Date post: | 26-Dec-2015 |
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Why is it cold in winter?
• We’re farther away from the sun?
NO!!
• We’re tilted away from the sun?
YES!!
Types of Snow Crystals:
The most basic snow crystal is a hexagonal prism and can come in many shapes and sizes.
The prism has 8 sides: 2 surfaces known as basal facets and 6 prism facets.
How does a dull hexagonal ice crystal make such beautiful and elaborate flakes? The intricate flakes come from the condition in which the ice crystals are formed.
Life History of a Snowstorm
• Powder
• Destructive metamorphism
• Constructive metamorphism
• Melt metamorphism
Constructive Metamorphism
• Temperature gradient in snowpack…where is it warmer, top or bottom?
• Ice sublimates, vapors moving up• Warmer top melts a little, joining grains as it refreezes• Lower sublimation continues, leaving depth hoar
• Creates subnivean zone• Destabilizes snow pack…avalanche danger!
Why Migrate?
The Pro’s
?The Con’s
• DANGEROUS! (more than half never return)
• DANGEROUS!! (going to unknown area; hiding places, food sources, etc.)
• DANGEROUS!!! (already inhabited with competitors)