"That is Snaefellsjokull a mountain about five thousand feet in height, one of the most remarkable in the whole island, and certainly doomed to be the most celebrated in the world, for through its crater we shall reach the centre of the earth.”
The Journey to the Centre of the Earth with Axel and uncle Otto is indeed an exciting experience. Jules Verne published the French original in 1864 and later a new improved version appeared in 1867. Since then the book has been translated into almost all languages, adapted to the big and small screens, made into video games, theme parks etc. With a combination of available scientific information of the day and fertile imagination Verne wove an extraordinary fiction. Central to the theme was the pure fantasy of subterranean volcanic tubes which facilitate the journey. Snæfellsjökull glacier and adjoining areas have now been developed into National Adventure Park by the Govt. of Iceland.Ever since its birth 4.5 billion years ago, the Earth has gradually been cooling down, radiating heat to space. Analysing the magnetic records of ancient igneous rocks, scientists detected a sharp increase in the strength of the Earth's magnetic field between 1 and 1.5 billion years ago. A "likely indication of the first occurrence of solid iron at Earth's centre and the point in Earth's history at which the solid inner core first started to "freeze" out from the cooling molten outer core", state scientists at the University of Liverpool.
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| Structure of Earth |
This cooling of the hot liquid outer core and consequent deposition of iron crystals on the inner core is a process in progress, though extremely slow. The inner core, 96% iron and the rest mostly nickel, manifests its presence in myriad ways including Earth's magnetic field and its rotation, but its existence could be detected only in 1906, when seismological measurements became possible. Since then seismological wave propagation studies together with simulation and modelling have extensively been used to gain information about Earth's interior.
The question how Earth's iron rich inner core which is hotter than the surface of the Sun remains a solid is not yet fully answered, though it is agreed upon that iron exists in some crystalline form. Experimental observations that seismic waves propagate faster in the North-South direction than in the East-West direction suggest a directionality for the core. The most plausible, generally accepted answer is the preferential alignment of the iron crystals with their long axis along the rotation axis of the earth. However that raises another the question: why such preferential crystalline alignment ? Because the Earth's core is not growing uniformly, say scientists. The east side under Indonesia's Banda sea is growing faster than the west side under Brazil. But gravity quickly evens out this discrepancy by aligning the crystals and restoring the spherical shape. And here comes the next question: why this lopsided growth? Looks like we need to wait for answers and more questions.
REFERENCES:
1. Journey to the centre of the Earth : Jules Verne
2. Is Earth’s core lopsided? Strange goings-on in our planet’s interior?.
3. Lopsided Growth of Earth'sInner Core
4. Dynamic history of the inner core constrained by seismic anisotropy. Frost, D.A., Lasbleis, M., Chandler, B. et al.Nature Geoscience. 3 June.2021
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