Cambrian Explosion:role of Earth's magnetic field (Introduction)

by David Turell @, Wednesday, October 26, 2016, 01:53 (1250 days ago) @ David Turell

Our magnetic field protects us from nasty radioactive particles and rays that could harm life. It was present during the Cambrian:

http://www.sciencedirect.com/science/article/pii/S1674987116300019

Abstract: "Life was limited for most of Earth's history, remaining at a primitive stage and mostly marine until about 0.55 Ga. In the Paleozoic, life eventually exploded and colonized the continental realm. Why had there been such a long period of delayed evolution of life? Early life was dominated by Archaea and Bacteria, which can survive ionizing radiation better than other organisms. The magnetic field preserves the atmosphere, which is the main shield of UV radiation. We explore the hypothesis that the Cambrian explosion of life could have been enabled by the increase of the magnetic field dipole intensity due to the solidification of the inner core, caused by the cooling of the Earth, and the concomitant decrease with time of the high-energy solar flux since the birth of the solar system. Therefore, the two phenomena could be responsible for the growth and thickening of the atmosphere and the development of land surface life."

"The solar wind has strong episodic flares, which hit and interact with the Earth's magnetic field. Moreover, the solar pressure on the magnetosphere was possibly higher in the past The magnetosphere contributes to maintaining the atmosphere, preventing it from being stripped by the solar wind. Moreover, the solar wind influences atmospheric and climate evolution. The magnetopause shape is deformed by the solar wind. Therefore, a stronger magnetic field should partly deviate the solar wind, allowing growth of the atmosphere, which in turn protects the Earth's surface from high-energy gamma and UV radiation. In fact the magnetosphere is one of the primary protections of the atmosphere and its oxygen content. Wei et al. suggested a link between oxygen escape, the magnetic field and extinction.

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"iggin et al. (2015) observed an increase in both average magnetic field strength and variability occurring between 1.5 and 1 billion years ago, and they interpreted these data as the best evidence for the nucleation of the inner core occurring during this interval.

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"Before the solidification of the inner core, the faster relative rotation of it relative to the external liquid core was obviously absent. This variation in time in Earth's dynamics should have modified the dipolar component of the magnetic field, which may have allowed the formation of a thicker atmosphere, and eventually the Ediacaran biota and the Cambrian explosion of life.

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"Another essential for living on the surface of the Earth is protection from destruction by radiation (Cockell and Horneck, 2001) and oxidative stress (Ardini et al., 2013). The most abundant and readily available radiation shield is water.

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"several lines of evidence suggest that the onset of the major phase of eukaryote basal diversification coincides with the formation of the Earth's solid inner core. In our interpretation, prior to this timespan, basal eukaryotes and bacteria were substantially affected by detrimental exposure to ionizing radiation, particularly in non-marine environments or in very few centimeter water-depth, possibly being counterbalanced by biofilm or waxy compound formation.

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"the shielding effects of water on UV-B radiation is important and it would have allowed microbial evolution to occur under water while the Earth's core and magnetic field protection started to develop and at that stage near-surface non-marine life also became possible."

Comment: The thesis of this fascinating article is that the magnetic field shielding the Earth from radiation, the fact that water is a great UV shield, that more oxygen appeared, plus other factors all in combination, prepared for the appearance of the Cambrian Explosion. Worth reading in toto but very long. Privileged Plant indeed! Chance or God's planning.


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