White Desert (known as Sahara el Beyda, with the word sahara meaning a desert). The White Desert of Egypt is located 45 km (28 mi) north of the town of Farafra. The desert has a white, cream color and has massive chalk rock formations that have been created as a result of occasional sandstorm in the area.
The majority of the valley is devoid of vegetation desert today. Rock and subsoil are usually made of limestone or chalk.
The valley is flat and is interrupted only by a few isolated standing conical hills – both north and south of the city of el-Farafra, they are called el-Qunna, mostly spoken el-Gunna (Arabic: القنة, al-Qunna, “the pinnacle “). East of el-Quss-Abu-Sa ? id plateaus are also numerous small limestone mountains witnesses.
The soil is blown with sand. It can be here but in places some minerals such as pyrite and marcasite (iron disulfide are both, but with different crystal form), especially in the north of the valley in the area of ? Ain Bischw?. The materials have been but never mined in mines.
The result is the desert from the remains of microscopic sea creatures whose habitat was located here before about 80 million years ago. After the disappearance of the sea winds ensured for the expression of today’s rock whose shape was determined by the composition and hardness of the rocks and their layer sequence. Occasionally can find fossils such as clams or sea urchins.
Video :
Photos :
Note : The above story is reprinted from materials provided by Wikipedia 1 &2
Copyright of The Video & Photos Owen To Geology Page
Book Name : Rocks and Minerals By : MONICA PRICE
KEVIN WALSH DK LONDON Senior Art Editor: Ina Stradins Senior Editor: Angeles Gavira Editors: Georgina Garner, Bella Pringle DTP Designer: John Goldsmid Production Controller: Melanie Dowland Managing Art Editor: Phil Ormerod Publishing Manager: Liz Wheeler Art Director :Bryn Walls Publishing Director: Jonathan Metcalf DK DELHI Designers: Romi Chakraborty,
Malavika Talukdar DTP Designers: Balwant Singh,
Sunil Sharma, Pankaj Sharma Editors : Glenda Fernandes, Rohan Sinha Managing Art Editor: Aparna Sharma
A study by University of Utah mining engineers and seismologists found 2,189 suspected seismic events before and after Utah’s deadly Crandall Canyon coal mine collapse in 2007, and 1,328 of those events have a high probability of being real: 759 seismic events before the collapse (many related to mining) and 569 aftershocks (some related to rescue efforts). The high-probability events shown here reveal seismic activity clustered in three areas, two of which already were known: near the east end of the mine (right) and where miners were working, toward the west end of the mine (left of center). But the third cluster, at the mine’s west end (far left) was revealed by the new study. It shows the collapse was at least as big and possibly larger than a 2008 University of Utah study that revealed the collapse extended from the east part of the mine to the area where miners were working. (Credit: Tex Kubacki, University of Utah)
A new University of Utah study has identified hundreds of previously unrecognized small aftershocks that happened after Utah’s deadly Crandall Canyon mine collapse in 2007, and they suggest the collapse was as big — and perhaps bigger — than shown in another study by the university in 2008.
Mapping out the locations of the aftershocks “helps us better delineate the extent of the collapse at Crandall canyon. It’s gotten bigger,” says Tex Kubacki, a University of Utah master’s student in mining engineering.
“We can see now that, prior to the collapse, the seismicity was occurring where the mining was taking place, and that after the collapse, the seismicity migrated to both ends of the collapse zone,” including the mine’s west end, he adds.
Kubacki was scheduled to present the findings Friday in Salt Lake City during the Seismological Society of America’s 2013 annual meeting.
Six coal miners died in the Aug. 6, 2007 mine collapse, and three rescuers died 10 days later. The mine’s owner initially blamed the collapse on an earthquake, but the University of Utah Seismograph Stations said it was the collapse itself, not an earthquake, that registered on seismometers.
A 2008 study by University of Utah seismologist Jim Pechmann found the epicenter of the collapse was near where the miners were working, and aftershocks showed the collapse area covered 50 acres, four times larger than originally thought, extending from crosscut 120 on the east to crosscut 143 on the west, where miners worked. A crosscut is a north-south tunnel intersecting the mine’s main east-west tunnels.
In the new study, the collapse area “looks like it goes farther west — to the full extent of the western end of the mine, Kubacki says.
Study co-author Michael “Kim” McCarter, a University of Utah professor of mining engineering, says the findings are tentative, but “might extend the collapse farther west.” He is puzzled because “some of that is in an area where no mining had occurred.”
Kubacki says one theory is that the seismic events at the west end and some of those at the eastern end of the mine may be caused by “faulting forming along a cone of collapse” centered over the mine.
Kubacki and McCarter conducted the new study with seismologists Keith Koper and Kris Pankow of the University of Utah Seismograph Stations. McCarter and Pankow also coauthored the 2008 study.
Before the new study, researchers knew of about 55 seismic events — down to magnitude 1.6 — near the mine before and after the collapse, which measured 3.9 on the local magnitude scale and 4.1 on the “moment” magnitude scale that better reflects energy release, Kubacki says.
The new study analyzed records of seismometers closest to the mine for evidence of tremors down to magnitudes minus-1, which Kubacki says is about one-tenth the energy released by a hand grenade. He found:
– Strong statistical evidence there were at least 759 seismic events before the mine collapse and 569 aftershocks.
– Weak evidence there were as many as 1,022 seismic events before the collapse and 1,167 aftershocks.
“We’ve discovered up to about 2,000 previously unknown events spanning from July 26 to Aug. 30, 2007,” Kubacki says, although some of the weak-evidence events may turn out not to be real or to be unrelated to the collapse.
The seismic events found in the new study show tremors clustered in three areas: the east end of the collapse area, the area where miners were working toward the mine’s west end, and — new in this study — at the mine’s west end, beyond where miners worked.
“We have three clusters to look at and try to come up with an explanation of why there were three,” McCarter says. “They are all related to the collapse.”
Some of the tremors in the eastern cluster are related to rescue attempts and a second collapse that killed three rescuers, but some remain unexplained, he adds.
Kubacki says most of the seismic activity before the collapse was due to mining, although scientists want to investigate whether any of those small jolts might have been signs of the impending collapse. So far, however, “there is nothing measured that would have said, ‘Here’s an event [mine collapse] that’s ready to happen,” McCarter says.
Kubacki came up with the new numbers of seismic events by analyzing the records of seismometers closest to Crandall Canyon (about 12 miles away). “We took the known seismic events already in the catalog and searched for events that looked the same,” he adds. “These new events kept popping up. There are tiny events that may show up on one station but not network-wide.”
“Any understanding we can get toward learning how and why mine collapses happen is going to be of interest to the mining community,” Kubacki says.
McCarter adds: “We are looking at the Crandall Canyon event because we have accurate logs and very extensive seismic data, and that provides a way of investigating the data to see if anything could be applied to other mines to improve safety.”
Note : The above story is reprinted from materials provided by University of Utah.
Outline of Dahalokely tokana with a human for scale, showing known bones in white and missing areas patterned after related animals. (Credit: Copyright Andrew Farke and Joseph Sertich)
The first new species of dinosaur from Madagascar in nearly a decade was announced today, filling an important gap in the island’s fossil record.
Dahalokely tokana (pronounced “dah-HAH-loo-KAY-lee too-KAH-nah”) is estimated to have been between nine and 14 feet long, and it lived around 90 million years ago. Dahalokely belongs to a group called abelisauroids, carnivorous dinosaurs common to the southern continents. Up to this point, no dinosaur remains from between 165 and 70 million years ago could be identified to the species level in Madagascar-a 95 million year gap in the fossil record. Dahalokely shortens this gap by 20 million years.
The fossils of Dahalokely were excavated in 2007 and 2010, near the city of Antsiranana (Diego-Suarez) in northernmost Madagascar. Bones recovered included vertebrae and ribs. Because this area of the skeleton is so distinct in some dinosaurs, the research team was able to definitively identify the specimen as a new species. Several unique features — including the shape of some cavities on the side of the vertebrae — were unlike those in any other dinosaur. Other features in the vertebrae identified Dahalokely as an abelisauroid dinosaur.
When Dahalokely was alive, Madagascar was connected to India, and the two landmasses were isolated in the middle of the Indian Ocean. Geological evidence indicates that India and Madagascar separated around 88 million years ago, just after Dahalokely lived. Thus, Dahalokely potentially could have been ancestral to animals that lived later in both Madagascar and India. However, not quite enough of Dahalokely is yet known to resolve this issue. The bones known so far preserve an intriguing mix of features found in dinosaurs from both Madagascar and India.
“We had always suspected that abelisauroids were in Madagascar 90 million years ago, because they were also found in younger rocks on the island. Dahalokely nicely confirms this hypothesis,” said project leader Andrew Farke, Augustyn Family Curator of Paleontology at the Raymond M. Alf Museum of Paleontology. Farke continued, “But, the fossils of Dahalokely are tantalizingly incomplete — there is so much more we want to know. Was Dahalokely closely related to later abelisauroids on Madagascar, or did it die out without descendents?”
The name “Dahalokely tokana” is from the Malagasy language, meaning “lonely small bandit.” This refers to the presumed carnivorous diet of the animal, as well as to the fact that it lived at a time when the landmasses of India and Madagascar together were isolated from the rest of the world.
“This dinosaur was closely related to other famous dinosaurs from the southern continents, like the horned Carnotaurus from Argentina and Majungasaurus, also from Madagascar,” said project member Joe Sertich, Curator of Dinosaurs at the Denver Museum of Nature & Science and the team member who discovered the new dinosaur. “This just reinforces the importance of exploring new areas around the world where undiscovered dinosaur species are still waiting,” added Sertich.
The research was funded by the Jurassic Foundation, Sigma Xi, National Science Foundation, and the Raymond M. Alf Museum of Paleontology. The paper naming Dahalokely appears in the April 18, 2013, release of the journal PLOS ONE.
Note : The above story is reprinted from materials provided by Raymond M. Alf Museum of Paleontology.
Earth’s Core provides a wealth of information for those people interested in Rocks, Gems and Minerals. it contains detailed information on hundreds of gems and minerals as well as a detail glossary of terms.
Earth’s Core is designed to be used on desktops set to 1024×768 or better, it requires 70MB of disk space.
Features
Detailed descriptions and images on 600 minerals
Detailed descriptions and images on 300 gems
Detailed descriptions and images on 200 rocks
900 glossary items
2100 pictures
Fully searchable content
PLUS, it also contains most of the features of my Periodic Table software;
Detailed information on each element, its allotropes, compounds, reactions and images.
Biographies for the important scientists and element discoverers
Screenshots
Information and pictures of the elements of the Periodic Table
This map, taken from a University of Utah video, shows colored dots to represent the locations of portable seismometers in the Earthscope array, which is funded by the National Science Foundation. Most are now located in the eastern part of the United States. Blue-green dots indicate low seismic activity, while yellow-orange-red dots indicate stronger seismic activity. The map shows that when superstorm Sandy turned west-northwest toward Long Island, New York City and New Jersey on Oct. 29, 2012, the seismometers “lit up” because of ground shaking by certain ocean waves imparting energy to the seafloor. (Credit: Keith Koper, University of Utah Seismograph Stations.)
When superstorm Sandy turned and took aim at New York City and Long Island last October, ocean waves hitting each other and the shore rattled the seafloor and much of the United States — shaking detected by seismometers across the country, University of Utah researchers found.”We detected seismic waves created by the oceans waves both hitting the East Coast and smashing into each other,” with the most intense seismic activity recorded when Sandy turned toward Long Island, New York and New Jersey, says Keith Koper, director of the University of Utah Seismograph Stations.
“We were able to track the hurricane by looking at the ‘microseisms’ [relatively small seismic waves] generated by Sandy,” says Oner Sufri, a University of Utah geology and geophysics doctoral student and first author of the study with Koper. “As the storm turned west-northwest, the seismometers lit up.”
Sufri was scheduled to present the preliminary, unpublished findings in Salt Lake City Thursday, April 18 during the Seismological Society of America’s annual meeting.
There is no magnitude scale for the microseisms generated by Sandy, but Koper says they range from roughly 2 to 3 on a quake magnitude scale. The conversion is difficult because earthquakes pack a quick punch, while storms unleash their energy for many hours.
The shaking was caused partly by waves hitting the East Coast, but much more by waves colliding with other waves in the ocean, setting up “standing waves” that reach the seafloor and transmit energy to it, Sufri and Koper say.
While many people may not realize it, earthquakes are not the only events that generate seismic waves. So do mining and mine collapses; storm winds, waves and tornadoes; traffic, construction and other urban activities; and meteors hitting Earth.
“They are not earthquakes; they are seismic waves,” says Koper, a seismologist and associate professor of geology and geophysics. “Seismic waves can be created by a range of causes. … We have beautiful seismic records of the meteor that hit Russia. That’s not an earthquake, but it created ground motion.”
While Sandy’s seismicity may be news to many, Koper says microseisms just as strong were detected before and after the superstorm from North Pacific and North Atlantic storms that never hit land but created “serious ocean wave action.”
Koper adds: “Hurricane Katrina in 2005 was recorded by a seismic array in California, and they could track the path of the storm remotely using seismometers.”
In a related study set for presentation on Friday at the seismology meeting, Koper and geophysics undergraduate student YeouHui Wong found preliminary evidence that seismometers near Utah’s Great Salt Lake are picking up seismic waves generated either by waves or winds on the lake.
Koper says researchers wonder if microseisms from storms and other causes might trigger tiny but real earthquakes, but “that hasn’t been investigated yet,” he says.
Earthscope Picks up Seismic Waves from Ocean Wave Collisions
The microseisms generated by Sandy were detected by Earthscope, a National Science Foundation-funded array of about 500 portable seismometers that were first placed in California in 2004 and have been leapfrogging eastward so that most now are located east of line running from Minnesota to east Texas, and west of a line from Lake Erie to Florida. Some remain scattered across the Midwest and West, with a heavier concentration in the Pacific Northwest.
Earthscope’s purpose is to use seismic waves from quakes and other sources to make images of Earth’s crust and upper mantle beneath North America — similar to how X-rays are used to make CT scans of the human body. To do it accurately, scientists must understand all sources of seismic waves.
Sufri says the new study included Earthscope data from Oct. 18 to Nov. 3, 2012, “which coincides with the passage of Hurricane Sandy, and we tried to understand microseisms that were generated.”
Sandy caused a damaging storm surge due to its size — almost 1,100 miles in diameter for tropical-storm-force winds — more than its intensity, which was 3 when it hit Cuba and 2 off the Northeast coast.
“The energy generated by Sandy is going to be used to image the crust and upper mantle under North America,” says Koper, noting that Earthscope uses years of seismic data to construct images. “We are using seismic waves created by ocean waves to make images of the continent.”
Normal ocean waves “decay with depth very quickly,” says Koper. But when Sandy turned, there was a sudden increase in waves hitting waves to create “standing waves” like those created when you throw two pebbles in a pond and the ripples intersect. “Pressure generated by standing waves remains significant at the seafloor,” he says.
“When Sandy made that turn to the northwest, although wind speeds didn’t get dramatically bigger, the seismic energy that was created got tremendously bigger because the ocean’s standing waves were larger from the wave-wave interaction,” he adds.
Not only did the seismic waves become more energetic, “but the periods got longer so, in a sense, the sound of those seismic waves got deeper — less treble, more bass — as the storm turned,” Koper says.
Seismic Tracking of Hurricanes
Seismologists can track Sandy and other big storms because seismometers detect three components of motion: one vertical and two horizontal. If most of the energy on a seismometer is detected with a north-south motion, it means the source of the energy is north or south of the device.
“If you have enough seismometers, you can get enough data to get arrows to point at the source,” Koper says.
He says the seismologists didn’t track Sandy in real time, but the seismographic data of the storm suggests it might be possible to help track storms in the future using their seismicity.
Sufri speculates that seismic tracking of storms might allow observations that satellites can miss, and perhaps could help researchers “understand how climate is changing and how it is affecting our oceans — are we seeing more intense storms and increasing numbers of storms?”
Koper says the Sandy study “is exploratory science where we are trying to learn fundamental things about how the atmosphere, oceans and solid Earth interact.”
Note : The above story is reprinted from materials provided by University of Utah.
This page houses links to the Noddy 3D Geological and Geophysical Modelling System. The Noddy modelling system allows you to rapidly build complex 3D geological models and calculate the resulting gravity and magnetic fields. It’s primary use in in teaching, although of course it does allow you to try out simply geological scenarios as well.
How Noddy Works:
In order to characterise the complex three dimensional structures that often cause geophysical anomalies it is necessary to have some understanding of the structural history of an area. The basis for this program is the ability to construct a complex geological history as a succession of relatively simple structural, sedimentary and igneous events. Each geological history is defined as a sequence of kinematic events, and each event is defined by a set of orientation, position and scaling parameters. The structural modelling used in this program were first written by M Jessell as part of an MSc at Imperial College, London University, in 1981, as an interactive map creation package, and later commercialised by www.encom.com.au after geophysical modelling capabilities and many other changes were made as part of an industry funded AMIRA collaboration between Monash University and the CSIRO. (Encom does not and will not support the version available here, so please don’t ask them).
The program consists of introducing geoelogical events to effect an infinite volume of rock. The displacement equations are defined explicitly or implicitly with respect to flat planes, so that the curvature of the earth is ignored. The displacement equations within this program are all unary, that is there is a one to one mapping of all points before and after each deformation event. The user is protected from these equations and is instead asked to describe the deformation in “normal” structural terms, such as strike and dip.
Manual (PDF)
Tutorials (PDF)
If you make a nice model, or class exercise, it would be great if you could send it to me [email protected] and I will create a set of user supplied examples. Known problems
1) With newer systems (VISTA, Windows 7) when you try to save files, the save dialog doesn’t have a space to type in the filename). Solution: start up noddy as administrator. License:
As of May 2009 this software is no longer subject to an commercial release, and hence is freely distributable (and hence is no longer the object of professional support, you get what you pay for!).
This software is provided ‘as-is’, without any express or implied warranty. In no event will the authors be held liable for any damages arising from the use of this software.Permission is granted to anyone to use this software for any purpose, including commercial applications, and to alter it and redistribute it freely, subject to the following restrictions:1) The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
2) Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
3) This notice may not be removed or altered from any source distribution.
Document license
Noddy for Windows ’95, ’98 and Windows NT, 2000/XP, Vista
Version 7.11This version originally commercialised by Encom Technology Pty. Limited:www.encom.com.au
but now supplied by TecTask
www.tectask.org at no cost
PLEASE CONTACT TECTASK FOR ANY FURTHER INFORMATION, THIS SOFTWARE IS NO LONGER SUPPORTED BY ENCOM
AND ENCOM CANNOT BE HELD LIABLE FOR ANY USAGE OF THIS PRODUCT.
As of May 2009 this software is no longer subject to an commercial release, and hence is freely distributabe (and hence is no longer the object of professional support, you get what you pay for!).
This software is provided ‘as-is’, without any express or implied warranty. In no event will the authors be held liable for any damages arising from the use of this software.
Permission is granted to anyone to use this software for any purpose, including commercial applications, and to alter it and redistribute it freely, subject to the following restrictions:
1) The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
2) Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
3) This notice may not be removed or altered from any source distribution.
The northeastern part of Yellowstone Caldera, with the Yellowstone River flowing through Hayden Valley and the caldera rim in the distance
A debate among scientists about the geologic formation of the supervolcano encompassing the region around Yellowstone National Park has taken a major step forward, thanks to new evidence provided by a team of international researchers led by University of Rhode Island Professor Christopher Kincaid.In a publication appearing in last week’s edition of Nature Geoscience, the URI team demonstrated that both sides of the debate may be right.
Using a state-of-the-art plate tectonic laboratory model, they showed that volcanism in the Yellowstone area was caused by severely deformed and defunct pieces of a former mantle plume. They further concluded that the plume was affected by circulation currents driven by the movement of tectonic plates at the Cascades subduction zone.
Mantle plumes are hot buoyant upwellings of magma inside Earth. Subduction zones are regions where dense oceanic tectonic plates dive beneath buoyant continental plates. The origins of the Yellowstone supervolcano have been argued for years, with sides disagreeing about the role of mantle plumes.
According to Kincaid, the simple view of mantle plumes is that they have a head and a tail, where the head rises to the surface, producing immense magma structures and the trailing tail interacts with the drifting surface plates to create a chain of smaller volcanoes of progressively younger age. But Yellowstone doesn’t fit this typical mold. Among its oddities, its eastward trail of smaller volcanoes called the Snake River Plain has a mirror-image volcanic chain, the High Lava Plain, that extends to the west. As a result, detractors say the two opposite trails of volcanoes and the curious north-south offset prove the plume model simply cannot work for this area, and that a plates-only model must be at work.
To examine these competing hypotheses, Kincaid, former graduate student Kelsey Druken, and colleagues at the Australian National University built a laboratory model of Earth’s interior using corn syrup to simulate fluid-like motion of Earth’s mantle. The corn syrup has properties that allow researchers to examine complex time changing, three-dimensional motions caused by the collisions of tectonic plates at subduction zones and their effect on unsuspecting buoyant plumes.
By using the model to simulate a mantle plume in the Yellowstone region, the researchers found that it reproduced the characteristically odd patterns in volcanism that are recorded in the rocks of the Pacific Northwest.
“Our model shows that a simple view of mantle plumes is not appropriate when they rise near subduction zones, and that these features get ripped apart in a way that seems to match the patterns in magma output in the northwestern U.S. over the past 20 million years,” said Kincaid, a professor of geological oceanography at the URI Graduate School of Oceanography. “The sinking plate produces a flow field that dominates the interaction with the plume, making the plume passive in many ways and trapping much of the magma producing energy well below the surface. What you see at the surface doesn’t look like what you’d expect from the simple models.”
The next step in Kincaid’s research is to conduct a similar analysis of the geologic formations in the region around the Tonga subduction zone and the Samoan Islands in the South Pacific, another area where some scientists dispute the role of mantle plumes.
According to Kincaid, “A goal of geological oceanography is to understand the relationship between Earth’s convecting interior and our oceans over the entire spectrum of geologic time. This feeds directly into the very pressing need for understanding where Earth’s ocean-climate system is headed, which clearly hinges on our understanding of how it has worked in past.”
Note : The above story is reprinted from materials provided by University of Rhode Island, via EurekAlert!, a service of AAAS.
Geocalc supports a wide range of ASCII text coordinate formats for import and export. Coordinates can be expressed as Latitudes and Longitudes, Easting and Northing or X,Y,Z. The following coordinate file formats are predefined:
Geocomp Spatial Data System (.PTS & .STR)
Geocomp Field File (.FLD)
GeoNav Coast File (.CST)
UKOOA P1/90
X Y Z
GeoCalc 4.20 is an ideal companion for Geocomp, GeoNav, or any other point-based spatial data system.
The Nile is a major north-flowing river in northeastern Africa, generally regarded as the longest river in the world. It is 6,650 km (4,130 miles) long. The Nile is an “international” river as its water resources are shared by eleven countries, namely, Tanzania, Uganda, Rwanda, Burundi, Democratic Republic of the Congo, Kenya, Ethiopia, Eritrea, South Sudan, Sudan and Egypt. In particular, the Nile River provides the primary water resource and so it is the life artery for its downstream countries such as Egypt and Sudan.
The Nile has two major tributaries, the White Nile and Blue Nile. The White Nile is longer and rises in the Great Lakes region of central Africa, with the most distant source still undetermined but located in either Rwanda or Burundi. It flows north through Tanzania, Lake Victoria, Uganda and South Sudan. The Blue Nile is the source of most of the water and fertile soil. It begins at Lake Tana in Ethiopia at 12°02′09″N 037°15′53″E and flows into Sudan from the southeast. The two rivers meet near the Sudanese capital of Khartoum.
The northern section of the river flows almost entirely through desert, from Sudan into Egypt, a country whose civilization has depended on the river since ancient times. Most of the population and cities of Egypt lie along those parts of the Nile valley north of Aswan, and nearly all the cultural and historical sites of Ancient Egypt are found along riverbanks. The Nile ends in a large delta that empties into the Mediterranean Sea.
Course
Above Khartoum the Nile is also known as the White Nile, a term also used in a limited sense to describe the section between Lake No and Khartoum. At Khartoum the river is joined by the Blue Nile. The White Nile starts in equatorial East Africa, and the Blue Nile begins in Ethiopia. Both branches are on the western flanks of the East African Rift.
The drainage basin of the Nile covers 3,254,555 square kilometres (1,256,591 sq mi), about 10% of the area of Africa. The Nile basin is complex, and because of this, the discharge at any given point along the mainstem depends on many factors including weather, diversions, evaporation and evapotranspiration, and groundwater flow.
Source
The source of the Nile is sometimes considered to be Lake Victoria, but the lake has feeder rivers of considerable size. The Kagera River, which flows into Lake Victoria near the Tanzanian town of Bukoba, is the longest feeder, although sources do not agree on which is the longest tributary of the Kagera and hence the most distant source of the Nile itself. It is either the Ruvyironza, which emerges in Bururi Province, Burundi, or the Nyabarongo, which flows from Nyungwe Forest in Rwanda. The two feeder rivers meet near Rusumo Falls on the Rwanda-Tanzania border.
A recent exploration party went to a place described as the source of the Rukarara tributary, and by hacking a path up steep jungle-choked mountain slopes in the Nyungwe forest found (in the dry season) an appreciable incoming surface flow for many miles upstream, and found a new source, giving the Nile a length of 4199 miles (6758 kilometers)
Lost headwaters
Formerly Lake Tanganyika drained northwards along the African Rift Valley into the White Nile, making the
Map showing the courses of the White and Blue Nile
Nile about 1,400 kilometres (870 mi) longer, until it was blocked in Miocene times by the bulk of the Virunga Volcanoes.
In Uganda
The Nile leaves Lake Victoria at Ripon Falls near Jinja, Uganda, as the Victoria Nile. It flows for approximately 500 kilometres (300 mi) farther, through Lake Kyoga, until it reaches Lake Albert. After leaving Lake Albert, the river is known as the Albert Nile.
In South Sudan
It then flows into South Sudan, where it is known as the Bahr al Jabal (“Sea of the Mountain”, possibly from Nahr al Jabal, “River of the Mountain”). The Bahr al Ghazal, itself 716 kilometres (445 mi) long, joins the Bahr al Jabal at a small lagoon called Lake No, after which the Nile becomes known as the Bahr al Abyad, or the White Nile, from the whitish clay suspended in its waters. When the Nile floods it leaves a rich silty deposit which fertilizes the soil. The Nile no longer floods in Egypt since the completion of the Aswan Dam in 1970. An anabranch river, the Bahr el Zeraf, flows out of the Nile’s Bahr al Jabal section and rejoins the White Nile.
The flow rate of the Bahr al Jabal at Mongalla, South Sudan is almost constant throughout the year and averages 1,048 m3/s (37,000 cu ft/s). After Mongalla, the Bahr Al Jabal enters the enormous swamps of the Sudd region of South Sudan. More than half of the Nile’s water is lost in this swamp to evaporation and transpiration. The average flow rate of the White Nile at the tails of the swamps is about 510 m3/s (18,000 cu ft/s). From here it soon meets with the Sobat River at Malakal. On an annual basis, the White Nile upstream of Malakal contributes about fifteen percent of the total outflow of the Nile River.
The average flow of the White Nile at Malakal, just below the Sobat River, is 924 m3/s (32,600 cu ft/s); the peak flow is approximately 1,218 m3/s (43,000 cu ft/s) in October and minimum flow is about 609 m3/s (21,500 cu ft/s) in April. This fluctuation is due the substantial variation in the flow of the Sobat, which has a minimum flow of about 99 m3/s (3,500 cu ft/s) in March and a peak flow of over 680 m3/s (24,000 cu ft/s) in October. During the dry season (January to June) the White Nile contributes between 70 percent and 90 percent of the total discharge from the Nile.
In Sudan
Below Renk the White Nile enters Sudan, it flows north to Khartoum and meets the Blue Nile.
The course of the Nile in Sudan is distinctive. It flows over six groups of cataracts, from the first at Aswan to the sixth at Sabaloka (just north of Khartoum) and then turns to flow southward before again returning to flow north. This is called the Great Bend of the Nile.
In the north of Sudan the river enters Lake Nasser (known in Sudan as Lake Nubia), the larger part of which is in Egypt.
In Egypt
The Nile near Beni Suef
Below the Aswan High Dam, at the northern limit of Lake Nasser, the Nile resumes its historic course.
North of Cairo, the Nile splits into two branches (or distributaries) that feed the Mediterranean: the Rosetta Branch to the west and the Damietta to the east, forming the Nile Delta.
Tributaries
Atbara River
Below the confluence with the Blue Nile the only major tributary is the Atbara River, roughly halfway to the
Composite satellite image of the White Nile.
sea, which originates in Ethiopia north of Lake Tana, and is around 800 kilometres (500 mi) long. The Atbara flows only while there is rain in Ethiopia and dries very rapidly. During the dry period of January to June, it typically dries up. It joins the Nile approximately 300 kilometres (200 mi) north of Khartoum.
Blue Nile
The Blue Nile springs from Lake Tana in the Ethiopian Highlands. The Blue Nile flows about 1,400 kilometres to Khartoum, where the Blue Nile and White Nile join to form the Nile. Ninety percent of the water and ninety-six percent of the transported sediment carried by the Nile originates in Ethiopia, with fifty-nine percent of the water from the Blue Nile (the rest being from the Tekezé, Atbarah, Sobat, and small tributaries). The erosion and transportation of silt only occurs during the Ethiopian rainy season in the summer, however, when rainfall is especially high on the Ethiopian Plateau; the rest of the year, the great rivers draining Ethiopia into the Nile (Sobat, Blue Nile, Tekezé, and Atbarah) have a weaker flow.
The flow of the Blue Nile varies considerably over its yearly cycle and is the main contribution to the large natural variation of the Nile flow. During the dry season the natural discharge of the Blue Nile can be as low as 113 m3/s (4,000 cu ft/s), although upstream dams regulate the flow of the river. During the wet season the peak flow of the Blue Nile often exceeds 5,663 m3/s (200,000 cu ft/s) in late August (a difference of a factor of 50).
Before the placement of dams on the river the yearly discharge varied by a factor of 15 at Aswan. Peak flows of over 8,212 m3/s (290,000 cu ft/s) occurred during late August and early September, and minimum flows of about 552 m3/s (19,500 cu ft/s) occurred during late April and early May.
Bahr el Ghazal and Sobat River
The Bahr al Ghazal and the Sobat River are the two most important tributaries of the White Nile in terms of discharge.The Bahr al Ghazal’s drainage basin is the largest of any of the Nile’s sub-basins, measuring 520,000 square kilometres (200,000 sq mi) in size, but it contributes a relatively small amount of water, about 2 m3/s (71 cu ft/s) annually, due to tremendous volumes of water being lost in the Sudd wetlands.
The Sobat River, which joins the Nile a short distance below Lake No, drains about half as much land, 225,000 km2 (86,900 sq mi), but contributes 412 cubic metres per second (14,500 cu ft/s) annually to the Nile. When in flood the Sobat carries a large amount of sediment, adding greatly to the White Nile’s color.
Yellow Nile
The Yellow Nile is a former tributary that connected the Ouaddaï Highlands of eastern Chad to the Nile River Valley c. 8000 to c. 1000 BC. Its remains are known as the Wadi Howar. The wadi passes through Gharb Darfur near the northern border with Chad and meets up with the Nile near the southern point of the Great Bend.
Note : The above story is reprinted from materials provided byWikipedia
Sea-floor mapping technology reveals volcanoes beneath the sea surface. (Credit: Image courtesy of British Antarctic Survey)
Scientists from British Antarctic Survey (BAS) have discovered previously unknown volcanoes in the ocean waters around the remote South Sandwich Islands.Using ship-borne sea-floor mapping technology during research cruises onboard the RRS James Clark Ross, the scientists found 12 volcanoes beneath the sea surface — some up to 3km high. They found 5km diameter craters left by collapsing volcanoes and 7 active volcanoes visible above the sea as a chain of islands.
The research is important also for understanding what happens when volcanoes erupt or collapse underwater and their potential for creating serious hazards such as tsunamis. Also this sub-sea landscape, with its waters warmed by volcanic activity creates a rich habitat for many species of wildlife and adds valuable new insight about life on earth.
Speaking at the International Symposium on Antarctic Earth Sciences in Edinburgh Dr Phil Leat from British Antarctic Survey said, “There is so much that we don’t understand about volcanic activity beneath the sea — it’s likely that volcanoes are erupting or collapsing all the time. The technologies that scientists can now use from ships not only give us an opportunity to piece together the story of the evolution of our earth, but they also help shed new light on the development of natural events that pose hazards for people living in more populated regions on the planet.”
Note : The above story is reprinted from materials provided by British Antarctic Survey, via EurekAlert!, a service of AAAS. *Public release date: 11-Jul-2011
This photo from December 2010 shows a one-meter long section of the West Antarctic Ice Sheet Divide core, with a dark layer of volcanic ash visible. (Credit: Heidi Roop)
In the last few decades, glaciers at the edge of the icy continent of Antarctica have been thinning, and research has shown the rate of thinning has accelerated and contributed significantly to sea level rise.New ice core research suggests that, while the changes are dramatic, they cannot be attributed with confidence to human-caused global warming, said Eric Steig, a University of Washington professor of Earth and space sciences.
Previous work by Steig has shown that rapid thinning of Antarctic glaciers was accompanied by rapid warming and changes in atmospheric circulation near the coast. His research with Qinghua Ding, a UW research associate, showed that the majority of Antarctic warming came during the 1990s in response to El Niño conditions in the tropical Pacific Ocean.
Their new research suggests the ’90s were not greatly different from some other decades — such as the 1830s and 1940s — that also showed marked temperature spikes.
“If we could look back at this region of Antarctica in the 1940s and 1830s, we would find that the regional climate would look a lot like it does today, and I think we also would find the glaciers retreating much as they are today,” said Steig, lead author of a paper on the findings published online April 14 in Nature Geoscience.
The researchers’ results are based on their analysis of a new ice core from the West Antarctic Ice Sheet Divide that goes back 2,000 years, along with a number of other ice core records going back about 200 years. They found that during that time there were several decades that exhibited similar climate patterns as the 1990s.
The most prominent of these in the last 200 years — the 1940s and the 1830s — were also periods of unusual El Niño activity like the 1990s. The implication, Steig said, is that rapid ice loss from Antarctica observed in the last few decades, particularly the ’90s, “may not be all that unusual.”
The same is not true for the Antarctic Peninsula, the part of the continent closer to South America, where rapid ice loss has been even more dramatic and where the changes are almost certainly a result of human-caused warming, Steig said.
But in the area where the new research was focused, the West Antarctic Ice Sheet, it is more difficult to detect the evidence of human-caused climate change. While changes in recent decades have been unusual and at the “upper bound of normal,” Steig said, they cannot be considered exceptional.
“The magnitude of unforced natural variability is very big in this area,” Steig said, “and that actually prevents us from answering the questions, ‘Is what we have been observing exceptional? Is this going to continue?'”
He said what happens to the West Antarctic Ice Sheet in the next few decades will depend greatly on what happens in the tropics.
The West Antarctic Ice Sheet is made up of layers of ice, greatly compressed, that correspond with a given year’s precipitation. Similar to tree rings, evidence preserved in each layer of ice can provide climate information for a specific time in the past at the site where the ice core was taken.
In this case, the researchers detected elevated levels of the isotope oxygen 18 in comparison with the more commonly found oxygen 16. Higher levels of oxygen 18 generally indicate higher air temperatures.
Levels of oxygen 18 in ice core samples from the 1990s were more elevated than for any other time in the last 200 years, but were very similar to levels reached during some earlier decades.
Note : The above story is reprinted from materials provided by University of Washington. The original article was written by Vince Stricherz.
Book Name : Fundamentals of Reservoir Engineering By : LP. DAKE
Senior Lecturer in Reservoir Engineering,
Shell Internationale Petroleum Maatschappij B. V.,
The Hague, The Netherlands
PREFACE
This teaching textbook in Hydrocarbon Reservoir Engineering is based on various lecture courses given by the author while employed in the Training Division of Shell Internationale Petroleum Maatschappij B.V. (SIPM), in the Hague, between 1974 and 1977.
The primary aim of the book is to present the basic physics of reservoir engineering, using the simplest and most straightforward of mathematical techniques. It is only through having a complete understanding of the physics that the engineer can hope to appreciate and solve complex reservoir engineering problems in a practical manner.
Researchers at Columbia Engineering and Boston University have developed the first method to map evaporation globally using weather stations, which will help scientists evaluate water resource management, assess recent trends of evaporation throughout the globe, and validate surface hydrologic models in various conditions. The study was published in the April 1 online Early Edition of Proceedings of the National Academy of Sciences (PNAS).
“This is the first time we’ve been able to map evaporation in a consistent way, using concrete measurements that are available around the world,” says Pierre Gentine, assistant professor of earth and environmental engineering at Columbia. “This is a big step forward in our understanding of how the water cycle impacts life on Earth.”
Earth’s surface hydrologic cycle comprises precipitation, runoff, and evaporation fluctuations. Scientists can measure precipitation across the globe using rain gauges or microwave remote sensing devices. In places where streamflow measurements are available, they can also measure the runoff. But measuring evaporation has always been difficult.
“Global measurements of evaporation have been a longstanding and frustrating challenge for the hydrologic community,” says Gentine. “And now, for the first time, we show that simple weather station measurements of air temperature and humidity can be used across the globe to obtain the daily evaporation.”
Evaporation is a key component of the hydrological cycle: it tells us how much water leaves the soil and therefore how much should be left there for a broad range of applications such as agriculture, water resource management, and weather forecasting.
Gentine, who studies the relationship between hydrology and atmospheric science and its impact on climate change, collaborated on this research with Guido D. Salvucci, professor and chair of the Department of Earth and Environmental Sciences at Boston University and the paper’s lead author. Using data from weather stations, widely available across the globe, they focused on evaporation and discovered an emergent relationship between evaporation and relative humidity that gave them the evaporation rates.
Gentine and Salvucci plan to provide daily maps of evaporation around the world that will enable scientists to evaluate changes in water table, calculate water requirements for agriculture, and measure more accurate evaporation fluctuations into the atmosphere.
“Sharing our data with researchers around the world will help us learn more about Earth’s hydrologic cycle and assess recent trends such as whether it is accelerating,” adds Gentine. “Acceleration could greatly impact our climate, locally, nationally, and globally.”
The research has been funded by the National Science Foundation.
Note : The above story is reprinted from materials provided by Columbia University School of Engineering and Applied Science.
This is a flesh reconstruction of embryonic dinosaur inside egg. (Credit: Artwork by D. Mazierski)
The great age of the embryos is unusual because almost all known dinosaur embryos are from the Cretaceous Period. The Cretaceous ended some 125 million years after the bones at the Lufeng site were buried and fossilized.
Led by University of Toronto Mississauga paleontologist Robert Reisz, an international team of scientists from Canada, Taiwan, the People’s Republic of China, Australia, and Germany excavated and analyzed over 200 bones from individuals at different stages of embryonic development.
“We are opening a new window into the lives of dinosaurs,” says Reisz. “This is the first time we’ve been able to track the growth of embryonic dinosaurs as they developed. Our findings will have a major impact on our understanding of the biology of these animals.”
The bones represent about 20 embryonic individuals of the long-necked sauropodomorph Lufengosaurus, the most common dinosaur in the region during the Early Jurassic period. An adult Lufengosaurus was approximately eight metres long.
The disarticulated bones probably came from several nests containing dinosaurs at various embryonic stages, giving Reisz’s team the rare opportunity to study ongoing growth patterns. Dinosaur embryos are more commonly found in single nests or partial nests, which offer only a snapshot of one developmental stage.
To investigate the dinosaurs’ development, the team concentrated on the largest embryonic bone, the femur. This bone showed a consistently rapid growth rate, doubling in length from 12 to 24 mm as the dinosaurs grew inside their eggs. Reisz says this very fast growth may indicate that sauropodomorphs like Lufengosaurus had a short incubation period.
Reisz’s team found the femurs were being reshaped even as they were in the egg. Examination of the bones’ anatomy and internal structure showed that as they contracted and pulled on the hard bone tissue, the dinosaurs’ muscles played an active role in changing the shape of the developing femur. “This suggests that dinosaurs, like modern birds, moved around inside their eggs,” says Reisz. “It represents the first evidence of such movement in a dinosaur.”
The Taiwanese members of the team also discovered organic material inside the embryonic bones. Using precisely targeted infrared spectroscopy, they conducted chemical analyses of the dinosaur bone and found evidence of what Reisz says may be collagen fibres. Collagen is a protein characteristically found in bone.
“The bones of ancient animals are transformed to rock during the fossilization process,” says Reisz. “To find remnants of proteins in the embryos is really remarkable, particularly since these specimens are over 100 million years older than other fossils containing similar organic material.”
Only about one square metre of the bonebed has been excavated to date, but this small area also yielded pieces of eggshell, the oldest known for any terrestrial vertebrate. Reisz says this is the first time that even fragments of such delicate dinosaur eggshells, less than 100 microns thick, have been found in good condition.
“A find such as the Lufeng bonebed is extraordinarily rare in the fossil record, and is valuable for both its great age and the opportunity it offers to study dinosaur embryology,” says Reisz. “It greatly enhances our knowledge of how these remarkable animals from the beginning of the Age of Dinosaurs grew.”
Notw : The above story is reprinted from materials provided by University of Toronto, via EurekAlert!, a service of AAAS.
Banded iron formations (BIFs) are chemically precipitated sedimentary rocks. They are composed of alternating thin (millimeter to centimeter scale) red, yellow, or cream colored layers of chert or jasper and black to dark gray iron oxides (predominantly magnetite and hematite), and/or iron carbonate (siderite) layers. Banded iron formations have greater than 15% sedimentary iron content. Banded iron formations are of economic interest as they host the world’s largest iron ore deposits and many gold deposits.
Algoma-type banded iron formations were deposited as chemical sediments along with other sedimentary rocks (such as greywacke and shale) and volcanics in and adjacent to volcanic arcs and spreading centers. Iron and silica were derived from hydrothermal sources associated with volcanic centres. Algoma-type iron formations are common in Archean green-stone belts, but may also occur in younger rocks.
Lake Superior-type banded iron formations were chemically precipitated on marine continental shelves and in shallow basins. They are commonly interlayered with other sedimentary or volcanic rocks such as shale and tuff. Most Lake Superior-type banded iron formations formed during the Paleoproterozoic, between 2.5 and 1.8 billion years ago. Prior to this, Earth’s primitive atmosphere and oceans had little or no free oxygen to react with iron, resulting in high iron concentrations in seawater. Iron may have been derived from the weathering of iron-rich rocks, transported to the sea as water-soluble Fe+2.
Alternatively, or in addition, both iron and silica may have been derived from submarine magmatic and hydrothermal activity. Under calm, shallow marine conditions, the iron in seawater combined with oxygen released during photosynthesis by Cyanobacteria (primitive blue-green algae, which began to proliferate in near-surface waters in the Paleoproterozoic) to precipitate magnetite (Fe3O4), which sank to the sea floor, forming an iron-rich layer.
It has been proposed that during periods when there was too great a concentration of oxygen (in excess of that required to bond with the iron in the seawater) due to an abundance of blue-green algae, the blue-green algae would have been reduced in numbers or destroyed. A temporary decrease in the oxygen content of the seawater then eventuated.
When magnetite formation was impeded due to a reduction in the amount of oxygen in seawater, a layer of silica and/or carbonate was deposited. With subsequent reestablishment of Cyanobacteria (and thus renewed production of oxygen), precipitation of iron recommenced. Repetitions of this cycle resulted in deposition of alternating iron-rich and silica- or carbonate-rich layers. Variations in the amount of iron in seawater, such as due to changes in volcanic activity, may have also led to rhythmic layering.
The large lateral extent of individual thin layers implies changes in oxygen or iron content of seawater to be regional, and necessitates calm depositional conditions. Iron and silica-rich layers, originally deposited as amorphous gels, subsequently lithified to form banded iron formations. The distribution of Lake Superior-type banded iron formations of the same age range in Precambrian cratons worldwide suggests that they record a period of global change in the oxygen content of the earth’s atmosphere and oceans. Also, the worldwide abundance of large, calm, shallow platforms where cyanobacterial mats flourished and banded iron formations were deposited may imply a global rise in sea level.
Primary carbonate in banded iron formations may be replaced by silica during diagenesis or deformation. The pronounced layering in banded iron formations may be further accentuated during deformation by pressure solution; silica and/or carbonate are dissolved and iron oxides such as hematite may crystallize along pressure solution (stylolite) surfaces.
Banded iron formations are highly anisotropic rocks. When shortened parallel to their layering, they deform to form angular to rounded folds, kink bands, and box folds. Folds in banded iron formations are typically doubly plunging and conical. Banded iron formations may interact with hot fluids channeled along faults and more permeable, interbedded horizons such as dolomite during deformation. This may remove large volumes of silica, resulting in concentration of iron. Iron, in the form of microplaty hematite can also crystallize in structurally controlled sites such as fold hinges and along detachment faults.
If there is sufficient enrichment, an iron ore body is formed. Iron may also be leached, redeposited and concentrated during weathering to form supergene iron ore deposits. Fibrous growth of quartz and minerals such as crocidolite (an amphibole, also known as asbestiform riebeckite) commonly occurs in banded iron formations during deformation due to dilation between layers, especially in fold hinges. Replacement of crocidolite by silica produces shimmering brown, yellow and orange “tiger-eye,” which is utilized in jewelry and for ornamental use.
Figure showing a dropstone imbedded in a banded iron formations in Canada’s Mackenzie Mountains. Source: Kerr’s article in Science 2000, Vol. 287
Complexity catalyst: Banded iron formations, such as these found in Ontario, Canada, show the chemical features of ancient seawater when they formed in iron-rich oceans billions of years ago. Credit: Stefan LalondeThis photo was taken by Bob Osburn during a 2006 Physical Geology field trip.Banded-iron formation from Port Handford, Western AustraliaBanded-iron formation from the Mesabi Iron Range, Minnesota, USA: Size: 7 cm
Artist’s rendering of a swimming theropod. (Credit: Nathan E. Rogers)
A University of Alberta researcher has identified some of the strongest evidence ever found that dinosaurs could paddle long distances.Working together with an international research team, U of A graduate student Scott Persons examined unusual claw marks left on a river bottom in China that is known to have been a major travel-way for dinosaurs.
Alongside easily identified fossilized footprints of many Cretaceous era animals including giant long neck dinosaur’s researchers found a series of claw marks that Persons says indicates a coordinated, left-right, left-right progression.
“What we have are scratches left by the tips of a two-legged dinosaur’s feet,” said Persons. “The dinosaur’s claw marks show it was swimming along in this river and just its tippy toes were touching bottom.”
The claw marks cover a distance of 15 meters which the researchers say is evidence of a dinosaur’s ability to swim with coordinated leg movements. The tracks were made by carnivorous theropod dinosaur that is estimated to have stood roughly 1 meter at the hip.
Fossilized rippling and evidence of mud cracks indicate that over 100 million years ago the river, in what is now China’s Szechuan Province, went through dry and wet cycles. The river bed, which Persons describes as a “dinosaur super-highway” has yielded plenty of full foot prints of other theropods and gigantic four-legged sauropods.
With just claw scratches on the river bottom to go with, Persons says the exact identity of the paddling dinosaur can’t be determined, but he suspects it could have been an early tyrannosaur or a Sinocalliopteryx. Both species of predators were known to have been in that area of China.
Persons is a U of A, PhD candidate and co-author of the research. It was published April 8 in the journal Chinese Science Bulletin.
Note : The above story is reprinted from materials provided by University of Alberta, via EurekAlert!, a service of AAAS.
Greenhouse effect on the Red Planet? Early on, Mars had giant active volcanoes, which would have released significant methane. Because of methane’s high greenhouse potential, even a thin atmosphere might have supported liquid water. (Credit: NASA)
A new study in Proceedings of the National Academy of Sciences suggests that the way carbon moves from within a planet to the surface plays a big role in the evolution of a planet’s atmosphere. If Mars released much of its carbon as methane, for example, it might have been warm enough to support liquid water.A new study of how carbon is trapped and released by iron-rich volcanic magma offers clues about the early atmospheric evolution on Mars and other terrestrial bodies.
The composition of a planet’s atmosphere has roots deep beneath its surface. When mantle material melts to form magma, it traps subsurface carbon. As magma moves upward toward the surface and pressure decreases, that carbon is released as a gas. On Earth, carbon is trapped in magma as carbonate and degassed as carbon dioxide, a greenhouse gas that helps Earth’s atmosphere trap heat from the sun. But how carbon is transferred from underground to the atmosphere in other planets — and how that might influence greenhouse conditions — wasn’t well understood.
“We know carbon goes from the solid mantle to the liquid magma, from liquid to gas and then out,” said Alberto Saal, professor of geological sciences at Brown and one of the study’s authors. “We want to understand how the different carbon species that are formed in the conditions that are relevant to the planet affect the transfer.”
This latest study, which also included researchers from Northwestern University and the Carnegie Institution of Washington, indicated that under conditions like those found in the mantles of Mars, the Moon and other bodies, carbon is trapped in the magmas mainly as a species called iron carbonyl and released as carbon monoxide and methane gas. Both gasses, methane especially, have high greenhouse potential.
The findings, published in the Proceedings of the National Academy of Sciences, suggest that when volcanism was widespread early in Mars’ history, it may have released enough methane to keep the planet significantly warmer than it is today.
A key difference between conditions in Earth’s mantle and the mantles of other terrestrial bodies is what scientists refer to as oxygen fugacity, the amount of free oxygen available to react with other elements. Earth’s mantle today has a relatively high oxygen fugacity, but in bodies like the Moon and early Mars, it is very low. To find out what how that lower oxygen fugacity affects carbon transfer, the researchers set up a series of experiments using volcanic basalt similar to those found on the Moon and Mars.
They melted the volcanic rock at varying pressures, temperature, and oxygen fugacities, using a powerful spectrometer to measure how much carbon was absorbed by the melt and in what form. They found that at low oxygen fugacities, carbon was trapped as iron carbonyl, something previous research hadn’t detected. At lower pressures, iron carbonyl degassed as carbon monoxide and methane.
“We found that you can dissolve in the magma more carbon at low oxygen fugacity than what was previously thought,” said Diane Wetzel, a Brown graduate student and the study’s lead author. “That plays a big role in the degassing of planetary interiors and in how that will then affect the evolution of atmospheres in different planetary bodies.”
Early in its history, Mars was home to giant active volcanoes, which means significant amounts of methane would have been released by carbon transfer. Because of methane’s greenhouse potential, which is much higher than that of carbon dioxide, the findings suggest that even a thin atmosphere early in Mars’ history might have created conditions warm enough for liquid water on the surface.
Other authors on the paper were Malcolm Rutherford from Brown, Steven Jacobson from Northwestern. and Erik Hauri from the Carnegie Institution. The work was supported by NASA, the National Science Foundation, the David and Lucile Packard Foundation, and the Deep Carbon Observatory.
Note: The above story is reprinted from materials provided by Brown University.
This is a simulation of the May 18, 1980 blast at Mount St. Helens (USA) at 380 seconds. (Credit: Istituto Nazionale di Geofisica e Vulcanologia, Italy.)
A 3-D model of a volcanic explosion, based on the 1980 eruption of Mount St. Helens in Washington state, may enhance our understanding of how some volcanic explosions occur and help identify of blast zones for potentially dangerous locations, according to an international team of volcanologists.
“We took on the modeling of enormously complicated pyroclastic density currents, notably the classic, notorious May 1980 lateral blast that destroyed 500 square kilometers of forested terrain at Mount St. Helens,” said Barry Voight, professor emeritus of geology and geological engineering, Penn State.
Mount St. Helens erupted catastrophically on May 18, 1980, creating a low-angle lateral blast with an astonishing energy and particle content. The blast lasted less than five minutes, but caused severe damage over 230 square miles, killing 57 people and destroying 250 homes and 47 bridges. The damage was not caused by lava flows, but by a fast moving current of superheated gas that carried with it a heavy load of debris.
“Volcanic lateral blasts are among the most spectacular and devastating of natural phenomena, but their dynamics are still poorly understood,” the researchers reported in the current issue of the journal Geology.
The researchers created the 3-D model using the parameters of the Mount St. Helens blast including equations to determine mass, momentum and the heat energy of the gas, along with the size, density, specific heat and thermal conductivity of the solid particles.
“We integrated a wide range of geophysical and geochemical data to develop rigorous initial and boundary conditions for hydrodynamics calculations that reproduced, to an amazing degree, the observed dynamics of the blast envelope,” said Voight.
The 3-D model reproduced the Mount St. Helens blast, closely matching the complicated boundaries of the region of devastation and observed results on the ground. In the model, the areas of ground where pressures imply that trees would be blown down fit the actual locations of destroyed forests.
“The calculations provided much insight into internal dynamics of the blast explosion cloud that could not be observed directly,” said Voight.
According to the researchers, the most important factors controlling where the blast travels and causes damage are a combination of gravity and the shape of the terrain. Pyroclastic blasts are blocked by mountains and channeled down river ravines and canyons.
Previous models of the Mount St. Helens blast considered it to be dominated by a supersonic expanding jet of gas that originated at the volcanic vent. However, the research team suggests that apart from an initial burst that impacted a region less than 3.6 miles from the vent, the blast current was gravity driven.
The researchers found that as the distance from the vent increased, the blast current weakened because of the energy lost while trying to go over obstacles. They also show spreading in all directions caused a slowing of the flow and that particle sedimentation removed energy from the flow.
“Our present results demonstrate that, where detailed geological constraints are available and thanks to the availability of modern supercomputers, 3-D transient and multiphase flow models can fairly accurately reproduce the main large-scale features of blast scenarios,” said Voight.
The researchers note that “such an improvement in our modeling capability will make it possible to more effectively map potential blast flows at blast-dangerous volcanoes worldwide.”
Other researchers on the team are Tomaso Esposti Ongaro and Augusto Neri, Istituto Nazionale di Geofisica e Vulcanologia, Pisa, Italy; C. Widiwidjayanti, formerly at Penn State but now at Nanyang Technological University, Singapore; and Amanda B. Clarke, Arizona State University.
The National Science Foundation and the European Commission supported this research. Researchers at the U.S. Voight began work at Mount St. Helens in 1980 as a researcher at the Geological Survey Cascade Volcano Observatory.
Note : The above story is reprinted from materials provided by Penn State, via EurekAlert!, a service of AAAS.
The mountain ranges of the North American Cordillera are made up of dozens of distinct crustal blocks. A new study clarifies their mode of origin and identifies a previously unknown oceanic plate that contributed to their assembly.
The extensive area of elevated topography that dominates the Western reaches of North America is exceptionally broad, encompassing the coastal ranges, the Rocky Mountains and the high plateaus in between. In fact, this mountain belt consists of dozens of crustal blocks of varying age and origin, which have been welded onto the American continent over the past 200 million years. “How these blocks arrived in North America has long been a puzzle,” says LMU geophysicist Karin Sigloch, who has now taken a closer look at the problem, in collaboration with the Canadian geologist Mitchell Mihalynuk.
Collisions and continental growth
One popular model for the accretion process postulates that a huge oceanic plate – the Farallon Plate – acted as a conveyor belt to sweep crustal fragments eastwards to the margin of American Plate, to which they were attached as the denser Farallon Plate was subducted under it. However, this scenario is at variance with several geological findings, and does not explain why the same phenomenon is not observed on the west coast of South America, the classical case of subduction of oceanic crust beneath a continental plate. The precise source of the crustal blocks themselves has also remained enigmatic, although geological studies suggest that they derive from several groups of volcanic islands. “The geological strata in North America have been highly deformed over the course of time, and are extremely difficult to interpret, so these findings have not been followed up,” says Sigloch.
Sigloch and Mihalynuk have now succeeded in assembling a comprehensive picture of the accretion process by incorporating geophysical findings obtained by seismic tomography. This technique makes it possible to probe the geophysical structure of the Earth’s interior down to the level of the lower mantle by analyzing the propagation velocities of seismic waves. The method can image the remnants of ancient tectonic plates at great depths, ocean floor that subducted, i.e., disappeared from the surface and sank back into the mantle, long time ago.
Intra-oceanic subduction of the Farallon Plate
Most surprisingly, the new data suggest that the Farallon Plate was far smaller than had been assumed, and underwent subduction well to the west of what was then the continental margin of North America. Instead it collided with, and subducted under, an intervening and previously unrecognized oceanic plate. Sigloch and Mihalynuk were able to locate the remnants of several deep-sea trenches that mark subduction sites at which oceanic plates plunge at a steep angle into the mantle and are drawn almost vertically into its depths. “The volcanic activity that accompanies the subduction process will have generated lots of new crustal material, which emerged in the form of island arcs along the line of the trenches, and provided the material for the crustal blocks,” Sigloch explains.
As these events were going on, the American Plate was advancing steadily westwards, as indicated by striped patterns of magnetized seafloor in the North Atlantic. The first to get consumed was the previously unknown oceanic plate, which can be detected seismologically beneath today’s east coast of North America. Only then did the continent begin to encounter the Farallon plate. On its westward journey, North America overrode one intervening island arc after another – annexing ever more of them for the construction of its wide mountains of the West.
Note: This story has been adapted from a news release issued by the Ludwig-Maximilians-Universität München
