Winter's Art: Ice Formations

Behold, the wonders of nature!  Winter is one of the best seasons to view beautiful snow and ice formations that occur over fields, engulf trees, and grow at lake shores.  Not only do they make for stunningly beautiful photos but the processes by which they form are very interesting as well!  In this edition of Turtle Talk, we’ll explore examples of unique ice formations that you can observe right outside your own front door!

Let’s begin with something that may be familiar—hoarfrost!  Originating from Old English, the word ‘hoar’ roughly translates to ‘showing signs of old age’.  When we think of snow and ice formation, the three phases of water come to mind: ice, liquid, and vapor (or gas).  As temperatures rise above 32^oF/0^oC, ice melts into liquid water and then evaporates into water vapor when water molecules have enough energy (in the form of heat) to break away from their bonds.  Water boils and jumps from liquid to vapor at 212^oF/100^oC; however, we commonly see melting and evaporation occur when temperatures are below freezing and the sun is out, warming the earth’s surfaces.  The sun, therefore, is responsible for causing this liquid-to-vapor phase change by delivering the energy needed in the form of small energy packets known as photons.  Interestingly, hoarfrost crystals form when water vapor flash-freezes into ice, skipping the liquid water phase entirely.  The delicate hoarfrost crystals typically form on a clear, windless, cold, and humid night and give trees the appearance of having white beards—thus the signs of old age.  Unfortunately, they are short-lived, often succumbing to the wind and the heat of the sun.

Compared to hoarfrost, rime ice is a little-known, yet beautiful, formation that occurs much less frequently.  Resembling an ever-thickening fog at its birth, rime ice forms as supercooled water droplets freeze on-contact with a surface, such as a tree branch or a spider’s web, that is below 32^oF. 

Due in part to its unique molecular structure and to the inclusion of foreign air particles, supercooled water remains in its liquid form when temperatures are below freezing.  As these droplets flash-freeze when contacting a cold surface, they form tiny, delicate, needle-like formations that sprout and grow outward from its surface.  Rime ice can be classified as either hard—a very dense ice formed in strong winds—or soft, having formed as a fragile, sugar-like crystal when winds are calm.  Rime ice crystals are best observed in the wee early morning hours, just as the sun is peaking out over the horizon!

Ice doesn’t just form sharp, spindly crystals; however, they can be round as well!  Ever wonder what those tiny little pellets of snow falling from the sky are called?  It’s not hail and it’s not sleet… it’s Graupel!  These small, opaque pellets range from 2-5mm in diameter and form as ice crystals fall through supercooled water droplets in clouds.  As the crystals tumble through the cloud, the supercooled water droplets adhere and bond to the ice crystals forming small round pellets.  Snow pellets (as they are also called) differ from hail in that they are softer and crumble under pressure, unlike these next ice formations, which can be found on shores around the world, including those of the Great Lakes!

Another round ice formation, the unique ice ball phenomenon, has been made famous in recent years by The Weather Channel and local meteorologists explaining their formation.  When temperatures are just below freezing, pressure from waves beneath the surface of ice sheets formed just offshore, continually break off chunks of ice of varying sizes. 

These pieces either pile up resembling broken shards of opaque glass or they are slowly churned and rolled by gentle waves into spheres.  As ice continues to build up, the ice balls (also known as ice eggs) continue to form and are eventually pushed onto shore where they continue to collect in numbers.  Ice balls can grow to more than a meter in diameter and can easily weigh more than 50 pounds.  These unique ice formations can be seen on the beaches of Finland, Russia, northern Germany, and the shores of Lake Michigan!

Like ice balls, you don’t need to go far to find volcanoes in Wisconsin!  Ice volcanoes form when waves push water up through a hole in an ice sheet that developed on the shore of a lake.  As newly-laid water continues to freeze around the hole, it forms a conically-shaped mound.  Increasing pressure from high-energy waves beneath the surface of the ice forces water up through the hole in the mound causing it to spurt out of the top, just like a volcanic eruption! 

Feeling lucky?  Consider yourself fortunate if you come across the extremely rare occurrence of blue ice on the Great Lakes!  Blue ice is normally associated with glaciers but can also be found in the

Antarctic and, on rare occasions, on Lake Michigan.  It forms when snow on top of the ice is compressed—squeezing out any air bubbles—causing the ice to increase in density.  Air bubbles tend to scatter incoming light, reflecting it back into the atmosphere, thus making ice and snow appear white in color.  White light is known as being polychromatic in that it contains all the wavelengths of the visible spectrum.  As air bubbles are removed from the ice through compression, and density increases, ice crystals enlarge, lengthening the path light must follow as it is absorbed.  As this path increases, light waves begin to react differently when they reach the ice and are no longer just reflected away as white light. 

Colors with longer wavelengths (red through green) become absorbed in the ice, whereas cool colors (blue and violet) with shorter wavelengths are scattered and reflected outward making the ice appear blue.  The older and denser the ice, the bluer the color appears and, quite possibly, the more luck you’ll have!

Although many of us would prefer warmer weather to the cold of winter, this is the only time of year to experience nature’s awe-inspiring displays of incredible ice formations!  While this short list only scratches the surface, there are many more unique ice formations that can be found here in Wisconsin and around the Great Lakes.  For example, check out the delectable pancake ice formation here!  Maple syrup, anyone?!

It's a Hoot--The Animal Joke of the Week!

Q: What time does a duck wake up?

A: At the quack of dawn!

Riddle Me This...

I grow down as I grow up.  What am I?

(A: esooG)

Phenomenal Phenology!

Here's what's happening this week:

• White-tailed deer bucks are shedding their antlers!
• Great Horned Owls begin nesting
• Skunk cabbage begins blooming
• Belted Kingfishers begin to arrive
• Song sparrows begin to arrive

And, we've already received reports of Eastern Bluebird arrivals!  

Critter Corner

Last week's photo was of an Eastern Gray Squirrel (Sciurus carolinensis), a very common mammal
native to North America. Eastern Gray squirrels build their nests--called dreys--using moss, dried grasses, feathers, and leaves as insulation. Nests can be high in the crook of a tree's trunk and limb or inside a hollow space in a tree, also known as a tree cavity. Known as scatter-hoarders, these tree squirrels spend all autumn gathering and scattering small caches of food (primarily nuts like
acorns, hickories, and walnuts) in the ground near their nests for the winter. In addition to using natural landmarks and their incredible sense of smell to find their caches (and those of other squirrels), grey squirrels experience an enlargement of their hippocampus--the primary memory section of the brain--beginning in late summer as they begin the mad dash to stash their loot. Who says a larger brain doesn't make you smarter? These clever squirrels will even pretend to burry food to make more work for other squirrels who might be watching! Unfortunately for squirrels, not all caches are found during the winter months and many of the nuts they leave behind buried in the soil sprout in the spring as baby trees! This is why grey squirrels (and fox squirrels) are said to be natural forest regenerators--a nice little ecosystem service that helps our forests continue to grow and support the ecosystem!

Can you guess this week's critter?

That's all for this week! Thanks for reading!

Stay wild & free & healthy as can be!

-CT

What's With Weather & Woolly Bears?

What’s black and brown, fuzzy, and curls in your hand when it’s picked up?  You guessed it—a woolly bear caterpillar!  The larval form of the Isabella Tiger Moth, Pyrrharctia isabella, also known as the woolly bear or woolly worm caterpillar, is found in northern Mexico, throughout the US and the southern third of Canada.  There are even reports of these moths being found in the arctic!

 This extraordinary species lives for a whopping 14 years beginning in an egg, where woolly bears will spend up to two weeks before hatching in either May or August.  Once freed from their eggs, the hungry little caterpillars begin to eat… everything!  Woolly bears are considered generalists, meaning they will consume a variety of leafy plants, including herbs, shrubs, and trees!  In contrast to this, the monarch caterpillar is a specialist, primarily feeding on milkweed plants, which give the monarchs their toxicity.  Unlike monarchs, woolly bears are not toxic and, therefore, are not aposematic—they don’t sport bright colors and patterns associated with the warning signals of toxicity like monarchs do. 

 Although woolly bears can be found throughout the summer, they are more commonly observed in the fall as the August generation travels across paths and roads seeking a good over-wintering hideout.  These little guys find refuge in places such as logs, under bark, and in rock cavities, which help protect them from the bitter cold of winter.  Additionally, woolly bears have a unique quality to their physiology that allows them to freeze solid throughout the winter and survive to thaw in the spring!  In fact, these caterpillars can survive in -76^oF temperatures!  How, you ask?  Well, this species is one of many that produces a kind of antifreeze in their tissues called a cryoprotectant.  This compound effectively lowers the freezing point, allowing the caterpillars to survive extremely cold temperatures, even after becoming a woolly bear-sicle! 

 The woolly bear carries on this ‘start and stop’ life cycle for most of its life, molting each year, until it finally garners enough resources to form a fuzzy brown cocoon in the spring.  After spending a month in their cocoons, they transform into pupas (a process known as pupation) and emerge as beautiful orange moths!  Then the race is on and the woolly bear moths have 24 hours to track down a mate and lay eggs before their life cycle finally comes to an end and they die.  As a moth, woolly bears are so driven to fulfill their niche, they don’t eat a bite during this stage of life! 

 Did you know woolly bears are famously known to predict the weather!  Well, almost.  From 1948 to 1956, Dr. C.H. Curran—then, the curator of insects at the American Museum of Natural History in New York City—began experimenting with woolly bears.  Each year, Curran collected woolly bears and counted their segments, noting the number of segments with spiny black hairs and those with brown.  Woolly bear caterpillars have 13 segments in total and around a third of them make up the rust-colored band in the middle, which widens when woolly bears molt.  If, on average, the woolly bears had more black on them, he predicted the coming winter would be horrendous.  However, if, on average, the caterpillars were more brown than black, Curran predicted a milder winter.  After making his predictions, he reported them to a friend at the New York Herald Tribune, who incidentally published Curran’s winter forecast in the paper, which is why woolly bear caterpillars are one of the most recognizable in the country, next to monarch caterpillars!  After eight years of counting, predicting, and analyzing winter weather results—Curran is said to admit that there just might be something to this old tale! 

 So, the next time you see a woolly bear caterpillar crossing the road, help it to the other side and take note of its coloration—was its brown band wide or narrow?  Were you able to forecast the winter weather accurately?  Let us know in the comments below!

It's a HOOT--The Animal Joke of the Week!

Q: What did the judge say when the skunk walked into the court room?

A: Odor in the court!

Riddle Me This...

I can fly, I can walk, and I can swim but I don't get wet.  What am I?

(A: wodahs s'drib a)

Phenomenal Phenology!

Here's what's happening this week:

• Red foxes begin mating
• Canada geese begin to arrive
• Beavers begin mating

Critter Corner!

Here's an easy one... this will get you warmed up for next week's challenge!

That's all for this week!

Stay wild & free & healthy as can be!

-CT