Earth's inner core

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The internal structure of Earth
The inner core is labeled Number 7 on this cross-section of the Earth.

The inner core is the very center of the Earth, and the hottest part of the planet. It is a mainly solid ball with a radius of about 1,220 km (760 mi), according to seismological studies.[1][2] It is believed to consist mostly of an ironnickel alloy and to be about the same temperature as the surface of the Sun: about 5700 K (5400 °C).[3]

The inner core was discovered by Inge Lehmann in 1929, using seismology. Lehmann was studying a large New Zealand earthquake. An earthquake makes vibrations which move through the inside of the Earth. The vibrations Lehmann studied seemed to be moving across something solid in the center of the planet. She called this the inner core. She wrote about it for many years, but it was not proved to exist until 1970.

The inner core is more than 5,000 kilometers below the earth's surface. The pressure in Earth's inner core is about 3,500,000 atmospheres.[4] Iron can only be solid at such high temperatures because its melting temperature increases dramatically at such pressures.[5]

References[change | change source]

  1. Monnereau et al, Marc (2010). "Lopsided growth of Earth's inner core". Science 328 (5981): 1014–1017. doi:10.1126/science.1186212 . PMID 20395477 .
  2. Engdahl E.R.; Flynn E.A. & Massé R.P. (1974). "Differential PkiKP travel times and the radius of the core". Geophys. J. Roy. Astr. Soc. 40 (3): 457–463. doi:10.1111/j.1365-246X.1974.tb05467.x .
  3. Alfè D.; Gillan M. & Price G.D. (2002). "Composition and temperature of the Earth’s core constrained by combining ab initio calculations and seismic data" (PDF). Earth and Planetary Science Letters 195 (1-2): 91–98. doi:10.1016/S0012-821X(01)00568-4 . http://www.es.ucl.ac.uk/people/d-price/papers/138.pdf.
  4. David. R. Lide, ed. (2006/2007). CRC Handbook of Chemistry and Physics (87th ed.). pp. 14–13. http://hbcpnetbase.com/.
  5. Aitta, Anneli (2006). "Iron melting curve with a tricritical point". Journal of Statistical Mechanics: Theory and Experiment (iop) 2006 (12): 12015–12030. doi:10.1088/1742-5468/2006/12/P12015 . http://stacks.iop.org/JSTAT/2006/P12015. or see preprints http://arxiv.org/pdf/cond-mat/0701283 , http://arxiv.org/pdf/0807.0187 .