Geology

Geology
The 366 daily episodes in 2014 were chronological snapshots of earth history, beginning with the Precambrian in January and on to the Cenozoic in December. You can find them all in the index in the right sidebar. In 2015, the daily episodes for each month were assembled into monthly packages (link in index at right), and a few new episodes were posted from 2015-18. You may be interested in a continuation of this blog on Substack at this location. Thanks for your interest!

Sunday, January 12, 2014

January 1: Origin of the Earth

About 4,600,000,000 years ago the Earth and Moon were assembled when dust, gases, and debris orbiting the sun came together under gravity. The process took at least a half a billion years, followed by a few tens of millions of years to form protoplanets. In rocky planets like the earth, radioactive elements decayed to generate heat (a process still going on today). The heat helped dense material like iron and nickel to migrate toward the Earth;s core, while lighter elements like silicon and aluminum were concentrated nearer the surface, eventually forming the Earth's crust.

Geologist Carl Owen Dunbar, author of a textbook on historical geology, was born January 1, 1891, at Hallowell, Kansas.

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3 comments:

  1. AnonymousApril 19, 2015 at 11:22 AM

    Thank you very much for the podcasts!
    I have 2 questions:
    1. Where did the radioactive elements come from? (from the Sun as elements' producer at nuclear synthesis reactions?)
    2. Why the heat helped the dense material migrate toward the core?
    I don't want to bother you with answering - I would be grateful with the links to reliable articles on that.
    Thank you!
    Karolina

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  2. Richard GibsonApril 19, 2015 at 12:19 PM

    Hello and thanks. Yes, the radioactive elements, all the elements, ultimately come from the sun and stars as thermonuclear reactors. The heat helps to mobilize everything - hot rock is more able to flow than cold rock, molten (liquid) rock even more so. So with heat available, denser materials will settle toward the earth's center of gravity, i.e. the core, while lighter elements like silicon and aluminum would tend to "float" toward the top, the crust. Here's a link - http://en.wikipedia.org/wiki/Planetary_differentiation

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  3. AnonymousNovember 7, 2017 at 1:50 AM

    The answer to the first question:

    https://commons.m.wikimedia.org/wiki/File:Nucleosynthesis_periodic_table.svg

    Based on: http://blog.sdss.org/2017/01/09/origin-of-the-elements-in-the-solar-system/

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