Earth Science: Plate Tectonics – Primeval Continents
Pangaea, Laurasia, Gondwana: these names are taken from the Earth’s history. Today the outlines of these three former continents can be recon- structed on the basis of models simulating continental drift.
The location of each continent today is the result of geologically recent tectonic changes. The further back an epoch is in the history of the Earth, the harder it is to imagine what the Earth would have looked like. The most recent research suggests that after the formation of the Earth’s crust, continental plates must have moved much more actively than previously thought.
Therefore several individual supercontinents must have formed from the land- masses. The earliest supercontinents were Kenorland about 2.5 billion years ago and Columbia about 1.5 billion years ago. The massive primeval continent Rodinia formed about 1.1 billion years ago. This supercontinent was surrounded by a gigantic ocean called Mirovia. It is thought that Rodinia disintegrated about 800 million years ago.
Gondwana and Laurentia
Toward the end of the Precambrian, South America, Africa, Australia, Antarctica, and India formed a massive coherent land- mass in the Southern Hemisphere of the Earth. The supercontinent Gondwana was separated from the supercontinent of the North- ern Hemisphere, Laurasia, by the Tethyan gateway, which varied in width. After the oceans retreated, the continents were flooded again. Distances between landmasses decreased once more during the Paleozoic.
Toward the end of the Cambrian about 500 million years ago, fragments of the continents collided and formed giant mountain ranges. Remains of the Caledonian mountain range can still be found today in the Appalachian Mountains, the Scottish Highlands, and in Norway. Toward the end of the Paleozoic, Gondwana and Laurentia combined to form the supercontinent Pangaea.
High mountains were created during the collisions, including the Variscan Belt, which has now been almost entirely eroded. The Tethys Ocean closed during this event.
Pangaea
Pangaea stretched from Pole to Pole and covered about a third of the Earth’s surface. The remaining part was taken up by the primeval ocean Panthalassa that sur- rounded all landmasses. A few shallow inland seas still existed, but they dried out relatively quickly.
About 200 million years ago, deep cracks and large rift valleys formed as the Pangaea “supercontinent” started to break up. The outlines of today’s continents became recognizable. The proto-Atlantic formed as an inland sea between Africa and North America during the Jurassic. The continents began to travel toward their current locations on the Earth’s surface.
The denomination of the continents used today emanates from Greek antiquity; Herodotus divided the Earth into Europe, Asia, and Africa. Nowadays seven areas are regarded as continents: Asia, Africa, North America, South America, Antarctica, Europe, and Australia.
THE PRIMEVAL OCEAN
Panthalassa is a global ocean that used to surround the supercontinent Pangaea dur-ing the late Paleozoic and the early Mesozoic. Its name originates from Greek and means “all oceans.” A wide gulf that was situated off the eastern coast of Pangaea called the Paleo-Tethys can still be found in today’s Mediterranean.
Panthlassa probably originated from Mirovia, a hypothetical primeval ocean once surrounding the supercontinent Rodinia