Earth's innermost core is solid: Scientists<\/p>\n
SAN FRANCISCO (Reuters): Inside a liquid core, the center of
\nthe Earth is solid, scientists said at a meeting of the American
\nGeophysical Union, providing the first direct evidence backing a
\nlong-held theory.<\/p>\n
The long-sought finding, which had been hinted at but never
\nproven, came from an analysis of seismic waves generated by a
\nvery strong earthquake that occurred in June 1996 about 360 miles
\n(600 kms) below Indonesia.<\/p>\n
Emile Okal, a professor of geological sciences at Northwestern
\nUniversity and an author of the study, said on Thursday that
\nscientists have known for some time that the Earth was composed
\nof a rocky mantle floating on a liquid core of molten iron.<\/p>\n
But geophysicists also speculated that at some greater depth,
\nthe pressure would be so high that the iron would become solid,
\nOkal said.<\/p>\n
In the 1930s, seismologists found a discontinuity in the
\nvelocity of waves that passed through the center of the Earth,
\nsuggesting there was some kind of layering. But the problem was
\nthat the waves carried the signature of a liquid, not a solid.<\/p>\n
Okal said a solid can be distinguished from a liquid in that
\nit can sustain two different kinds of waves, while a liquid can
\nonly sustain one. Only the first type of wave, characteristic of
\nliquids, had ever been observed coming from the Earth's core.<\/p>\n
But Okal and his colleague in France, Yves Cansi, used a
\nseismic network spread across France to study the Indonesian
\nearthquake and were able for the first time to detect the seismic
\nsignature of a solid.<\/p>\n
Okal said the finding could be of value in the field of
\nmaterials sciences because it indicates iron behaves in a unique
\nway under tremendous pressure.<\/p>\n
\"Understanding how the qualities of materials are affected
\nunder extremely high temperatures -- millions of times the
\natmospheric pressure -- might be applicable for different
\nmaterials at not-so-heavy pressures,\" he said.<\/p>",
"url": "https:\/\/jawawa.id\/newsitem\/earths-innermost-core-is-solid-scientists-1447893297",
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