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What does the land under Antarctica’s ice sheet look like?

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Re: What does the land under Antarctica’s ice sheet look like?

#31

Post by jameshart »

mFixman wrote: post #29
jameshart wrote: post #23

Earlier quoted context omitted.

But there’s none at the North Pole. One pattern that is curiously consistent is that broadly land tends to be antipodal to ocean (and not just because there’s more ocean in general - there’s a genuine statistical skew) - so having land at one pole and none at the other matches that overall pattern. ( https://www.geodatos.net/en/antipodes ) Basically a surprisingly large proportion of antipodal pairs have land at one…

Is antipodal land a physical property of Earth's continents, or is it mathematical fact of distribution on spheres? If we distribute chunks of land randomly on a sphere we would expect roughly the same amount of land on any randomly-chosen hemisphere. But what can we say about the average amount of land in the hemisphere with the most land? My intuition says that in an Earth-like sphere, with 29% land and 71% water,…

It also depends on how strongly clustered the land tends to be - if the land is all going to be continuous then presumably there are more distributions of that land that are weighted towards a single hemisphere.

Suspect there’s something to do with the fractal dimension of the coastlines as well. Agreed - sounds like a rich vein of math.

Re: What does the land under Antarctica’s ice sheet look like?

#32

Post by jameshart »

SketchySeaBeast wrote: post #26
jameshart wrote: post #23

Earlier quoted context omitted.

But there’s none at the North Pole. One pattern that is curiously consistent is that broadly land tends to be antipodal to ocean (and not just because there’s more ocean in general - there’s a genuine statistical skew) - so having land at one pole and none at the other matches that overall pattern. ( https://www.geodatos.net/en/antipodes ) Basically a surprisingly large proportion of antipodal pairs have land at one…

To me that really looks like pattern matching where there isn't actually any (though I'd like to know more details around the "statistical skew")- saying that there's a lot of antipodal land-water or water-water pairs only makes sense considering the vast majority of the planet is water. Regardless, it's just an interesting snapshot in time considering continental drift.

30% of the surface is land. But only 15% of land has land antipodal to it, which certainly initially feels like less than you would expect by random chance.

It’s easy to fall into some counterintuitive fallacies reasoning about this though because we’re considering a spherical surface pairwise and you might be tempted to say ‘ah, but we’re counting the antipodal land twice so that probably accounts for the 15%/30% thing’ - but I don’t think that follows; that 15% with land antipodal to it can be thought of as two sets of 7.5% of the land, which are antipodal to one another - the ‘double counting’ doesn’t work that way to eliminate the anomaly.

Re: What does the land under Antarctica’s ice sheet look like?

#34

Post by perhonen »

Tepix wrote: post #13

Are there any interesting sci-fi novels or games that take place in the (far) future in Antarctica with humanity being forced away from the equator by the increasing temperatures?

It doesn't take place in Antarctica, but The Drowned World by J.G. Ballard describes such a future - the last remnants of civilization have retreated to Greenland, and London is a flooded tropical lagoon.

Re: What does the land under Antarctica’s ice sheet look like?

#35

Post by SketchySeaBeast »

jameshart wrote: post #32
SketchySeaBeast wrote: post #26

Earlier quoted context omitted.

To me that really looks like pattern matching where there isn't actually any (though I'd like to know more details around the "statistical skew")- saying that there's a lot of antipodal land-water or water-water pairs only makes sense considering the vast majority of the planet is water. Regardless, it's just an interesting snapshot in time considering continental drift.

30% of the surface is land. But only 15% of land has land antipodal to it, which certainly initially feels like less than you would expect by random chance. It’s easy to fall into some counterintuitive fallacies reasoning about this though because we’re considering a spherical surface pairwise and you might be tempted to say ‘ah, but we’re counting the antipodal land twice so that probably accounts for the 15%/30% th…

Just for curiosities sake I fell down the rabbit hole and ran the numbers (please someone correct me if I'm wrong on this - it's been a loooooong time since I did statistics). This is all assuming some sort of even distribution of land/water, so the numbers don't reflect real world continental distribution, but I don't know how to account for that.

We have a 30% chance of picking a random point on Earth and getting land. Because earth is so big and these theoretical points are so small I'm going to assume that one point of land existing doesn't effect the odds of another piece of land existing. So that's two antipodal points, each with a 30% chance of being land.

Putting that into a probability calculator (again, long time since statistics) that gives us odds of both point A & B being land as 9%. If we flip that around and go with the 30% land and 70% water odds we end up with a chance of 21%. It seems like there's actually MORE land that's antipodal to other land than we'd expect statistically? I must have some bad math here.

Re: What does the land under Antarctica’s ice sheet look like?

#37

Post by usrusr »

idoh wrote: post #36

Time to demote Antarctica to an archipelago? (And join Pluto on the geographic name B-team)

I believe that the term you were looking for was toponymy, avoids the awkwardness of "geography, but off-earth": and join Pluto on the toponymic B-team.

Re: What does the land under Antarctica’s ice sheet look like?

#39

Post by s1artibartfast »

mFixman wrote: post #29
jameshart wrote: post #23

Earlier quoted context omitted.

But there’s none at the North Pole. One pattern that is curiously consistent is that broadly land tends to be antipodal to ocean (and not just because there’s more ocean in general - there’s a genuine statistical skew) - so having land at one pole and none at the other matches that overall pattern. ( https://www.geodatos.net/en/antipodes ) Basically a surprisingly large proportion of antipodal pairs have land at one…

Is antipodal land a physical property of Earth's continents, or is it mathematical fact of distribution on spheres? If we distribute chunks of land randomly on a sphere we would expect roughly the same amount of land on any randomly-chosen hemisphere. But what can we say about the average amount of land in the hemisphere with the most land? My intuition says that in an Earth-like sphere, with 29% land and 71% water,…

My understanding is that it is a physical property, arising from the fact that crustal basically all crustal growth occurs in ocean floors .

The locations of the continents spend the vast majority of the time either approaching a clustered state, or leaving it.

Because the thick continents with land are a minority of the surface [2], They only briefly pass through a period of even dispersal when passing from one clustered state to another.

>My intuition says that in an Earth-like sphere, with 29% land and 71% water, there's a high chance of there existing a hemisphere with almost all of the land

Can you explain more? If you have 7 or so plates with land, why would you expect them to have a high chance of being in the same hemisphere? The math is the same as flipping a coin 7 times. Flip the first and see which side it lands on, then flip the remaining 6 and see how many match the same hemisphere. What am I missing?

https://www.youtube.com/watch?v=gQqQhZp4uG8

https://www.imperial.ac.uk/news/199334/scientists-find-link-...

Re: What does the land under Antarctica’s ice sheet look like?

#40

Post by mFixman »

s1artibartfast wrote: post #39
mFixman wrote: post #29

Earlier quoted context omitted.

Is antipodal land a physical property of Earth's continents, or is it mathematical fact of distribution on spheres? If we distribute chunks of land randomly on a sphere we would expect roughly the same amount of land on any randomly-chosen hemisphere. But what can we say about the average amount of land in the hemisphere with the most land? My intuition says that in an Earth-like sphere, with 29% land and 71% water,…

My understanding is that it is a physical property, arising from the fact that crustal basically all crustal growth occurs in ocean floors . The locations of the continents spend the vast majority of the time either approaching a clustered state, or leaving it. Because the thick continents with land are a minority of the surface [2], They only briefly pass through a period of even dispersal when passing from one clus…

> The math is the same as flipping a coin 7 times [...]

I'm not saying that a particular hemisphere has a high change of having most of the land; I'm saying that there will be a hemisphere that has this chance.

29% of Earth is land and 80% of this land is in the land hemisphere, so this problem would be the equivalent of rolling a D48 14 times and placing the dice on a table so that any 11 of the rolled numbers are visible if I look at it from the top.

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