Speculations on the Earth's Thermal History

Research Article| February 01, 1965 Speculations on the Earth's Thermal History FRANCIS BIRCH FRANCIS BIRCH Hoffman Laboratory, Harvard University, Cambridge, Mass. Search for other works by this author on: GSW Google Scholar Author and Article Information FRANCIS BIRCH Hoffman Laboratory, Harvard University, Cambridge, Mass. Publisher: Geological Society of America Received: 23 Dec 1964 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Copyright © 1965, The Geological Society of America, Inc. Copyright is not claimed on any material prepared by U.S. government employees within the scope of their employment. GSA Bulletin (1965) 76 (2): 133–154. https://doi.org/10.1130/0016-7606(1965)76[133:SOTETH]2.0.CO;2 Article history Received: 23 Dec 1964 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation FRANCIS BIRCH; Speculations on the Earth's Thermal History. GSA Bulletin 1965;; 76 (2): 133–154. doi: https://doi.org/10.1130/0016-7606(1965)76[133:SOTETH]2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The gross structure of the Earth's interior—mantle and core with their subdivisions—affords evidence of the thermal evolution. The principal event was the formation of a liquid iron core from an initially cool unsorted conglomerate after about 500 m.y. of heating by radioactivity and tidal friction. Core formation was accompanied by conversion of gravitational energy to heat, the deep interior reaching temperatures of 4000°–5000°; this process was completed about 4500 m.y. ago. Fractional melting of the mantle concentrated radioactive and "lithophile" elements in the upper mantle and transition zone, leaving the lower mantle devoid of radioactivity. Formation of stable continental crust became possible after this upward concentration and decay of radioactivity, beginning about 3500 m.y. ago. Further concentration of the radioactive elements in the continental crust has left the subcontinental mantle impoverished by comparison with the suboceanic mantle. Present temperatures are consequently higher in the suboceanic mantle than at the same depths beneath continents, approaching or reaching melting temperatures beneath the oceans while cooling continues beneath continents. The required concentrations of radioactive elements appear to be in reasonable agreement with existing measurements if the primitive undifferentiated Earth resembled the meteorite Orgueil in its radioactive content. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.