F15PE, identify the following cloud types from a brief description.  A. It was once proposed that they were composed of volcanic ash or meteoric dust, because they were only first reported in 1885, shortly after the eruption 
F15PE, identify the following cloud types from a brief description.  A. It was once proposed that they were composed of volcanic ash or meteoric dust, because they were only first reported in 1885, shortly after the eruption of Krakatoa. It is now known that they are composed primarily of ice crystals. They are the highest clouds in the atmosphere, forming in the mesosphere, and are only visible at twilight in the high latitudes.
F15PE, identify the following cloud types from a brief description.  
Noctilucent Clouds or Polar Mesospheric Clouds