ve helped along the process of fossilization of this wood because it’s been seasoned, dried out, and varnished. It’s much less edible than it was in its original state on the tree.

With clothes, a lot of them are made from plastic polymer objects or cotton—plant materials. So they will fossilize just as plants do. They can preserve a good deal of the fabric. Under the right circumstances, one can preserve leaf cells and the like for millions of years—but the chemistry will change, they will become carbonized. You will lose the colors, and they’ll become black shapes.

Even paper is fossilizable. Now clearly, if that makes it into a stratum, it will become a carbonized lump. Probably the information on the pages is not easily fossilizable. It would be very hard to read newsprint from pages.

This computer I have in front of me, I see plastic, titanium, bits of rubber, a fair bit of this—if buried in the stratum—it will at least leave a nice oblong detail and impression, probably parts of the structure itself. But the information will be gone. Just as we can fossilize a songbird, it’s much harder to fossilize the song itself.

Q: Are some cities more likely to preserve technofossils than others?

A: In San Francisco, Earth’s crust is rising. It’s being eroded and the material is being washed away to areas where the crust is subsiding. So an upland place like San Francisco will be eroded, and the fragments will wash into the sea. Los Angeles and the northwest of Britain—Manchester, say—are also on long-term upward-moving crust. These are both also destined to be eroded away.

New Orleans, in contrast, is on a delta. It’s on what’s called a tectonic escalator, going downwards because that’s what the crust is doing, and because it’s being loaded by all the sand and mud being washed off from the Mississippi River. New Orleans is ripe for fossilization, all of the structures, the pilings, the concrete pilings, tens of meters into the ground to keep the skyscrapers up. And all of the stuff that’s underground: pipework, sewage, the electric.

Other places might be Amsterdam, Venice, Shanghai, coastal deltas on coastal plains. These places are ripe for fossilization.

Q: What will future beings be able to infer about us from these fossils?

A: The technofossils will strike them as quite different as anything that’s come before. We have the whole history we see through archaeology. Metals—Bronze [Age] first, then Iron and so on, different types of tools. And then we go into the Industrial Revolution and on to the space age and beyond.

If you’re looking at the point of the perspective of the future paleontologist, either human or nonhuman or space visitor or hyperevolved rat or whatever, as a geologist one thing will strike them. will be crammed into a very small physical space. The stratum itself may not be much more than a few meters thick. In many places, it may only be a few centimeters thick. It will probably appear instantaneous, and it will be very hard work to figure out the path of this hyperevolution of the technofossils within the human stratum.

Note : The above story is based on materials provided by Angus Chen , © 2014 American Association for the Advancement of Science. All Rights Reserved.

Paramelaconite

Paramelaconite Location: Algoma Mine, Otonagon County, Michigan, USA. Copyright: © Jeff Weissman / Photographic Guide to Mineral Species

Chemical Formula: Cu2Cu2O3
Locality: Copper Queen mine, Bisbee, Arizona, USA.
Name Origin: Named from the Greek for near and melaconite, which in turn was named for black and dust, now a synonym for tenorite.

Paramelaconite is a rare, black-colored copper oxide mineral with formula Cu21+Cu22+O3 (or Cu4O3). It was discovered in the Copper Queen Mine in Bisbee, Arizona, about 1890. It was described in 1892 and more fully in 1941. Its name is derived from the Greek word for “near” and the similar mineral melaconite, now known as tenorite.

Description and occurrence

Paramelaconite is black to black with a slight purple tint in color, and is white with a pinkish brown tint in reflected light. The mineral occurs with massive habit or as crystals up to 7.5 centimetres (3.0 in). A yellow color is formed when the mineral is dissolved in hydrochloric acid, a blue color when dissolved in nitric acid, and a slightly brown precipitate when exposed to ammonium hydroxide. When heated, paramelaconite breaks down into a mixture of tenorite and cuprite.

Paramelaconite is a very rare mineral; many specimens purported as such are in fact mixtures of cuprite and tenorite. Paramelaconite forms as a secondary mineral in hydrothermal deposits of copper. It occurs in association with atacamite, chrysocolla, connellite, cuprite, dioptase, goethite, malachite, plancheite, and tenorite. The mineral has been found in Cyprus, the United Kingdom, and the United States.

History

Discovery date: 1891
Town of Origin: MINE COPPER QUEEN, BISBEE, COCHISE CO., ARIZONA
Country of Origin: USA

Optical properties

Optical and misc. Properties : Opaque

Physical properties

Hardness: 4,50
Density: from 6,10 to 6,11
Color : black; purplish black
Luster : adamantine; bright
Streak: brownish black
Break: conchoidal
Cleavage: NO

Photos:

Paramelaconite, Brochantite, Cuprite Locality: Ojuela Mine, Mapimí, Mun. de Mapimí, Durango, Mexico © Rolf Luetcke specimen and photo.

Volcanic mayhem drove major burst of evolution

Life’s forge (Image: Sigurgeir Sigurjonsson/Plainpicture)

OUR planet is home to a glorious variety of animals, but it might not have been. Were it not for the birth pangs of a mega-continent, the evolution of animals could have stopped at its earliest stages.
We now have the best evidence yet that an enormous wave of volcanism, caused by several continents crashing together to form the even greater landmass known as Gondwana, was the reason for a sharp rise in global temperature. This change was the driving force for evolutionary explosions that made life more diverse and laid the foundations for all future animal species.

Volcanoes can cause global warming because eruptions often spew huge amounts of the greenhouse gas carbon dioxide. Now a study of volcanic rocks from early in life’s evolutionary story shows that such eruptions coincided with a change in the climate from frigid chill to sweltering heat.

This swing, and the way it affected the oceans, caused an explosion of evolutionary diversity, followed by a mass extinction when temperatures got too hot. Then, when Gondwana had formed and the volcanism died down, the planet cooled and life began to bloom again. The findings add to evidence that plate tectonics and living things are linked (see “Shaky worlds may harbour life”).

Last year, a study suggested that microbes helped form continents by encouraging volcanic activity (New Scientist, 23 November 2013, p 10). Now Ryan McKenzie of the University of Texas at Austin and colleagues have shown that, in turn, volcanism may have shaped life during the crucial Cambrian period .

Before the Cambrian, over 600 million years ago, Earth was virtually covered in ice. The first animals arose on this “Snowball Earth”, but these “Ediacarans” did not look like modern animals.

Then came the Cambrian explosion. “You had single cell organisms, single cell, single cell, then weird Ediacaran oddballs, and – suddenly – snails and bivalves and sea stars and a whole range of groups that typify the record for the rest of time,” says McKenzie’s colleague Paul Myrow of Colorado College in Colorado Springs.

The animals that appeared during the Cambrian explosion gave rise to all the major groups alive today, from worms to starfish. But each group only contained a few species, and got no further. The next period is known as the Dead Interval, and was marked by mass extinctions. It was another 50 million years before animal life blossomed once more, during the Ordovician.

We already knew that Earth’s temperature changed dramatically over these periods. It thawed in the early Cambrian then became stiflingly hot during the Dead Interval, before cooling again. “These are huge climate swings, from Snowball Earth to one of the warmest intervals of Earth history in the Cambrian,” says Lee Kump of Penn State University in University Park.

Volcanic activity during the formation of Gondwana has been suggested as a driver of these violent changes, but Kump says the evidence for increased volcanism was “a house of cards”.

McKenzie’s new evidence comes from tiny zircon crystals. Zircons are only formed in particular volcanic eruptions that are triggered when continental masses crash into each other, so they act as a record of past continental collisions. McKenzie assembled zircon counts from rocks laid down in the last 3 billion years, from all around the world.

He noticed that zircons were rare from Snowball Earth but common in the Cambrian. It seems a horde of volcanoes began spewing just before the Cambrian, and their activity reached a peak during the Dead Interval (Geology, doi.org/qvp).

“We hypothesise that CO2 outgassing from continental volcanic arcs drove major climate shifts,” says McKenzie.

Kump agrees: “This to my knowledge is the first direct and compelling assessment of changes in arc volcanism over this critical interval.”

“This is a fundamentally new and radical idea,” says Cin-ty Lee of Rice University in Houston, Texas.

Myrow says the formation of Gondwana offers the best explanation for the extra volcanoes. “Throughout the Cambrian two big continental masses were coming together to make Gondwana,” he says. The collision generated infernal heat that melted rock and created long chains of volcanoes. “You’re making volcanoes like mad,” says Myrow. “They produce carbon dioxide and temperatures get very, very hot.”

As well as heating the planet, the extra CO2 acidified the oceans. Many ocean creatures are sensitive to changes in acidity, so this could help explain the Dead Interval. Then the volcanism died off once Gondwana had formed, CO2 levels fell and a huge diversity of reef-based animals appeared.

“Now we have greater confidence that volcanism and its effect on the greenhouse gas content of the atmosphere drove climate change in deep time,” says Kump. “This had direct effects on rates of biotic diversification.”

Changes in tectonic activity would go on to affect life on Earth throughout its history, but not always in such a helpful way. For instance, almost all animal and plant life was abruptly wiped out at the end of the Permian period 251 million years ago, a time known as the Great Dying. Rapid climate change triggered by intense volcanic activity could well be to blame. Tectonics may give, but it also takes away.

Note : The above story is based on materials provided by  Catherine Brahic Magazine issue 2952.  © Copyright Reed Business Information Ltd.

New study suggests more and longer atmospheric stagnation events due to global warming

Characteristic change in air stagnation components. Credit: Nature Climate Change (2014) doi:10.1038/nclimate2272

A new study conducted by researchers at Stanford University has led to findings indicating that much of the world can expect to have more atmospheric stagnation events as the future unfolds. In their paper published in Nature Climate Change, the researchers describe how they ran a variety of computer models that took into account a continued increase in greenhouse gas emissions—they report that taken together, the models predict that approximately 55 percent of the world’s population can expect to be impacted by future stagnation events.

Stagnation is an atmospheric phenomenon where an air mass remains in place over a geographic region for an extended period of time. They tend to happen due to the convergence of specific weather conditions—light wind patterns near the surface, other light wind patterns occurring higher up, and a lack of rain. During normal weather periods, wind and rain combine to clean the air around metropolitan areas—when rain fails to fall and there is little wind to push pollution away from an area, particulates and other types of pollution levels climb, putting those that live in the area at risk of health problems.

The collection of computer models run by the team at Stanford also suggest that stagnation events are likely to last longer—increasing by an average of 40 days a year. The result the team notes, is likely to be an increase in heart and lung complications in people in those areas, contributing to an associated climb in the number of premature deaths due to air pollutants—numbering perhaps in the millions. They also note that Mexico, India and parts of the western U.S. are likely to be most at risk of health impacts from an increase in stagnation events, as all three will have more and longer such events and all three are heavily populated.

The researchers suggest that at some point, the entire planet will be impacted by stagnation events. That means governments and health workers will need to make plans on how to handle the problems as they begin to occur. They add that the only real solution to the problem is to begin curbing greenhouse gas emissions now, preventing the events from occurring in the first place.

More information: Occurrence and persistence of future atmospheric stagnation events, Nature Climate Change (2014) DOI: 10.1038/nclimate2272

Abstract
Poor air quality causes an estimated 2.6–4.4 million premature deaths per year. Hazardous conditions form when meteorological components allow the accumulation of pollutants in the near-surface atmosphere. Global-warming-driven changes to atmospheric circulation and the hydrological cycle are expected to alter the meteorological components that control pollutant build-up and dispersal, but the magnitude, direction, geographic footprint and public health impact of this alteration remain unclear. We used an air stagnation index and an ensemble of bias-corrected climate model simulations to quantify the response of stagnation occurrence and persistence to global warming. Our analysis projects increases in stagnation occurrence that cover 55% of the current global population, with areas of increase affecting ten times more people than areas of decrease. By the late twenty-first century, robust increases of up to 40 days per year are projected throughout the majority of the tropics and subtropics, as well as within isolated mid-latitude regions. Potential impacts over India, Mexico and the western US are particularly acute owing to the intersection of large populations and increases in the persistence of stagnation events, including those of extreme duration. These results indicate that anthropogenic climate change is likely to alter the level of pollutant management required to meet future air quality targets.

Note : The above story is based on materials provided by © 2014 Phys.org

Paradamite

Ojuela Mine, Mapimí, Mun. de Mapimí, Durango, Mexico © MJO

Chemical Formula: Zn2(AsO4)(OH)
Locality: Ojuela mine, Mapimi, Durango, Mexico
Name Origin: Named as the dimorph of adamite.

Paradamite is dimorphous with a famous arsenic mineral, namely adamite. Dimorphous means that the two minerals have the same formula, but different structures (di means two; morphous means shape). Paradamite’s different structure produces only slight differences in physical properties. Most obvious however is the difference in crystal forms. Adamite’s typical form is wedge shaped prismatic crystals with diamond-shaped cross-sections. Paradamite’s form is more tabular in character and very different from adamite’s. Although their names are similar and their chemistry is the same; paradamite and adamite are absolutely distinct minerals.

Optical properties

Optical and misc. Properties:Transparent
Refractive Index: from 1,72 to 1,78
Axial angle 2V : 50°

Physical properties

Color : pale yellow
Luster: vitreous.
Transparency: Crystals are transparent to translucent.
Crystal System: triclinic; bar 1.
Crystal Habits include rounded tabular crystals, usually aggregated.
Cleavage: perfect.
Fracture: uneven.
Hardness: 3.5.
Specific Gravity: approximately 4.5 – 4.6 (heavy for translucent minerals)
Streak: white.

Photos:

Paradamite Mina Ojuela, Mapimi, Durango,Mexico Miniature, 4.4 x 3.3 x 2.0 cm “Courtesy of Rob Lavinsky, The Arkenstone, www.iRocks.com”
Paradamite Location: Ojuela mine, Mapimi, Druango, Mexico. Copyright: © Lou Perloff / Photo Atlas of Minerals
Paradamite Locality: Ojuela Mine, Mapimí, Mun. de Mapimí, Durango, Mexico Photo Copyright © Marcus J. Origlieri
Paradamite Mina Ojuela, Mapimi, Durango, Mexico Miniature, 4.9 x 3.8 x 3.8 cm “Courtesy of Rob Lavinsky, The Arkenstone, www.iRocks.com”

Regional weather extremes linked to atmospheric variations

View on Europe from a height of satellites (stock image). Changes to air flow patterns around the Northern Hemisphere are a major influence on prolonged bouts of unseasonal weather – whether it be hot, cold, wet or dry. Credit: © Anton Balazh / Fotolia

Variations in high-altitude wind patterns expose particular parts of Europe, Asia and the US to different extreme weather conditions, a new study has shown.
Changes to air flow patterns around the Northern Hemisphere are a major influence on prolonged bouts of unseasonal weather — whether it be hot, cold, wet or dry.

The high altitude winds normally blow from west to east around the planet, but do not follow a straight path. The flow meanders to the north and south, in a wave-like path.

These wave patterns are responsible for sucking either warm air from the tropics, or cold air from the Arctic, to Europe, Asia, or the US. They can also influence rainfall by steering rain-laden storms.

Pioneering new research, carried out by the University of Exeter and the University of Melbourne, has shown that the development of these wave patterns leaves certain Northern Hemisphere regions more susceptible to different types of prolonged, extreme weather.

Dr James Screen, a Mathematics Research Fellow at the University of Exeter and lead author of the study, said: “The impacts of large and slow moving atmospheric waves are different in different places. In some places amplified waves increase the chance of unusually hot conditions, and in others the risk of cold, wet or dry conditions.”

The study showed that larger waves can lead to droughts in central North America, Europe and central Asia, and western Asia exposed to prolonged wet spells. It also shows western North America and central Asia are more prone to heat waves, while eastern North America is more likely to experience prolonged outbreaks of cold.

The collaborative study used detailed land-based climate observations to identify episodes of abnormal temperature and rainfall from 1979-2012 and then examined the wave patterns during these events.

Co-author Professor Ian Simmonds, from the School of Earth Sciences at the University of Melbourne, said the weather extremes they examined were month-long heat waves, cold spells, droughts and prolonged wet periods, which occurred over large areas.

He said: “The study revealed that these types of events are strongly related to well-developed wave patterns, and that these patterns increase the chance of heat waves in western North America and central Asia, cold outbreaks in eastern North America, droughts in central North America, Europe and central Asia, and wet spells in western Asia.

“The findings are very important for decision makers in assessing the risk of, and planning for the impacts of, extreme weather events in the future.”

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

Murray River

Map of the course of the Murray River

Table of Contents

The Murray River (River Murray in South Australia) is Australia’s longest river. At 2,508 kilometres (1,558 mi) in length, the Murray rises in the Australian Alps, draining the western side of Australia’s highest mountains and, for most of its length, meanders across Australia’s inland plains, forming the border between the states of New South Wales and Victoria as it flows to the northwest, before turning south for its final 500 kilometres (310 mi) or so into South Australia, reaching the ocean at Lake Alexandrina.
The water of the Murray flows through several lakes that fluctuate in salinity (and were often fresh until recent decades) including Lake Alexandrina and The Coorong before emptying through the Murray Mouth into the southeastern portion of the Indian Ocean, often referenced on Australian maps as the Southern Ocean, near Goolwa. Despite discharging considerable volumes of water at times, particularly before the advent of largescale river regulation, the Mouth has always been comparatively small and shallow.

As of 2010, the Murray River system receives 58 percent of its natural flow. It is perhaps Australia’s most important irrigated region, and it is widely known as the food bowl of the nation.

Geography

The Murray River forms part of the 3,750 km (2,330 mi) long combined Murray-Darling river system which drains most of inland Victoria, New South Wales, and southern Queensland. Overall the catchment area is one seventh of Australia’s total land mass. The Murray carries only a small fraction of the water of comparably-sized rivers in other parts of the world, and with a great annual variability of its flow. In its natural state it has even been known to dry up completely during extreme droughts, although that is extremely rare, with only two or three instances of this occurring since official record keeping began.

The Murray River makes up much of the border between the Australian states of Victoria and New South Wales. Where it does, the border is the top of the bank of the southern side of the river (i.e., none of the river itself is actually in Victoria). This boundary definition can be ambiguous, since the river changes course, and some of the river banks have been modified.

West of the line of longitude 141°E, the river continues as the border between Victoria and South Australia for 3.6 km (2.2 mi), where this is the only stretch where a state border runs down the middle of the river. This was due to a miscalculation during the 1840s, when the border was originally surveyed. Past this point, the Murray River is entirely within the state of South Australia.

River life

The Murray River (and associated tributaries) support a variety of unique river life adapted to its vagaries. This includes a variety of native fish such as the famous Murray cod, trout cod, golden perch, Macquarie perch, silver perch, eel-tailed catfish, Australian smelt, and western carp gudgeon, and other aquatic species like the Murray short-necked turtle, Murray River crayfish, broad-clawed yabbies, and the large clawed Macrobrachium shrimp, as well as aquatic species more widely distributed through southeastern Australia such as common longnecked turtles, common yabbies, the small claw-less paratya shrimp, water rats, and platypus. The Murray River also supports fringing corridors and forests of the river red gum.

The health of the Murray River has declined significantly since European settlement, particularly due to river regulation, and much of its aquatic life including native fish are now declining, rare or endangered. Recent extreme droughts (2000 – 07) have put significant stress on river red gum forests, with mounting concern over their long term survival. The Murray has also flooded on occasion, the most significant of which was the flood of 1956, which inundated many towns on the lower Murray and which lasted for up to six months.

Introduced fish species such as carp, gambusia, weather loach, redfin perch, brown trout, and rainbow trout have also had serious negative effects on native fish, while carp have contributed to environmental degradation of the Murray River and tributaries by destroying aquatic plants and permanently raising turbidity. In some segments of the Murray, carp have become the only species found.

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

Painite

Painite and Ruby Kyauk-pyat-thet, Mogok, Burma Miniature, 4 x 3.5 x 3 cm “Courtesy of Rob Lavinsky, The Arkenstone, www.iRocks.com”

Chemical Formula: CaZrAl9(BO3)O15
Locality: Ohngaing, Mogok district, Sagaing, Myanmar.
Name Origin: Named for A. C. D. Pain (-1971), British gem collector who first noticed the mineral.
Painite is a very rare borate mineral. It was first found in Myanmar by British mineralogist and gem dealer Arthur C.D. Pain in the 1950s. When it was confirmed as a new mineral species, the mineral was named after him.

The chemical makeup of painite contains calcium, zirconium, boron, aluminium and oxygen (CaZrAl9(BO3)O15). The mineral also contains trace amounts of chromium and vanadium. Painite has an orange-red to brownish-red color similar to topaz due to trace amounts of iron. The crystals are naturally hexagonal in shape, and, until late 2004, only two had been cut into faceted gemstones.

Discovery and occurrence

For many years, only three small painite crystals were known to exist. Before 2005 there were fewer than 25 known crystals found, though more material has been unearthed recently in Myanmar.

More recently, painite specimens have been discovered at a new location in northern Myanmar. It is believed that further excavations in this area will yield more painite crystals.

Extensive exploration in the Mogok region has identified several new painite occurrences that have been vigorously explored resulting in several thousand new painite specimens. Most of the recent crystals and fragments are dark, opaque, incomplete crystals. A modest number of transparent crystals have been found and have been either saved as crystals or cut into gemstones.

Originally few of the known painite specimens were privately owned. The rest of the stones were distributed between the British Museum of Natural History, Gemological Institute of America, California Institute of Technology and the GRS Gem Research Laboratory in Lucerne, Switzerland.

History

Discovery date: 1956
Town of Origin : MOGOK, OHNGAING, SAGAING
Country of Origin : BIRMANIE

Optical properties

Optical and misc. Properties : Translucide – Transparent
Refractive Index: from 1,78 to 1,81

Physical properties

Hardness: 8,00
Density: 4,03
Color : garnet-red; orange red; red orange; brownish; brownish red
Luster : vitreous
Streak : white

Photos:

Painite with Corundum Mogok, Mandalay  Burma Specimen size: 3.4 × 0.7 × 0.7 cm = 1.3” × 0.3” × 0.3” © Fabre Minerals

Could Pulses in Earth’s Magnetic Field Forecast Earthquakes?

John L. Wiley/Creative Commons

In the days leading up to some recent moderate-sized earthquakes, instruments nearby have picked up brief low-frequency pulses in Earth’s magnetic field. A few scientists have proposed that such pulses, which seemed to become stronger and more frequent just before the earthquakes occurred, could serve as an early warning sign for impending seismic activity. Now, a team has come up with a model for how these magnetic pulses might be generated, though some critics say they may have a humanmade origin.

Brief fluctuations in Earth’s magnetic field have been detected before many earthquakes in the past 50 years, says Friedemann Freund, a crystallographer at San Jose State University in California. For example, in the weeks before a magnitude-5.4 quake struck about 15 kilometers northeast of San Jose in October 2007, an instrument near the epicenter sensed a number of unusual magnetic pulses, presumably emanating from deep in the Earth. (The largest of them measured 30 nanoteslas, which is about 1/100,000th the typical strength of the planet’s magnetic field measured at Earth’s surface.) Those blips became more frequent as the day of the earthquake approached, Freund says. More recently, prior to several medium- to moderate-sized quakes in Peru, two sensitive magnetometers recorded the same sort of pulses.

One big puzzle, Freund notes, has been how such pulses could be generated. Now, he and his colleagues suggest that these blips stem from microscopic changes in crystals in rocks under seismic stress deep within Earth. In many types of rocks, particularly volcanic rocks that have substantial amounts of water locked inside them, crystals are chock-full of oxygen-oxygen bonds called peroxy bonds. (These bonds formed long ago, after chemical changes split some of the water molecules, freeing the hydrogen atoms to bond together and then diffuse out of the rocks as gas.) When those rocks are squeezed, say, by the sides of a fault zone scraping past one another, some of the peroxy bonds break. Those broken bonds release negatively charged electrons, which remain trapped in place, and create positively charged “holes” in the crystal, Freund explains. In lab experiments, the electrical disturbances associated with those holes diffuse through the surrounding rocks at speeds of about 100 meters per second.

Freund and his team propose that the same process might be happening within Earth’s crust. As stress on large volumes of rock builds in advance of an impending quake, many, many of these electrical holes are created inside them. It’s the mass migration of such holes that creates the large electrical currents responsible for generating the low-frequency magnetic pulses that make their way to detectors on Earth’s surface, they say.

For the Peruvian quakes, most of the pulses sensed by the magnetometers ranged between one-sixth and one-quarter of a second long. But some lasted up to 2 seconds, Freund says—a length that strongly suggests that the pulses weren’t triggered by lightning, either nearby or far away, which some critics of his model have proposed as an alternative explanation. More importantly, he notes, with data from the two sensors in Peru he and his colleagues were able to pinpoint the strongest of those pulses as originating within a few kilometers of the epicenters of subsequent quakes, they report in a paper posted to the arXiv preprint server. For now, Freund admits, the team’s model is preliminary: The paper has been submitted to a journal and is now being reviewed by other scientists.

“This paper only makes sense if the observations [of magnetic pulses] are good,” says John Ebel, a seismologist at Boston College, who wasn’t involved in the research. He points out that two instruments aren’t sufficient to pinpoint the location of an event; to truly “triangulate” an event you need at least three sensors.

But another aspect of the team’s findings is even more worrying, he notes: “I’m concerned that the pulses are not originating deep within the Earth.” It’s possible, he continues, that the blips may have some inexplicable humanmade origin. Decades ago, Ebel notes, his Boston-based magnetometers started picking up a series of odd pulses every morning. Eventually, he and his colleagues identified the sources of those gremlins: It was the engineers cranking up Boston’s trolley cars at a rail yard a few kilometers away from the instruments.

Even if the magnetic pulses originate within Earth along seismic zones under stress, Freund says, the blips don’t always foretell a quake. It’s more likely to be the pattern of pulses—and, in particular, changes in their size and frequency—that Freund and his colleagues say might offer scientists a crystal ball for impending temblors.

Note : The above story is based on materials provided by Sid Perkins ” sciencemag “

How Did the Moon Really Form?

NASA/JPL-Caltech

Planetary scientists have long believed that our moon formed following a collision between Earth and another planet, but studies of Earth and moon rocks suggest otherwise. A new analysis of the composition of moon rocks brought back by Apollo astronauts may help finally resolve the mystery.

Here’s the current thinking about how the moon formed. Early in its history, Earth was struck a glancing blow by a Mars-sized planet. That planet was destroyed by the impact, but much of its debris—and some of Earth’s—formed into a disk around Earth that eventually coalesced into the moon. Much evidence supports this scenario. The moon would have ended up hot, boiling off light elements and water, leaving the arid rocky moon we see today; the moon has a small core, consistent with being made from parts of the colliding planet and outer parts of Earth; the Earth-moon system rotates fast, consistent with a glancing blow.

But one bit of evidence just doesn’t fit: the composition of moon rocks. Researchers have found that rocks from different parts of the solar system (brought to Earth as meteorites) have subtle differences in their composition. Oxygen, for example, comes in different varieties, called isotopes. Oxygen-16 (O-16) is the most common type, followed by oxygen-17 (O-17)—which has one extra neutron in its nucleus—and oxygen-18, with two extra neutrons. Meteorites from different parts of the solar system have different proportions of these isotopes. So a rock from Mars would have a markedly different ratio of O-17 compared with O-16 than, say, a piece of an asteroid or a rock from Earth. These ratios are so reliable that researchers use them to identify where meteorites come from.

Here’s the puzzle: The giant impact hypothesis predicts that the moon should be made of about 70% to 90% material from the impactor, so its isotope ratios should be different from Earth’s. But ever since researchers got hold of Apollo moon rocks for analysis, they have failed to find any significant difference in isotope ratios on Earth and the moon. Studies of the isotopes of oxygen, titanium, calcium, silicon, and tungsten have all drawn a blank.

This discrepancy has troubled planetary scientists so much that in recent years they have put forward a number of alternative scenarios to explain the moon’s origins. One hypothesis suggests that there could have been much greater mixing between Earth and the debris disk as it coalesced after the impact, or if Earth was hit head-on by a similarly sized impactor, their remains could have mixed completely. Another possibility is that a fast-spinning Earth could have been hit by a much smaller impactor, which would have provided little material for the moon. Yet it has been hard to show how you could get from one of those events to the Earth-moon system we have today.

Researchers would prefer to stick with the original, plain vanilla impact scenario because it explains so many things so well. New results, published online today in Science, will give them some hope. Lunar rocks have a measurably higher ratio of O-17 over O-16 compared with those from Earth. The new study began because a team of researchers led by Daniel Herwartz of the University of Cologne in Germany had recently upgraded its mass spectrometer—a form of supersensitive atomic scale—and decided to test the device out on the Earth-moon isotope problem. “Our analysis is now an order of magnitude better than other laboratories,” says team member Andreas Pack of the University of Göttingen in Germany.

They started out analyzing moon rocks that arrived on Earth as meteorites but found that the weathering these rocks experienced on Earth was skewing the results. So they got hold of some rock samples from NASA that had been brought back by Apollo missions 11, 12, and 16. They extracted oxygen from all the samples and then passed it through the spectrometer to find out the proportions of each isotope. Their conclusion was that the lunar samples had an O-17 to O-16 ratio that was 12 parts per million higher than rocks derived from Earth’s mantle. This difference “supports the view that the Moon formed by a giant collision of the proto-Earth with [an impactor],” the team writes. “It is a relief that a [disparity in ratios] has been found, since the total absence of difference between Earth and moon would be hard to explain,” comments planetary scientist David Stevenson of the California Institute of Technology in Pasadena, in an e-mail.

The team acknowledges other possible explanations for the difference, including that Earth was bombarded by material with a lower oxygen isotope ratio at some time after the impact. “Now that a difference has been found, many will work to confirm or deny it and do battle over what it means,” Stevenson says.

The team says the results suggest that the moon is a roughly 50-50 mix of Earth and impactor material. Moreover, the high oxygen isotope ratio suggests that the impactor was principally made of a rare material called enstatite chondrite. The vast majority of meteorites that land on Earth are chondrites, but only about 2% of those are enstatite chondrites. “The possible significance of enstatite chondrites is interesting, but at present we are stuck with speculating about the bodies that went into making Earth, since they are no longer around,” Stevenson says.

Note : The above story is based on materials provided by Daniel Clery ” sciencemag “

Orthoclase

Orthoclase and smoky quartz Gebel quarry – Cuasso al Monte – Ceresio Valley – Varese prov. – Lombardy – Italy Specimen weight:315 gr. Crystal size:mm. 23 Overall size: 112mm x 103 mm x 41 mm © minservice

Chemical Formula: KAlSi3O8
Locality: Common world wide occurrences.
Name Origin: From the Greek orthos – “right” and kalo -” I cleave” in allusion to the mineral’s right angle of good cleavage.

Orthoclase (endmember formula KAlSi3O8) is an important tectosilicate mineral which forms igneous rock. The name is from the Greek for “straight fracture,” because its two cleavage planes are at right angles to each other. Alternate names are potassium feldspar and K-feldspar. The gem known as moonstone  is largely composed of orthoclase.

Formation and Subtypes

Orthoclase is a common constituent of most granites and other felsic igneous rocks and often forms huge crystals and masses in pegmatite.

Typically, the pure potassium endmember of orthoclase forms a solid solution with albite, the sodium endmember (NaAlSi3O8), of plagioclase. While slowly cooling within the earth, sodium-rich albite lamellae form by exsolution, enriching the remaining orthoclase with potassium. The resulting intergrowth of the two feldspars is called perthite.

The higher-temperature polymorph of orthoclase is sanidine. Sanidine is common in rapidly cooled volcanic rocks such as obsidian and felsic pyroclastic rocks, and is notably found in trachytes of the Drachenfels, Germany. The lower-temperature polymorph of orthoclase is microcline. Adularia is found in low temperature hydrothermal deposits, in the Adula Alps of Switzerland. The largest documented single crystal of orthoclase was found in Ural mountains, Russia. It measured ~10×10×0.4 m and weighed ~100 tons.

History

Discovery date : 1823

Optical properties

Optical and misc. Properties : Transparent – Translucide – fluorescent- Gemme, pierre fine
Refractive Index: from 1,51 to 1,52
Axial angle 2V: 35-75°

Physical properties

Hardness : from 6,00 to 6,50
Density: from 2,55 to 2,63
Color: colorless; white; grey; yellow; grey yellow; pink red; reddish; green; greenish; pink
Luster : vitreous; nacreous
Streak : white
Break : irregular; conchoidal; splintery
Cleavage : Yes

Photos:

Orthoclase 4.1×3.8×2.8 cm Bear Lake Diggings Gooderham Ontario, Canada Copyright © David K. Joyce Minerals
Orthoclase Montecatini quarry, Baveno, Piedmont, Italy Specimen weight:181 gr. Crystal size:40 mm Overall size: 78mm x 68 mm x 48 mm © minservice
Orthoclase Montecatini quarry, Baveno, Piedmont, Italy Specimen weight:135 gr. Crystal size:35 mm Overall size: 78mm x 62 mm x 55 mm © minservice

Earth’s breathable atmosphere tied to plate tectonics?

A new study links continents and plate tectonics to the rise of oxygen on Earth. Credit: The International Space Station

The rise of oxygen is one of the biggest puzzle in Earth’s history. Our planet’s atmosphere started out oxygen-free. Then, around 3.5 billion years ago, tiny microbes called cyanobacteria (or blue-green algae) learned out to carry out photosynthesis. They began using energy from sunlight to make their food from carbon dioxide and water, giving off oxygen as waste.
But it took another 3 billion years for oxygen levels to climb from trace amounts to at least 20 percent of the atmosphere, or high enough to support the emergence of complex life. And so far the mechanism behind that rise has remained unclear.

Now a new study by University of Exeter biochemist Benjamin Mills and his colleagues offers a new potential clue.

Using a computer model, they showed that plate tectonics may have indirectly fueled the sharp increase in oxygen between 1.5 billion and half a billion years ago. In particular, a process tied to the way continents remove carbon dioxide from the atmosphere may have increased the supply of phosphorus, a key nutrient for photosynthetic microbes in the ocean. The paper was published this month in the Proceedings of the National Academy of Science.

“This is a novel perspective for the late Proterozoic—a critical time of dramatic climate change, rising oxygen in the ocean and atmosphere, and origins and diversification of complex life,” says Timothy Lyons, a biogeochemist not involved in the study.

From Seafloor to Terrestrial “Weathering’

Continents play a crucial role in the carbon cycle by removing carbon dioxide from the atmosphere. Carbon dioxide mixes with rain water, forming a weak acid (carbonic acid) which slowly wears down or “weathers” rocks on land.

The process releases minerals such as calcium and magnesium from the rocks. These minerals then combine with carbonate and settle at the bottom of the ocean forming layers of calcium carbonate, or limestone.

In other words, the weathering process simply pulls carbon from the atmosphere and turns it into a layer of sediment on the seafloor.

However, continental rocks aren’t the only route by which carbon is removed from the atmosphere. Ocean ridges, the places where fresh crust is made on the seafloor, can undergo a similar “weathering” process. In fact, seafloor weathering was the main route of carbon removal in the early chapter of Earth’s history, before the formation of continents.

According to the new study, the rise of oxygen may have been due to a shift in balance between the two processes—between seafloor and continental weathering.

Potential Culprits

What caused that shift? The model looked at two factors: a brighter sun, and a slowdown in fresh crust production.

Our sun has slowly been getting brighter. It’s now 20 to 30 percent brighter than when our Earth first formed. Because the weathering process depends on temperature, a brighter Sun may have sped up the process on land. What’s more, the amount of fresh ocean floor formed has slowed down over time. And the weathering process generally happens with the newer crust. Taken together, these two factor may have shifted the balance between the seafloor and the terrestrial process.

The Phosphorus Boost

But why does that shift matter? “Rocks on continents contain phosphorus, which is a key limiting nutrient for photosynthetic microbes,” Mills says.

The terrestrial weathering increases the amount of phosphorus in streams and rivers, and ultimately in the ocean. The amount of phosphorus then dictates how much photosynthesis, hence how much oxygen is produced.

“The paper a great step forward,” says Lyons. “The fundamental mechanistic perspective, particularly the co-consideration of seafloor and continental processes, is broadly relevant and clever.”

One drawback, though, Lyons says, is that the model doesn’t account for the shorter-term variations of oxygen’s up and down. “The model, as proposed, isn’t able to explain the details of the transition,” Lyons adds. “But overall it still support the long term increase in oxygen.”

Implications for Astrobiology

The study provides an indirect link between plate tectonic and continents on one hand and the evolution of complex life on the other, an idea worth keeping in mind in the search for life beyond our world.

“This is not the only reason oxygen rose to high levels, but it seems to be an important piece of the puzzle. Whilst the carbon cycle can function without large continents, it seems that their emergence was critical to our own evolution,” Mills says in a news release.

Mills later adds in a phone interview:

“A large number of key limiting nutrients, and not just phosphate, come from the continents. It seems that to develop a biosphere like we have on this planet, you’re going to need significant continental area.”

In fact, the recycling of continents via plate tectonics has become of major interest for many astrobiologists. Several have argued that, along with water, plate tectonics could be an essential requirement for life.

“What I like in particular is the rigorous links between tectonic drivers and oxygen (and life by association), which must be a considered in any view of extrasolar planets and their ability to sustain life through nutrient balances—with oxygenation as a possible consequence,” Lyons adds. “Plate tectonics and relationships to nutrient cycling, phosphorus in particular, should be an essential part in any exploration for life—on the early Earth and farther from home.”

More information:
Benjamin Mills, Timothy M. Lenton, and Andrew J. Watson. “Proterozoic oxygen rise linked to shifting balance between seafloor and terrestrial weathering.” PNAS 2014 ; published ahead of print June 9, 2014, DOI: 10.1073/pnas.1321679111

Note : The above story is based on materials provided by courtesy of NASA’s Astrobiology Magazine. Explore the Earth and beyond at Astrobio.net

Swarm reveals Earth’s changing magnetism

Changes in Earth’s magnetic field from January to June 2014 as measured by the Swarm constellation of satellites. These changes are based on the magnetic signals that stem from Earth’s core. Shades of red represent areas of strengthening, while blues show areas of weakening over the 6-month period. Credit: ESA/DTU Space

The first set of high-resolution results from ESA’s three-satellite Swarm constellation reveals the most recent changes in the magnetic field that protects our planet.
Launched in November 2013, Swarm is providing unprecedented insights into the complex workings of Earth’s magnetic field, which safeguards us from the bombarding cosmic radiation and charged particles.

Measurements made over the past six months confirm the general trend of the field’s weakening, with the most dramatic declines over the Western Hemisphere.

But in other areas, such as the southern Indian Ocean, the magnetic field has strengthened since January.

The latest measurements also confirm the movement of magnetic North towards Siberia.

These changes are based on the magnetic signals stemming from Earth’s core. Over the coming months, scientists will analyse the data to unravel the magnetic contributions from other sources, namely the mantle, crust, oceans, ionosphere and magnetosphere.

This will provide new insight into many natural processes, from those occurring deep inside our planet to space weather triggered by solar activity. In turn, this information will yield a better understanding of why the magnetic field is weakening.

“These initial results demonstrate the excellent performance of Swarm,” said Rune Floberghagen, ESA’s Swarm Mission Manager.

“With unprecedented resolution, the data also exhibit Swarm’s capability to map fine-scale features of the magnetic field.”

The first results were presented June 19, 2014 at the ‘Third Swarm Science Meeting’ in Copenhagen, Denmark.

Sofie Carsten Nielsen, Danish Minister of Higher Education and Science, highlighted the Danish contribution to the mission. Swarm continues the legacy of the Danish Ørsted satellite, which is still operational, as well as the German Champ mission. Swarm’s core instrument — the Vector Field Magnetometer — was provided by the Technical University of Denmark.

Denmark’s National Space Institute, DTU Space, has a leading role — together with 10 European and Canadian research institutes — in the Swarm Satellite Constellation Application and Research Facility, which produces advanced models based on Swarm data describing each of the various sources of the measured field.

“I’m extremely happy to see that Swarm has materialised,” said Kristian Pedersen, Director of DTU Space.

Note : The above story is based on materials provided by European Space Agency.

Opal

OPAL Welo, Afar Province, Ethiopia Thumbnail, 1.2 x 1.1 x 0.4 cm “Courtesy of Rob Lavinsky, The Arkenstone, www.iRocks.com”

Chemical Formula: SiO2·nH2O
Locality: World wide occurrences.
Name Origin: From the Old Indian upala – “precious stone.”

What is Opal?

“What is Opal?” Opal is a hydrated amorphous form of silica; its water content may range from 3% to 21% by weight, but is usually between 6% and 10%. Because of its amorphous character it is classed as a mineraloid, unlike the other crystalline forms of silica which are classed as minerals. It is deposited at a relatively low temperature and may occur in the fissures of almost any kind of rock, being most commonly found with limonite, sandstone, rhyolite, marl and basalt. Opal is the national gemstone of Australia, which produces 97% of the world’s supply. This includes the production of the state of South Australia, which accounts for approximately 80% of the world’s supply.

The internal structure of precious opal makes it diffract light; depending on the conditions in which it formed, it can take on many colors. Precious opal ranges from clear through white, gray, red, orange, yellow, green, blue, magenta, rose, pink, slate, olive, brown, and black. Of these hues, the reds against black are the most rare, whereas white and greens are the most common. It varies in optical density from opaque to semi-transparent.

Common opal, called “potch” by miners, does not show the display of color exhibited in precious opal.

Related:
Types of Opal
Why is Australian Opal Unique?
How Do Opalised Fossils Form?

Optical properties

Optical and misc. Properties:  Transparent  –   Opaque  –   Translucide
Refractive Index: from 1,43 to 1,45

Physical Properties

Cleavage: None
Color:     White, Yellow, Red, Brown, Blue.
Density: 1.9 – 2.3, Average = 2.09
Diaphaneity: Transparent to translucent to opaque
Fracture: Conchoidal – Fractures developed in brittle materials characterized by smoothly curving surfaces, (e.g. quartz).
Luminescence: Fluorescent, Short UV=greenish yellow, Long UV=white.
Luster: Vitreous – Dull
Streak: white

Photos :

OPAL Welo, Afar Province, Ethiopia Thumbnail, 3.1 x 2.3 x 0.8 cm “Courtesy of Rob Lavinsky, The Arkenstone, www.iRocks.com”
OPAL Welo, Afar Province, Ethiopia Thumbnail, 1.3 x 0.9 x 0.6 cm “Courtesy of Rob Lavinsky, The Arkenstone, www.iRocks.com”
OPAL Welo, Afar Province, Ethiopia Thumbnail, 1.9 x 1.2 x 0.5 cm “Courtesy of Rob Lavinsky, The Arkenstone, www.iRocks.com”
OPAL Welo, Afar Province, Ethiopia Thumbnail, 1.3 x 1.1 x 0.8 cm “Courtesy of Rob Lavinsky, The Arkenstone, www.iRocks.com”
Name: Opal Locality: Mexico Weight: 2.46 carats Size: 9.50 x 6.05 mm © minclassics.
1...279280281...336Page 280 of 336

Related Articles

All
Facebook Instagram Linkedin TikTok Twitter Youtube
© 2011-2025. All Rights Reserved.