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Science British researchers find direct evidence of solid inner core of Earth
Science British researchers find direct evidence of solid inner core of Earth | British researchers find direct evidence of solid inner core of Earth |
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| by William Atkins | |
| Monday, 18 August 2008 | |
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Science DiscussionsAs we continue to explore and learn more about the solar system and the Universe, in general, we are still discovering and learning more about our home planet Earth. Such is the case with its inner structure. [Author's note: This article was edited on 8/21/08 to more accurately reflect the solid nature of the inner core of the Earth, along with scientists' difficulties in accummulating direct evidence to prove it is solid.] British geophysicists James Wookey and George Helffrich, both from the Department of Earth Sciences at the University of Bristol (United Kingdom) summarized their findings in the August 14, 2008 Nature article “Inner-core shear-wave anisotropy and texture from an observation of PKJKP waves.” The Earth’s inner structure is known to contain a core of two layers: an outer core (believed to be molten material, mostly iron) and an inner core. Whether the inner core is solid has been difficult to directly prove by scientists. Thus, Wookey and Helfrich state in the abstract to their paper: “Since the discovery of the Earth's core a century ago, and the subsequent discovery of a solid inner core (postulated to have formed by the freezing of iron) seismologists have striven to understand this most remote part of the deep Earth.” Earlier measurements of the inner core were inconclusive by scientific investigations. Scientists have been only able to inaccurately measure low-frequency vibrations and ineffectively use a much too small network of seismometers. In addition, they are continually hampered by too much background noise (from surface and underground interferences). (Seismometers measure artificial and natural motions of the Earth, including those of seismic waves generated by earthquakes, nuclear explosions, and other such sources.) In all cases, the data was difficult to analyze and satisfactory "direct" evidence was difficult to acquire as to the solid nature of the Earth's inner core. The British geophysicists comment, within their abstract, about the inconclusive nature of Earth's inner core by science, “The most direct evidence for a solid inner core would be the observation of shear-mode body waves that traverse it, but these phases are extremely difficult to observe. Two reported observations in short-period data have proved controversial. Arguably more successful have been studies of longer-period data, but such averaging limits the usefulness of the observations to reported sightings.” However, on February 22, 2008, an earthquake hit southeastern Africa in Mozambique. The earthquake was large in size but short in its duration. The eight-second motion that the magnitude-7 earthquake generated sent waves into the Earth’s core, which were re-directed back to the surface of the Earth. Some of the seismic waves found their way to Japan where they were recorded by over 700 seismometers. Page two states the British pair's conclusions. |
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