Barely freezing cold and slow moving damp air conspire to grow long frost
crystals on sheltered surfaces.|
When temperatures are at the edge of freezing, crystals grow on
their edges, molecules hitting the broader sides bouncing off. The
orientation of the molecules and their polar charged areas at the edges
being more likely to capture stray water molecules that bounce against
them, than the "fulfilled" non-charged surfaces along the crystal's
Snowflakes form in a similar manner in the clouds, where the first few
molecules that bump into each other determine much of the shape of the
snow crystal that will form. On land, the surface that the first water
molecules land on determines their orientation, and so strongly influences
the form of the resulting frost crystal.
When temperatures are colder, molecules stick wherever they land, so
growth takes place on all surfaces, producing nubbin-like crystals instead
of delicate flakes and hair.
These long frost crystals cover a branch by the roadside in the
Santa Cruz mountains.
The growth at these crystal's ends makes them very similar to
crystals found in frost heaves.