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Post Info TOPIC: Tectonic Plates
Blobrana


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Plate tectonics
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Heat from Earth's core could be underlying force in plate tectonics

For decades, scientists have theorized that the movement of Earth's tectonic plates is driven largely by negative buoyancy created as they cool. New research, however, shows plate dynamics are driven significantly by the additional force of heat drawn from the Earth's core.
The new findings also challenge the theory that underwater mountain ranges known as mid-ocean ridges are passive boundaries between moving plates. The findings show the East Pacific Rise, the Earth's dominant mid-ocean ridge, is dynamic as heat is transferred.
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Blobrana


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Case of Earth's missing continental crust solved: It sank

How do you make half the mass of two continents disappear? To answer that question, you first need to discover that it's missing.
That's what a trio of University of Chicago geoscientists and their collaborator did, and their explanation for where the mass went significantly changes prevailing ideas about what can happen when continents collide. It also has important implications for our understanding of when the continents grew to their present size and how the chemistry of the Earth's interior has evolved.
The study, published online Sept. 19 in Nature Geoscience, examines the collision of Eurasia and India, which began about 60 million years ago, created the Himalayas and is still in (slow) progress. The scientists computed with unprecedented precision the amount of landmass, or "continental crust," before and after the collision.
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Blobrana


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Novel experiments give glimpses of Earth's interior dynamics

Results from new geophysical experiments led by a researcher at Scripps Institution of Oceanography at UC San Diego are helping scientists understand the complex forces unfolding tens of miles below the planet's surface.
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Blobrana


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Slippery zone found under tectonic plate

A surprise discovery has shown scientists how Earth's tectonic plates slide across the top of the planet's mantle.
Researchers were using explosives to collect seismic data on the plate boundary, 15 to 30 kilometres below New Zealand's earthquake-prone capital city, Wellington.
However, they were surprised to find they were getting data back from nearly 100 kilometres deep, where the base of the tectonic plate interacts with the underlying upper mantle.
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Blobrana


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Earth's crust
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Oldest bit of crust firms up idea of a cool early Earth

With the help of a tiny fragment of zircon extracted from a remote rock outcrop in Australia, the picture of how our planet became habitable to life about 4.4 billion years ago is coming into sharper focus.
Writing today (Feb. 23, 2014) in the journal Nature Geoscience, an international team of researchers led by University of Wisconsin-Madison geoscience Professor John Valley reveals data that confirm the Earth's crust first formed at least 4.4 billion years ago, just 160 million years after the formation of our solar system. The work shows, Valley says, that the time when our planet was a fiery ball covered in a magma ocean came earlier.
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Blobrana


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Earth's crust was unstable in the Archean eon and dripped down into the mantle

Earth's mantle temperatures during the Archean eon, which commenced some 4 billion years ago, were significantly higher than they are today. According to recent model calculations, the Archean crust that formed under these conditions was so dense that large portions of it were recycled back into the mantle. This is the conclusion reached by Dr. Tim Johnson who is currently studying the evolution of the Earth's crust as a member of the research team led by Professor Richard White of the Institute of Geosciences at Johannes Gutenberg University Mainz (JGU). According to the calculations, this dense primary crust would have descended vertically in drip form. In contrast, the movements of today's tectonic plates involve largely lateral movements with oceanic lithosphere recycled in subduction zones. The findings add to our understanding of how cratons and plate tectonics, and thus also the Earth's current continents, came into being.
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Blobrana


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Plate tectonics
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Scripps Scientists Image Deep Magma beneath Pacific Seafloor Volcano

Since the plate tectonics revolution of the 1960s, scientists have known that new seafloor is created throughout the major ocean basins at linear chains of volcanoes known as mid-ocean ridges. But where exactly does the erupted magma come from?
Researchers at Scripps Institution of Oceanography at UC San Diego now have a better idea after capturing a unique image of a site deep in the earth where magma is generated.
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Blobrana


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Scripps Scientists Discover 'Lubricant' for Earth's Tectonic Plates

Scientists at Scripps Institution of Oceanography at UC San Diego have found a layer of liquefied molten rock in Earth's mantle that may be acting as a lubricant for the sliding motions of the planet's massive tectonic plates. The discovery may carry far-reaching implications, from solving basic geological functions of the planet to a better understanding of volcanism and earthquakes.
The scientists discovered the magma layer at the Middle America trench offshore Nicaragua. Using advanced seafloor electromagnetic imaging technology pioneered at Scripps, the scientists imaged a 25-kilometre-thick layer of partially melted mantle rock below the edge of the Cocos plate where it moves underneath Central America.
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Studying Ancient Earth's Geochemistry

Researchers still have much to learn about the volcanism that shaped our planet's early history. New evidence from a team led by Carnegie's Frances Jenner demonstrates that some of the tectonic processes driving volcanic activity, such as those taking place today, were occurring as early as 3.8 billion years ago. Their work is published in Geology.
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Title: Hafnium isotope evidence for a transition in the dynamics of continental growth 3.2 Gyr ago
Authors: T. Næraa, A. Scherstén, M. T. Rosing, A. I. S. Kemp, J. E. Hoffmann, T. F. Kokfelt & M. J. Whitehouse

Earth's lithosphere probably experienced an evolution towards the modern plate tectonic regime, owing to secular changes in mantle temperature. Radiogenic isotope variations are interpreted as evidence for the declining rates of continental crustal growth over time, with some estimates suggesting that over 70% of the present continental crustal reservoir was extracted by the end of the Archaean eon. Patterns of crustal growth and reworking in rocks younger than three billion years (Gyr) are thought to reflect the assembly and break-up of supercontinents by Wilson cycle processes and mark an important change in lithosphere dynamics. In southern West Greenland numerous studies have, however, argued for subduction settings and crust growth by arc accretion back to 3.8 Gyr ago, suggesting that modern-day tectonic regimes operated during the formation of the earliest crustal rock record.

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