فارسي | English
  About Us | About Iran | Contact Us | Staff Info[Geoportal Info] [Maps] [Mining Info] [Other Activities]  
 
  News | Events | Photo Gallery | Downloads | Links | Kids  Search    Region    Scale    Subject   :Access to information by   Home | Newest   
 

New titles:
 The Legacy of the 1992 Nicaragua Tsunami
 How friction evolves during an earthquake (By simulating quakes in a lab, engineers study the way that friction changes along a fault during a seismic event)
 USGS on Fire: It's not a matter of
 Ancient Earth's hot interior created 'graveyard' of continental slabs
 Supervolcanoes: A key to America's electric future?
 USGS publishes a new blueprint that can help make subduction zone areas more resilient
 Is the next gold mine in Bulgaria
 A Closer Look at an Undersea Source of Alaskan Earthquakes
 More than 210 killed by earthquake in Iran-Iraq border region
 Four systems out there and hurricane season hasn't even hit its peak yet
News Report
 
Avalanches more complex than previously thought
1395/10/13
NGDIR News Section--New study observes inner workings of avalanche with innovative technology.
  
   Avalanches can throw up a powdery cloud of snow as they violently charge down mountains, obscuring their inner workings from scientists.
  
   But new observations of artificially-triggered avalanches in Switzerland's Vallee de la Sionne have penetrated this powdery veil. Scientists used an innovative radar system, sensors on a pylon and video equipment to get perhaps the best look at avalanches yet.
  
   They report in a new study that avalanches have a more complex internal structure than previously known. The new study finds rather than being one mass of snow, avalanches are made up of many internal surges that can overtake each other as the avalanche gathers snow and moves downhill.
  
   Understanding avalanche mechanics is important for predicting their potential path, which could help mitigate their destruction, according to the study's authors. Avalanches kill about 100 people every year in the European Alps alone and those near infrastructure can cause millions of dollars in damage.
  
   The new study, published in the Journal of Geophysical Research: Earth Surface, a journal of the American Geophysical Union, is one of the first to probe the internal structure of avalanches in this detail, according to the study's authors.
  
   "It is changing the view we have on avalanches," said Anselm Kohler, a Ph.D. student at the Swiss Federal Institute for Snow and Avalanche Research in Davos, Switzerland, and Durham University in the United Kingdom.
  
   "If you were just thinking of some mass going down the mountain, you would say 'Well it has a front and it has a tail and it comes down.' But what this radar shows is that there is a much more complicated internal structure," said Kohler, lead author of the new research that was also featured in a recent BBC special on avalanches.
  
   Going downhill
   Avalanches are spawned by disruptions to huge masses of packed, unstable snow, and in the Alps, they can reach speeds of about 200 kilometers (125 miles) per hour. A prime location for studying avalanches and the mechanics driving them is the snowy Vallee de la Sionne in southwestern Switzerland.
  
   There, researchers use various equipment to observe avalanche dynamics and measure properties such as speed, direction and pressure. However, naturally-caused avalanches are unpredictable and hard to observe during their short lifespans.
  
   To get around this, researchers use explosives to artificially trigger an avalanche. In the new study, Kohler and his colleagues artificially triggered five avalanches in the Vallee de la Sionne and observed them with state-of-the-art equipment.
  
   In the past, researchers have used Doppler radar to detect an avalanche's speed under the powder cloud. However, Doppler radar has poor resolution, preventing it from seeing an avalanche's internal structures, which are areas where snow is more densely packed. GEODAR, an avalanche-specific radar used in the new study, is able to observe the location of internal structures in the avalanche at a high resolution.
  
   "Most of the dynamics happens below the powder cloud, so we have to use some device to penetrate through the cloud," Kohler said. By combining video analysis with radar images, the researchers could see different portions of the powder cloud in each avalanche and the snow flowing beneath them.
  
   What they found was striking: The avalanches were not just single masses of smoothly moving snow. Rather, the avalanches contained multiple internal surges of snow moving at very different speeds.
  
   Frequently, these internal surges overtook the leading edge of the avalanche, a phenomenon not accounted for by current models.
  
   "We had this idea that it happened, but it was never shown so clearly," said Dieter Issler, a physicist at the Norwegian Geotechnical Institute in Oslo, who was not involved with the new study. "[The new study] is really a quantum leap in the possibilities of studying the internals of snow avalanches."
  
   One of the possible reasons behind the different surge speeds is a difference in friction-some parts of the avalanche have greater contact with the ground than others, Kohler said. Where there is greater friction, the avalanche slows down.
  
   Kohler and his colleagues plan to probe avalanches more deeply in the future, adding lateral views of avalanches that would allow for an extra dimension of study into the mysteries beneath the powder. A better understanding of these surges and other avalanche mechanics could help scientists improve their ability to model avalanches and predict their paths, according to the study's authors.
  
   "This study emphasizes and shows in a clear and graphical manner how complex snow avalanches can be and usually are," Issler said. "Despite this enormous complexity... there is hope that with good instrumentation and ingenious experimentation methods, we can start to unravel even fine details of the dynamics and have a better understanding how snow avalanches... show more complexity."
  
   By AGU

 
 
Publications  Library
Glossary  Papers
 
 
 
 
FAQ  Members
Job Offer  Training
 
 
 
 
• NanoBioEarth Database 
• Medical Geology Database 
• Geological Atlas of Roads 
• 4th National Development Plan 
• Marine Geology 
• Geography information 
• Mines and Deposits of Iran 
• Landslide Database of Iran 
• Exploration Area DB 
• Copper Database 
• Gold Database  
• Geoscience Laboratories 
• Mineral Information 
• Bibliographic Database 
• Geochemistry Database 
• Earthquake database 
• Abandoned mines DB of Iran 
• Mineral processing database 
• Minerals database 
 
 
 
 
Login Name:
Password:
Sign Up for membership ]
 
 
 
   Others Activities:• Geo Hazard Of South Caspian • Geoscience database of ALBA • Geoscience Database of ECO 
• GEOLOGICAL SURVEY OF IRAN • Tajikistan Geoscience Database • Geo Database of Venezuela • 4th National Development Plan 
• Export & Import Regulation Act     
 
 
Maps:• Map of Iran's Last Earthquake • Distribution Map of mineral Processing Plants 
• Mineral Distribution Map of Iran • Geosciences laboratories distribution map of Iran • Orohydrographic Map of Iran 
• Select state on iran map • Geological Map of Iran(1:1000, 000 Scale) • 2500 K Magnetic Lineament Map of Iran 
• Map of Iran's Earthquake    
 
Best viewed:1024*768
National Geoscience Database Of IRAN
URL:www.ngdir.ir
Contact Mail:Info@ngdir.ir
 
 
 Search with:           
Designed by Payvand Software Group  Privacy | Copyright | Disclaimer