* Astronomy

Members Login
Username 
 
Password 
    Remember Me  
Post Info TOPIC: Mount Everest


L

Posts: 131433
Date:
Himalayan mega-earthquakes
Permalink  
 


Computer simulations indicate that Himalayan mega-earthquakes must occur every 1,000 years or so to empty a reservoir of energy in southern Tibet not released by smaller earthquakes, according to a paper that will appear in the Nov. 9 issue of the journal Nature.
Colorado researchers Roger Bilham and Nicole Feldl co-authored the paper "Great Himalayan Earthquakes and the Tibetan Plateau." Their research was funded by the National Science Foundation.

Read more

__________________


L

Posts: 131433
Date:
Xtreme Everest team
Permalink  
 


Nine members of the Xtreme Everest team have reached the summit of Cho Oyu and have returned safely to Kathmandu, Nepal. Xtreme Everest is a group of doctors and scientists coordinated by the UCL Centre for Aviation, Space and Extreme studying how the human body functions in extreme environments.

Source

__________________


L

Posts: 131433
Date:
Tibetan plateau
Permalink  
 


Chinese scientists will carry out a research expedition to the central area of China's largest uninhabited region in October.
The central area of the Qinghai-Tibetan plateau is 2,500-km-long and 100-km-wide with altitude differences of over 1,000-meters. Rivers to the north of the plateau watershed run to the Pacific and rivers south to the Indian Ocean.

"Our task is to research the geological formation of the watershed and its influence on climate in China and the world" - Ding Lin, leader of the expedition team and researcher at the Institute of Tibetan Plateau Research of the Chinese Academy of Sciences.

Source

__________________


L

Posts: 131433
Date:
RE: Mount Everest
Permalink  
 


A 20-member team of British based medicos is preparing to carry out medical lab experiments on the slopes of South Col of Mt Everest, which they said would be the world's highest laboratory.
The medical research team of Xtreme Everest will make the first ever measurements of blood oxygen in the 'death zone', at altitudes above 8,000m where the human body has struggled -and frequently failed to survive-to find out effects on the human body in high altitude.

The team plans to take measurements of oxygen in arterial blood at extreme high altitude above 8,000 metres for the first time. It is anticipated that up to ten members of the team will summit Everest.
The Centre for Aviation, Space and Extreme Environment Medicine (CASE) team of the University College London (UCL) will lead the expedition scheduled for May 2007.
The experts will measure the amount of oxygen in their own blood along with running tests to see how well their brains, lungs and metabolism are working at such extreme altitude. They have asked for 208 volunteers having good level of fitness for the 23-day expedition, Parkinson said. Volunteers desiring to taking part need to pay 2,395, which includes return flights from the UK to Kathmandu and another 500 for scientific research.

Read more

__________________


L

Posts: 131433
Date:
Himalayan foreland basin
Permalink  
 


Title: Ganges basin geometry records a pre-15 Ma isostatic rebound of Himalaya
Authors: Jean-Louis Mugnier and Pascale Huyghe

ABSTRACT
The Tertiary continental strata of the Himalayan foreland basin are subdivided into two groups, but the meaning of this subdivision was previously unclear. From the analysis of drill holes, seismic lines, dated sections, outcrops, and balanced cross sections, we find that the southward migration rate of the depositional pinch-out of the younger group is 19 5 mm/yr and equals the Himalayan shortening rate. This equality shows that the flexural foreland basin development is mainly controlled by the motion of the thrust load.
The long-term pinch-out migration rate was slower for the older synorogenic group. Erosion locally occurred at the end of its deposition, due to tectonic reactivation of lineaments of the Indian shield. We suggest that this change in the basin development is linked to the detachment of the subducted Indian lithosphere that decreased the slab pull and increased the mean compressive stress within the Indian plate, whereas the plate motion remained constant. The most important implication of our work is that the associated isostatic rebound could have increased the Himalayan elevation prior to 15 Ma.

Source


__________________


L

Posts: 131433
Date:
Tibetan Plateau
Permalink  
 


Geologists have learned that the height of the Tibetan Plateau, a vast, elevated region of central Asia sometimes called "the roof of the world," has remained remarkably constant for at least 35 million years.

David Rowley from the University of Chicago and Brian Currie of Miami University in Ohio report their finding in the February 9 issue of the journal Nature.
Before their last expedition to Tibet, the geologists expected to find evidence that the plateau was rising 35 million years ago, the result of large-scale geologic forces grinding India and Asia against one another. They found instead that the plateau has stood at its current high elevation for at least 35 million years.
The best explanation for Rowley and Currie's finding: the plateau has widened progressively northward as the Earth's crust thickened.

"This explanation is at odds with a popular theory that has survived since the 1980s" - Chris Beaumont, geological oceanographer, Dalhousie University in Halifax, Nova Scotia, Canada.

India and Asia began colliding 50 million years ago as a result of plate tectonics, a large-scale geologic force that slowly moves the continents around the Earth's surface. The collision took place in an area that once may have resembled the tropical Indonesian Island of Sumatra, and it produced the Tibetan Plateau. Today, the plateau stretches for 190,000 square miles at an elevation of approximately 16,000 feet.

"It looks not a whole lot different in places from Kansas. You could convince yourself that you're in Kansas, except that you're breathing a little too hard" - David Rowley, Professor and Chairman of the Geophysical Sciences Department at Chicago.

According to a popular theory, both the Earth's crust--the planet's outermost solid layer--and the upper portion of the mantle layer that lies below the crust thicken as the continents collide. Then the crust containing the plateau would have "bobbed up", while the mantle fell away and sank deep into the Earth.
Rowley and Currie's research, which is funded by the National Science Foundation, supports the idea that the collision has deformed the crust, but not the mantle.

"The bottom of the crust is weak and any attempt to increase the elevation increases the stress on the bottom of the crust, and that crust is now capable of flowing" - David Rowley.

The Nature paper is based on a technique that Rowley and a colleague developed in the late 1990s to determine the elevation of ancient land surfaces.

"It turns out that elevation is one of the most sensitive monitors of large-scale processes happening within the Earth" - David Rowley.

The technique relies on precise measurement of oxygen isotopes, different varieties of oxygen atoms that are found in rocks formed at various elevations. Water vapour derived from the oceans displays a well-defined isotopic composition that changes in a predictable way as air masses rise, cool and condense with elevation.
As precipitation seeps into the soil, it becomes incorporated into nodules of calcium carbonate, a chemical compound found in rocks around the world. An oxygen isotopic analysis of these nodules reveals the elevation at which they were created, as Rowley and his University of Chicago colleague Ray Pierrehumbert reported in 2001.
The technique is accurate to within approximately 2,000 feet, and it is especially sensitive at elevations of three to five kilometres.

"For asking questions about the height of the Himalayas, the height of Tibet, the height of the Andes, it's terrific. But if you go to small mountain ranges or small elevation differences, you're probably not going to be able to say much with confidence" - David Rowley.

Previous efforts aimed at reconstructing the elevation history of mountain ranges depended on comparing tree species that live today at various elevations with the species found in the distant past as indicated by fossilized leaves and pollen. But temperature, rainfall and climate change can influence the distribution of tree species, along with elevation.

"It's not always clear which one is the driver" - David Rowley.

As for the Tibetan Plateau, Rowley plans to examine even older rocks to see if he can take a scientific snapshot of the area as it began to rise. From this, scientists will be better able to answer a critical question: how fast does the concentration of heat-generating radioactive elements in thickening crust limit its strength?

"Some people had earlier argued that it took, 10, 20, 30 million years before you got enough heat production to limit that strength" - David Rowley.

"The significance of this research should not be underestimated. It demonstrates how a critical observation has the potential to advance our understanding of continental deformation" - Chris Beaumont.

http://geosci.uchicago.edu/~rowley/

__________________


L

Posts: 131433
Date:
RE: Mount Everest
Permalink  
 


Everest, the world's highest peak straddling the border between Tibet and Nepal, is about 3.7 meters shorter than previous estimates after China conducted a new survey of the mountain this year.

According to Chen Bangzhu, Director General of the State Bureau of Surveying and Mapping, Mount Everest stood 8,844.43 meters above sea level, with a margin of error of about 0.21 meters.
In May a Chinese expedition climbed to the top of Mount Everest, known to Chinese as Qomolangma, to determine whether the world's tallest mountain was still growing.

"The data is so far the most detailed and precise among (those from) all previous surveys domestically and internationally. We cannot arrive at the conclusion now that the Everest has become shorter, because there have been problems ... of surveying technology with previous measurements."- Chen Bangzhu.

In 1975, Chinese scientists measured the height of Everest at 8,848.13 meters (29,029 feet, 3 inches), a few centimetres more than an Indian survey had found in the 1950s.
In 1999, a U.S. team measured the mountain at 8,850 meters.
The glaciers on Everest are shrinking on the Tibetan side faster than ever because of global warming.

__________________


L

Posts: 131433
Date:
Tibetan Plateau
Permalink  
 


Chinese researchers have discovered that the Tibetan Plateau, dubbed "the roof of the world", is moving northward and eastward at 7 to 30 millimetres a year.

"The plateau is moving because it's being pushed by the Indian plate" - Dr. Tan Kai, researcher with China Seismological Bureau who is collecting data for a global positioning system (GPS) survey.

A collision between the Indian Plate and the Eurasia Continent Plate 40 million years ago shaped the Tibet Plateau and its surrounding geological features.
As the two plates of the earth's crust are still colliding, the plateau is moving north by more than 20 millimetres and is growing taller by several millimetres a year, too.
Dr. Tan and his colleagues have found that Lhasa, on the southern end of the plateau, is moving 30 millimetres a year northeast at an angle of 38 degrees. Meanwhile, the Kunlun Mountains in the central plateau is moving 21 millimetres a year at 61 degrees. The Qilian Mountains further north are moving between 7 to 14 millimetres a year, at an angle of 80 degrees.

"Which means the entire plateau is moving seven to 30 millimetres a year on average. Such moves are barely noticeable and will not change the Chinese continental plate any time soon. But they're still significant from the geological point of view" - Dr. Tan Kai.

The Kunlun mountain range is one of the longest mountain chains in Asia, extending more than 3000 km. It runs along the western border of China southwards beside the Pamir range, then curves to the East, to form the border range of northern Tibet.
The seismological bureau has conducted more than 50 GPS surveys on the Tibetan Plateau since 1991. China has 1,056 survey stations, of which 340 are in neighbouring country Tibet.

The GSP surveys can capture real-time, highly precise data to calculate velocity of the crustal movement. Results of the surveys will help scientists study the formation and evolution of the plateau and evaluate the region's risk of earthquake and other geological disasters.

__________________


L

Posts: 131433
Date:
RE: Mount Everest
Permalink  
 


A team of geophysicists at the University of Colorado at Boulder has developed a new technique to visualize the colliding rock bodies beneath the Himalaya with unprecedented detail, answering a number of questions about the world's highest mountains and providing a new tool for assessing earthquake hazards.

The study, "Imaging the Indian Subcontinent Beneath the Himalaya" appears in the June 30 issue of the journal Nature. Anne Sheehan, Roger Bilham, Vera Schulte-Pelkum and Gaspar Monsalve of CU-Boulder's Cooperative Institute for Research in Environmental Sciences and department of geological sciences worked on the project along with scientists from the State University of New York at Binghamton and Kathmandu, Nepal.

"We imaged the boundary between the Indian and Asian tectonic plates by developing a new technique that highlights strongly deformed rocks beneath Earth's surface, and applied it to data we collected with a network of temporary seismic sensors deployed in Nepal and Tibet" - Schulte-Pelkum, the paper's lead author and a CIRES researcher.

The network included 29 broadband seismometers operated by the CU-Boulder and SUNY Binghamton teams. About 1,700 earthquakes from as far away as Europe, Alaska and Japan were recorded during an 18-month period starting in 2001. The study was funded primarily by the National Science Foundation.

"Our images of the crust and upper mantle show how the upper Indian crust fragments and is incorporated in the Himalaya, while the lower crust slides under Tibet and undergoes alterations that may help explain how the plateau maintains its high altitude" - Schulte-Pelkum.

Sheehan said Schulte-Pelkum developed a truly novel method to visualize the forces at work underneath the Himalaya. "It's very exciting, and it's something we can use elsewhere to analyze shear in the crust"

Shear zones are similar to faults, Schulte-Pelkum said. Faults are brittle structures at or near the surface of the earth, while shear zones are found at depths of 10 miles or more where heat causes more ductile, or flowing, rock movement.

In subduction zones such as where India and Asia collide, however, earthquakes along brittle faults can occur at depth because rock temperatures are cooler, the researchers said.

The collision of India into Asia forms the Himalaya, the world's highest mountain chain, and Tibet, the world's largest high plateau.
"From surface geology, we know that India dives under Asia. In Nepal, this slip is expressed in very large, destructive earthquakes that occur somewhere along the base of the mountains a few times a century." - Schulte-Pelkum.

However, the infrequency of the tremors had left scientists with few clues as to the structure of the region.
"During the interval between these earthquakes, the shallow fault between under thrusting India and overriding Asia is seismically quiet and difficult to detect"- Schulte-Pelkum.

Sheehan explained that until now, geophysicists could analyze the movement of rock bodies only on the surface, where deformation can be directly observed.

With the team's new method, geophysicists can study the deep crust and determine the direction rocks are being sheared. The shearing is similar to a deck of cards being spread out on a table, Sheehan explained. "We can see how the deep crust has moved. Seeing where these structures are and how they have moved in the subsurface helps us better understand where local hazards are.

"If we can more accurately calculate the subsurface geometries, we can improve our estimations of how the ground will shake during an earthquake. We can't predict earthquakes, but we can get a better idea of how an earthquake's energy will radiate. The Los Angeles Basin has all sorts of folds and faults and subsurface shear, so it would be another potential place to apply some of these techniques to get high-resolution images" - Anne Sheehan, an associate professor of geological sciences at CU-Boulder and a CIRES researcher.

Source: University of Colorado at Boulder


__________________


L

Posts: 131433
Date:
RE: Himalayan mountain
Permalink  
 


This stunning aerial view shows the rugged snow covered peaks of a Himalayan mountain range in Nepal.


Expand

The seventh-highest peak on the planet, Dhaulagiri, is the high point on the horizon at the left while in the foreground lies the southern Tibetan Plateau of China. But, contrary to appearances, this picture wasn't taken from an airliner cruising at 30,000 feet. Instead it was taken with a 35mm camera and telephoto lens by the Expedition 1 crew aboard the International Space Station -- orbiting 200 nautical miles above the Earth.
The Himalayan Mountains were created by crustal plate tectonics on planet Earth some 70 million years ago, as the Indian plate began a collision with the Eurasian plate. Himalayan uplift still continues today at a rate of a few millimetres per year.


__________________
«First  <  16 7 8 9  >  Last»  | Page of 9  sorted by
Quick Reply

Please log in to post quick replies.



Create your own FREE Forum
Report Abuse
Powered by ActiveBoard