From Lutz U

Geology 101 / Intro. Religion

Dear Bryan,

In less than a week I will be officiating a wedding on what (we hope) will be a frozen lake in Wisconsin. You're from Wisconsin, and word on the street is that you've done some ice fishing. I'm wondering if I could pick your brain about this whole using-a-lake-as-a-floor business.

I've seen people ice skate and cross-country ski on frozen lakes, and I've seen those little huts parked in the middle of a vast expanse of whiteness that are presumably used for fishing. Although I bet other business has gone on in there as well.

I have a couple of questions. First of all, how cold does it really need to be outside to ensure that the lake is rock-solid? I know water freezes at thirty-two degrees, but it seems like that's cutting it close. What's a good number? Would you say twenty degrees was totally safe? For how many days do you think the lake needs to have been frozen? And what is the highest ambient temperature in which you would venture out on a lake? Also, does it matter how much weight is on the ice? For instance, at this wedding there will be forty people. Should I ask certain people to stand on the shore?

As an aside, you know that whole Jesus-walking-on-water business? Don't you think it might just have been a frozen lake? If you're uncomfortable with that last question, I can always ask someone in the clergy. Do you know any ministers, preachers, priests, or whatnot?

Don't feel obligated to answer all of my questions. Just the ones you have answers to.



Hey Lisa!

First question, how cold does it have to be? That's kind of a trick question, actually. The air temperature is not specifically related to the temperature of the water. It takes a long time of below-freezing weather to get the entire body of water cold enough to actually start to freeze. Not to mention, it depends on the type of water supply. For example, a spring-fed lake will always be more treacherous and tougher to gauge due to the constant supply of warmer water from under the surface of the ice. Therefore, what is frozen thick enough to drive a car across in most places will have sheets of ice so thin a duck or goose can break through it and get something to eat. 

Moving water, like a river, or a lake in a river system, will have similar problems. Slower-moving water will start to freeze first. This narrows the area the water can flow and increases the speed of the river, making it increasingly tough to freeze entirely. On larger rivers there are patches of black ice (very thin ice that looks like the rest of the ice pack) that can be very hazardous. So there's no calculation like 10 days at 20 degrees equals safely frozen lake. Perfect example: If you are ice fishing on 8 inches of ice and the air is 35 degrees, the hole you drilled to fish in will start to freeze in 15-20 minutes. The water and the existing ice will maintain the freezing of the water even without the assistance of the air temperature.

Still lakes with no springs or moving water freeze from the outside towards the center, or from shallowest water to the deepest. So on many lakes around here you might see open water a few hundred yards from someone's ice shanty (those little huts to which you refer) or the truck they drove out to the shanty. I tend to be more cautious than that. I usually look for 6-8" of ice to feel totally safe ice fishing. The Department of Natural Resources actually puts out safety information every year and will post signals on many lakes in the area indicating whether it is safe or not.

Now, just like it takes a long time for the lake to freeze, it also takes a long time for a lake to thaw. I have been out ice fishing on a 45 or 50 degree day where puddles form on the top of the ice. It seems a little disconcerting until you remember there's 15-25 inches of ice beneath your feet, and water that is barely above freezing below that. Ice and water take a long time to change temperature. The bigger the body of water, the longer it takes. 

Now on to the specifics of the wedding. With the brutal and constant cold of this winter, nothing short of the temperature being over 90 for a week straight would make me worry about the lake still being frozen or the number of people being in an area. Many lakes are so deeply frozen right now that people are worrying about the fish population in the spring, as many will actually get caught in frozen pockets and freeze in the ice pack, or there will be so little water left under the ice that the fish will suffocate from lack of oxygen.

Remember, ice is an amazingly powerful force. It can strip continents in glacial waves. It can split boulders or roads if even a small bit of water finds its way into a crack and freezes. That's why there's so much road work in Wisconsin every spring. Crews have to go out and fill splits and breaks in the roads caused by the freezing and thawing of water in the roads. Bottom line for the wedding: You could put an entire Panzer tank division on the ice and I wouldn't worry about the ice so much as cracking.

On to the Jesus question. As you may or may not know, I was actually training to be a priest in the Roman Catholic seminary a few years back. I have degrees in comparative religious studies and theology, as well as some training in philosophy. I am happy to add my two cents to your question, though I also have a bunch of connections in the faith who would also be glad to talk to you.

I am going to give you two answers. The first is simple and to the point, the second will be a little more theologically complex, but hopefully still helpful. According to the Bible, the disciples were on a boat to Capernaum when they got caught up in a terrible storm. Jesus had stayed behind to pray and so was not with them. They thought they were going to die. They held on and cried out for help and the storm calmed. In the distance they saw Jesus walking across the waves toward them and calming the storm. Jesus then called out to Peter and told him it was safe. Peter stepped out on the water and walked toward Jesus but got scared about halfway to Him and began to sink. Jesus lifted him back onto the surface and chastised him for his lack of faith.

But to answer your question, it absolutely could have been ice! Several scholars have actually suggested as much, based on the body of water that the disciples were traveling on. It would also explain Peter's sinking if he stepped onto an area of thinner ice. One of the perils of their trip, even after surviving the storm, might have been the presence of ice floes in the normal channels of safe passage.

Now a question for you: Does it matter? This was the best critical question that I was asked in the seminary, and it can be applied to all facets of all faiths. What if Jesus never performed a miracle? Would it make His example of kindness and love any less inspiring? I say it wouldn't.

Take the miracle of loaves and fishes. A huge crowd comes to listen to a sermon from Jesus. They begin to grow hungry but the disciples say they only have 3 fish and 5 loaves of bread, far too little to feed everyone. However, Jesus tells them to pass out everything they have, and by the end it is said that everyone was full and there were baskets of leftover scraps and loaves of bread. Interpretation:  Jesus being a living god multiplies the food to feed everyone present. Pretty amazing! 

Optional interpretation: Jesus and his impoverished brothers give every scrap of food they have away to the crowd. Inspired by this dramatic act of charity, others begin to do the same, taking out any food they have with them and sharing it with the strangers they are gathered with. At the end, everyone is well fed and there is even extra to spare. Does either interpretation take anything away from its being a miracle? The message remains the same either way: When you do all you can for others, everyone wins. Whether it’s a physical miracle or a miraculous act of charity from 5,000 strangers, it is still miraculous.

This may be a more in-depth answer than you were looking for, but I hope it answers some things. As a man of intelligence and a man of faith I have spent many hours on such topics trying to reconcile the two, which can seemingly be at odds. However, the more I learn both scientifically and spiritually, the less I see it that way. Whether a deity made everything in six days from nothing or the world evolved and flexed into the complicated system of interconnected life over the course of billions of years, it doesn't matter. Both options are equally miraculous in my eyes, and both are guided by an intelligent system beyond my limited understanding, which I happen to call God. Science is merely a way of explaining the continuously changing miracle of beauty and power that is life.

Wow, I just realized how much I've written. If you have any other questions or follow-ups, feel free to ask! I hope this has been a help in answering your questions!

Bryan VanMeter


Dear Bryan,

Thank you so much for that very considered response. My ice-cracking concerns were completely unfounded. As it turns out, Lake Mendota had about two feet of ice, which I’ve heard is strong enough to hold an 18-wheeler. I very much liked that safety thickness chart. It’s hard to believe that a couple inches of ice could hold a whole person, even Jesus. So, frankly, I wouldn’t mess around until it got a little thicker. I have other questions like, how fun is it to saw through ice? And what tool do you use? But I feel like that should wait for another time.

Let’s talk about Jesus. I had no recollection of your seminary background when I asked the question, which was really just an aside. But I love the idea that an aside turned into the main course and I learned some things I may never have even thought about. I very much liked your alternate interpretations of miracles. And I think it’s easy to forget (especially for people who don’t have an active religious life) that ultimately the point of most religions is for people to behave better—charity begets charity. It’s not like there’s any religious tenet that encourages being a jackass. That said, even without a religious practice, we should all be striving to be more decent. Somehow, that straightforward principle is easy to forget.

Obviously, my religious education is next to nothing. But I will admit that turning water into wine sounds like a pretty nifty trick, and I would likely make quite a pest of myself if I knew someone who could do that.

I suppose, however, it’s also possible to look at it this way: Water is required to grow grapes, which then can be fermented into wine. And if fermentation isn’t a miracle, I don’t know what is.

Thanks again, Bryan.



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