Transcript What is Snow???

LET IT
SNOW
What is Snow???
Snowflakes are the result of water vapor
FREEZING onto a condensation nucleus.
(dust, dirt, etc)
Elaborate patterns develop as
the crystals grow.
Moisture and Temperature Influence
Crystal Type
Microphysical Properties of Snow
Primary snow grain types:
Plate (new snow)
Column (new snow)
Dendrite (new snow)
Images from:
The Snowflake: Winter’s Secret Beauty
-- by Kenneth Libbrecht and Patricia Rasmussen
Plates
Columns
Dendrites
Needles
Graupel
(Melted grains)
ARTIFICAL SNOW
TYPES OF SNOW CRYSTALS
MORE INFO HERE…
AND HERE.
The Changing Snow Pack…
• Snow has three main metamorphism
processes.
– Destructive Metamorphism
– Constructive Metamorphism
– Melt Metamorphism
Destructive Metamorphism
• The shape and
structure of the flake
is destroyed, but the
mechanical strength
of snow is increased
due to the Hydrogen
bonding of individual
ice grains.
• (AKA Sintering)
Constructive or Temperature
Gradient Metamorphism
• This happens after
destructive phase. Here
the water vapor moves
upward resulting from
the temperature gradient
of the snow and the
pores. This creates more
space in the subnivean
environment below the
surface of the snow
known as the depth
hoar.
Insulative Value and the Subnivean
Environment
• The AIR SPACE IN THE SNOW creates
good insulation from the cold temperatures
above the snow pack.
• Many plants, insects and animals rely on
the snow cover to keep safe and “warm”
for the winter.
Melt Metamorphism
• The final stage of snow
metamorphism is Melt.
Snow is exposed to
temperatures above
freezing. Water vapors
move Down (and up
from the ground)
creating a crust layer
in the middle.
Quinzhee Construction
Quinzhee Construction Lab
• Quinzhee is the Inuit word for snow shelter. It is
made by hollowing out a pile snow. Used by
native Americans who lived in forested areas.
• Igloo: Constructed by using blocks of wind
packed snow (or ice). Used by native
Americans who lived in open areas.
Design Features
•
•
•
•
Dome shape = structural stability
Thick walls = insulation
Vent holes – escape of moisture
A raised platform takes advantage of warmer air
higher up
• A small, low entrance prevents loss of warm air
• The entrance hole positioned perpendicular to
the prevailing wind is protected from direct wind
drafts
• Step 1: Shoveling
– Shovel a pile of snow
into a mound big
enough to hold as
many people in your
group.
- Poke sticks 1 foot in.
– Let the mound
“Sinter” for at least
four hours. (snow
crystals will bond
strong) (Hydrogen
Bond)
–
• Step 2: DIGGING
- Need to have a person
outside shelter at all times in
case it collapses.
– Keep entrance small and low.
– Hollow the shelter out from
the top down. (DIG UP!!!)
– Stop digging when you see
the sticks.
• Step 3: Sleeping
– Make elevated snow
beds (above the door)
to allows cold air to
flow down.
– Poke an air vent on
ceiling to allow moister
to escape.
– Block door with
backpack.