Hoar-frost Etymology

Hoar-frost ice crystal growing on a grass stem

Our modern-day English term, "hoar-frost," grew like a fruit from a number of older root languages. By combining the two words' meanings, the term attempts to describe ice crystals that form on the ground or low vegetation, by water vapor sublimating directly into ice without turning to liquid first.

Going back in time, "hoar" grew out of the Middle English, "hore," which came from the Old English, "hār," itself originating from the Proto-Germanic, "hairaz." It is cognate, or related to Old Norse "hārr," Old High German, "hēr," and Old Slavonic, "sěrǔ." The first known use of "hoar" was in 1567, while its roots grew down into the 11th century.


Thick hoar-frost covers opening to squirrel den

Growing forward in time, the Proto-Germanic, "frusta," turned into the Old High German, "frost," then adopted into Old English as "forst" and "frost." Both of these terms were common in English from around 1400 until late in that century, when "frost" was the sole literary survivor. The Old High German "frost" is related to the "frost" of Old Saxon and Old Frisian, and to the "vorst" of Middle Dutch and Dutch. The related term, "freeze," is from the Old English, "freosan," and German / Old High German / Proto-Germanic, "frieren" / "friosan" / "freusanan." 

The root words for hoar led from venerable to grey-haired, morphing into a term that tethers the vision of white ice crystals to that of an old man's beard. The root words for frost led from a generic, "to freeze," to the slightly more specific, "turn to ice."

These days, our winter walks through the woods and over to the frozen creek lead here and there through patches of what one might call, "hore-forst." As we move on through November and the temperature keeps dipping, frost will eventually form on my hoary beard, freezing lips and cheeks until my own English starts sounding rather old.

Spring in Fits and Starts

Spring arrives to these woods in fits and starts. But at least mud season is finally winding down here at the end of the road. Our days are above freezing for the most part, but nights are still cold enough to firm up the mud bog between here and pavement, some miles away. If we want to go to town, we go early. But really, who wants to go to town?

In this part of northwestern Montana, the high and low temperatures on April 15th averaged 56F and 31F over the past eight years. We'll still see snow flurries into May, maybe even June. But the ice and snow linger less as the nighttime temps crawl upwards. Still, as long as it freezes overnight, we get to watch for interesting weather creations.

Spent high noon today down by the creek. A little snow lingers in the deeper shadows, but not along the stream banks where snow melt has steadily raised the water level over the last week. Soon, grayling and trout will wriggle up into this current. But today's curiosities were splash-cicles, ice creations wherever the water gets rowdy enough for a splash zone.

Where dried grass stems bend down towards the gurgling water, one yellowed twig danced back and forth. Where it ended, water droplets washed across an ephemeral ice globe dangling just above the surface. Plum-size today, but I'll check to see if it's still around tomorrow. Nearby, a bright red dogwood stem dipped into the churning bubbles, weighed down by a half-inch coating of clear ice - denser and heavier than winter rime.  In a few weeks time, fragile green leaves will replace these icicles. Only then will we say we made it through another Montana winter.

A Celebrated Snow Job

While Texas and Alaska compete for the tallest tales, Montana softly fluttered its way into the winter-time record books with a larger-than-life tale from 126 years ago today.

On January 28, 1887, the largest snowflakes ever reported were observed at Ft. Keogh, near present day Miles City. According to the report, a freak storm produced snowflakes the size of pancakes, 15" across and 7" thick. A nearby rancher described the mega-flakes as "bigger than milk pans." And in spite of the lack of any photographs or corroborating evidence, this report remains in the Guinness World Records.

U.S. Army Band and Guard Mount wearing buffalo coats at Ft. Keogh,
Montana, during the winter of 1880. (L.A. Huffman photograph)

Snowflakes are aggregations of hundreds of individual ice crystals. Physics doesn't preclude mega-snowflakes, but winds and collisions with other flakes would take heavy tolls on fragile, Frisbee-size flakes. While normal size snowflakes flutter to the ground at an average speed of 66.9" (1.7 m) per second, mega-flakes reportedly fall at twice this speed.

Now, most of your normal size snowflakes (from, oh let's just say Texas or Alaska) are less than 0.5" across. But there are scattered reports from "reliable observers" of extraordinary snowflakes estimated from 2" to 6" wide.

Weather officials in Berlin, January 1915, reported on a storm that produced snowflakes that were 4" across and shaped like round dishes with up-turned lips. And a September 1970 snowstorm in Laramie, Wyoming, reportedly produced 3" mega-flakes. In all likelihood, larger than normal snowflakes probably fall every day in winter, somewhere on Earth, but there just aren't many people out in these storms with rulers and cameras.

The tiny building blocks of snowflakes - those individual ice crystals - are mostly less than 0.25" wide. But ice crystals in nature have been reported up to 0.5" wide, and grown in the lab up to a whopping 1" wide. A crystal's shape is determined by the micro-climate it passes through while forming in the clouds and falling to the ground. No two ice crystals are exactly alike because no two take the exact same path.

Modern-day Montana also made history of sorts, just one year ago today. That report of world-record snowflakes, from 1877, was celebrated with the only Google doodle that (as far as I know) celebrates Montana.

The giant search engine uses its animated artwork to celebrate an eclectic assortment of historical events. On this day last year, Google users watched a giant snowflake settle onto a winter field where a cow grazed peacefully. By clicking on the doodle, millions of people around the globe were directed to one of Montana's little-known - and totally unsubstantiated - moments in history.

Google doodle from January 28, 2012

The ABC's of ICE

Words about ice and snow fill libraries. Here's about one snowball's worth.

ABOUT THE SCIENCE

The compound we call water can change from vapor to ice crystals without first becoming liquid, a process known as, "deposition." (The reverse process, "sublimation," occurs when ice crystals turn to vapor without becoming liquid.)  Snowflakes are composed of ice crystals that form in the clouds, while frost is composed of ice crystals that form on a surface - both via deposition. 

Ice crystals grow in many distinct patterns, from simple, hollow columns to complex, fern-like steller dendrites. Most ice crystals are six-sided. Triangular crystals are the second-most common, and the rare ice crystal can have up to 12 sides.

The formation of snow depends on air temperature in the clouds, not near the ground. But the heaviest snowfalls typically occur when it is relatively warm near the ground (around 15°F) simply because warm air holds more moisture than cold air. While it can be too dry to snow, it cannot be too cold to snow.

Technically speaking, snow is a mineral. Uncompacted fresh snow is 90-95% trapped air. The amount of water in most fresh snow varies between 4% and 10%, which means that 10" of fresh snow would melt down to as little as 0.4" or as much as 1" of liquid water.

The oldest ice discovered to date is approximately 750,000 years old and located in the headquarters building at Glacier National Park. Just kidding. Sort of. Actually, the oldest ice found to date was in Antarctica.

BEFORE NOW, SNOW HISTORY

The ice crystals in snowflakes seem to have captivated our imagination forever. The first written description of tiny six-sided ice crystals was published in a Chinese book, "Disconnection," in the year BC 135.  Some well-known deep-thinkers who were captivated to the point of studying ice crystals included the Bavarian bishop Albertus Magnus (1250), German mathematician Johannes Kepler (1611), French philosopher René  Descartes (1637), English architect Robert Hooke (1665), Japanese painter Shiba Kōkan (1796), and British physicist John Tyndall (1872).

Wilson "Snowflake" Bentley (1865-1931)

In January of 1885, an American farmer by the name of Wilson Bentley was the first person to successfully photograph individual ice crystals, by painstakingly experimenting with and adapting a bellows camera and microscope. He photographed more than 5,000 ice crystals during his lifetime, and published a book-catalogue in 1931 with the clever title, "Snow Crystals."

Starting with Bentley's book-catelogue, Japanese nuclear physicist Ukichiro Nakaya further classified ice crystals and divided them into 41 different types. Nakaya also created the first artificial ice crystal in 1936. His classification was later expanded by two Japanese meteorologists in 1966 to include 80 different types of ice crystals - our current number.

A new kind of crystal made its first appearance in 1878, when the first snowglobe-like object was displayed at the Paris World Fair. Two years later, Austrian Erwin Perzy patented his "Glass Globe With Snow Effect," starting a business that his grandson continues to this day, still working in the same Vienna building where his grandfather had worked. 

COUNTING RECORDS

About 12% of the Earth's land surface is currently covered with permanent snow and ice fields. On a local scale, the most snow ever recorded in a single storm was 15.75' at Mt Shasta Ski Bowl, in California, between 13-19 February 1959. The most snow ever recorded in a 24-hr period was 63" at Georgetown, Colorado, on December 4, 1913.  I have also read that a single snowstorm can drop 40 million tons of snow, but I can't find any verification of that calculation.

Montana runs wide and deep, so there is considerable variation in the annual average snowfall (from NOAA National Climatic Data). The snowiest Montana town is Cooke City with an average of 201 inches, and the least likely town to find a snowman is Glendive, with an average of 20 inches of snow per year. Other towns averages in descending order: West Glacier 117", Bozeman 91", Great Falls 63", Butte 62", Kalispell 56", Billings 55", Helena 38", Missoula 38".

On the related subject of air temperature, the official low record was -128.6°F on July 21, 1983, in Antarctica. But Montana bears the distinction of having the record low temp in the lower 48 states. On January 20, 1954, it was a brisk -69.7°F at Rogers Pass, near Helena. Montana also holds the record for greatest temperature range ever recorded in one 24-hour period. On January 23-24, 1916, the air temperature in Browning fell from 44°F to -56°F, a difference of 100°F.

Finally, the major Inuit ("Eskimo") languages each contain only a dozen or so root words for snow, about the same as English. Usually around this time of year you might hear that "Eskimos" have over 400 names for different kinds of snow. But that is one of those urban legends that just won't melt and go away.

All about snow (National Snow and Ice Data Center)
Snowflakes under an electron microscope (pictures)
Field guide to snowflakes  (book)

Of Wind and Waves

Ice shards in the lake today

I spotted a dog barking at a frog this afternoon (left), while walking along the edge of our frozen lake. Do you see it? That's okay, neither does my wife. Funny but I never see animals in clouds.

Winter's been chasing its tail here at the end of the road, and the lake was about 90% frozen over when the sun went down. But a warm front arrived overnight, bringing rain and wind this morning.

The little 10% patch of open water was room enough for the 30-40 knot wind to kick up whitecaps and chew away at the frozen edges of ice, which ran for more than half a mile across the lake. Over the course of several hours, the wind and waves crashed the smooth sheet of ice into so many tinkling ice cubes.

Night has returned, but standing in the yard I can still hear the shards of ice softly clinking together like wine glasses in a darkened banquet hall. In a few days we'll watch the surface re-freeze once again, for a third time this winter. But only after a deep freeze will the first foolhardy ice fisherman emerge.

Your Own Private Halo

Lunar halo at midnight, with Jupiter on the left side

If you happened to be wandering around western Montana this morning, in the wee hours after midnight, you probably noticed a glowing halo around the 99% full moon. With Jupiter riding shotgun at ten o'clock high, it made for an impressive sight. But what does it mean?

Lunar halos are optical illusions that occur when moonlight (reflected sunlight) passes through high, thin cirrus clouds floating in the night sky at more than 20,000 feet above your frozen nose. The light gets refracted (bent) and reflected (bounced) by millions of tiny, six-sided ice crystals that form these clouds. Refracted light is bent at a 22 degree angle, so the halo will invariably occur 22 degrees away from the light coming straight-line from the moon to your eyes. That's about the width of your fist when held at arm's length.

Because moonlight is so dim, compared to direct sunlight, lunar halos are usually colorless. But under optimum conditions you might see lunar halos with red on the inside and blue on the outside - the familiar rainbow color gradient.

Cirrus clouds often form the leading edge of a low pressure system - what we call a storm - and precede the storm by a day or two. So there really is a little science behind the adage, "Ring around the moon means rain soon." During last month's 100% full moon, sky watchers on the east coast saw a lunar halo the night before Hurricane Sandy made landfall. On the night of Sandy's landfall, people in the Midwest saw a lunar halo as the same low pressure system headed their way.

The hexagon-shaped ice crystals must be oriented just so, relative to your eyes, for the bent light to glance in your precise direction. That means the lunar halo you see is created from different ice crystals than the halo seen by the shivering person standing next to you. In other words, every lunar halo is unique to each viewer - your own private halo.

You can see more examples of cool, natural light effects here.

Dihydrogen Monoxide in Winter

One crisp and perfectly calm morning, many winters ago, I found myself wandering along the icy north shore of Lake McDonald, a skinny 10-mile-long lake in Glacier Park. I had noticed ice-free waters at the far end, but from this vantage the silent lake was frozen over as far as one could see.

The silence broke wthout warning.

The single sheet of surface ice started heaving towards me, and the leading edge began crawling up the inclined beach. When the crackling and tinkling of so many ice cubes faded away 30 seconds later, almost a mile of beach was covered with a six-foot-wide pile of broken ice. The marching ice was probably more amazing to me than it was to the lone Chickadee perched nearby, but neither one of us felt the distant wind that pushed the tons of ice ashore.

Such is winter in mysterious Montana.

All the glory and wonder of our landscapes take a backseat to the powers of ice. Dihydrogen monoxide (also known as "water") has some unusual properties that make magical things possible, like ice crystals, snowflakes and glaciers -- and maybe even life on Earth.

All life that we know of is water-based. And with the possible exception of a few antifreeze-producing insect cells, all cellular activity (i.e. "life") takes place in the narrow temperature range between the boiling and freezing points of water.

Water reaches its maximum density at 39F (4C). As it approaches its 32F (0C) freezing point, water molecules must spread out to line up into crystalline forms. More empty space (9% increase) between molecules means lower density. If not for that rare property, lakes and oceans would freeze solid from the bottom up, instead of forming a thin insulating layer of surface ice, and Earth might just be another frozen, lifeless planet.

We should celebrate the fact that ice floats in water -- while digging our cars out of the snow -- even if the stuff falls from the sky all winter.

Inside a winter cloud, a freezing water molecule forms a tiny, six-sided crystal. As this new crystal gets blown about, more water molecules adhere and grow branches from the prism's six corners. Because the conditions are nearly identical on each corner, each branch might grow to look like the other five.

The result is a magical ice crystal that is usually less than one-quarter inch wide. Some are perfectly symmetrical, but most are not. The final form can take many shapes, including a star, plate, bullet, needle or prism. Some crystals look very similar, but no two are exactly alike.

Because they are now heavier than water vapor, these beautiful ice crystals begin falling towards Earth and colliding with each other to form snowflakes. The crystals stick to each other better when it is relatively warmer, and they are more fragile when it's colder. That 's why early spring snowflakes tend to be bigger than frigid midwinter snowflakes.

Snowflake after snowflake makes piles of snow, and piles and piles of snow make excellent insulation.

Within a few hours of landing, the uppermost layers of ice crystals interlock and form a crust. Once insulated from the cold air, the snow on the bottom is melted by the Earth's latent heat, and water vapor from the melting crystals migrates upward where it refreezes and reinforces the crust. Over time, a network of ice columns and air spaces about an inch tall forms below the snow insulation, and the temperature here will remain 1 or 2 degrees above freezing all winter, regardless of the air temperatures above the snow.

This "subnivean" world forms a warm winter habitat for short Montanans, like mice, voles and shrews. And these in turn form the winter diets of coyotes, foxes and some owls. These predator species have a keen sense of hearing, and can pinpoint the invisible rodents rustling around under the snow. Canids pounce feet first, and owls dive into and punch through the crust with clenched feet. They quickly sniff (canids) and feel (owls) through the pile of broken ice crystals and grab their stunned snack.

When a pile accumulates more snow and ice in winter than it looses in summer, it becomes a (non-moving) snowfield, which might eventually grow into a deep (moving) glacier.

Ice fractures easily if it's less than 160 feet (49 meters) deep. But if the ice grows deeper, the pressure of its own weight will make it act more like plastic. Flexible ice on flat ground begins to ooze out from underneath its own weight, while thick ice laying on a slope begins to flow downhill. Friction slows the glacier's bottom and edges, but the middle can move almost 100 feet (30 meters) per day.

These rivers of ice created many of the cool landscapes of northern Montana -- features like drumlins, moraines, erratics and aretes.

In the Tobacco Valley, the tadpole-shaped hills of the "Eureka Drumlin Field" are so many piles of leftover glacial till. The town of Polson sits atop a terminal moraine (a massive pile of rocky debris) that was carried down-valley by a glacier, and which also helped dam the waters of Flathead Lake.

"Erratics" are Canadian-born granite bolders that were delivered to and deposited in non-granitic eastern and central Montana by glaciers. In central Montana, a massive glacier also pushed a portion of the Missouri River many miles southward.

In southwestern Montana, crumbled ice from a massive glacier blocked the flow of the Clark Fork River and created "Glacial Lake Missoula," between 13,000 and 15,000 years ago. The lake was 2,000 feet (610 meters) deep at its highest level. The ice dam crumbled and reformed at least 41 times, sending scouring flash floods across Idaho and the eastern half of Washington. There were seven such glacial lakes in Montana.

Montana's Glacier National Park was named, not for todays' remnant glaciers, but for the massive, mile-deep glaciers from many thousands of years ago. When the most recent glacial period ended some 10,000 years ago, the melting glaciers left behind the famaliar U-shaped valleys and knife-edge ridges ("aretes") that we see today. In 1850, the park still harbored 150 smallish glaciers. Today, 26 glaciers remain, and these are predicted to melt away within the next 10 years.

Ice is still hard at work today -- especially here in Montana. The repeated freeze/thaw cycles continue to create more of our most ubiquitous landforms, the highway "pothole." In spite of our warming climate, many of these potholes are predicted to grow larger in the years to come.

Behind the molecule: Long winters can also lead to unusual behaviors. Several college students created the "Dihydrogen Monoxide Research Division," to warn people about the dangers of water (and to illustrate the lack of scientific literacy). This in turn led to the creation of "Friends of Hydrogen Hydroxide."