In A Nutshell
Ice seems like one of the most straightforward concepts out there—it’s just frozen water. But there are many, many different types of ice, forming under different conditions and even in different temperatures. For example, glaze ice forms when water that’s above freezing hits a cold surface that supercools it and forms a clear coating. Hail is ice that starts as frozen rain, growing as it rises and falls through the atmosphere. And pack ice is frozen seawater that freezes at varying temperatures because of the salt content.
The Whole Bushel
Some of us in colder climates have to think about ice way more than we’d really like to, but we probably don’t think about ice as being anything more than water that freezes. Worldwide ice is not, however, created equal.
Broadly, there are two main types of ice: that created by fresh water and that created by salt water. While the formation and freezing temperature of freshwater ice is pretty consistent, saltwater ice (also known as “pack ice”) can freeze at varying temperatures because of the salt content of the water.
Glaciers are the largest examples of freshwater ice in the world, and most form from snow that gets compacted and freezes. When parts of glaciers break off in the water, they’re called icebergs. And icebergs that get further broken up by the ocean waters are ice floes.
Glaciers and icebergs are also one of the places you’ll find old ice, which is ice that’s been around for more than one melting season. Also known as multi-year ice, it floats on water and freezes water at the bottom to make more ice that counteracts the ice that’s thawing from the top.
Perhaps one of the most breathtaking of ice formations that’s found in ocean waters is the ice breccia. This occurs when chunks of ice that have been formed in different areas, under different conditions, and at different times freeze together to form a patchwork of ice. Before ice accumulations freeze and they’re only swept together by tides or currents, they’re called brash ice.
We’ve all seen those breathtakingly beautiful photos of ice mounds rising out of a low-lying plateau of ice—those are called floeberg ice. Little mounds are floebits.
Those of us that live in areas with winters stricken by snow and freezing temperatures have an all-too-familiar relationship with ice, but we might not appreciate the natural marvel that it really is. Glaze ice is one of our major annoyances; it forms when the air isn’t quite freezing, but the ground (or other surfaces) the rain falls on are still very, very cold. When the water is supercooled by the cold surface, it forms a clear sheet of ice. When it’s on roads and parking lots, it’s known as black ice. Otherwise, it’s often just called clear ice.
Hail occurs when freezing rain falls and then is lifted back up through the atmosphere, increasing with size as it rises and falls.
There’s even a term for that miserable mix of snow, water, and ice that can make driving downright dangerous—slush ice. And that thin, brittle covering of ice that happens on calm waters when winter is just starting? That’s ice rind, and it’s defined and thin, easily breakable new ice. When it becomes a little thicker and stronger, then it’s nilas ice.
And that fine, crystalline ice suspended in water just when it starts to freeze? There’s a name for that, too—frazil ice.
Ice isn’t created the same on the molecular level, either. At least 12 different types of ice have been discovered based on the shape of the crystals that form (they can be cubic, tetragonal, monodinic, rhombohedral, or even non-crystalline), have different types of symmetry, and even vastly different densities.