CONTINENTAL DRIFT

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Continental drift : 

A.VIDYASAKAR Continental drift

What is Continental Drift? : 

What is Continental Drift? Continental drift is the movement of the Earth's continents relative to each other. The hypothesis that continents 'drift' was first put forward by Abraham Ortelius in 1596.

Who Proposed & When? : 

Who Proposed & When? In 1915, the German geographer and meteorologist Alfred Wegener first proposed the theory of continental drift, which states that parts of the Earth's crust slowly drift a top a liquid core.

Transition of proto to planet earth : 

Transition of proto to planet earth

Types of magmas : 

Types of magmas Granitic magma - 75-80% silica content Andesitic magma- 50-55% silica content Basaltic magma-40-45% silica content

Viscosity : 

Viscosity Granitic magmas have very high vicosity. Andesitic magmas have intermediate viscosity. Basaltic magmas have very low viscosity of all. (more silica content make magma to be highly vicous)

High viscosity : 

High viscosity

Basaltic lava : 

Basaltic lava

Granitic lava : 

Granitic lava

Prime evil time : 

Prime evil time

The Rain started : 

The Rain started

Ocean : 

Ocean

Pangaea : 

Pangaea Wegener hypothesized that there was a gigantic supercontinent 200 million years ago, which he named Pangaea, meaning "All-earth".

Evidence that continents 'drift' : 

Evidence that continents 'drift' Evidence for continental drift is now extensive. Similar plant and animal fossils are found around different continent shores, suggesting that they were once joined. The fossils of Mesosaurus, a freshwater reptile rather like a small crocodile, found both in Brazil and South Africa, are one example; another is the discovery of fossils of the land reptile Lystrosaurus from rocks of the same age from locations in South America, Africa, and Antarctica. There is also living evidence — the same animals

Plant Fossil Evidence in Support of the Theory : 

Plant Fossil Evidence in Support of the Theory Eduard Suess was an Austrian geologist who first realized that there had once been a land bridge connecting South America, Africa, India, Australia, and Antarctica. He named this large land mass Gondwanaland (named after a district in India where the fossil plant Glossopteris was found). This was the southern supercontinent formed after Pangaea broke up during the Jurassic period. Suess based his deductions on the fossil plant Glossopteris, which is found throughout India, South America, southern Africa, Australia, and Antarctica.

Evidence : 

Evidence

Sonar operation : 

Sonar operation Sonar was invented by USA. It was first used by US navy to examine the ocean bottom.

TRENCH : 

TRENCH If the deep sea trench was close to the continent, the mountain ranges was on the edge of the continent.

The Andes : 

The Andes

TRENCH : 

TRENCH

trench : 

trench

Ridge : 

Ridge Oceanic Ridges – Are basaltic (iron rich)

Rock Magnetism : 

Rock Magnetism Consider basaltic lava is coming out and they are iron rich. Each mineral in basalt is magnetite. Whenever it drops down below the curie point ,each one of those grains of magnetite become magnetized, and the magnetic field of each one of those grains duplicates whatever magnetic field exist at the time of its information.

Magnetic orientation : 

Magnetic orientation

Magnetic orientation : 

Magnetic orientation

magnetism with magnetometer : 

magnetism with magnetometer

magnetometer : 

magnetometer The magnetic orientation are observed by the instrument called magnetometer.

Bands of Reading : 

Bands of Reading

High intensity reading : 

High intensity reading

Low intensity reading : 

Low intensity reading

Sea-Floor Spreading : 

Sea-Floor Spreading

Slide 32: 

Ocean floor moves like a conveyor belt carrying continents with it. New ocean floor forms along cracks in the ocean crust as molten material erupts from the mantle spreading out and pushing older rocks to the sides of the crack. New ocean floor is continually added by the process of sea-floor spreading.

Convectional cells : 

Convectional cells This convectional current was first suggested by a british geologist A.HOLMES in 1927. The high heat flow associated with the oceanic ridges suggests that convection currents exist within the earth.These currents are believed to be responsible for the movement of crustal plates.

Convectional currents : 

Convectional currents

Tensional zone or rift zone : 

Tensional zone or rift zone

Rift valley : 

Rift valley

Is continent moving or plate? : 

Is continent moving or plate?

Which moves? : 

Which moves?

Continental drift from Precambrian to the future : 

Continental drift from Precambrian to the future Late Precambrian Supercontinent and Ice House World This map illustrates the  break-up of the supercontinent, Rodinia, which formed 1100 million years ago.   The Late Precambrian was  an "Ice House" World, much like the present-day

Cambrian: the beginning of the Paleozoic Era : 

Cambrian: the beginning of the Paleozoic Era Animals with hard-shells appeared in great numbers for the first time during the Cambrian.  The continents were flooded by shallow seas.  The supercontinent of Gondwana had just formed and was located near the South Pole.

Ancient Oceans Separate the Continents : 

Ancient Oceans Separate the Continents During the Ordovician ancient oceans separated the barren continents of Laurentia, Baltica, Siberia and Gondwana.  The end of the Ordovician was one of the coldest times in Earth history.  Ice covered much of the southern region of Gondwana

Continents Begin to Collide as Paleozoic Oceans Close : 

Continents Begin to Collide as Paleozoic Oceans Close Laurentia collides with Baltica closing the northen branch of the Iapetus Ocean and forming the "Old Red Sandstone" continent.  Coral reefs expand and land plants begin to colonize the barren continents

The Devonian Was the Age of Fish! : 

The Devonian Was the Age of Fish! By the Devonian the early Paleozoic oceans were closing, forming a "pre-Pangea".  Freshwater fish were able to migrate from the southern hemisphere continents to North America and Europe.  Forests grew for the first time in the equatorial regions of Artic Canada.

During the Early Carboniferous Pangea Begins to Form : 

During the Early Carboniferous Pangea Begins to Form During the Early Carboniferous the Paleozoic oceans between Euramerica and Gondwana began to close, forming the Appalachian and Variscan mountains.   An ice cap grew at the South Pole as four-legged vertebrates evolved in the coal swamps near the Equator.

The Late Carboniferous a Time of Great Coal Swamps : 

The Late Carboniferous a Time of Great Coal Swamps By the Late Carboniferous the continents that make up modern North America and Europe had collided with the southern continents of Gondwana to form  the western half of Pangea.  Ice covered much of the southern hemisphere and vast coal swamps formed along the equator.

the end of the Permian was Greatest Extinction of All Time : 

the end of the Permian was Greatest Extinction of All Time Vast  deserts covered western Pangea during the Permian as reptiles spread across the face of the supercontinent.  99% of all life perished during the extinction event that marked the end of the Paleozoic Era.

At the end of the Triassic, Pangea began to rift apart : 

At the end of the Triassic, Pangea began to rift apart The supercontinent of Pangea, mostly assembled by the Triassic, allowed land animals to migrate from the South Pole to the North Pole.  Life began to rediversify after the great Permo-Triassic extinction and warm-water faunas spread across Tethys.

Early Jurassic, the Dinosaurs spread across Pangea : 

Early Jurassic, the Dinosaurs spread across Pangea By the Early Jurassic, south-central Asia had assembled.  A wide Tethys ocean separated the northern continents from Gondwana.  Though Pangea was intact, the first rumblings of continental break up could be heard.

Pangea Begins to Rift Apart : 

Pangea Begins to Rift Apart The supercontinent of Pangea began to break apart in the Middle Jurassic.  In the Late Jurassic the Central Atlantic Ocean was a narrow ocean separating Africa from eastern North America.   Eastern Gondwana had begun to separate form Western Gondwana

New Oceans Begin to Open : 

New Oceans Begin to Open During the Cretaceous the South Atlantic Ocean opened.  India separated from Madagascar and raced northward on a collision course with Eurasia. Notice that North America was connected to Europe, and that Australia was still joined to Antarctica.

The End of the Dinosaurs : 

The End of the Dinosaurs The bull's eye marks the location of the Chicxulub impact site.   The impact of a 10 mile wide comet caused global climate changes that killed the dinosaurs and many other forms of life.  By the Late Cretaceous the oceans had widened, and India approached the southern margin of Asia.

During the Early Cenozoic India began to Collide with Asia. : 

During the Early Cenozoic India began to Collide with Asia. 50 - 55 million  years ago India began to collide with Asia forming the Tibetan plateau and Himalayas.  Australia, which was attached to Antarctica, began to move rapidly northward.

The World Assumes a Modern Configuration : 

The World Assumes a Modern Configuration 20 million years ago, Antarctica was covered by ice and the northern continents were cooling rapidly.  The world has taken on a "modern" look, but notice that Florida and parts of Asia were flooded by the sea.

The Earth has been in an Ice House Climate for the last 30 million : 

The Earth has been in an Ice House Climate for the last 30 million When the Earth is in its "Ice House" climate mode, there is ice at the poles.  The polar ice sheet expands and contacts because of variations in the Earth's orbit (Milankovitch cycles).  The last expansion of the polar ice sheets took place about 18,000 years ago

The Present-day world has well defined climatic zones. : 

The Present-day world has well defined climatic zones. We are entering a new phase of continental collision that will ultimately result in the formation of a new Pangea supercontinent in the future.  Global climate is warming because we are leaving an Ice Age and because we are adding greenhouse gases to the atmosphere.

This is the way the World may look like 50 million years from now! : 

This is the way the World may look like 50 million years from now! If we continue present-day plate motions the Atlantic will widen, Africa will collide with Europe closing the Mediterranean, Australia will collide with S.E. Asia, and California will slide northward up the coast to Alaska

The Atlantic Ocean begins to Close : 

The Atlantic Ocean begins to Close New subduction zones along the eastern coasts of North America and South America will begin to consume the ocean floor separating North America from Africa.  About 100 million years from now the present-day Mid-Atlantic Ridge will be subducted and the continents will come closer together

"Pangea Ultima" will form 250 million years in the Future : 

"Pangea Ultima" will form 250 million years in the Future The next Pangea, "Pangea Ultima" will form as a result of the subduction of the ocean floor of the North and South Atlantic beneath eastern North America and South America.  This supercontinent will have a small ocean basin trapped at its center.

Thank you : 

Thank you

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