Geography Reference
In-Depth Information
FIGURE 4.1
The Wegener-Bergeron-Findeisen mechanism for snow crystal growth in the atmo-
sphere. Greater saturation vapor pressure over liquid water than over ice causes supercooled
droplets to evaporate and ice crystals to grow. (Image courtesy of L. R. Dexter and K. Birkeland.)
FIGURE 4.2
A classic example of the six-sided hexagonal crystal structure of ice I. (Image courtesy of
K. Libbricht.)
For 40 years around the turn of the twentieth century, a dedicated photographer
named Wilson Bentley took thousands of photographs of newly fallen snowflakes while
braving the outdoor conditions of New England winters (Figs. 4.3, 4.4). Bentley cata-
loged his snowflake photographs into different types based on similar form character-
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