system
Given the following post, respond as if you're commenting on Reddit:
human
is there a reason land masses seem to get thinner towards their southern portions? 

I was looking at a world map and noticed that there seems to be a trend with land masses where they get 'thinner' towards their southern portion. e.g., Africa, South America, and North America all have much wider northern portions than southern. 

is this purely coincidence, or is there some geological/natural reason for it to happen? 

(note: I recognize that 'north' and 'south' is arbitrary, so I guess I'm more interested in how/why there seems to be a trend, not the nature of the trend itself)
gpt
I think this can best be explained by looking at the plate boundaries, in particular the mid-Atlantic ridge. This is more-or-less North-South trending. The eastern side of the Pacific is the same. This is what has defined the shape of continents in part.  
The real reason that it appears this way is most likely coincidence, and a slight cognitive bias!