(Why) Is there more landmass on Earth's Northern hemisphere than the Southern Hemisphere?

Question

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)?

Answer 1

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.

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.

Answer 2

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.

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.

Answer 3

Present distribution of land masses have occurred due to the movement of tectonic plates. The real reason of the movement of plates is not precisely known, but it is perhaps related with the events that are occurring inside the Earth's interior, there is molten lava where several circles of waves are in continuous movement. There are several cells of such waves. There are two types of areas, one where waves converge, while another where up-moving waves diverge in opposite direction below the crust. In the areas where waves converge, the land mass is concentrated over there. While in areas with diverging waves below, the crust moves away from there.

Land masses have converged around North pole, probably because of these converging waves. This phenomena is geophysically very complex and needs extensive and deep research.

Answer 4

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.

Answer 5

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.

Answer 6

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.