It all began with a rift, similar to today's East Africa Rift. This rift flow probably came from the Proto-Tethys Ocean's mid-ocean ridge. As this microcontinent drifted from Gondwana, a mid-ocean ridge was forming between them, forcing Avalonia to head across the aging Iapetus Ocean, this occurred in the early part of Middle Ordovician. For much of the Late Ordovician, the Rheic Ocean appears to have widened as fast as today's East Pacific Rise (at 17 cm/year). When Baltica and Laurentia collided with each other in the Latest Ordovician to form the megacontinent of Euramerica, the Rheic ocean had already expanded, replacing most of the Iapetus Ocean, which has now become a narrow seaway, between Avalonia and Laurentia. The ocean began to close in the Devonian, when the supercontinent of Gondwana drifted towards Euramerica. By the Late Devonian, the Rheic Ocean became a narrow ocean that sutured between Gondwana and Euramerica. In the Early Carboniferous (Mississippian), the eastern part of the Rheic Ocean had already closed, due to the collision of the Eastern United States with Africa. Later, South America collided against southern United States, completely closing the ocean. These collisions created orogenies - the Ouachita-Alleghenian-Variscan orogeny.