Gondwana
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- This article is about the ancient supercontinent of Gondwana. For the region of India called Gondwana, see Gondwana (India).
Gondwana.JPG
The southern supercontinent Gondwana (originally Gondwanaland) included most of the landmasses which make up today's continents of the southern hemisphere, including Antarctica, South America, Africa, Madagascar, India, Arabia, Australia-New Guinea and New Zealand. It was formed in the early Jurassic about 200 million years ago by the break-up of Pangaea. The other continents at that time -- North America and Eurasia -- were still joined, forming the northern supercontinent, Laurasia.
Although Gondwana was centered roughly where Antarctica is today (at the extreme south of the globe), the climate was generally mild. During the Mesozoic, average global temperatures were considerably warmer than they are today. Gondwana was then host to a huge variety of flora and fauna for many millions of years.
The supercontinent began to break up in the late Jurassic (about 160 million years ago) when Africa became separated and began to drift slowly northwards. The next large block to break away was India, in the early Cretaceous (about 125 million years ago). New Zealand followed about 80 million years ago, only about 15 million years before the Cretaceous-Tertiary extinction event wiped out about 50% of all species on the planet, most notably the dinosaurs.
As the age of mammals got underway, the continent of Australia-New Guinea began to gradually separate and move north (55 million years ago), rotating about its axis to begin with, and thus retaining some connection with the remainder of Gondwana for a considerable time.
About 45 million years ago, the Indian subcontinent collided with Asia, forcing the crust to buckle and forming the Himalaya. At about the same time, the southern-most portion of Australia (modern Tasmania) finally separated from what is now Antarctica, allowing ocean currents to flow between the two continents for the first time. This in turn produced cooler and dryer climates on the two landmasses.
Far more significant as a world climatic event, however, was the separation of South America from Antarctica sometime during the Oligocene, perhaps 30 million years ago. With the opening of Drake Passage, there was now no barrier to force the cold waters of the Southern Ocean north, to be exchanged with warmer tropical water. Instead, a cold circumpolar current developed and Antarctica became what it is today: a frigid continent which locks up much of the world's fresh water as ice. Sea temperatures dropped by almost 10 degrees, and the global climate became much colder.
About 15 million years ago, New Guinea began to collide with southern Asia, once again pushing up high mountains, and more recently still, South America became joined to North America via the Isthmus of Panama.
The continent was named by Eduard Suess after Gondwana, a region of eastern India where some of the geology of the ancient continent was determined.
See also
External link
- Animation showing the dispersal of Gondwanaland (http://earth.leeds.ac.uk/~greg/Gond.html)
- Another animation (http://kartoweb.itc.nl/gondwana/index.asp)da:Gondwanaland
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