Gondwana

Gondwana

Gondwana was a large landmass, sometimes called a supercontinent. It was made of several big, stable pieces of Earth's crust called cratons. These pieces joined together about 800 to 650 million years ago. They included places like modern-day South America, Africa, Antarctica, Australia, Arabia, and the Indian subcontinent.

Eventually, Gondwana became the biggest part of the Earth's land during the Paleozoic Era. It covered about one-fifth of the Earth's surface. Later, it joined with another landmass called Laurasia to form an even bigger supercontinent called Pangaea.

Gondwana started to break apart during the Triassic period. It kept splitting up during the Early Jurassic, about 180 million years ago. The last part of this breaking up happened when Antarctica moved away from South America and Australia. This created the Drake and Tasmanian Passages. Because of this history, places that were once part of Gondwana share some of the same plants and animals even today.

Name

The continent of Gondwana was named by the Austrian scientist Eduard Suess after the Indian region of the same name. This region's name comes from Sanskrit and means "forest of the Gonds". Some scientists use the term "Gondwanaland" to make the idea of the supercontinent different from the region.

Formation

Gondwana formed very slowly during the Neoproterozoic and Paleozoic periods. It was created when many parts of Earth's crust moved together. An important part, called the Mozambique Belt, formed between 800 and 650 million years ago. Later, places like India, Australia, and Antarctica joined, making the big landmass we call Gondwana. Many geological changes happened over hundreds of millions of years to make this happen.

Peri-Gondwana development: Paleozoic rifts and accretions

Many pieces of land joined with Eurasia when Gondwana existed, but we do not know if they started near Gondwana or earlier. For example, some land pieces in Central Asia, called the "Kazakh" and "Mongolian terranes", joined together in the late Silurian.

In the early Paleozoic, a land area that is now part of France, called the Armorican terrane, was close to Gondwana. Rocks from the Iberian Peninsula show it was once part of Gondwana before moving away near the end of the Paleozoic.

Southeast Asia formed from pieces that came from Gondwana and other areas. This happened in three steps: First, in the Devonian period, parts of China and nearby areas moved away from Gondwana. Second, in the Late Carboniferous to Early Permian, more pieces joined Asia. Third, in the Late Triassic to Late Jurassic, even more pieces moved and joined Asia.

Gondwana’s northern edge stayed mostly quiet during the Paleozoic. The opening of the Neo-Tethys Ocean in the Early Permian created many land pieces that later moved toward Eurasia. These pieces stretch from Turkey to northeastern India and include areas in modern Turkey, Georgia, Iran, the Caspian Sea, Afghanistan, northern Pakistan, and Tibet.

Southwestern accretions

During the Neoproterozoic to Paleozoic, some land pieces moved away from the edge of Gondwana and later joined back as the Iapetus Ocean closed. In the Paleozoic, parts of southern South America formed from blocks that came from other areas. One piece, called Cuyania, may have come from Laurentia and joined Gondwana in the Ordovician. Later, the Chilenia terrane joined next to it. The Patagonian terrane crashed into Gondwana in the late Paleozoic. An island arc called Chaitenia joined Patagonia in what is now south-central Chile during the Devonian.

Gondwana as part of Pangaea: Late Paleozoic to Early Mesozoic

Main article: Pangaea

Gondwana and Laurasia joined together to form a huge supercontinent called Pangaea during the Carboniferous period. Later, Pangaea began to break apart in the Mid-Jurassic when the Central Atlantic opened.

The joining of Gondwana and Laurasia closed oceans such as the Rheic and Paleo-Tethys. This created big mountain ranges like the Variscan-Appalachian Mountains, stretching from Mexico to Europe. Other land pieces like Baltica joined with Siberia and Kazakhstania, forming the Uralian orogeny. These changes affected Earth’s climate and sea levels, causing big shifts in where sediments settled.

Break-up

Antarctica was the center of Gondwana. As the landmass broke apart, it spread outwards in a clockwise direction. The break-up began with big volcanic eruptions called the Karoo-Ferrar igneous province around 200 to 170 million years ago. This helped split Gondwana into smaller pieces.

Gondwana started to break up in the early Jurassic period. As it separated, new oceans formed between the continents. For example, the western Indian Ocean formed between Madagascar and Africa about 150 million years ago. The eastern Indian Ocean formed between India and Antarctica around 120 million years ago. The South Atlantic Ocean opened as South America and Africa drifted apart, beginning around 126 million years ago. These changes reshaped Earth’s continents and affected global climates and animal and plant life.

Biogeography

See also: Evolutionary history of plants

Gondwana played an important role in where plants and animals live today. Many plants that lived on Gondwana long ago can still be found in places like South America, Africa, Australia, and Antarctica. For example, trees like Glossopteris and Dicroidium were common there at different times.

Gondwana was home to many kinds of plants. At first, simple land plants such as Baragwanathia grew there. Later, large trees like Archaeopteris covered the coastal areas. Over time, new plants appeared, such as conifers and flowering plants, which are still around today. The changes in Gondwana helped shape the plant life we see in many parts of the world now.