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.