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Author Topic: Do surface locations change their longitude and latitude due to tectonics?  (Read 8838 times)

Offline gigi

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just wondering...
if the plates are constantly moving, won't places change in their latitude and longitude over the course of time?
« Last Edit: 31/07/2008 00:46:17 by chris »


 

blakestyger

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I would have thought so, but - if everything is moving where will the fixed point be to measure it all from? I don't know if the N and S Poles would do as their coordinates are all zeros (aren't they?)
Erm, big gap in knowledge exposed here - someone may know though. Fascinating question.
 

Offline frethack

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I would have thought so, but - if everything is moving where will the fixed point be to measure it all from? I don't know if the N and S Poles would do as their coordinates are all zeros (aren't they?)

Geographic N and S, as well as all lat and long lines, are relatively stable thanks to our moons balancing effect on our rotation (magnetic N and S move constantly...even flipping).  No matter where the continents move, the grid would stay the same (well...hypothetically...there technically was no grid until recently because there were no people to invent and interpret it...but I degress).

To answer the question, yes...places change latitude and longitude all throughout geologic time.  For instance, not too long ago (until about 50 million years or so ago.  (dont remember the exact dates offhand, but whats a few million years between friends) Antarctica was at a much higher latitude and supported a vast diversity of life.  Ahhh...the good ol' days

frethack
« Last Edit: 23/07/2008 22:34:43 by frethack »
 

Offline gigi

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and the wondering continues.
we all know that the plates move,(although a snail would win the race).
let's say it moves 1cm per year, and in 10 years it will be about 10cm, unless there's some other geological process like subduction and stuff,are atlases/globes/maps updated in a fixed amount of years or something?
 

lyner

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Where you actually are, on the Earth's surface, relative to other places is a more complicated business than at first sight.
The Earth isn't spherical and the plates keep moving around. The best you can do is to choose a time and base all your charts and maps on an arbitrary North (related to the rotation of the Earth and the apparent position of the stars) and an average radius.
It doesn't help that the charts are all 'projections' of a notional sphere onto a flat surface.
The Lat and Long on a chart / map and where your GPS receiver tell you that you are is all based on what 'chart datum' is used for your chart. It is a fact that two different charts may show the same location to be at two different lats and longs, depending upon which datum the charts are based on.

Next time you are in an aeroplane, bound for somewhere exotic, bear in mind that the pilot may not actually KNOW exactly where you are. It's all near enough for Jazz, though, and, once they get near their destination, they've sorted out any inaccuracies.
 

blakestyger

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No matter where the continents move, the grid would stay the same ...

But surely, as the meridian goes through Greenwich, if hypothetically the UK moved east relative to New York, say, then if you were in New York the meridian would be to the west of Greenwich as the continent moved 'under' the grid - wouldn't it?
 

lyner

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The Greenwich Meridian is very much like Greenwich Mean Time. They are both artificial constructs, of course, and 'worked' when they were invented because the measurement system was relatively crude. If we choose to relate all our longitudes to a line through Greenwich  then that is quite arbitrary - but handy. When the vagaries of time and the Earth's crust movements started to be measurable then we needed to think again. I think Greenich Meridian is still the 'origin, for longitude, though. The Poles are defined in terms of the apparent centre of rotation of the stars.
If Greenwich were to be moving steadily westwards every year, would you say that was affecting clock Time (making each year longer) or our Longitude? It's an arbitrary choice.

You may think it's a problem on Earth but think about what the situation is on Jupiter! The whole surface is swirling around and the Great Red Spot, a vortex, is the only distinguishable feature.
 

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