Okay, I'm going to geek out here, but bear with me because this is cool. I was talking with my ESRI tech support folks this morning (Thanks for all your help, Margaret - You rock!) about difficulties in calculating magnetic declination in our mapping software.
For those who don't know, I'm a GIS analyst. That's something like a cartographer and database manager at the same time. When people ask my profession, I generally say "Map Geek"; it saves time.
Right now we have a crew out in the field and they needed to know what the magnetic declination is where they are. Don't know what magnetic declination is? Allow me to elucidate. Everybody gets the idea of the North Pole. Santa. Polar bears. That point where all the longitude lines come together at what we two-dimensionally think of as the "top" of the planet. This is called true north. Here's the deal. When you're walking around with your compass, it's not pointing to Santa at true north. It's pointing to magnetic north. Confused? I don't blame you. Essentially you can think of the earth as a big fat magnet and it so happens that the north pole of that magnetic doesn't sit exactly where true north is. Inconvenient, seeing as how all our little human conventions like latitude and longitude coordinates are centered around Santa at true north.
So how do you get from the compass pointing to magnetic north to Santa and the elves at true north? Well there is a really complicated equation designed by Very Smart People to figure what the difference between magnetic and true north really is, and that difference is called magnetic declination. (Insert your "aha!" here.)
So, forget Santa and let's travel back to my office in Dixon where I'm on the phone with ESRI tech support and Margaret is explaining to me why my mapping software can't figure out what the magnetic declination at a given point really is.
(This is where is gets cool.)
The magnetic north pole is moving. You had probably heard this before. I'm pretty sure I had, probably in some college course in geology where I was diligently doing the crossword puzzle in the student paper while thinking to myself, "why oh why will I ever need to know this stuff?" (Ironic, that.)
In fact, the average position of the magnetic north pole is moving about 40 km per year! That's something like me saying, "Gee, I want to live in Oakland. Nah, I don't like Oakland anymore. Let's move to Berkeley. Forget Berkeley. Too many hippies. Now I want to live in Richmond." And if you've ever been stuck in traffic in the Bay Area, you know that's a pretty good distance. In fact, if the magnetic north pole sticks to its same rate of change and trajectory, it could be in Siberia by 2050.
Wait, Shannon. Did you say that it's moving from it's average position? Good catch. I did indeed. The location of magnetic north also jumps around on a daily basis due to ionic particles from the sun, as much as 85 km! So today my house is in Sacramento but tomorrow it'll be in Vallejo. You know, whatever.
Isn't that mind-bogglingly, stupendously, fantastically amazing? Isn't geology the coolest thing ever?
So what's up with all this movement? Does this have anything to do with that magnetic field reversal thing? Not so much. Every now and then (200,000 years or so) the magnetic poles of the earth trade and the south becomes north and the north becomes south and people like me who have no sense of direction are totally unaffected. Supposedly we're about 780,000 years overdue for one of these but the little variations we're talking about are different. The yearly drift has more to do with irregularities in the earth's outer core as I understand it. And, really, who's perfect?
Or this whole thing could be a plot and the magnetic north pole could really be controlled by Santa Claus whose trying to keep compass-carrying nay-sayers out of the north pole so he can get some work done and bring me some presents.
So what do I tell my field crew? "Forget it, guys. I can't even find Santa Claus. No declination for you." Not exactly. The Canadian government (the closest country to the fickle magnetic north pole right now) has a calculator on their webpage to figure out declination. Incidentally, that's where I learned all these fascinating facts and figures that I've just imparted to you, so check out their site for more info.