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Earth's continental crust
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How the Earth grew, 3 billion years ago

The growth rate of the Earth's continental crust was high during the first 1.5 billion years of the planet's history then decreased markedly for the next 3 billion years to the present day, according to new research from the University of Bristol, published 16 March in Science. This sharp decrease indicates a dramatic change in the way the continental crust was generated and preserved.
The Earth is around 4.5 billion years old. At present 75 per cent of the continental crust - the crust we live on - is less than 1 billion years old, and only around 7 per cent of it is made up of rocks of Archaean age (that is older than 2.5 billion years).
What is striking, and perhaps unexpected, is that there is increasing evidence that large volumes of continental crust were generated before 2.5 billion years ago.

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RE: Tectonic Plates
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How oldest continents were formed

Geologists at the Universities of Bonn and Cologne have come up with a new theory on the formation of the oldest continents. The earth's structure can be compared to an orange: its crust is the peel supported by the earth's heavy mantle. That peel is made up of a continental crust 30 to 40 kilometres thick. It is much lighter than the thinner oceanic crust and protrudes from the earth's mantle because of its lower density, like an iceberg in the sea.
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Neue Theorie zur Entstehung der ältesten Kontinente

Geologen der Universitäten Bonn und Köln legen in der April-Ausgabe der Zeitschrift "Geology" wissenschaftliche Ergebnisse vor, aus denen sich ein neues Bild der frühesten Phase der Kontinentbildung ergibt. Bislang ging die Forschung davon aus, dass die ersten Kontinentalgesteine vor rund vier Milliarden Jahren entstanden, indem ozeanische Urkruste durch plattentektonische Bewegungen im Erdmantel versank und in groben Tiefen schmolz. Untersuchungen der Bonn-Kölner Wissenschaftler stellen nun dieses Modell in Frage und legen nahe, dass die Bildung der ersten Kontinentfragmente in viel geringeren Tiefen erfolgte und die Ausgangsgesteine wahrscheinlich nie versenkt worden sind. Dies hat weitreichende Konsequenzen für unsere Vorstellungen von der Entwicklung der frühen Erde.
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Earth Story: Centre Of The Earth


Broadcast (1998) What drives the tectonic plates as they glide over the Earth's surface? Searching for an answer scientists have probed our planet to its core. In this realm of unimaginably high temperatures and pressures matter takes on new forms and solid rock can behave like a fluid. As vast masses of rock flow slowly within the Earth, so the surface moves and changes. Gigantic plumes of hot material can well up from the depths, triggering huge volcanic eruptions and causing the crust to bulge and break. The result may be the splitting of a continent.



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Wilson Cycle
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Diamonds help date Earth's sea cycles

The locations of the largest features on Earth - oceans, mountain ranges, volcanoes and even the continents themselves - are explained by plate tectonics, the relentless motion of the pieces that make up the outer skin of our planet.
The cycle of oceans that were formed when continents broke apart and destroyed when continents came together is called the Wilson Cycle, after John Tuzo Wilson, a Canadian geologist who first proposed the idea in the mid-1960s.
But when did the Wilson Cycle start?

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RE: Tectonic Plates
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Volcanoes dragged into chasm in seabed by tectonic action



New sonar images deep in the Pacific Ocean reveal huge volcanoes being slowly dragged one-by-one into a great ravine in the seabed.
The extraordinary images were captured along the Tonga Trench, which runs north from New Zealand towards Tonga and Samoa, during a research expedition last summer.

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Undersea mountains march into the abyss

Startling new images from the depths of the Pacific Ocean reveal one of Earth's most violent processes: the destruction of massive underwater mountains.
The pictures were created by sonar in waters up to 6km deep.
They expose how tectonic action is dragging giant volcanoes into a chasm in the seabed.

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650 Million Years in under 2 minutes



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RE: Plate tectonics
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Earth's birth: Inert gases provide clues

Inert gases trapped inside Earth's interior provide clues into the processes responsible for its birth and the evolution of oceans and atmosphere, a new study says.
The study shows atmospheric gases are mixed in the mantle inside Earth's interior, during the process called 'subduction', when tectonic plates collide and submerge beneath volcanoes in subduction zones, the journal Nature Geoscience reports.

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Diamonds pinpoint start of colliding continents

Jewellers abhor diamond impurities, but they are a bonanza for scientists. Safely encased in the super-hard diamond, impurities are unaltered, ancient minerals that can tell the story of Earths distant past. Researchers analysed data from the literature of over 4,000 of these mineral inclusions to find that continents started the cycle of breaking apart, drifting, and colliding about 3 billion years ago. The research, published in the July 22, 2011, issue of Science, pinpoints when this so-called Wilson cycle began.
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