15
$\begingroup$

This Question on Worldbuilding is based on the presumption that there is a greater amount of landmass on the Earth's Northern Hemisphere than there is on the Southern Hemisphere.

While researching to form an answer to this question, I found it difficult to find a map that accurately portrays which hemisphere actually has a greater landmass, and started thinking about the actual nature of the question - assuming there is a greater concentration of landmass in the Northern Hemisphere than the South, why is that?

Does it have anything to do with the rotational procession of the Earth? Is it more related to the Earth's natural fault lines? Or is there something else that influences a greater accumulation of land mass on our Northern Hemisphere (if that is, in fact, an accurate assumption)?

$\endgroup$
  • 4
    $\begingroup$ It hasn't always been the case, but currently landmass is split 68/32% north/south, giving the northern hemisphere twice the landmass of the southern hemisphere. I suspect the 'why' is plate tectonics but I'll leave it to our resident geo people to explain. $\endgroup$ – casey May 6 '15 at 14:39
  • $\begingroup$ It would take multiple earths to provide a statistically significant answer to this question. However, looking at maps of the plates online, it appears there are major components of motion acting to move most continents to the north, e.g. the Indian plate. So my unfounded hypothesis is that once the Antarctic plate drifted over the south pole, the spreading forces tended to move the rest of the continents northward. $\endgroup$ – haresfur Feb 15 '16 at 1:49
9
$\begingroup$

It would be a strange coincidence (but of course possible) if the landmass would be exactly evenly divided between the northern and southern hemispheres, as defined by the equator. However, you can cut the globe with another plane and form two hemispheres that have the same landmass, eg. any vertical plane that goes through the Geographical centre of Earth.

Map of @whuber

Calculation of Geographical centre of Earth by whuber at GIS stackexchange

The landmass distribution is largely depending of the location of the continental plates, but Global Paleogeography maps also suggest that the breakup of Pangaea follows other laws than an even distribution between north and south hemisphere.

The problems to find a map that accurately portrays which hemisphere actually has a greater landmass, is probably related to the fact that many popular (and in many ways useful!) map projections are not made to show area relations. Use a globe or equal area projection to compare the size of landmasses.

This might also be an interesting article for you and a starting point for further research: Riguzzi et al. (2009) Can Earth's rotation and tidal despinning drive plate tectonics?. The authors argue that there is a correlation between tectonic movements and rotation of the Earth and the Moon's revolution plane. Tomographic data of slab dip angles support the point and this might also be part of an explanation why earthquakes and volcanism varies along the latitudes and might be rare in the polar regions.

$\endgroup$
  • 1
    $\begingroup$ ARE earthquakes & vulcanism rare in polar regions? And if so, is it due to more than the chance arrangement of plates? (Plus the fact that there is simply less area at the poles.) Certainly there are volcanos in both Antarctica and Alaska/Siberia, and major earthquakes have happened in Alaska. $\endgroup$ – jamesqf May 6 '15 at 18:23
  • $\begingroup$ I also have a lot of questions about the article. Maybe it's pure apophenia, but it can add an interesting perspective. The authors didn't see any earthquakes MW >7 for polar regions. (Check fig5 in the article). However, as far as I can see, it's not corrected for geometrically decreasing area / latitude bin (A Mercator distribution, so to say). $\endgroup$ – Tactopoda May 6 '15 at 21:00
3
$\begingroup$

In the attached JPL graphic from Heflin et al, 2007.9- every data point located south of the equator shows a northward component of motion (except the Nazca plate west of South America and a small portion of the Eurasian plate in Indonesia). Australia, for example, is moving dramatically northeastward, compared to other regions.

enter image description here

If landmass evacuation from the southern hemisphere has progressed similarly for tens of millions of years, it should not be a surprise our world map looks as it does.

Additionally, as Pangaea disburses, continental material appears to be converging in the western Pacific and diverging from the mid-Atlantic Ridge. After emerging from a north-south line in the Atlantic pushing South America and Africa apart, landmass ostensibly meets on the opposite side of the earth in the Mariana subduction zone. This complex motion, combined with my northward angular momentum theory, creates the disjointed continental drift we observe.

Again, this is a long held theory of mine.

$\endgroup$
  • $\begingroup$ The 'complex motion' you describe is indeed complex, but have been described in detail for decades. Apart from GPS derived position data, geological and geophysical methods look in detail how continents were connected in Gondwana and earlier. We also try to reconstruct earlier supercontinents (Rodinia, Nuna and even older) and I haven't seen any consistent pattern of northward angular momentum. You'll need stronger arguments to convince me. $\endgroup$ – Tactopoda Jan 13 '17 at 11:04
  • 1
    $\begingroup$ A good tool to 'play' with tectonic plates and understand the relations is Gplates. It's free and rather easy to use with tutorials and good documentation. There are also a number of studies available that look in detail on the Pangea breakup and present continental drift. $\endgroup$ – Tactopoda Jan 13 '17 at 11:07
  • $\begingroup$ Again, it is wrong. Also you should edit this information into your existing answer not add a new one. $\endgroup$ – bon Jan 13 '17 at 12:31
-2
$\begingroup$

While I cannot give a good explanation, at least I can give additional information.
Antartica, continent that is just in the south of the Earth, is completely surrounded by rifts, where new land in constantly in creation and pushing north and south. As result adjacent plates are forced north while Antartica rises. Therefore, that ridge helps to explain current land distribution.

Probably in the future we'll see more land than now in the north hemisphere.

$\endgroup$
  • 3
    $\begingroup$ Antarctica doesn't rise in response to being surrounded by spreading ridges. The ridges move away from Antarctica in order to make space for the new ocean crust. $\endgroup$ – bon Jan 13 '17 at 15:08
  • 3
    $\begingroup$ When Antarctic uplift is discussed, it's often in the context of postglacial rebound. However, deeper processes are probably the cause of regional uplift in eg. Gamburtsev Mountain Range and Transantarctic Mountains. $\endgroup$ – Tactopoda Jan 14 '17 at 5:43
-6
$\begingroup$

There are 3 independent forces at play on moveable objects like continents on the surface of a rotating sphere.

  1. Coriolis force: moves continents in the N. Hemisphere towards the N.Pole and those in the S. Hemisphere towards the S. Pole. There is no angular momentum that pushes all crustal mass towards just one pole.

  2. Subduction/Emission ie. Deep Thermal forces move continents from emission zones to subductions zones.

  3. Rebalancing forces after heavy meteor bombardments in Either Hemisphere will rebalance by shifting crustal plates away from the Hemisphere that has been hit. In two dimensions if you put a 'balancing lead slug' on a slider ring on an unbalanced car wheel then the slug will move to the balance position when the wheel is in motion. Equatorial meteor hits will have only muted effects.

The first two of these forces must eventually lead to both hemispheres having equal total crustal plate masses. Given average sial density of 2.2 that means roughly equal crustal areas should be present by now.

Thus the current 60:30 N:S distribution indicates a recent heavy meteorite strike to the S Hemisphere. S.Africa stands out as the hit zone due to the shape of the E.Rift Valley and extensive heavy metal placements in that area. The rough equispacing of Africa, Australia and S.America also tend to support this given the ratio of their areas.

The Third force will enable one hemisphere to be weighted with more crust to counteract a heavy meteor presence in the other hemisphere.

$\endgroup$
  • 5
    $\begingroup$ This is pseudoscientific nonsense. $\endgroup$ – bon Nov 21 '17 at 13:26
-7
$\begingroup$

Floating continents on a rotating sphere follow the "right-hand rule". A dynamic force vector acts toward the north on a globe spinning counter clockwise, when looking down upon the north pole. I surmise that over eons, land masses have been relentlessly forced northward with a measurable angular momentum.

A casual glance at the tapered appearance of South America, Africa, Greenland and the Indian subcontinent add anecdotal evidence to the theory. South America looks like a bubble moving northward with greatest mass at the north and a thinning tail on the south end. India, again with a tapered southern edge, has been moving north so dramatically that the Himalaya mountains were shoved skyward.

I've never heard this theory advanced by anyone, but it seems plausible to me. Alfred Wegener offered his tectonic plate theory in 1912. This would be a corollary to that.

$\endgroup$
  • 7
    $\begingroup$ Tectonics is indeed a fascinating topic and the early theories about continental drift started from observing the present map. However, I'm sorry to say, your theory is challenged by rather massive geological and geophysical data. If you have a look at the supercontinental cycle, you'll see that continents have moved in all directions. We are still living in the time of Pangea and Gondwana breakup, and continental plates are mainly radiating away from that assembly. Moreover, the continental crust is not heavy, it's actually sort of floating on the denser mantle. $\endgroup$ – Tactopoda Jan 12 '17 at 9:44

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.