When I was a girl I remember seeing gigantic sheets of ice creeping across the shore of Lake Mille Lacs and up onto the road skirting it. I was fascinated by the phenomenon and amazed at the stupendous plates of ice that jutted skyward, making the highway nearly impassable.
While awed, I have fear and respect for ice-covered water. Nervousness about ice might have resulted from a childhood incident. I clearly remember the day.
After what might have been unbearable begging on my part, my Uncle Razz took me ice fishing. While he gathered the gear my ma bundled me up. We drove to the lake and walked out onto the ice. I remember having a hard time keeping up with Uncle Razz. To get a better picture of the scene, imagine a limber man, 6-foot-5, being trailed by a petite, 4-foot girl tightly packaged in winter wear. Needless to say, my uncle's stride was significantly longer than mine.
When we reached our destination Razz unloaded his tackle while I danced around, thrilled by my good fortune of being on the ice. Just as my uncle settled into pursuing fish -- KERPLUNK! No it wasn't a lunker fish snapping on his bait. It was me twirling into another angler's hole!
For all you who are cringing I want to say in my defense that I didn't see the hole. A skim of ice and snow had formed over it, rendering it invisible.
A litany of expletives rang from my uncle's mouth. Suffice it to say our outing ended as I struggled with ice-laden snowpants and boots to keep pace with Uncle Razz, who stomped off towards the car. I don't believe he ever took me fishing again.
This memory came to mind when Christine Lupella, editor of the "Pine River Journal," sent me photos of ice heaves. She took the photos on Big Trout Lake near Manhattan Beach and wondered if I had ever written about ice heaves. I hadn't, and here's some brief information about them.
There isn't much data about ice heaves and pressure ridges. My files yielded information on ice dynamics, ice out, ice safety, ice changes and ice-related fatalities, but nothing on ice heaves. My Encyclopedia Britannica had nothing and the Internet had mostly data related to ice safety.
But an article written by Jacqueline D. LaPerriere that appeared in the Alaska Science Forum almost 20 years ago had the following information.
Pressure ridges are caused by an infrequent weather pattern. After ice forms on a lake the air temperature usually stays below freezing. But if the air temperature goes above freezing ice expands like any other solid when warmed. The shoreline resists the outward expansion of ice, so it heaves and cracks near the center of the lake. Then the resulting plates of ice can slide past each other and rest on top of each other, leaving open water.
Drifting snow can insulate open spots that have formed. This is called expansion cracking and is quite common. I'm not sure if ice heaves and pressure ridges are exactly the same. I'll continue to research the subject and report my findings.
Next week I'll write about ice safety and ice-related fatalities. In the meantime, don't look for me on the ice. I'll be the one watching from shore, muttering about the uncertainty of ice.
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