The Ordovician Period started at a major extinction event called the Cambrian-Ordovician extinction events some time about 485.4 ± 1.9 Ma. During the Ordovician the southern continents were collected into a single continent called Gondwana. Gondwana started the period in the equatorial latitudes and, as the period progressed, drifted toward the South Pole. Early in the Ordovician the continents Laurentia, Siberia and Baltica were still independent continents (since the break-up of the supercontinent Pannotia earlier), but Baltica began to move toward Laurentia later in the period, causing the Iapetus Ocean to shrink between them. Also, Avalonia broke free from Gondwana and began to head north toward Laurentia. The Rheic Ocean was formed as a result of this. By the end of the period, Gondwana had neared or approached the pole and was largely glaciated. COUNT 5
QSN1 How long ago did the Ordovician period begin? ANS1 485.4 ± 1.9 Ma. QSN2 Which event precipitated the Ordovician period? ANS2 the Cambrian-Ordovician extinction QSN3 What was the name of the large southernmost continent during the Ordovician? ANS3 Gondwana QSN4 Which ocean decreased in size with the movement of Baltica in the Ordovician? ANS4 Iapetus Ocean QSN5 What continent fractured off Gondwana in the direction of Laurentia? ANS5 Avalonia