By Dr. Robert Thorson

Imagine a beautiful stalagmite in your neighborhood. Well, imagine no more! Though the megaicicles clinging to road cuts across the state are technically not stalagmites, they form in much the same way. And to my mind, these frozen ribbons and drips of blue-tinged ice are even more beautiful than the precipitated drips of limestone that hang pendant in underground caverns.

Mother Nature must be trying to compensate us for the pervasive ugliness of exit ramp culture. Indeed, the biggest and most beautiful icicles usually grace the worst parts of our daily commutes, those on wide, multi-lane highways crowded with cars and trucks. Here’s why.

The postwar car culture fueled demand for wider, flatter highways, which necessitated deeper hillside cuts. This left many roads bounded by tall, artificial cliffs. The drilling and blasting that exposed the rock widened and connected existing fractures and created new ones.

In Connecticut’s hilly terrain of the eastern and western highlands and the traprock ridges of the central valley, rock usually lies at shallow depth. There, groundwater exists in countless fractures between blocks of impermeable rock. Following fractures that are wide enough to transmit water and are properly aligned, the water flows downward from the surface where snow is melting.

However, rock, particularly if its crystals have been fused by metamorphic and igneous processes, is a much better conductor of heat than soil. So on cold winter nights, the freezing point of water can be well below the surface. At that point, water freezes in the fractures, forcing unfrozen water above the fractures to move elsewhere, often to higher, more visible levels.

Even when there is no surface melting, water moves continuously underground, unfrozen because some of the heat put in during the previous summer remains. It is this water that seeps from road cuts and – sometimes – freezes on the rock surface. The water is drawn to new road cuts because they have more seepages than older cliffs, whose seepages disappear over time.

Now the stage is now set for creating mega-icicles, the size and shape of which are controlled by local conditions. If the flow is too strong or too weak, an icicle won’t form because there is either too much heat or too little water.

If a moderate flow seeps from the top of the cliff, the water will dribble down the rock surface as a thin veneer until the summer heat is lost and freezing takes place. This sheet of ice will then thicken layer by layer, until it begins to force the flow outward from the original point of seepage, leading to the rounded forms we see as misshapen columns glued to the cliff.

The third possibility is the most interesting, and explains why ribbons and sheets of ice almost completely veneer some cliffs like the most beautiful travertine walls in a cave. In this case, the water freezes at the point of seepage. This forces the flow elsewhere, either upward to form one or more draping ribbons if the fractures are aligned vertically, or sideways to form a pleated curtain if quasi-horizontal.

Only when an area of the cliff is sealed off completely with ice will the flow stop. And by then, the beauty is there, and will remain so for well into spring. Daffodils and ice make for interesting companions.

And the colors? Icicles hanging from your gutters are elongated cones of transparent, colorless ice. They are clear because there are few tiny bubbles of the sort that make milky quartz milky. And they are colorless because the ice isn’t thick enough to scatter enough light.

Roadside mega-icicles, however, are both thick enough to scatter blues and aquamarines, and contain an abundance of dissolved minerals that give rise to other colors and give the ice all variations in cloudiness.

There’s a silver lining in every cloud. In this case, blue crystalline beauty amid the most traffic-congested roads.