Ormonde de Kay, Jr. first proposed the "theory of continental drip"
magazine (Winter 1973), although it was more of an observation than a theory. He wrote:
Continental drip is the tendency of land masses to drip, droop, sag, depend, or hang down — like wet paint in the Sherwin-Williams trademark — except that they cling to the Earth's surface below the equator instead of falling off into space.
De Kay's article was meant to be tongue-in-cheek, and there have been several elaborations of his theory in the same vein, such as here
However, it's true. Continents and peninsulas do seem to "drip" south — Africa, South America, Baja California, Florida, Greenland, Scandinavia, Italy, Greece, India, Malaysia, Indochina, and Korea.
So why? Is there a reason? De Kay wrote:
A few possible explanations come to mind: some palaeomagnetic force, for example, unsuspected and therefore undetected, centered in massive, mountainous Antarctica and perpetually tugging at the lower hems of land masses. Or drip might somehow be the result of the Earth's rotation, or of lunar attraction.
But like I said, De Kay wasn't being completely serious. The closest I've been able to find in the way of a genuine scientific response to this mystery is in New Scientist
magazine (Dec 18, 1999
), when a reader wrote in asking about the dripping continents and received the following response:
The present pattern of landmasses is just one of many that has occurred as the continents, starting with super continent Pangaea, have wandered all over the globe during the past few hundred million years. In another few hundred million the continents and their positions and shapes will all look quite different again, so not too much can be read into today’s pattern.
In other words, there really is no reason for the dripping. It's just random chance.