With the first real snow, I have been re-enchanted by the amazing properties of water – to stick together in liquid droplets, to wash together in giant waves – and to crystallize. Snowflakes are tiny wonders that display innumerable patterns of crystallization when you catch them on a dark background like a fuzzy black mitten. It is hard to believe that they are made up of water. But, the similarity of these structures to the patterns you find on frozen puddles is a testament to their close relationship and evidence of water’s common properties despite its many forms. Crystals are just one of those.
A crystal is basically just a regular pattern of molecules. Instead of being all jumbled up, these molecules line themselves up neatly to make a three-dimensional structure. Just how they align determines the exact form of the crystal that results. The flat surfaces of crystals are called facets and the number of facets determines a crystal’s shape. Crystals often form as a liquid cools and the molecules slow down their movement.
This happens in water. It also happens in magma where minerals cool into crystals of different shapes and colors. Quartz is one of the most common along the Maine shore. But, garnets are another one that is easy to miss since their darker red color sometimes blends with the grays in the granite. You can actually pick these individual crystal gems out of the rocks to look more closely at their structure.
A simple way to study crystals at home is to look at salt or sugar. The regular tiny crystal structure of each of these isn’t very interesting, but if you liquefy them, you can get them to recrystallize in bigger, more varied chunks. This is a fun experiment to do with sugar in particular, especially if you add a little color and/or flavor to the mix. You basically end up with rock candy. You could do the same with salt, but it wouldn’t result in a tasty treat.
Some of the most audacious forms of water occur when crystals come together as ice along waterways – bold, jagged pieces jutting up, or smooth lumpy drips coating the rocks. Ice formations often look like they are right out of a Dr. Seuss book. These shapes can be particularly weird along saltwater shores because the structure of salt ice is incredibly malleable. It can range from dense and clear to mushy and opaque. That has a lot to do with crystals – not just of water, but also of salt.
When you add these salt and ice crystals together, they sort of get in each other’s way. That’s part of why salt water freezes at a lower temperature than fresh. The salt keeps the water from packing together as tightly, so you get these tiny open spaces that can make salt ice squishy. However, sometimes when salt water freezes, the water molecules push the salt out of the way.
That’s when you see clearer, denser ice floating on the surface of salt water. If you look carefully, you can often see a salty crust along the edges of the ice. It’s more powdery and can be brushed off with your hand. The remaining ice is made mostly of densely packed water molecules and is quite strong.
Ice is important for the marine ecosystem in several ways. First, it is an excellent insulator. While you may not be eager to go for a swim in the ocean in the winter, the water is actually warmer than the air temperature. Water has an impressive ability to stay at a constant temperature and larger bodies of water, like the ocean, can maintain their summer “heat” far into the winter season.
But, when air temperatures have been frigid for a long period of time, seawater temperatures too begin to plummet. Having a layer of ice on the surface is like putting a blanket on top of you. It helps keep whatever “warmth” remains in the water there throughout the winter. This helps maintain a livable environment for the creatures that stick around through the winter.
Sea ice is also an important mode of transportation – both for plants and for animals. Animals are able to access places that are otherwise far away by traveling on large chunks of ice, or in some cases, frozen-over bays. Deer might walk across a cove to discover new habitat, for example. Other animals like seals might take a rest from swimming by plopping themselves onto a chunk of ice for a while. Plants can even take a ride like when chunks of marsh grass are frozen, uprooted, and carried to a new location. Then, there are also the changes that ice makes to the shoreline by crunching and grinding against it and reshaping the landscape.
Look closely at ice crystals along edges of leaves and hanging from the doorways of buildings and then take a closer look at the salt ice along the shore to appreciate the vast array of crystal structures that are part of our coastal ecology.
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