permafrost [ˈpɜ:rməfrɔ:st]

例句:

• It isn't called permafrost if it melts annually.
  来自SA
• Perhaps this is caused by the sudden melting of subsurface permafrost.
  可能是地下永久冻土突然融化所造成.
  
• This is the vegetational climate of arctic permafrost regions.
  这是北极永冻地区的植物气候.
  
• The harder the material under the permafrost is, the larger the chamber charge required.
  永冻层之下的土壤越硬, 所需要的药室装药量也越大.
  
• Methane gas from permafrost is a decay product.
  来自SA
• That submarine permafrost is perilously close to thawing.
  来自SA