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   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Below the surface: Researchers uncover reasons to rethink how mountains   
   are built    
      
     Date:   
         June 2, 2023   
     Source:   
         Colorado State University   
     Summary:   
         A study suggests that the answers to how and why mountains form are   
         buried deeper than once thought. Clues in the landscape of southern   
         Italy allowed researchers to produce a long-term, continuous record   
         of rock uplift, the longest and most complete record of its kind.   
      
      
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   FULL STORY   
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   A study led by Colorado State University suggests that the answers to   
   how and why mountains form are buried deeper than once thought.   
      
   "Mountain building is a fundamental process of how Earth behaves," said   
   Sean Gallen, lead author and CSU assistant professor of geosciences,   
   "and this study suggests that we may not understand that as well as   
   we thought we did."  Gallen and his team generated new data sets and   
   techniques to use landscapes to reconstruct long-term histories of   
   mountain building in southern Italy. Their novel approach yielded some   
   "confounding" results, according to Gallen.   
      
   In subduction zones, like the one in Calabria in southern Italy, one   
   tectonic plate dives beneath another plate. Mountains in these settings   
   are believed to have formed through the crumpling and thickening of   
   Earth's crust.   
      
   The team combined measurements that recorded geologically short and long   
   timescales, from thousands of years to tens of millions of years. Like a   
   "geologic tape recorder" of the tectonic history, the landscape filled   
   in the rest.   
      
   "In southern Italy, the landscape actually is the bridge between these   
   different methods that we typically use," Gallen said.   
      
   The flat, high-elevation patches of the landscape along the "toe" of   
   the Italian peninsula represent a time when mountain formation was slow,   
   and a steep transition below marks a rapid acceleration. These clues in   
   the landscape allowed the researchers to produce a long-term, continuous   
   record of rock uplift, the longest and most complete record of its kind.   
      
   "We would expect to see a correlation between the rate at which the plate   
   is diving down beneath the other plate through time and our rock uplift   
   history, and we don't see that," Gallen said.   
      
   Crumpling and thickening of the crust appears to be secondary to another   
   process in the formation of the Calabrian mountains. Data points   
   to descension of the lower plate through the Earth's mantle and its   
   alteration of the mantle flow field as the primary factor controlling   
   rock uplift.   
      
   "The results suggest that the typical way we view mountain building   
   doesn't hold for southern Italy," Gallen said. "It appears to be   
   controlled by things that are much deeper within the Earth system. This   
   behavior has been seen in models but never in nature. This is the first   
   time we think we've observed it."  Gallen cautioned that more data is   
   needed to confirm whether their interpretation is correct, but it is   
   backed by existing numerical models.   
      
   Scientists have previously connected mountain height to tectonic plate   
   interactions within Earth's plastically flowing mantle, but this research   
   indicates for the first time that this mechanism is the dominant force   
   in mountain building in subduction zones.   
      
   "The records we have produced imply that deep earth signals appear   
   to dominate what's happening at the surface," Gallen said. "I've been   
   working in the Mediterranean for 15 years, and this result has profoundly   
   changed the way I think about these subduction zones."  Transformative,   
   transparent research The new techniques developed for this study offer   
   a breakthrough in constructing long-term rock uplift histories.   
      
   The team created a unified framework based on a collection of standard   
   geomorphology measurements -- thermochronology, cosmogenic nuclides,   
   bedrock river profiles and the record of past sea levels found in marine   
   terraces. The novel approach goes back further in time than other methods   
   and uses different data sets to constrain modeling in a unique way.   
      
   The method is best applied to active systems, where the modern landscape   
   offers clues to its history. The further back in geologic time a system   
   was active, the harder it is to reconstruct its history with confidence.   
      
   Software developed for the study, published in Nature Geoscience, is   
   freely available for other researchers to use. Gallen hopes the new   
   techniques will stimulate research and discoveries in other areas.   
      
   Co-authors on the study are Nikki M. Seymour, Christoph Glotzbach,   
   Daniel F.   
      
   Stockli and Paul O'Sullivan. The Department of Geosciences is in the   
   Warner College of Natural Resources.   
      
       * RELATED_TOPICS   
             o Earth_&_Climate   
                   # Geology # Earthquakes # Natural_Disasters # Weather   
             o Fossils_&_Ruins   
                   # Early_Climate # Fossils # Origin_of_Life # Evolution   
       * RELATED_TERMS   
             o Fossil o Annual_sedimentary_layer o Geology_of_the_Himalaya   
             o Volcano o Sedimentary_rock o Precambrian o Metamorphic_rock   
             o Rogue_wave_(oceanography)   
      
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   Story Source: Materials provided by Colorado_State_University. Original   
   written by Jayme DeLoss. Note: Content may be edited for style and length.   
      
      
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   Journal Reference:   
      1. Sean F. Gallen, Nikki M. Seymour, Christoph Glotzbach, Daniel   
      F. Stockli,   
         Paul O'Sullivan. Calabrian forearc uplift paced by slab-mantle   
         interactions during subduction retreat. Nature Geoscience, 2023;   
         DOI: 10.1038/s41561-023-01185-4   
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   Link to news story:   
   https://www.sciencedaily.com/releases/2023/06/230602115057.htm   
      
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