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This programme looks at heat generation within the Earth's lithosphere, and the conduction of heat from deep inside the Earth. Geoff Brown (OU) introduces the programme with a brief review of some... of the ideas of plate tectonics; he then shows us the local evidence for an underlying granite batholith at Skidaw in the Lake District (including outcropping granites and the results of a gravity survey). We then see drilling at the shallowest point of the granite, and look at core samples. Analysis of these in the laboratory enables us to estimate the abundance of heat producing (radioactive) minerals within the granite, and its thermal conductivity. Richard Thorpe (OU) in the studio, analyses these data and relates them to the heat flow/heat generation data for Britain as a whole. Because of the different ages of crust in different parts of the country, he is able to fit national data to two distinct heat flow/heat generation lines. He concludes the programme with a model of convective heat flow through the Earth's crust, in which glycerine changes its density in response to heat or cooling and convection currents can be observed as "shadows" when light is shone through a transparent tank of glycerine onto a screen. Both seafloor spreading and subduction can be effectively modelled in this way.
Metadata describing this Open University video programme
Module code and title: S237, "The Earth, structure, composition and evolution"
Item code: S237; 08; 1983
First transmission date: 03-07-1983
Published: 1983
Rights Statement:
Restrictions on use:
Duration: 00:24:00
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Producer: Nick Brenton
Contributors: Geoff Brown; Richard Thorpe
Publisher: BBC Open University
Keyword(s): Earth's crust; Granite batholith; Lithosphere; Plate tectonics; Radioactive decay; Seafloor spreading; Subduction; Thermal conductivity
Production number: FOUS254K
Videofinder number: 1596
Available to public: no