Continental drift: Wegener, Pangaea and the break-up

Detail

1. The starting point: continents move

• Continents cover 29 per cent of the earth's surface. The rest, about 71 per cent, is ocean.
• The continents have not always been where they are now.
• They have moved in the past.

• They are still moving, and they will keep moving.

• Continental drift means the slow, sideways movement of continents across the earth's surface over millions of years.

2. The first clue: matching Atlantic coastlines

• The Atlantic coasts look like two halves of one jigsaw
• The east coast of South America (for example, the bulge of Brazil) fits into the west coast of Africa (the Gulf of Guinea).
• The coasts of North America and Europe also face each other in the same way across the North Atlantic.

• This made scholars think that the Americas, Europe and Africa were once joined.

• Abraham Ortelius (a Dutch map maker) was the first to suggest this, in 1596.

• He wrote that the Americas were "torn away from Europe and Africa … by earthquakes and floods" [2].

• He said that a careful look at the coastlines shows the "vestiges of the rupture" (the marks left where the land tore apart) [2].

• Antonio Pellegrini drew a map that showed the three continents joined together.

• These were only ideas based on how the maps looked. Neither man gave a full theory.

3. Alfred Wegener and the continental drift theory (1912)

• Alfred Wegener (1880-1930) was a German meteorologist (a scientist who studies weather and climate).

• He first trained as an astronomer. He was also a geophysicist (a scientist who studies the physics of the earth) [3][4].

• In 1912 he put forward a complete continental drift theory.

• Core idea: all the continents were once one landmass. This landmass broke up, and the pieces slowly drifted to where they are today.

• It was the first full statement of the continental drift idea [4].

• He set out the theory in detail in his book The Origin of Continents and Oceans (1915) [5].

• He died in 1930 on an expedition to Greenland [2][3].
• Why many scientists rejected it at first
• Wegener could not give a mechanism, meaning he could not explain what force was strong enough to push whole continents [2][3].
• The English geophysicist Harold Jeffreys argued that solid continental rock could not plough through the ocean floor without breaking up [2].

• Wegener was also seen as an outsider to the world of geology [3].

• When it was accepted: in the 1960s. By then sea-floor spreading had been shown, through the work of Harry Hess and the ocean-floor maps of Marie Tharp [3]. Sea-floor spreading is the process by which new ocean floor forms at mid-ocean ridges and moves outwards on both sides.

4. Wegener's world: Pangaea and Panthalassa

Name	Meaning	What it was	Present-day trace
Pangaea	"all earth" (Greek)	The single supercontinent (a very large landmass made of all or most continents joined together)	Today's continents are its broken pieces
Panthalassa	"all water"	One huge ocean (mega-ocean) around Pangaea	The Pacific Ocean is thought to be what is left of it

• Timing:
• Wegener thought Pangaea existed from about 350 to 245 million years ago [5].
• Pangaea was fully put together by the Early Permian period, about 299 to 273 million years ago [5].
• It began to break up about 200 million years ago. USGS gives a range of 225 to 200 million years ago [2].

5. The break-up, step by step

• Step 1: Pangaea starts to split (about 200 million years ago).
• Step 2: Two large landmasses form
• Laurasia: the northern landmass.
• Gondwanaland: the southern landmass.

• The South African geologist Alexander Du Toit (a professor at Witwatersrand University and a strong supporter of Wegener) developed this two-part model [2].

• Step 3: The Tethys Sea opens between them. The Tethys Sea was a long, narrow sea between Laurasia and Gondwanaland. Sediments laid down in it were later pushed up to form the Himalayas.

• Step 4: Both landmasses keep breaking up into the continents we know today.

Feature	Laurasia	Gondwanaland
Hemisphere	Northern	Southern
Became	North America, Europe, most of Asia (but not India)	South America, Africa, Madagascar, India, Australia, Antarctica
Name comes from	Laurentia (old core of North America) + Eurasia	The Gond region of central India
Lifespan	Formed when Pangaea split	About 600-550 million years ago to 180 million years ago, as a southern supercontinent [3]

• Trap: India is part of Gondwanaland, not Laurasia, even though India is in Asia today.

6. Gondwanaland and India

• Gondwanaland is named after the Gond region of central India.

• The rocks and fossils there match those of the other southern continents (Africa, South America, Australia, Antarctica).

• India's old neighbour was Africa. India was part of Gondwana, with Africa next to it. It later broke away and moved north towards Asia (NCERT, Class 7).

• The Gondwana rocks of India today
• The Gondwana Supergroup (a thick group of rock layers laid down at the time of Gondwanaland) holds India's main stores of coal, refractory clays (clays that can stand very high heat) and coal bed methane (natural gas trapped in coal seams) [6].
• These rocks lie unconformably on much older Proterozoic rocks [6]. "Unconformably" means there is a time gap between the two rock layers, where rocks were worn away or never laid down.

• Marine Gondwana Fossil Park, Manendragarh (district Sarguja, Chhattisgarh): sea fossils from the Permian period (280-240 million years ago) in the Talchir Formation of the Gondwana Supergroup [6].

• Glossopteris: a key Gondwana plant

• Glossopteris was a seed plant, now extinct, that once covered the southern continents [7].
• Its fossils are found in India, Australia, South America, Africa and Antarctica. One plant could not have spread across seas and such different climates unless these lands were joined [2][3].
• In the coal mines of Jharkhand, fossils of at least 14 species of Glossopteris and its close relatives have been found. The first-ever juvenile male cone of Glossopteris was found in the Damodar Basin [7].

7. Other proof Wegener used (in brief)

Proof	What it shows
Jigsaw fit of the coasts of South America and Africa, with matching rock layers	The two were once one block [2][3]
Mesosaurus (a small freshwater reptile) found only in southern Africa and South America	A freshwater animal could not have swum across the Atlantic [3]
Coal (made from tropical plants) found in Antarctica	Antarctica once lay nearer the equator [2]
Glacial deposits in today's warm, dry areas, such as the Vaal River valley, South Africa	These lands were once near the South Pole [2]

8. Later correction: Pangaea was not the first supercontinent

• Pangaea was itself made when older continental masses came together.

• Continents have been wandering all through geological time. They join together, then split apart, again and again.

• This repeated joining and splitting is called the supercontinent cycle [5].

• Rodinia was an earlier supercontinent. It existed about 1 billion years ago and began to break up more than 700 million years ago [3][5].
• Sequence to remember (oldest → youngest): Rodinia → Gondwana (southern block, about 600-550 million years ago) → Pangaea (Early Permian) → Laurasia and Gondwanaland (from about 200 million years ago) → today's continents.

Prelims Hooks

• Abraham Ortelius (1596), a Dutch map maker, was the first to suggest the Americas, Europe and Africa were once joined. It was not Wegener.
• Alfred Wegener was a meteorologist, not a geologist by training. Theory in 1912, book The Origin of Continents and Oceans in 1915, died in Greenland in 1930.
• Pangaea = "all earth"; Panthalassa = "all water". The Pacific is regarded as what remains of Panthalassa.
• Pangaea began to break up about 200 million years ago. It split into Laurasia (north) and Gondwanaland (south), with the Tethys Sea between them.
• Trap: India belonged to Gondwanaland, not Laurasia. Laurasia = North America + Europe + most of Asia.
• Gondwanaland included South America, Africa, Madagascar, India, Australia and Antarctica. It is named after the Gond region of central India.
• Glossopteris (a plant) and Mesosaurus (a freshwater reptile) are fossil proof of drift. Mesosaurus is found only in southern Africa and South America.
• Marine Gondwana Fossil Park, Manendragarh is in Chhattisgarh, in Permian rocks of the Talchir Formation.
• Main objection to Wegener: he had no mechanism. Acceptance came in the 1960s through sea-floor spreading (Hess).
• Supercontinent order: Rodinia (about 1 billion years ago) → Pangaea → Laurasia/Gondwanaland.

Mains Points

• How the idea grew: it began as a guess from maps (Ortelius, 1596). Wegener (1912) turned it into a theory backed by proof: the coastline fit, matching rocks, fossils (Glossopteris, Mesosaurus) and signs of old climates (coal in Antarctica, glacial deposits in South Africa). He failed only on the mechanism, which sea-floor spreading and plate tectonics later supplied. This is a good example of how science corrects itself.
• Why it matters for India's land and economy: India was part of Gondwanaland. As a result:
• India's main coal is found in Gondwana rocks, laid down in old river basins such as the Damodar.
• India shares rocks and fossils with Africa, Antarctica and Australia.

• India broke away and moved north, and its collision with Asia closed the Tethys Sea and raised the Himalayas.

• Continents are not fixed: Pangaea was made from older blocks such as Rodinia, and continents are still moving today. Ocean shapes, mountain belts, where earthquakes happen and where minerals are found all come from this long cycle of continents joining and splitting.