The latest chinook has blown away the snow and polished up the ice at a beaver pond that I know up in Kananaskis Country. So I strapped on my crampons and wandered out on the frozen surface to have a look. There were all kinds of cool things both in and on the ice.
The wind had blown sticks and spruce cones and tendrils of lichen from the surrounding trees, and bubbles of methane that had tried to make their way to the surface but got caught as the water froze were stacked like white pancakes. Methane is a gas formed as plant material on the bottom of the pond is broken down by bacteria. Held by water pressure and the surrounding detritus, it accumulates until it builds up enough volume to break free and rise through the water column. In the spring, summer, and most of the fall, the gas pops through the surface and scatters with the wind. That sulphury, rotten-egg smell you get a whiff of driving by a slough? That’s methane.
Or maybe flatulent beavers. Same process, different source.
But as the ice starts to form in late fall, the bubbles of methane get trapped below the hard surface. And as the ice thickens, more and more bubbles get trapped. A lot of times bubbles rising from the same spot on the pond bottom get trapped in stacks. Thanks to the even pressure of water coming from every angle, the gas bubbles start off perfectly spherical. But when they hit the underside of the ice, that same pressure causes them to take on a more flattened shape. Ice forms around them and they turn into formations that look like piles of coins or cookies. And it’s not just methane that gets trapped in the ice. Twigs, spruce needles, beaver nibblings and water plants end up suspended in the ice as well.
A lot of times, there’s so much gas trapped in the ice that it turns cloudy and translucent. But this winter, thanks to the sudden, deep cold we had at the beginning of the season, the ice, at least on this beaver pond, froze fast and clear as glass.
Photographing these bubbles and the various things locked in the ice isn’t difficult but there are a few challenges. First, make sure the ice you’re walking on is safe, at least 15 centimetres thick. Stay away from any open water and never – and I mean never – venture out onto ice over flowing water. It might seem like its thick enough to be safe but ice formed over flowing water is full of air pockets and places where the water flowing underneath has eroded the ice from below. Don’t trust it.
Wear crampons or some kind of slip-on ice gripper on your boots. Needless to say, ice is slippery and you’ll have a lot more fun taking pictures if you’re not constantly worried about falling on your head. Use a polarizing filter to take some of the glare off the ice surface. If you don’t have one with you – I didn’t have mine for these pictures – try to wear dark clothing to minimize getting your own reflection in the photos.
Winter is here and the ice is nice! So grab a camera and go find a pond. Have fun!