They have crashed into one big group then split along tectonic plate lines numerous times in the past. Pangaea was the last great conjunction, and that supercontinent split apart about 250 million years ago.
Pannotia, formed about 600 million years ago during the Proterozoic eon, and lasted until 540 million years ago. Before Pannotia, there was Rodinia, which lasted from about 1.1 billion years ago until about 750 million years ago. The exact configuration and geodynamic history of Rodinia are not nearly as well understood as Pannotia and Pangaea.
A million years isn’t a long time in geologic terms though, so don’t expect them to all bump back together that quickly.