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.
Play the podcast:
Download Podcast - January 1
Geologist Carl Owen Dunbar, author of a textbook on historical geology, was born January 1, 1891, at Hallowell, Kansas.
Play the podcast:
Download Podcast - January 1
Thank you very much for the podcasts!
ReplyDeleteI 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
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
ReplyDeleteThe answer to the first question:
ReplyDeletehttps://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/