The landmass known as Gondwana comprised most of what is present-day Antarctica, South America, Africa, Madagascar, Australia-New Guinea, and New Zealand, as well as Arabia and the Indian subcontinent of the Northern hemisphere.
Some 250 to 180 million years ago, it formed part of the single supercontinent Pangea.
Now, Eagles, working with Matthais König from the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven, Germany, has devised a new computer model for the evolution of this landmass.
The calculations show that the supercontinent was simply too big to stay in one piece and cracked apart forming two enormous land masses.
Details of the research are published this month in the Geophysical Journal International.