Short Essay on the Lakes of Molten Rock in Earth’s Core

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A recent discovery about the earth’s core as published in The Times of India (9-6-1988) reads as follows:

Washington June 8. (PTI). Scientists have now found that the supposedly smooth hot ball of iron at the earth’s core is not smooth but has vast mountain-range sized bumps and valleys with upside down lakes of molten rocks between them.

Other such startling discoveries have been made by scientists who can now see deep inside the earth. Using for over past two years seismic tomography, which produces X-ray like images down to the core of the planet, they can photograph for the first time objects deep under the ground.

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This technique will help to solve mysteries, that have baffled scientists for decades, such as why satellites do not fly smoothly in orbit but bob up and down like codes on water, rising and falling hundreds of feet on each tour, and why the day varies in length as the earth spins jerkily on its axis.

Analyzing these recent findings the “Washington Post” said in an article that the answers to these small puzzles and to the greater ones, such as what makes the continents move, lie deep inside the earth and are just beginning to emerge as geophysicists work with seismic tomography.

Harvard, the Massachusetts Institute of Technology, the California Institute of Technology and the University of California at San Diego have teams working with the new tomographic technology.

One recent discovery is that the earth’s core, a 4000-mile- diameter ball of molten iron, is not the perfect sphere as depicted in geology texts in this century. The tomography images show vast mountains and valleys six or seven miles high and deep, which are upside down because they are made of rock while the core inside them is hot liquid iron.

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As they are upside down in relation to the earth’s surface, the features on the surface of the earth’s core have been dubbed “anti- continents” and “anti-oceans.”

Some researchers believe that these mountains have oceans of lighter density iron between them, thus making the upside down array somewhat like anti-continents and anti-oceans 1800 miles deep.

At the centre of the core the pressure is so great that not even temperatures of 12,000 degrees Fahrenheit can keep the iron liquid. It is compressed into a solid again, in hexagonal crystals lined so that signals passed through them are as if they were a single thousands-mile wide crystal.

Even as recently as 10 years ago researchers had no idea at 411 that these features existed. They had pictured the planet as an onion with one smooth layer of rock after another-crust, mantle and core.

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The new information explains a variety of phenomena, including why the plates of the earth’s crust move and why such huge features as the Pacific Ocean exist, the paper said.

A Harvard University physicist, Mr Adam Dziewonsxi, said “We are beginning to get ourselves into a position where we can see and understand the whole machine inside the earth, at least in its basic parts and this is new.”

Scientists now say that although the earth seems solid, its mantle behaves like a very slow-moving fluid over hundreds of millions of years. Seventy per cent of the earth’s mass is in its mantle that is the rocky midsection.

If the pictures were speeded up, it would show an extremely hot iron core radiating heat like a flame on a stove, and above it the mantle boiling like thick pea soup.

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The lighter elements rise to the top to form a tougher scum on the surface. On the earth, it is the crust that floats and is divided into abutting “plates”.

These plates ride atop the rolling convection of the earth in which hotter, less dense rock boils up under the crust. Colder, denser rock from the surface sinks, warms and eventually cycles back to the surface over several hundred million years.

The heaviest material, iron, sinks and becomes the core.

Other features recently discovered include great masses of slabs of material that used to be in the earth’s crust and are now sinking through its mantle.

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The plates at the earth’s surface collide with massive but excru­ciatingly slow force. At some edges or subduction zones one plate is forced under another and a great slab, cooler and denser than what is below, sinks into the mantle.

The slab of the Pacific plate that is sliding under Asia is now believed to have flattened out at 400 miles down supporting the idea of an upper boundary. The sinking slabs remain cooler than the surround­ing material for tens of millions of years.

All the continents were once bunched together in a grand mass called Pangaea. Since then the continents have broken up and drifted. The cold slab now under North America was ocean bottom in Pangaea days.

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