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Geologists reveal correlation between earthquakes, landslides

Devin McPhillips is a research associate in the Department of Earth Sciences. Credit: Syracuse University

A geologist in Syracuse University’s College of Arts and Sciences has demonstrated that earthquakes—not climate change, as previously thought—affect the rate of landslides in Peru.

The finding is the subject of an article in Nature Geoscience by Devin McPhillips, a research associate in the Department of Earth Sciences. He co-wrote the article with Paul Bierman, professor of geology at The University of Vermont; and Dylan Rood, a lecturer at Imperial College London (U.K.).

“Geologic records of landslide activity offer rare glimpses into landscapes evolving under the influence of tectonics and climate,” says McPhillips, whose expertise includes geomorphology and tectonics. “Because deposits from individual landslides are unlikely to be preserved, it’s difficult to reconstruct landslide activity in the geologic past. Therefore, we’ve developed a method that measures landslide activity before and after the last glacial-interglacial climate transition in Peru.”

McPhillips and his team have spent the past several years in the Western Andes Mountains, studying cobbles in the Quebrada Veladera river channel and in an adjacent fill terrace. By measuring the amount of a nuclide known as Beryllium-10 (Be-10) in each area’s cobble population, they’ve been able to calculate erosion rates over tens of thousands of years.

The result? The range of Be concentrations in terrace cobbles from a relatively wet period, more than 16,000 years ago, was no different from those found in river channel cobbles from more recent arid periods.

“This suggests that the amount of erosion from landslides has not changed in response to climatic changes,” McPhillips says. “Our integrated millennial-scale record of landslides implies that earthquakes may be the primary landslide trigger.”

McPhillips says the study is the first to study landslides by measuring individual particles of river sediment, as opposed to amalgamating all the particles and then measuring a single concentration.

“These concentrations provide a robust record of hill-slope behavior over long timescales,” he adds. “Millennial-scale records of landslide activity, especially in settings without preserved landslide deposits, are an important complement to studies documenting modern landslide inventories.”

Earthquakes are a regular occurrence in Peru, which is located at the nexus of the small Nazca oceanic plate and the larger South American crustal plate. The ongoing subduction, or sliding, of the Nazca Plate under the South American Plate has spawned considerable tectonic activity.

“Peru is rife with earthquakes, landslides, volcanic eruptions, and tectonic uplift,” McPhillips adds. “By studying its past, we may be able to better predict and prepare for future calamities.”

Reference:
Millennial-scale record of landslides in the Andes consistent with earthquake trigger, Nature Geoscience (2014) DOI: 10.1038/ngeo2278

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

Berkeley Lab Scientists ID New Driver Behind Arctic Warming

This simulation, from the Community Earth System Model, shows decadally averaged radiative surface temperature changes during the 2030s after far-infrared surface emissivity properties are taken into account. The right color bar depicts temperature change in Kelvin. Credit: Berkeley Lab

Scientists have identified a mechanism that could turn out to be a big contributor to warming in the Arctic region and melting sea ice.

The research was led by scientists from the US Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab). They studied a long-wavelength region of the electromagnetic spectrum called far infrared. It’s invisible to our eyes but accounts for about half the energy emitted by Earth’s surface. This process balances out incoming solar energy.

Despite its importance in the planet’s energy budget, it’s difficult to measure a surface’s effectiveness in emitting far-infrared energy. In addition, its influence on the planet’s climate is not well represented in climate models. The models assume that all surfaces are 100 percent efficient in emitting far-infrared energy.

That’s not the case. The scientists found that open oceans are much less efficient than sea ice when it comes to emitting in the far-infrared region of the spectrum. This means that the Arctic Ocean traps much of the energy in far-infrared radiation, a previously unknown phenomenon that is likely contributing to the warming of the polar climate.

Their research appears in the online early edition of the Proceedings of the National Academy of Sciences.

“Far-infrared surface emissivity is an unexplored topic, but it deserves more attention. Our research found that non-frozen surfaces are poor emitters compared to frozen surfaces. And this discrepancy has a much bigger impact on the polar climate than today’s models indicate,” says Daniel Feldman, a scientist in Berkeley Lab’s Earth Sciences Division and lead author of the paper.

“Based on our findings, we recommend that more efforts be made to measure far-infrared surface emissivity. These measurements will help climate models better simulate the effects of this phenomenon on Earth’s climate,” Feldman says.

He conducted the research with Bill Collins, who is head of Earth Sciences Division’s Climate Sciences Department. Scientists from the University of Colorado, Boulder and the University of Michigan also contributed to the research.

The far-infrared region of the electromagnetic spectrum spans wavelengths that are between 15 and 100 microns (a micron is one-millionth of a meter). It’s a subset of infrared radiation, which spans wavelengths between 5 and 100 microns. In comparison, visible light, which is another form of electromagnetic radiation, has a much shorter wavelength of between 390 and 700 nanometers (a nanometer is one billionth of a meter).

Many of today’s spectrometers cannot detect far-infrared wavelengths, which explains the dearth of field measurements. Because of this, scientists have extrapolated the effects of far-infrared surface emissions based on what’s known at the wavelengths measured by today’s spectrometers.

Feldman and colleagues suspected this approach is overly simplistic, so they refined the numbers by reviewing published studies of far-infrared surface properties. They used this information to develop calculations that were run on a global atmosphere climate model called the Community Earth System Model, which is closely tied to the Department of Energy’s Accelerated Climate Model for Energy (ACME).

The simulations revealed that far-infrared surface emissions have the biggest impact on the climates of arid high-latitude and high-altitude regions.

In the Arctic, the simulations found that open oceans hold more far-infrared energy than sea ice, resulting in warmer oceans, melting sea ice, and a 2-degree Celsius increase in the polar climate after only a 25-year run.

This could help explain why polar warming is most pronounced during the three-month winter when there is no sun. It also complements a process in which darker oceans absorb more solar energy than sea ice.

“Earth continues to emit energy in the far infrared during the polar winter,” Feldman says. “And because ocean surfaces trap this energy, the system is warmer throughout the year as opposed to only when the sun is out.”

The simulations revealed a similar warming affect on the Tibetan plateau, where there was five percent less snowpack after a 25-year run. This means more non-frozen surface area to trap far-infrared energy, which further contributes to warming in the region.

“We found that in very arid areas, the extent to which the surface emits far-infrared energy really matters. It controls the thermal energy budget for the entire region, so we need to measure and model it better,” says Feldman.

Reference:
Daniel R. Feldman, William D. Collinsa, Robert Pincus, Xianglei Huang, And Xiuhong Chen. Far-infrared surface emissivity and climate. PNAS, November 2014 DOI: 10.1073/pnas.1413640111

Note : The above story is based on materials provided by DOE/Lawrence Berkeley National Laboratory.

Fracture-controlled erodibility, great rock climbing

Matthes Crest, just south of Tuolumne Meadows, is a famous climbing locality. The ridge owes its prominence to the glacial erosion of tabular fracture clusters lying on either side of it. Credit: Frank Klein.

Tuolumne Meadows in Yosemite National Park is an iconic American landscape: It is a sub-alpine meadow surrounded by glacially sculpted granitic outcrops in the Sierra Nevada Mountains. Because of its accessibility and aesthetic appeal, it is a focal point for both vacationers (up to 4,200 people per day) and geoscientists. It also has historical significance: The idea for a Yosemite National Park came to John Muir and Robert Underwood Johnson over a campfire there.

As the largest sub-alpine meadow in the Sierra Nevada, Tuolumne Meadows is also a geomorphic anomaly: The presence of broad and open topography is commonly associated with bedrock erodibility. In contrast, the nearby vertical rock walls—including Cathedral Peak, Matthes Crest, and Lembert Dome—suggest bedrock durability. Despite these geomorphic differences, the entire region is underlain by the same lithology, the Cathedral Peak Granodiorite.

In this new study published in the November 2014 issue of GSA Today, authors Richard A. Becker, Basil Tikoff, Paul R. Riley, and Neal R. Iverson present evidence that this anomalous landscape is the result of preferential glacial erosion of highly fractured bedrock. In particular, tabular fracture clusters (TFCs) are common in the Cathedral Peak Granodiorite in the Tuolumne Meadows area. TFCs are dense networks of sub-parallel opening-mode fractures that are clustered into discrete, tabular (book-like) zones.

The authors conclude that Tuolumne Meadows resulted from ice flowing perpendicularly to high TFC concentrations. In contrast, ice flowing parallel to variable TFC concentrations formed the vertical rock walls. Thus, the exceptional rock climbing around Tuolumne Meadows is a direct result of fracture-controlled variations in erodibility—on the 10 meter to 100 meter scale—within a single lithology. This finding supports the contention that landscape evolution is strongly controlled by bedrock fracturing and that tectonic processes that result in fracturing may generally exert a fundamental and underappreciated role in geomorphology.

Reference:
“Preexisting fractures and the formation of an iconic American landscape: Tuolumne Meadows, Yosemite National Park, USA.” GSA Today. DOI: 10.1130/GSATG203A.1

Note : The above story is based on materials provided by Geological Society of America

Sediment supply drives floodplain evolution in Amazon Basin

Solimões, the section of the upper Amazon River. Image: Wikipedia.

A new study of the Amazon River basin shows lowland rivers that carry large volumes of sediment meander more across floodplains and create more oxbow lakes than rivers that carry less sediment.

The findings have implication for the Amazonian river system, which may be significantly altered by proposed mega-dams that would disrupt sediment supplies.

Researchers from Cardiff University’s School of Earth and Ocean Sciences examined 20 reaches within the Amazon Basin from Landsat imagery spanning nearly 20 years (1985 to 2013).

They found rivers transporting larger amounts of sediment migrated more, and noted that channel movement did not depend on either the slope of the channel or the river discharge.

The research gives scientists insight into the contrasting behavioural properties of rivers where sediment is an imposed variable – e.g. resulting from glacial, volcanic, or human activity – and rivers were the main sediment supply is from local bank erosion.

Dr José Constantine, Lecturer in Earth Sciences at Cardiff University’s School of Earth & Ocean Sciences and lead author of the paper said: “We found that the speed at which the meanders migrated for each of the rivers studied depended on the river’s supply of sand and silt. The meanders of rivers carrying more sediment migrated faster than those carrying less sediment, and were also more frequently cut off and abandoned to form U-shaped lakes. If sediment loads are reduced—by a dam, for example—meander migration is expected to slow, and thus the reshaping of the floodplain environment is affected.”

Reference:
Sediment supply as a driver of river meandering and floodplain evolution in the Amazon Basin, Nature Geoscience, dx.doi.org/10.1038/ngeo2282

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

Nizhnyaya Tunguska River

Map of the Yenisei basin that shows the Nizhnyaya Tunguska river

Nizhnyaya Tunguska is a river in Siberia, Russia, flows through the Irkutsk Oblast and the Krasnoyarsk Krai. The river is a right tributary of the Yenisei joining it at Turukhansk (see Siberian River Routes). Settlements on the river include Tura, Yukti and Simenga. The ice-free period on the Lower Tunguska starts in mid-June and ends in the first half of October.

Hydrography

The second largest right tributary of Yenisei joins it near town Turukhansk. According character of stream, constitution of river’s valley and its shores it can be divided into two parts: the first one starts at the source of the river and continues down to village Preobrazhenskoye and the second section of the river lies downstream of this village in a canyon-like relief.

Upper stream

The first part of Lower Tunguska has length 580 km and occupies wide valley with flat slopes which is formed basically of sand and clay deposits. The speed of flow at rafts reaches 0.4-0.6 m/s and drops significantly at the stretches of river’s channel.

This section of river has meandering channel approaching closely Lena River, another great Siberian river. The minimum distance between them is as short as 15 km in the neighbourhood of town Kirensk. All the upper stream of Nizhnyaya Tunguska is in range of the Irkutsk Oblast.

Lower stream

Downstream of village Preobrazhenskoye the Lower Tunguska flows in the narrow and deep valley with high, often rocky shores. Entire landscape here has volcanic origins with plateau Putorana to the north of the river, the relief alters the flow of Nizhnyaya Tunguska to west direction. The river channel frequently has lake-like widenings with lengths up to 20 km and longer. The locations with close approaches of crystalline layers create numerous rapids on the river. The most significant of them has its names: “Sakko”, “Vivinskiy”, “Uchamsky” and “Bolshoy” (Russian: Большой, Big). The locations of rapids on the river has relatively high speeds of water flux reaching 3–5 m/s. In some places downstream of rapids the river channel becomes very deep with maximum depths 60–100 m. In the river’s lowest flow, downstream of join with its tributary river Severnaya, Nizhnyaya Tunguska runs between limestone rocks, which steeply rise from the water. The speeds of flow here grows to 1-1.5 m/s.

The channel and water flow of river’s lower stream has its own distinguishing features, which can be met in some places at Nizhnyaya Tunguska, including follows:

  • The stripes of stones with sizes 10–40 cm, which stretches near water along shore line. This peculiar feature of arctic stony rivers with local name “bechevnick” is being formed during every seasonal period of ice drift and river inundation at spring. At some locations this sort of pebbles is polished and pressed together to that extent that it creates a cobbled road of its own kind.
  • The slopes of river canyon during its evolution underwent stone avalanches which formed stone runs with sizes of individual rocks as big as 1.5 m in diameter. These slide-slopes has local name “korga” and create zones of calm backwater downstream.
  • The stream in the channel of Lower Tunguska sometimes forms whirlpools. They originate downstream of cliffs which press the flow to the opposite shore. These whirlpools can reach depths of river floor down to 100 m deep and is most frequent during highwater periods at early summer.

Tributaries

The most significant tributaries of Nizhnyaya Tunguska are: right one — Eika, Kochechum, Yambuckan, Vivi, Tutonchana, Erachimo, Severnaya; left one – Nepa, Bolshaya Erema, Teteya, Ilimpeya, Nidym, Taymura, Uchami. The most prominent of them is Kochechum, which joins it from the north near Tura. The average annual discharge of Kochechum is 600 m3/s, the area of its basin is nearly 100,000 km².

In a whole, the right tributaries of Lower Tunguska dominate over left inflows adding a greater amount of water to the river than the left one. The river has not big lakes in its basin, the biggest lake is Vivi has surface area 229 km². Incoming amount of water to Nizhnyaya Tunguska is strongly season dependant.

Hydrology

The value of average water discharge of Lower Tunguska gives it eleventh place amongst largest rivers of Russia. The annual water discharge of river’s mouth is equal to 3,680 m3/s. The minimum value observed in 1967 was equal to 2,861 m3/s, the maximum one was 4,690 m3/s in 1974 or, respectively, for estuary of the river it corresponds to ~3,093 m3/s and ~5,070 m3/s. Water supply of the river is due to melting snow and summer rains. During winter season Lower Tunguska contains little water as its basin lies in the region of permafrost and it has not subterranean water sources. According hydrological observations during 52 years, the minimum average monthly discharge was equal to 27.8 m3/s in March 1969 — it was exceptionally dry winter — and the maximum value corresponds to June 1959 and is equal to 31,500 m3/s. The diagram below contains mean values of monthly average discharges calculated on the base of 52-year long period of observations at hydrological station “Bolshoy Porog”.

The 73 per cent of entire annual water yield corresponds to the period of spring-summer season.The amplitude of water level variations in the lower stream of Nizhnyaya Tunguska is very high and is highest among all notable rivers of Russia. The narrow places of river channel jam ice during its seasonal drift creating temporal dams which blocks normal water flow and raises water level up to 30–35 m above mean value. The summer break-up and drifting of ice passes very violently, it leaves traces in the form of torned apart uprooted trees, polished rocks etc. During some days of spring freshets the river’s discharge can peak at 74,000-112,000 m3/s and it supplies 50-60% of water volume to the lower stream of Yenisei river in the time of its seasonal inundation.

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

First Swedish hard-rock diamonds discovered

Microphotograph of garnet containing mineral inclusions of diamond, quartz, rutile and carbonates. Credit: Åke RoséZ

An Uppsala-led research group has presented the first verified discovery of diamonds in Swedish bedrock. The diamonds are small, but provide important clues to the geological evolution of rocks.

‘The diamonds we have found are of more scientific value than economical, but they are real diamonds’, says Jaroslaw Majka at the Centre for Experimental Mineralogy, Petrology and Geochemistry, who has led the study

While diamonds have reputedly been found loose while panning for gold in northern Sweden, none of these have been undisputed, and none have been found inside a rock.

When a continent collides with an island arc or another continent, parts of the crust of the subducted continent may be buried to depths exceeding 100 kilometres, and exposed to pressures which can cause formation of diamond. These are nowhere near the size of normal gemstone diamonds, but provide important clues to the geological evolution of rocks.

The burial process leads to a substantial density increase in silicon dioxide-rich rocks which should inhibit its exhumation (‘uplifting’) back to Earth’s surface. However, in rare cases diamond-bearing rocks can be observed at the surface. Such silicon dioxide-rich rocks containing diamonds have now been discovered in Sweden (the Snasahögarna mountains in Jämtland) by a group of researchers and students from Uppsala University (Jaroslaw Majka, Åke Rosen and Iwona Klonowska) together with colleagues from Slovakia, Germany, Poland and Japan.

This discovery calls for a general reconsideration of existing exhumation models of deeply buried continental crust. Jaroslaw Majka and the group have proposed that exhumation can be facilitated by local reduction of horizontal compressive stress to a level below the lithostatic pressure, resulting from the downward extraction of the Earth’s mantle wedge above the subducting continental crust. This new and innovative mechanism would work more or less like a mega-scale vacuum-cleaner, which sucks heavy diamond-bearing rocks back to the surface.

Notably, the discovery started with a Masters´ project of Åke Rosen, who presented his first results during a meeting organized by the Mineralogical Society of Sweden (SMS) in 2013.

The results are published in the article “Microdiamond discovered in the Seve Nappe (Scandinavian Caledonides) and its exhumation by the “vacuum-cleaner” mechanism”  in the highly-ranked journal Geology.

Reference:
“Microdiamond discovered in the Seve Nappe (Scandinavian Caledonides) and its exhumation by the ‘vacuum-cleaner’ mechanism.” Geology, G36108.1, first published on October 24, 2014, DOI: 10.1130/G36108.1

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

Massive geographic change may have triggered explosion of animal life

A new analysis from The University of Texas at Austin’s Institute for Geophysics suggests a deep oceanic gateway, shown in blue, developed between the Pacific and Iapetus oceans immediately before the Cambrian sea level rise and explosion of life in the fossil record, isolating Laurentia from the supercontinent Gondwanaland. Credit: Ian Dalziel

New analysis of geologic history may help solve the riddle of the ‘Cambrian explosion’

AUSTIN, Texas— A new analysis of geologic history may help solve the riddle of the “Cambrian explosion,” the rapid diversification of animal life in the fossil record 530 million years ago that has puzzled scientists since the time of Charles Darwin.

A paper by Ian Dalziel of The University of Texas at Austin’s Jackson School of Geosciences, published in the November issue of Geology, a journal of the Geological Society of America, suggests a major tectonic event may have triggered the rise in sea level and other environmental changes that accompanied the apparent burst of life.

The Cambrian explosion is one of the most significant events in Earth’s 4.5-billion-year history. The surge of evolution led to the sudden appearance of almost all modern animal groups. Fossils from the Cambrian explosion document the rapid evolution of life on Earth, but its cause has been a mystery.

The sudden burst of new life is also called “Darwin’s dilemma” because it appears to contradict Charles Darwin’s hypothesis of gradual evolution by natural selection.

“At the boundary between the Precambrian and Cambrian periods, something big happened tectonically that triggered the spreading of shallow ocean water across the continents, which is clearly tied in time and space to the sudden explosion of multicellular, hard-shelled life on the planet,” said Dalziel, a research professor at the Institute for Geophysics and a professor in the Department of Geological Sciences.

Beyond the sea level rise itself, the ancient geologic and geographic changes probably led to a buildup of oxygen in the atmosphere and a change in ocean chemistry, allowing more complex life-forms to evolve, he said.

The paper is the first to integrate geological evidence from five present-day continents — North America, South America, Africa, Australia and Antarctica — in addressing paleogeography at that critical time.

Dalziel proposes that present-day North America was still attached to the southern continents until sometime into the Cambrian period. Current reconstructions of the globe’s geography during the early Cambrian show the ancient continent of Laurentia — the ancestral core of North America — as already having separated from the supercontinent Gondwanaland.

In contrast, Dalziel suggests the development of a deep oceanic gateway between the Pacific and Iapetus (ancestral Atlantic) oceans isolated Laurentia in the early Cambrian, a geographic makeover that immediately preceded the global sea level rise and apparent explosion of life.

“The reason people didn’t make this connection before was because they hadn’t looked at all the rock records on the different present-day continents,” he said.

The rock record in Antarctica, for example, comes from the very remote Ellsworth Mountains.

“People have wondered for a long time what rifted off there, and I think it was probably North America, opening up this deep seaway,” Dalziel said. “It appears ancient North America was initially attached to Antarctica and part of South America, not to Europe and Africa, as has been widely believed.”

Although the new analysis adds to evidence suggesting a massive tectonic shift caused the seas to rise more than half a billion years ago, Dalziel said more research is needed to determine whether this new chain of paleogeographic events can truly explain the sudden rise of multicellular life in the fossil record.

“I’m not claiming this is the ultimate explanation of the Cambrian explosion,” Dalziel said. “But it may help to explain what was happening at that time.”

Reference:
First published online September 26, 2014, doi: 10.1130/G35886.1

Note : The above story is based on materials provided by University of Texas at Austin

Study of Chile earthquake finds new rock structure that affects earthquake rupture

University of Liverpool Seismologists monitored aftershocks from the 2010 quake using networks of sensitive recording instruments located on the Pacific seabed and in Chile. These measurements were used to generate the 3-D images of the deep subsurface. Credit: Stephen Hicks, University of Liverpool

Researchers from the University of Liverpool have found an unusual mass of rock deep in the active fault line beneath Chile which influenced the rupture size of a massive earthquake that struck the region in 2010.

The geological structure, which was not previously known about, is unusually dense and large for this depth in the Earth’s crust. The body was revealed using 3-D seismic images of Earth’s interior based on the monitoring of vibrations on the Pacific seafloor caused by aftershocks from the magnitude 8.8 Chile earthquake. This imaging works in a similar way to CT scans that are used in hospitals.

Analysis of the 2010 earthquake also revealed that this structure played a key role in the movement of the fault, causing the rupture to suddenly slow down.

Seismologists think that the block of rock was once part of Earth’s mantle and may have formed around 220 million years ago, during the period of time known as the Triassic.

Liverpool Seismologist, Stephen Hicks from the School of Environmental Sciences, who led the research, said: “It was previously thought that dense geological bodies in an active fault zone may cause more movement of the fault during an earthquake.”

“However, our research suggests that these blocks of rock may in fact cause the earthquake rupture to suddenly slow down. But this slowing down can generate stronger shaking at the surface, which is more damaging to man-made structures.”

“It is now clear that ancient geology plays a big role in the generation of future earthquakes and their subsequent aftershocks.”

Professor Andreas Rietbrock, head of the Earthquake Seismology and Geodynamics research group added: “This work has clearly shown the potential of 3D ‘seismic’ images to further our understanding of the earthquake rupture process.

We are currently establishing the Liverpool Earth Observatory (LEO), which will allow us together with our international partners, to carry out similar studies in other tectonically active regions such as northern Chile, Indonesia, New Zealand and the northwest coast United States. This work is vital for understanding risk exposure in these countries from both ground shaking and tsunamis.”

Chile is located on the Pacific Ring of Fire, where the sinking of tectonic plates generates many of the world’s largest earthquakes.

The 2010 magnitude 8.8 earthquake in Chile is one of the best-recorded earthquakes, giving seismologists the best insight to date into the ruptures of mega-quakes.

The research, funded by the Natural Environment Research Council, is published in the journal Earth and Planetary Science Letters.

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

Fossil treasures at risk in Morocco desert town

A REPLICA of tyrannosaurus skeleton is displayed in Erfoud, Morocco.—AFP

ERFOUD: In the middle of a sprawling palm grove in Morocco’s remote eastern desert, inhabitants of an oasis town watch over a rare and vanishing treasure.

At the entrance of a traditional town house visitors are welcomed by a piece of Erfoud’s unusual bounty: the petrified skeleton of a prehistoric creature.

This huge ammonite is one of hundreds of archaeological jewels in and around the town of 30,000 people, which geologists and archaeologists have called “the largest open air fossil museum in the world”.

During the Palaeozoic era — about 540 million to 250 million years ago — the southeast of Morocco lay under the sea, according to Abdelmajid Messoudi, who runs a gift shop in the town.

Local collector Abdeslam Kassmi says the area is today home to “close to 500 varieties of fossils spread over 100 square kilometres [40 square miles]” including trilobites, which are between 410 and 500 million years old.

But scientists warn that over-excavation and lax controls on fossil sales are seriously damaging Erfoud’s archaeological and cultural heritage.

In the town’s museum, once an exhibition space, a fine cloud of dust hangs above craftsmen who are working to cut, carve and polish the fossils pulled from the ground.

After transporting blocks of stone from a quarry on the outskirts of town, “workers cut them into pieces, then the artisans sculpt them into diverse objects such as fountains, bathtubs and even tables,” Massoudi says.

In a region traditionally renowned for its dates — Morocco is one of the world’s largest producers — the fossil trade is a rare year-round source of sustainable income for the people of Erfoud.

It also allows the town to attract tourists, some of whom are seeking to enlarge their prehistoric collections.

‘Scientific value’

Ibrahim, a craftsman in his 60s, has spent half his life sculpting fossils, a discipline he says requires “time, dexterity and patience”.

“You need to work slowly so you don’t damage these pieces, which are often very valuable. Working on just one stone can take up to 20 hours,” said Ibrahim.

Away from the artisans and artefacts of Erfoud’s museum, several other buildings house some of the town’s rarest and oldest fossils.

In one of these treasure troves, Kassmi jealously guards dozens of items.

Their value is hard to estimate. While some of the smallest pieces are available to buy — with prices starting at around 300 euros ($380) — others are part of Kassmi’s private collection that he has established “as a legacy for generations to come,” he says.

Among fossils telling the prehistoric history of the area are petrified skeletons of dinosaurs dating back 65 million years as well as the solidified remains of turtles and crocodiles.

But such historical jewels are under threat, according to Lachen Kabiri, professor at the nearby University of Errachidia.

He cites over-excavation, the rise in exploration sites and traders selling fossils at knock-down prices as causes for concern.

“Erfoud is world famous but its scientific development” is lacking, he says.

Morocco’s desert southeast is part of a network of biosphere reserves protected by Unesco and a 1970 agreement that prevents the illegal import and export of cultural artefacts in these areas.

Without specifically mentioning fossils, a Moroccan law also prohibits the illicit trade.

Nevertheless, rare fossils are available to buy in bazaars across Morocco’s southeast, and even in the tourist hotspot of Marrakech. Many end up in museums in Europe and North America.

No data exists on the rate of fossil theft in the region, but Kabiri wants Moroccan authorities to create “ecological reserves” and increase efforts to track down and regain Ersoul’s stolen ancient riches.

Video : Fossil treasures at risk in Morocco desert town

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

Fossil treasures at risk in Morocco desert town

Hundreds of archeological jewels in and around the town of 30,000 people prompt geologists and archeologists to call the Erfoud area “the largest open air fossil museum in the world”.

Magma Pancakes beneath Lake Toba

Lake Toba, Indonesia. Credit: © saidin jusoh / Fotolia

The tremendous amounts of lava that are emitted during super-eruptions accumulate over millions of years prior to the event in the Earth’s crust. These reservoirs consist of magma that intrudes into the crust in the form of numerous horizontally oriented sheets resting on top of each other like a pile of pancakes.

A team of geoscientists from Novosibirsk, Paris and Potsdam presents these results in the current issue of Science. The scientists investigate the question on where the tremendous amounts of material that are ejected to from huge calderas during super-eruptions actually originate. Here we are not dealing with large volcanic eruptions of the size of Pinatubo of Mount St. Helens, here we are talking about extreme events: The Toba caldera in the Sumatra subduction zone in Indonesia originated from one of the largest volcanic eruption in recent Earth history, about 74,000 years ago. It emitted the enormous amount of 2,800 cubic kilometers of volcanic material with a dramatic global impact on climate and environment. Hereby, the 80 km long Lake Toba was formed.

Geoscientists were interested in finding out: How can the gigantic amounts of eruptible material required to form such a super volcano accumulate in the Earth’s crust. Was this a singular event thousands of years ago or can it happen again?

Researchers from the GFZ German Research Centre for Geosciences successfully installed a seismometer network in the Toba area to investigate these questions and provided the data to all participating scientists via the GEOFON data archive. GFZ scientist, Christoph Sens-Schönfelder, a co-author of the study explains: “With a new seismological method we were able to investigate the internal structure of the magma reservoir beneath the Toba-caldera. We found that the middle crust below the Toba supervolcano is horizontally layered.” The answer thus lies in the structure of the magma reservoir. Here, below 7 kilometers the crust consists of many, mostly horizontal, magmatic intrusions still containing molten material.

New seismological technique

It was already suspected that the large volume of magma ejected during the supervolcanic eruption had slowly accumulated over the last few millions of years in the form of consequently emplaced intrusions. This could now be confirmed with the results of field measurements. The GFZ scientists used a novel seismological method for this purpose. Over a six-month period they recorded the ambient seismic noise, the natural vibrations which usually are regarded as disturbing signals. With a statistical approach they analyzed the data and discovered that the velocity of seismic waves beneath Toba depends on the direction in which the waves shear the Earth’s crust. Above 7 kilometers depth the deposits of the last eruption formed a zone of low velocities. Below this depth the seismic anisotropy is caused by horizontally layered intrusions that structure the reservoir like a pile of pancakes. This is reflected in the seismic data.

Supervolcanoes

Not only in Indonesia, but also in other parts of the world there are such supervoclcanoes, which erupt only every couple of hundred thousand years but then in gigantic eruptions. Because of their size those volcanoes do not build up mountains but manifest themselves with their huge carter formed during the eruption — the caldera. Other known supervolcanoes include the area of the Yellow-Stone-Park, volcanoes in the Andes, and the caldera of Lake-Taupo in New Zealand. The present study helps to better understand the processes that lead to such super-eruptions.

Reference:
K. Jaxybulatov, N. M. Shapiro, I. Koulakov, A. Mordret, M. Landes, C. Sens-Schonfelder. A large magmatic sill complex beneath the Toba caldera. Science, 2014; 346 (6209): 617 DOI: 10.1126/science.1258582

Note : The above story is based on materials provided by Helmholtz Centre Potsdam – GFZ German Research Centre for Geosciences.

Seeing dinosaur feathers in a new light

Feathers close up (stock image). The researchers’ hypothesis: The evolution of feathers made dinosaurs more colorful, which in turn had a profoundly positive impact on communication, the selection of mates and on dinosaurs’ procreation. Credit: © thawats / Fotolia

Why were dinosaurs covered in a cloak of feathers long before the early bird species Archaeopteryx first attempted flight? Researchers from the University of Bonn and the University of Göttingen attempt to answer precisely that question in their article “Beyond the Rainbow” in the latest issue of the journal Science. The research team postulates that these ancient reptiles had a highly developed ability to discern color. Their hypothesis: The evolution of feathers made dinosaurs more colorful, which in turn had a profoundly positive impact on communication, the selection of mates and on dinosaurs’ procreation.

The suggestion that birds and dinosaurs are close relatives dates back to the 19th century, the time when the father of evolutionary theory, Charles Darwin, was hard at work. But it took over 130 years for the first real proof to come to light with numerous discoveries of the remains of feathered dinosaurs, primarily in fossil sites in China. Thanks to these fossil finds, we now know that birds descend from a branch of medium-sized predatory dinosaurs, the so-called theropods. Tyrannosaurus rex and also velociraptors, made famous by the film Jurassic Park, are representative of these two-legged meat eaters. Just like later birds, these predatory dinosaurs had feathers — long before Archaeopteryx lifted itself off the ground. But why was this, particularly when dinosaurs could not fly?

Dinosaurs’ color vision

“Up until now, the evolution of feathers was mainly considered to be an adaptation related to flight or to warm-bloodedness, seasoned with a few speculations about display capabilities” says the article’s first author, Marie-Claire Koschowitz of the Steinmann Institute for Geology, Mineralogy and Paleontology at the University of Bonn. “I was never really convinced by any of these theories. There has to be some particularly important feature attached to feathers that makes them so unique and caused them to spread so rapidly amongst the ancestors of the birds we know today,” explains Koschowitz. She now suggests that this feature is found in dinosaurs’ color vision. After analyzing dinosaurs’ genetic relationships to reptiles and birds, the researcher determined that dinosaurs not only possessed the three color receptors for red, green and blue that the human eye possesses, but that they, like their closest living relatives, crocodiles and birds, were probably also able to see extremely short-wave and ultraviolet light by means of an additional receptor. “Based on the phylogenetic relationships and the presence of tetrachromacy in recent tetrapods it is most likely that the stem species-of all terrestrial vertebrates had photo receptors to detect blue, green, red and uv,” says Dr. Christian Fischer of the University of Göttingen.

This makes the world much more colorful for most animals than it is for human beings and other mammals. Mammals generally have rather poor color vision or even no color vision at all because they tended to be nocturnal during the early stages of their evolution. In contrast, numerous studies on the social behavior and choice of mates among reptiles and birds, which are active during the day, have shown that information transmitted via color exerts an enormous influence on those animals’ ability to communicate and procreate successfully.

Feathers allowed for more visible signals than did fur

We know from dinosaur fossil finds that the precursors to feathers resembled hairs similar to mammals’ fur. They served primarily to protect the smaller predatory dinosaurs — which would eventually give rise to birds — from losing too much body heat. The problem with these hair-like forerunners of feathers and with fur is that neither allow for much color, but tend instead to come in basic patterns of brown and yellow tones as well as in black and white. Large flat feathers solved this shortcoming by providing for the display of color and heat insulation at the same time. Their broad surface area, created by interlocked strands of keratin, allows for the constant refraction of light, which consequently produces what is referred to as structural coloration. This refraction of light is absolutely necessary to produce colors such as blue and green, the effect of metallic-like shimmering or even colors in the UV spectrum. “Feathers enable a much more noticeable optical signaling than fur would allow. Iridescent birds of paradise and hummingbirds are just two among a wealth of examples,” explains Koschowitz.

This work means we must see the evolution of feathers in a whole new light. They provided for a nearly infinite variety of colors and patterns while simultaneously providing heat insulation. Prof. Dr. Martin Sander of the University of Bonn’s Steinmann Institute summarizes the implications of this development: “This allowed dinosaurs to not only show off their colorful feathery attire, but to be warm-blooded animals at the same time — something mammals never managed.”

Reference:
M.-C. Koschowitz, C. Fischer, M. Sander. Beyond the rainbow. Science, 2014; 346 (6208): 416 DOI: 10.1126/science.1258957

Note : The above story is based on materials provided by Universität Bonn

New Study Finds Oceans Arrived Early to Earth

In this illustration of the early solar system, the dashed white line represents the snow line — the transition from the hotter inner solar system, where water ice is not stable (brown) to the outer Solar system, where water ice is stable (blue). Two possible ways that the inner solar system received water are: water molecules sticking to dust grains inside the “snow line” (as shown in the inset) and carbonaceous chondrite material flung into the inner solar system by the effect of gravity from protoJupiter. With either scenario, water must accrete to the inner planets within the first ca. 10 million years of solar system formation. Credit: Illustration by Jack Cook, Woods Hole Oceanographic Institution

Earth is known as the Blue Planet because of its oceans, which cover more than 70 percent of the planet’s surface and are home to the world’s greatest diversity of life. While water is essential for life on the planet, the answers to two key questions have eluded us: where did Earth’s water come from and when?

While some hypothesize that water came late to Earth, well after the planet had formed, findings from a new study led by scientists at the Woods Hole Oceanographic Institution (WHOI) significantly move back the clock for the first evidence of water on Earth and in the inner solar system.

“The answer to one of the basic questions is that our oceans were always here. We didn’t get them from a late process, as was previously thought,” said Adam Sarafian, the lead author of the paper published Oct. 31, 2014, in the journal Science and a MIT/WHOI Joint Program student in the Geology and Geophysics Department.

One school of thought was that planets originally formed dry, due to the high-energy, high-impact process of planet formation, and that the water came later from sources such as comets or “wet” asteroids, which are largely composed of ices and gases.

“With giant asteroids and meteors colliding, there’s a lot of destruction,” said Horst Marschall, a geologist at WHOI and coauthor of the paper. “Some people have argued that any water molecules that were present as the planets were forming would have evaporated or been blown off into space, and that surface water as it exists on our planet today, must have come much, much later — hundreds of millions of years later.”

The study’s authors turned to another potential source of Earth’s water — carbonaceous chondrites. The most primitive known meteorites, carbonaceous chondrites, were formed in the same swirl of dust, grit, ice and gasses that gave rise to the sun some 4.6 billion years ago, well before the planets were formed.

“These primitive meteorites resemble the bulk solar system composition,” said WHOI geologist and coauthor Sune Nielsen. “They have quite a lot of water in them, and have been thought of before as candidates for the origin of Earth’s water.”

In order to determine the source of water in planetary bodies, scientists measure the ratio between the two stable isotopes of hydrogen: deuterium and hydrogen. Different regions of the solar system are characterized by highly variable ratios of these isotopes. The study’s authors knew the ratio for carbonaceous chondrites and reasoned that if they could compare that to an object that was known to crystallize while Earth was actively accreting then they could gauge when water appeared on Earth.

To test this hypothesis, the research team, which also includes Francis McCubbin from the Institute of Meteoritics at the University of New Mexico and Brian Monteleone of WHOI, utilized meteorite samples provided by NASA from the asteroid 4-Vesta. The asteroid 4-Vesta, which formed in the same region of the solar system as Earth, has a surface of basaltic rock — frozen lava. These basaltic meteorites from 4-Vesta are known as eucrites and carry a unique signature of one of the oldest hydrogen reservoirs in the solar system. Their age — approximately 14 million years after the solar system formed — makes them ideal for determining the source of water in the inner solar system at a time when Earth was in its main building phase. The researchers analyzed five different samples at the Northeast National Ion Microprobe Facility — a state-of-the-art national facility housed at WHOI that utilizes secondary ion mass spectrometers. This is the first time hydrogen isotopes have been measured in eucrite meteorites.

The measurements show that 4-Vesta contains the same hydrogen isotopic composition as carbonaceous chondrites, which is also that of Earth. That, combined with nitrogen isotope data, points to carbonaceous chondrites as the most likely common source of water.

“The study shows that Earth’s water most likely accreted at the same time as the rock. The planet formed as a wet planet with water on the surface,” Marschall said.

While the findings don’t preclude a late addition of water on Earth, it shows that it wasn’t necessary since the right amount and composition of water was present at a very early stage.

“An implication of that is that life on our planet could have started to begin very early,” added Nielsen. “Knowing that water came early to the inner solar system also means that the other inner planets could have been wet early and evolved life before they became the harsh environments they are today.”

Reference:
A. R. Sarafian, S. G. Nielsen, H. R. Marschall, F. M. McCubbin, B. D. Monteleone. Early accretion of water in the inner solar system from a carbonaceous chondrite-like source. Science, 2014; 346 (6209): 623 DOI: 10.1126/science.1256717

Note : The above story is based on materials provided by Woods Hole Oceanographic Institution.

Lack of oxygen delayed the rise of animals on Earth

Christopher Reinhard and Noah Planavsky conduct research for the study in China. Credit: Yale University

Geologists are letting the air out of a nagging mystery about the development of animal life on Earth.

Scientists have long speculated as to why animal species didn’t flourish sooner, once sufficient oxygen covered Earth’s surface. Animals began to prosper at the end of the Proterozoic period, about 800 million years ago — but what about the billion-year stretch before that, when most researchers think there also was plenty of oxygen?

Well, it seems the air wasn’t so great then, after all.

In a study published Oct. 30 in Science, Yale researcher Noah Planavsky and his colleagues found that oxygen levels during the “boring billion” period were only 0.1% of what they are today. In other words, Earth’s atmosphere couldn’t have supported a diversity of creatures, no matter what genetic advancements were poised to occur.

“There is no question that genetic and ecological innovation must ultimately be behind the rise of animals, but it is equally unavoidable that animals need a certain level of oxygen,” said Planavsky, co-lead author of the research along with Christopher Reinhard of the Georgia Institute of Technology. “We’re providing the first evidence that oxygen levels were low enough during this period to potentially prevent the rise of animals.”

The scientists found their evidence by analyzing chromium (Cr) isotopes in ancient sediments from China, Australia, Canada, and the United States. Chromium is found in Earth’s continental crust, and chromium oxidation is directly linked to the presence of free oxygen in the atmosphere.

Specifically, the team studied samples deposited in shallow, iron-rich ocean areas, near the shore. They compared their data with other samples taken from younger locales known to have higher levels of oxygen.

Oxygen’s role in controlling the first appearance of animals has long vexed scientists. “We were missing the right approach until now,” Planavsky said. “Chromium gave us the proxy.” Previous estimates put the oxygen level at 40% of today’s conditions during pre-animal times, leaving open the possibility that oxygen was already plentiful enough to support animal life.

In the new study, the researchers acknowledged that oxygen levels were “highly dynamic” in the early atmosphere, with the potential for occasional spikes. However, they said, “It seems clear that there is a first-order difference in the nature of Earth surface Cr cycling” before and after the rise of animals.

“If we are right, our results will really change how people view the origins of animals and other complex life, and their relationships to the co-evolving environment,” said co-author Tim Lyons of the University of California-Riverside. “This could be a game changer.”

“There’s a lot of interest right now in a broader discussion surrounding the role that environmental stability played in the evolution of complex life, and we think our results are a significant contribution to that,” Reinhard said.

Funding sources for the research included the NASA Exobiology Program and the National Science Foundation’s Earth-Life Transitions program, awarded to Planavsky, Reinhard, and Lyons.

The other members of the research team included Xiangli Wang, a postdoctoral fellow at Yale; Thomas Johnson, of the University of Illinois; Danielle Thomson, of Carleton University; Peter McGoldrick, of the University of Tasmania; and Woodward Fischer, of the California Institute of Technology.

Reference:
N. J. Planavsky, C. T. Reinhard, X. Wang, D. Thomson, P. McGoldrick, R. H. Rainbird, T. Johnson, W. W. Fischer, T. W. Lyons. Low Mid-Proterozoic atmospheric oxygen levels and the delayed rise of animals. Science, 2014; 346 (6209): 635 DOI: 10.1126/science.1258410

Note: The above story is based on materials provided by Yale University. The original article was written by Jim Shelton.

They know the drill: Leading the league in boring through ice sheets

Kristina Slawny (left) and Jay Johnson (right) stand next to the Deep Ice Sheet Coring Drill, designed and managed by the Ice Drilling Design and Operations group at the University of Wisconsin-Madison. Credit: Jay Johnson

Wisconsin is famous for its ice fishers — the stalwarts who drill holes through lake ice in the hope of catching a winter dinner. Less well known are the state’s big-league ice drillers — specialists who design huge drills and use them to drill deep into ice in Greenland and Antarctica, places where even summer seems like winter.

The quarry at these drills includes some of the biggest catches in science.

A hot-water drill designed and built at the University of Wisconsin-Madison’s Space Science and Engineering Center (SSEC) and the Physical Sciences Laboratory was critical to the success of IceCube, a swarm of neutrino detectors at the South Pole that has opened a new frontier in astronomy.

Hollow coring drills designed and managed by UW-Madison’s Ice Drilling Design and Operations (IDDO) program are used to extract ice cores that can analyze the past atmosphere, says Shaun Marcott, an assistant professor of geoscience at UW-Madison. Marcott was the first author of a paper published today in the journal Nature documenting carbon dioxide in the atmosphere between 23,000 and 9,000 years ago, based on data from an 11,000-foot hole in Antarctica.

The ice drilling program traces its roots to Charles Bentley, a legendary UW-Madison glaciologist and polar expert. The program is funded by the National Science Foundation and housed in the Space Science and Engineering Center.

“Building on Charlie’s achievements, IceCube enhanced our competency of drilling expertise,” says IDDO principal investigator Mark Mulligan. “A 2000 award from the National Science Foundation brought in more engineers and technicians who understand coring and drilling.”

IDDO program director Kristina Slawny spent six austral summers on the West Antarctic Ice Sheet Divide project, which provided cores for Marcott’s climate study. “It’s an experience like no other,” she says. “We sleep in unheated single tents that get really warm in the day and quite cold at night.”

Crew compatibility is “huge,” says Slawny, “and in a remote environment we focus on it, so we’ve had really good continuity in our driller hiring. Once a group has worked together, we want them to stay. When everyone is cold and tired, they can get agitated easily, but for the most part, the crew was happy to be down there.”

Still, “everything goes wrong, even the stuff you don’t expect,” she says. “One year it’s mechanical, the next year it’s electrical. One of our staffers, Jay Johnson, is a brilliant engineer and machinist who can fix anything, but it can take long hours and sleepless nights to keep the drill running.”

Many projects under development require mobile drills, says Mulligan. “The science community has said we need a certain type of core in a certain location, but you may only be able to get there with a helicopter or small plane. That forces us to design smaller, or make something that can be set up relatively quickly. Agile and mobile are very big words.”

As concerns about the climatic effects of greenhouse gases mount, Marcott says deep, old ice offers a ground-truthing function. “How do you know that today’s carbon dioxide variations are even meaningful?” he asks. “We have only 50 years of instrument data.”

Climate studies require a much longer horizon, Marcott adds. “When I measure CO2 from 20,000 years ago, I actually have air from 20,000 years ago, and so I can measure the concentration of CO2 directly. There is no other way to do that.”

Much of the credit, Marcott says, is due to UW’s ace ice drillers. “Without the ice cores being as pristine as they are, without the drillers being able to take out every single core unbroken to provide us with a 70,000-year record of CO2, we would not be able to understand how this powerful greenhouse gas has affected our planet in the past.”

Today, carbon dioxide is growing at 2 parts per million per year — 20 times faster than the preindustrial situation recorded in the ice cores. But even at the slower rate, climate reacted very quickly to changing levels of the key greenhouse gas, Marcott says. “It’s not just a gradual change from an ice age to an interglacial. We need to know how the Earth system works, but without these ice cores, and the great effort from the drilling team, we would not be in a position to know.”

Note : The above story is based on materials provided by University of Wisconsin-Madison. The original article was written by David Tenenbaum.

Icelandic volcano system has been spewing lava since early September

This evening view of a lava fountain at the volcano’s central vent shows striking contrast between molten lava and surrounding rock and glacial ice. Erupting lava is thrown 50-100 meters into the air above the vents.

Jeffrey Karson, a Syracuse University geologist who recently traveled to Iceland to monitor the early stages of the eruption, says the lava field now covers more than 22 square miles (or 14,000 acres), nearly the size of Manhattan.

Iceland, which is made up of lava flows, hasn’t witnessed anything of the sort in 40 years. The country’s most recent major eruption took place in 2010, when ash from the Eyafjallajökull volcano disrupted air travel for more than a week across parts of Europe.

“The lava that erupted at Eyafjallajökull was much less extensive than what we’re seeing now,” says Karson, an Earth sciences professor in the College of Arts and Sciences. “This one doesn’t show any signs of slowing down.

An expert in structural geology and tectonics and the co-founder of the Syracuse University Lava Project, Karson regularly travels to Iceland to study faulting and volcanic structures. His latest trip in September gave him a first-hand glimpse—much of it from close range—of the ongoing eruption fed by the Bárðarbunga volcano, located under the country’s most extensive glacier. On average, the system produces enough lava, every five minutes, to fill an area the size of a football field.

“The eruption is the result of the spreading apart of two tectonic plates [the Eurasian Plate and North American Plate], which are literally pulling Iceland apart,” says Karson, who is collaborating with investigators at the University of Iceland’s Institute of Earth Sciences. “As the plates diverge, magma from deep in the Earth is injected upward to fill the gaps. Individual eruptions can last for months, or even years.”

Karson adds that the eruption has been one of the most closely studied ever: “Iceland is a natural laboratory that allows us to study volcanoes and faulting across a range of disciplines, including geochemistry, geophysics, geology and petrology. Everything we learn there adds to our understanding of how the Earth works.”

An overflight view taken on Sept. 8 shows the main eruptive site, known as “Baugur” (Icelandic for “ring” or “circle”). The eruption is the result of the spreading apart of two tectonic plates, the Eurasian and North American.
Jeffrey Karson, an expert in structural geology and tectonics, gets within two kilometers of the main eruptive vents. His collaboration with investigators at the University of Iceland Institute of Earth Sciences gives him a first-hand view of the early stages of the eruption.
Open fissures above subsurface magma conduit or channels feed the volcano’s eruptive vents.
A view of the eruptive plume, captured Sept. 9, was taken from about 50 kilometers to the north of the main vents. Jeffrey Karson, Earth sciences professor in the College of Arts and Sciences, describes this eruption as one of the most closely studied ever, with Iceland as a natural laboratory.

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

Urban seismic network detects human sounds

Vibrational signature of Blue Line Metro trains as they move through Long Beach, Calif. Riahi/Scripps Oceanographic Institution

When listening to the Earth, what clues can seismic data reveal about the impact of urban life? Although naturally occurring vibrations have proven extremely useful to seismologists, until now the vibrations caused by humans haven’t been explored in any real depth.

Scripps Institution of Oceanography researchers Nima Riahi, a postdoctoral fellow, and Peter Gerstoft, a geophysicist, will describe their efforts to tap into an urban seismic network to monitor the traffic of trains, planes, automobiles and other modes of human transport. They will present the work this week at the 168th Meeting of the Acoustical Society of America (ASA), which will be held October 27-31, 2014, at the Indianapolis Marriott Downtown Hotel.

Traffic in urban areas generates both acoustic and seismic “noise.” While seismic noise typically isn’t perceptible by humans, it could prove to be an interesting data source for traffic information systems in the near future.

“Earlier this year an industrial partner offered us access to a large vibration dataset acquired over the city of Long Beach, Calif., so we seized the opportunity,” explained Riahi.

This particular dataset consists of a 5,300-geophone network — deployed as part of a hydrocarbon industry survey — covering an area of more than 70 km2. Geophone devices are commonly used to record energy waves reflected by the subsurface geology as a way of mapping out geologic structures or track earthquakes.

“By recording vibrations via geophones spaced roughly every 100 meters (300 feet), we were able to look into activity in Long Beach with a resolution below a typical city block,” said Riahi.

This begs the question: What urban processes can the space and time structure of vibrational intensity reveal?

Much to their surprise, Riahi and Gerstoft discovered that “by using mostly standard signal processing, we can follow a metro schedule, count aircraft and their acceleration on a runway, and even see larger vehicles on a 10-lane highway.” More refined techniques and algorithms may well uncover many other types of humanmade signals within the Earth.

These findings indicate that urban vibrations can serve as a new data source to observe cities. “Traffic monitoring tasks are an important and obvious application, but other uses may be involved in urban area characterization in which the type and schedule of activities can be visualized, so that it’s possible to vibrationally identify industrial, residential or office zones,” Riahi added.

Note : The above story is based on materials provided by Acoustical Society of America (ASA).

Rio Grande River

Map of the Rio Grande drainage basin

The Rio Grande is a river that flows from south central Colorado in the United States to the Gulf of Mexico. Along the way it forms part of the Mexico–United States border. According to the International Boundary and Water Commission, its total length was 1,896 miles (3,051 km) in the late 1980s, though course shifts occasionally result in length changes. Depending on how it is measured, the Rio Grande is the fourth or fifth longest river system in North America.

The river serves as a natural border between the U.S. state of Texas and the Mexican states of Chihuahua, Coahuila, Nuevo León, and Tamaulipas. A very short stretch of the river serves as the boundary between the U.S. states of Texas and New Mexico. Since the mid–20th century, heavy water consumption of farms and cities along with many large hydroelectric dams on the river has left only 20% of its natural discharge to flow to the Gulf. Near the river’s mouth, the heavily irrigated Rio Grande Valley is an important agricultural region. The Rio Grande is one of 19 Great Waters recognized by America’s Great Waters Coalition.

The Rio Grande’s watershed covers 182,200 square miles (472,000 km2). Many endorheic basins are situated within, or adjacent to, the Rio Grande’s basin, and these are sometimes included in the river basin’s total area, increasing its size to about 336,000 square miles (870,000 km2).

Geography

The Rio Grande rises in the western part of the Rio Grande National Forest in the U.S. state of Colorado. The river is formed by the joining of several streams at the base of Canby Mountain in the San Juan Mountains, just east of the Continental Divide. From there, it flows through the San Luis Valley, then south into New Mexico, passing through Española, Albuquerque, and Las Cruces to El Paso, Texas and Ciudad Juárez, Chihuahua.

Below El Paso it serves as part of the border between the United States and Mexico. The official river border measurement ranges from 889 miles (1,431 km) to 1,248 miles (2,008 km), depending on how the river is measured. A major tributary, the Rio Conchos, enters at Ojinaga, Chihuahua, below El Paso, and supplies most of the water in the border segment. Other well-known tributaries include the Pecos and the smaller Devils, which join the Rio Grande on the site of Amistad Dam. Despite its name and length, the Rio Grande is not navigable by ocean-going ships, nor do smaller passenger boats or cargo barges use it as a route. It is barely navigable at all, except by small boats in a few places.

The Rio Grande rises in high mountains and flows for much of its length at high elevation; El Paso is 3,762 feet (1,147 m) above sea level. In New Mexico, the river flows through the Rio Grande rift from one sediment-filled basin to another, cutting canyons between the basins and supporting a fragile bosque ecosystem on its flood plain. From El Paso eastward, the river flows through desert. Only in the sub-tropical lower Rio Grande Valley is there extensive irrigated agriculture. The river ends in a small sandy delta at the Gulf of Mexico. During portions of 2001 and 2002 the mouth of the Rio Grande was blocked by a sandbar. In the fall of 2003 the sandbar was cleared by high river flows of about 7,063 cubic feet per second (200 m3/s).

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

Gas-spewing Icelandic volcano stuns scientists

Record amounts of gas have spewed from Iceland’s Holuhraun plain. © Arctic-Images/Corbis

Icelandic sunrises and sunsets have been tinged blood red, of late. Above the maritime bustle of Reykjavik’s harbour and the city’s towering concrete Hallgrímskirkja church, volcanic pollution gives the skies an eerie glow.

For eight weeks, lava has been spurting out of a fissure in the ground radiating from the Bárðarbunga volcano, about 250 kilometres from Reykjavik. Sulphur dioxide has been spurting too — 35,000 tonnes of it a day, more than twice the amount spewing from all of Europe’s smokestacks. The gas has spread across the Icelandic countryside, causing people to wheeze and trapping some indoors.

The record-setting amount of pollution has surprised even volcanologists in the middle of a major project funded by the European Union to understand the island’s fiery activity. They had been preparing for a repeat of the 2010 Eyjafjallajökull eruption, which led to a billowing ash plume that grounded planes across Europe. “Everybody was expecting a big ash cloud, and now we have something totally different,” says Anja Schmidt, an atmospheric modeller at the University of Leeds, UK, who studies how volcanic gases spread.

The timing of the eruption was just about perfect for the project, called FUTUREVOLC. The initiative aims to use Iceland as a natural laboratory to understand how magma makes its way from deep in Earth’s crust to the surface — to do so, its organizers have focused on four of Iceland’s most active volcanoes, one of which is Bárðarbunga. The researchers used extra seismometers and global-positioning-system (GPS) stations to bolster the monitoring network maintained by the Icelandic Meteorological Office and the University of Iceland, both in Reykjavik. And they used these to measure the events leading up to and after the eruption with unprecedented detail.

The long march

Earthquakes began shaking Bárðarbunga on 16 August. For two weeks, researchers watched as seismic activity marched north and east, towards the edge of the ice cap that covers the volcano. GPS stations measured the ground flexing upward as huge amounts of magma shifted underground. “The seismic shows us the detail, and the GPS shows us the volume,” says Kristín Vogfjörð, a seismologist at the Icelandic Meteorological Office and co-leader of FUTUREVOLC.

For 45 kilometres, the magma crept along, cooling and forming an underground sheet known as a dike. By 29 August, it had made it to the edge of the ice cap and begun erupting into a barren plain called Holuhraun.

Since then, the eruption has spewed at least half a cubic kilometre of lava, making it the largest lava-producing eruption in Iceland since 1947. But the quantity of gas is what has startled scientists most. Chunks of rock collected from the eruption show how gas-rich the lava is; the rocks are porous, filled with air pockets where the gas has leaked out.

With the right winds, the sulphur that Holuhraun produces can reach as far as the European continent, where Austria has recorded more sulphur in its air than any time since the industrial clean-up of the 1980s.

FUTUREVOLC has placed some basic gas-monitoring equipment at its volcanoes, including two types of spectrometer at the Holuhraun site. One measures concentrations of SO2 by studying how it absorbs particular wavelengths of sunlight. The other scans for multiple gasses simultaneously.

Both types of instrument rely on daylight to make their measurements, and the encroaching darkness of the high northern winter will limit their usefulness, says Sara Barsotti, an atmospheric physicist at the Icelandic Meteorological Office. (Even getting to the eruption site, which is remote, is getting harder as the winter sets in.) Researchers will try to continue making as many gas measurements on the ground as possible, and compare those to the rough estimates made by satellites, Barsotti says.

Icelandic officials are trying to work out how much of a hazard the sulphur is and whether they can predict its movement more accurately. The meteorological office has begun issuing forecasts of where the gas is likely to travel each day. Sulphur spikes as high as 21,000 micrograms per cubic metre were measured last weekend in the town of Höfn; the World Health Organization recommends no more than 500 micrograms per cubic metre for a 10-minute exposure.

No one has died in the eruption, and the plume is not high enough to penetrate the stratosphere and cause widespread climate perturbations. But the million tonnes of sulphur emitted so far are an unprecedented experiment in testing the effects of toxic-gas exposure, Barsotti says.

Lessons from Iceland may prove useful in understanding long-term gas exposure in other volcanic regions, such as Japan, Indonesia and Hawaii. In the early 2000s, residents around the Miyake-jima volcano in Japan were evacuated when it began erupting with roughly the same level of sulphur emissions.

In Iceland, the last similar event was a fissure eruption known as the Krafla fires that began in 1975 and lasted on and off until 1984, says Freysteinn Sigmundsson, a volcanologist at the University of Iceland and co-leader of FUTUREVOLC. If the current eruption is tapping magma deep in the crust, as the lava’s volume and chemistry suggest, then it, too, may continue for months or even years.

“This eruption comes at a good time for the project,” Sigmundsson says, waving out his office window at Reykjavik’s red skies. “We don’t see an end in sight.”

Note : The above story is based on materials provided by Nature 514, 543–544 (30 October 2014) doi:10.1038/514543a .The article written by Alexandra Witze.

Glacier song

Gorner Glacier, Swiss Alps. Credit: Image courtesy NASA

Mountain glaciers represent one of the largest repositories of fresh water in alpine regions. However, little is known about the processes by which water moves through these systems. In this study published in Geology on 24 Oct. 2014, David S. Heeszel and colleagues use seismic recordings collected near Lake Gornersee in the Swiss Alps to look for signs of water moving through fractures near the glacier bed. Analysis of these recordings reveals, for the first time, that harmonic tremor occurs within mountain glaciers and that individual icequakes at the glacier base can exhibit harmonic properties.

These observations suggest that there is a complex network of fluid-induced fracture processes at the glacier base. Because glacial lake drainage events can occur with little or no warning, there is the potential for damaging floods in valleys below the glacier. Unfortunately, because the water moves under and through the glacier, surface observations alone cannot predict lake drainage events.

Modeling changes in the observed harmonic frequencies indicates that the spectral characteristics of seismic data can provide important information about hydraulic fracture geometry and fluid pressure at depth, leading to important insights into subglacial hydrologic processes. Future modeling of these processes may lead to improved glacial outburst flood hazard predictions.

Reference:
D. S. Heeszel, F. Walter, D. L. Kilb. Humming glaciers. Geology, 2014; DOI: 10.1130/G35994.1

Note : The above story is based on materials provided by Geological Society of America.

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