To begin the Triassic Period (245 m.y.a.), all landmasses were assembled into a single continent called Pangaea. By the end of the Triassic Period, Pangaea began to split. The dispersed fragments of Pangaea are the existing continents of North America, South America, Africa, Europe, Asia, Australia, and Antarctica.

First, let us examine the configuration of the supercontinent of Pangaea. Note the latitudinal distribution of the landmass and the surrounding Panthalassa Ocean.

• What would be the influence of such a large landmass on climate in the interior?
• How would the evolution and the diversity of life be influenced by its break-up?
  

The following is the story of the break-up of Pangaea.

I. During the Triassic Period, Pangaea began splitting into two smaller supercontinents. Enormous rift systems (similar to the East African rift valley of today, but much larger) began splitting up the supercontinent. Some of these rifts failed to form aulacogens (e.g. Niger, Mississippi, Amazon).

Rifting of Pangaea separated North America, Europe, and Asia (Laurasia) from the southern landmass of South America, Africa, Antarctica, India, and Australia (Gondwana). The North Atlantic began forming (from south to north) as Africa separated from North America. Somewhat later, N. America also was separated from South America. A large inland sea, the Tethys Sea, existed between Eurasia and Africa.

II. Gondwana break-up.

A. Antarctica and Australia (still together) separated from South America and Africa. This is a big one. Wait to you see what this does to climate! This began during the Cretaceous Period but northward motion accelerated by 45 m.y.a. Today Australia is still moving north. This northward motion is being accommodated by subduction under Indonesia. Guess why Indonesia has so mountainous and has high seismicity and many volcanoes?

B. India separated and began a long march to its appointment with Asia.

C. South America and Africa began separating, forming a young South Atlantic Ocean.

D. South America was still connected to Antarctica

III. Finishing Touches (last 65 million years).

A. Most of Australia's separation from Antarctica occurred during this time. The Australian plate still moves northward today.

B. The North and South Atlantic continued to widen.

C. Europe separated from Greenland

D. Greenland separated from North America

E. South America separated from Antarctica (23 m.y.a.)

F. India collided with Asia (~45 m.y.a.). Fast northward motion of India (~15-20cm/yr) and formation of the Himalayans, Tibetan Plateau, etc.

G. North America and South America joined by Central American landbridge (3 m.y.a.). After its separation from Africa, S. America was an island continent until very recently. Subduction at the Middle American Trench created a volcanic arc which finally connected North and South America. Isolation of S. America had produced many types marsupial mammals and placental mammals found nowhere else. The land connection allowed mixing of assemblages, with many S. American mammals becoming extinct. Some S. America mammals migrated north (e.g. armadillo, opossum, porcupine, and ground sloth).

Pangaea- The name proposed by Alfred Wegener for a supercontinent that existed at the end of the Paleozoic Era and consisted of all the Earth's landmasses.

Panthalassa Ocean- The Late Paleozoic worldwide ocean that surrounded the supercontinent Pangaea.

Gondwana- One of six major Paleozoic continents; composed of the present-day continents of South America, Africa, Antarctica, Australia, and India, and parts of other continents such as southern Europe, Arabia, and Florida; began fragmenting during the Triassic Period.

Laurasia- A Late Paleozoic, Northern Hemisphere continent composed of the present-day continents of North America, Greenland, Europe, and Asia.

Tethys Sea- An immense seaway that separated Gondwanaland from Laurasia during the Mesozoic Era.

trade winds-Steady winds blowing from areas of high pressure at 30° north and south latitudes toward the area of lower pressure at the equator. This pressure differential produces the northeast and southeast trade winds in the Northern and Southern Hemispheres, respectively.

aulacogen- A sediment-filled, inactive rift of a triple junction that formed above a rising mantle plume.