In the Ordovician (450 my), a long chain of volcanic islands called an island arc, which had formed in the Iapetus Ocean, moved toward and finally collided with proto-North America.
(a long chain of volcanic islands; called; an island arc, which had formed in the Iapetus Ocean; L:In the Ordovician) (an island arc; had formed; L:in the Iapetus Ocean)
a long chain of volcanic islands an island arc
called had formed
an island arc, which had formed in the Iapetus Ocean L:In the Ordovician
L:in the Iapetus Ocean