Final answer:
The driving force behind the splitting of supercontinents like Pangaea and Gondwana is continental rifting, which is part of plate tectonics. Alfred Wegener first proposed the idea of continental drift, which was later confirmed by evidence such as matching fossils and geological features across continents.
Step-by-step explanation:
The driving force that splits a supercontinent, such as Pangaea or Gondwana, is the process of continental rifting which is part of the broader concept of plate tectonics. Initially proposed by Alfred Wegener in 1915 as continental drift, this theory has evolved with new evidence and understanding of Earth’s geology. Wegener's theory was based on four key pieces of evidence: the congruence in shapes of continents, matching fossils on separated continents, matching mountain ranges, and paleoclimatic data indicating past positions of continents. Over time, and with further research, particularly in the 1960s, the mechanisms behind continental drift were better understood, including the role of mid-ocean ridges and the circulation of the mantle causing the movement of tectonic plates.
The breakup of supercontinents changed global climates, led to intense volcanic activity, and drastically altered the distribution of flora and fauna across the planet. For instance, the unique distribution of the plant family Proteaceae across Australia, southern Africa, and South America is best explained by their presence prior to the break-up of Gondwana.