1、This map illustrates the break-up of the supercontinent, Rodinia, which formed 1100 million years ago. The Late Precambrian was an “Ice House“ World, much like the present-day.,Animals with hard-shells appeared in great numbers for the first time during the Cambrian. The continents were flooded by s
2、hallow seas. The supercontinent of Gondwana had just formed and was located near the South Pole.,During the Ordovician ancient oceans separated the barren continents of Laurentia, Baltica, Siberia and Gondwana. The end of the Ordovician was one of the coldest times in Earth history. Ice covered much
3、 of the southern region of Gondwana.,Laurentia collides with Baltica closing the northen branch of the Iapetus Ocean and forming the “Old Red Sandstone“ continent. Coral reefs expand and land plants begin to colonize the barren continents.,By the Devonian the early Paleozoic oceans were closing, for
4、ming a “pre-Pangea“. Freshwater fish were able to migrate from the southern hemisphere continents to North America and Europe. Forests grew for the first time in the equatorial regions of Artic Canada.,During the Early Carboniferous the Paleozoic oceans between Euramerica and Gondwana began to close
5、, forming the Appalachian and Variscan mountains. An ice cap grew at the South Pole as four-legged vertebrates evolved in the coal swamps near the Equator.,During the Early Carboniferous Pangea Begins to Form.,By the Late Carboniferous the continents that make up modern North America and Europe had
6、collided with the southern continents of Gondwana to form the western half of Pangea. Ice covered much of the southern hemisphere and vast coal swamps formed along the equator.,Vast deserts covered western Pangea during the Permian as reptiles spread across the face of the supercontinent. 99% of all
7、 life perished during the extinction event that marked the end of the Paleozoic Era.,The supercontinent of Pangea, mostly assembled by the Triassic, allowed land animals to migrate from the South Pole to the North Pole. Life began to rediversify after the great Permo-Triassic extinction and warm-wat
8、er faunas spread across Tethys.,By the Early Jurassic, south-central Asia had assembled. A wide Tethys ocean separated the northern continents from Gondwana. Though Pangea was intact, the first rumblings of continental break up could be heard.,The supercontinent of Pangea began to break apart in the
9、 Middle Jurassic. In the Late Jurassic the Central Atlantic Ocean was a narrow ocean separating Africa from eastern North America. Eastern Gondwana had begun to separate form Western Gondwana.,During the Cretaceous the South Atlantic Ocean opened. India separated from Madagascar and raced northward
10、on a collision course with Eurasia. Notice that North America was connected to Europe, and that Australia was still joined to Antarctica.,The bulls eye marks the location of the Chicxulub impact site. The impact of a 10 mile wide comet caused global climate changes that killed the dinosaurs and many
11、 other forms of life. By the Late Cretaceous the oceans had widened, and India approached the southern margin of Asia.,50 - 55 million years ago India began to collide with Asia forming the Tibetan plateau and Himalayas. Australia, which was attached to Antarctica, began to move rapidly northward.,2
12、0 million years ago, Antarctica was coverd by ice and the northern continents were cooling rapidly. The world has taken on a “modern“ look, but notice that Florida and parts of Asia were flooded by the sea.,When the Earth is in its “Ice House“ climate mode, there is ice at the poles. The polar ice s
13、heet expands and contacts because of variations in the Earths orbit (Milankovitch cycles). The last expansion of the polar ice sheets took place about 18,000 years ago.,We are entering a new phase of continental collision that will ultimately result in the formation of a new Pangea supercontinent in
14、 the future. Global climate is warming because we are leaving an Ice Age and because we are adding greenhouse gases to the atmosphere.,If we continue present-day plate motions the Atlantic will widen, Africa will collide with Europe closingthe Mediterranean, Australia will collide with S.E. Asia, an
15、d California will slide northward up the coast to Alaska.,New subduction zones along the eastern coasts of North America and South America will begin to consume the ocean floor separating North America from Africa. About 100 million years from now the present-day Mid-Atlantic Ridge will be subducted and the continents will come closer together.,The next Pangea, “Pangea Ultima“ will form as a result of the subduction of the ocean floor of the North and South Atlantic beneath eastern North America and South America. This supercontinent will have a small ocean basin trapped at its center.,
