Tag Archives: snow

The Uniqueness of Water

Water is a natural substance that all of us encounter on a daily basis.  We rinse with it to clean ourselves and we drink it to stay healthy.  In addition, more than 60% of the human body is comprised of water.  But have you ever stopped to consider the uniqueness of this molecule that plays an intricate part of our lives and bodies?

H2O Molecule
Diagram of a water molecule. Figure by Melyssa Smith

Perhaps the beauty of water begins with the simplicity of its molecule, H2O.  It is made-up of only two elements: two hydrogen atoms (H2) and one oxygen atom (O).  The H atoms create a slight positive electrical charge on one end of the molecule (a positive pole), while the O atom creates a slight negative charge (a negative pole).  This polarity helps liquid water attract to, surround and break apart more substances than any other known liquid.  Thus, scientists call water a “universal solvent” – something that many other substances (e.g. salt, sugar, powdered hot cocoa) can dissolve into.  This attractive quality is how water is able to transport many vital minerals and nutrients throughout our soils, plants and environment.

Waterstrider_wiki
A Water Strider, kept afloat by the surface tension of water. https://upload.wikimedia.org/wikipedia/commons/1/1a/WaterstriderEnWiki.jpg

Not only does water bind easily to other substances (adhesion), but it also sticks well to itself (cohesion).  The positive and negative ends of water molecules attract to each other and form water droplets.  These dual properties help explain how water can ascent up the trunks of trees – water clings to the inner walls of the xylem in tree trunks and pulls other water molecules along, travelling up against the forces of gravity.  You can observe water’s cohesive forces by filling up a glass of water slightly over the rim; water will hold onto itself and not spill over the sides.  Similarly, surface tension enables spiders and insects, such as the water strider, to walk on the surface of the water.  And so this seemingly simple molecule is capable of amazing feats.

Water has special physical qualities as well.  Unlike any other material on Earth, water can exist in solid, liquid and gaseous forms naturally.  The gas form floats freely in the air we breathe, with many molecules moving haphazardly far away from each other.  This vapor can condense into clouds and return water to the earth as either rain or snow.  When we hear the word “water” we usually think of the liquid form, and that’s probably because ~70% of our planet is covered in oceans.  Snow and ice are examples of water’s solid phase, with molecules tightly packed and organized into crystalline structures.  Unlike most other materials, the solid phase of water is less dense than its liquid form, which means ice can float atop liquid water.  This property is useful in lakes during the wintertime, as surface ice acts as an insulating layer for the water below, shielding aquatic life from extremely cold temperatures.  Clearly, water is a necessary ingredient for survival.

2013 letchworth falls downstream winter
A frozen Letchworth Falls, Letchworth State Park, Castile, NY. All three physical states of water are present: solid (ice and snow), gas (air) and liquid (stream below). Photo by OPRHP

New York State has more than 70,000 miles of rivers and streams and around 7,600 lakes, ponds and reservoirs.  Additionally, we are fortunate to share our borders with two Great Lakes, Lake Erie and Lake Ontario.  Whether flowing, still, above or below ground, water is a ubiquitous feature in New York State Parks.  It supports life and creates habitats for aquatic plants and animals.  At the same time, water provides endless opportunities for recreation.

Many of our State Parks offer outdoor activities which involve water.  Check out the 2016 Empire Passport to learn more about how you can access our state parks in any season.  From swimming, boating and water skiing in the summer, to snowshoeing, sledding and cross-country skiing in the winter, to fishing (ice, fly or reel) year round — there is water-filled fun for every age all year long.  The unusual chemical and physical properties that make water so valuable are also what make water so unique and enjoyable.

Post by Melyssa Smith and Erin Lennon (OPRHP Water Quality team)

Resources:

Water as a universal solvent – http://water.usgs.gov/edu/solvent.html

New York State’s land and water resources – http://www.dec.ny.gov/61.html

Unusual properties of water – http://chemwiki.ucdavis.edu/Physical_Chemistry/Physical_Properties_of_Matter/Bulk_Properties/Unusual_Properties_of_Water

Flitting Crystals

“Snow”

by William Cullen Bryant

Here delicate snow-stars, out of the cloud,
Come floating down in airy play,
Like spangles dropped from the glistening crowd
That whiten by night the Milky Way.

Snow is that magical precipitation that turns our stark winter landscape into a winter wonderland; gives school children joy at the possibility of a day off – SNOW DAY; and gives commuters white knuckles as they navigate home on slippery roads.  Snow is what we expect to see each winter here in New York State.  But what is snow?  How is it formed?  Is it true that no two flakes are the same?

Snow will form in clouds between the temperatures of -39˚F and 32˚F.  Clouds are mostly filled with tiny water droplets, tiny meaning that thousands can fit in a period.  Microscopic dust and salt particles from the land and sea are also found in clouds.

As the dust and salt cool in a cloud, they attract the tiny water droplets which stick and freeze to the particles – beginingthe formation of a snow flake (or the scientific term snow crystal).  These tiny snowflakes grow by collecting more water molecules.  When they get too heavy to be in the cloud they start to fall to the ground.  As they fall, they bump into other snowflakes causing pieces (tiny crystals) of the snowflake to break off which become new snow flakes.  The humidity and temperature inside the clouds will determine which type of snowflake is formed.  If the air is moist and warm (25o-32o F) large flakes will form.  If it is cold and the cloud has little moisture, the snow that forms resembles tiny columns.  Figure 1 illustrates how different types of snowflakes form in different cloud conditions.

Figure 1. Snowflake shapes at different temperatures and humidity (“Supersaturation”). From: http://mrsgallscience.wikispaces.com/Snowflakes
Figure 1. Snowflake shapes at different temperatures and humidity (“Supersaturation”).
From: http://mrsgallscience.wikispaces.com/Snowflakes.

Why do snowflakes have a six-sided symmetry? Snowflakes are six-sided because of the way that the individual water molecules connect together – they form hexagonal lattices which give the snowflakes six-sided symmetry.

Eight common types of snowflakes are:

Hexagonal Plate Crystal:

Hexagonal Bentley & Humphreys P. 45

Six-sided flat crystals with various amounts of surface patterns.  Largest of these can be just under ¼” across.  Hexagonal plate crystals are found in most snow falls.

Stellar Crystal or Dendrite:

Stellar Bentley 7 Humphreys P. 149

Stellar crystals are six-pointed star shaped snowflakes. These flakes can be up to 1/2″ across.  They can be found in low numbers in most snow falls.  Formed in the low atmosphere when the temperatures are not too cold and the humidity is high, sometimes the stellar crystal flakes join together to form large flakes that are 2” across.  The gentle drifting of the stellar crystal flakes gives a tranquil feeling to snowfalls.

Column Crystal:

Columns Bentley & Humphreys P. 210

Forming in cold clouds and low moisture, column crystal flakes are six sided and can be hollow inside.  During the winter, column crystals are commonly found in the high, wispy cirrus clouds.  They help to create a halo around the moon on winter nights. The halo is created by moonlight streaming through these ¼” crystals.  Rarely do these crystals fall to the ground.

Asymmetrical Crystal:

Asymmetrical Bentley & Humphreys P. 210

Asymmetrical Crystals are another common snowflake.  They appear to be many hexagonal plates stuck together and have been mistaken for stellar crystals.  They are about 3/8” across.

Bullet Crystal:

Bullet Bentley & Humphreys P. 210

Bullet crystals are column crystals that look like one end was sharpened with a pencil sharpener to form a hexagonal pyramid.  They can be seen either singly or in groups of three, attached by the points of the pyramid.

Tsuzumi Crystal:

Tsuzumi Bentley & Humphreys P. 210

Named for the Japanese drum of the same design, Tsuzumi crystals are column crystals with hexagonal plate crystals at each end.   They form when the column crystals bump into the hexagonal plate crystals as the snow falls.

Needles:

Needles Bentley & Humphreys P. 210

Needles are fine, six-sided columns with a point at each end; they range in length from ¼” to ¾” long.  This is one of the most common types of snow flake in a snow storm.  Sometimes the needle flakes freeze together during the descent forming conglomerate flakes.  These conglomerate flakes quickly break apart as soon as the flakes hit the ground.

Stellar Hexagonal Plate Crystals:

Stellar Hex Bentley & Humphreys P. 111

Stellar Hexagonal Plate Crystals are some of the most stunning snowflakes.  They form when either a stellar crystal goes through a hexagonal plate crystal cloud condition or a hexagonal plate crystal goes through a stellar crystal condition.  These are some of the most common snowflakes in a storm.

So is it true that no two snowflakes are alike?

During school vacation try one of these family activities – preserving snowflakes or making a snow catcher.

Post by Susan Carver, OPRHP.

 

Sources:

Bentley, W. A. and W. J. Humphreys, Snow crystals: 2453 illustrations, Dover Publications, New York, 1962.

Griffin, Julia, The science of snowflakes, and why no two are alike, PBS NewsHour, 22 December 2011, http://www.pbs.org/newshour/rundown/the-science-of-snowflakes/.

Martin, Jacqueline Briggs, Snowflake Bentley, Hougton Mifflin, Boston, 1998.

National Oceanic and Atmospheric Administration, How do snowflakes form?  The science behind snow.

Stokes, Donald, Stokes nature guides: a guide to nature in winter, Little Brown and Company, Boston, 1976.

National Snow and Ice Data Introduction to Snow.

 

 

 

 

Subnivean Life: A World Beneath the Snow

                                 Definition of “subnivean”:                                 the zone in or underneath the snowpack. 

Entrance hole in the snow.
Entrance hole in the snow. Photo by Patty Wakefield, OPRHP.

During the winter months when the temperatures fall into the single digits or below zero, and snow covers the landscape, survival in such harsh conditions is often challenging. Have you ever thought about the small mammals that reside in the fields along some of our country roads? One of those critters is the meadow vole (Microtus pennsylvanicus); which means small ears of Pennsylvania. The meadow vole is an integral part of the food chain for many prey species such as the red-tailed hawk (Buteo jamaicensis) and the red fox (Vulpes vulpes).

Meadow vole Photo courtesy of www.fcps.edu.
Meadow vole Photo courtesy of http://www.fcps.edu.

How do they survive? Meadow voles form runways or paths in dense grass in fields and/or wooded areas in the spring and summer months. You can see evidence of these tunnels by entrance holes.

Grass entrance
Entrance holes. Photo courtesy of http://www.pbase.com.

 

Grass Tunnels
Tunnels. Photo courtesy of http://www.pennlive.com.

These runways allow the meadow voles to forage, reproduce and survive while protecting them from predation. Meadow voles also dig shallow burrows where nests are constructed. During the winter months, the tunnels are under the snow.

Tunnels1

 

The snow actually works as an insulator to help protect them from the cold.

Tunnels2
Evidence of snow tunnels (2 images). Photos by Patty Wakefield, OPRHP.

Meadow voles often eat the green basal (bottom) parts of grass, berries and the cambium (under bark) of small saplings and bushes.

Tree damage
Sapling chewed by voles. Photo courtesy of http://www.tlehcs.com.
Cute voles eating
Voles eating berries. Photo courtesy of http://www.mnginteractive.com.

 

Next time you take a walk in a State Park see if you can find traces of these remarkable little winter warriors. The beauty and wonders of nature is all around us. We need just take the time to observe and see what we can see.

Post by Patty Wakefield.