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The programme begins with John Wright, Reader in Earth Sciences at The Open University, posing the question "Has the structure of the earth changed, and, if so, how?" Dr. R. S. Thorpe loo...ks for a possible model of the primeval earth in the present solar system, and considers meteorites, their origin in the asteroid belt. Showing examples of different kinds of meteorites, he uses their structure and composition to postulate the composition of the primeval earth. John Wright then discusses how a homogenous earth of this composition could become the layered structure we know, using a blast furnace as an analogy of how the layers became chemically differentiated.
Metadata describing this Open University video programme
Item code: S2-2; 03
First transmission date: 29-07-1972
Published: 1972
Rights Statement:
Restrictions on use:
Duration: 00:23:14
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Producer: Michael Freeman
Contributors: Richard Thorpe; John Wright
Publisher: BBC Open University
Keyword(s): Blast furnace; Meteorite composition; Primeval Earth model; Structure of the Earth
Footage description: John Wright uses a cut-away model of the earth's layer structure as an aid to his brief introduction to geochronology. He explains the difficulty of examining the earth's structure (the interior) by direct measurements and introduces Richard Thorpe. Thorpe begins a discussion on the use of meteorites as sources of information for the study of earth's interior. Shot of a schematic drawing of the solar system showing the planets as far as Jupiter and including the Asteroid Belt. Shot of the night sky showing a meteor trail . Shot of the giant meteorite crater in Arizona (1 mile diameter). Shot of the schematic drawing of the solar system again. Earth's orbit is outlined. Possible orbits of meteors are shown. These have been calculated from visual sightings of their trails in the atmosphere. The Pribram orbit, the most accurately measured meteorite orbit to date, is outlined. Thorpe uses this information to speculate on the origin of meteorites. Thorpe shows a meteorite which fell on Leicester in 1965. He examines the external features of the sample and makes several deductions from them. Thorpe examines and discusses the internal features of each of 5 main types of meteorites. 1. Iron meteorite. A sample has been sliced open and etched so that crystal features can be seen. Thorpe uses a blown up photograph of this section to study it in detail. 2. Stony iron meteorite. Thorpe points out details and speculates on its origin. 3. Acondrite meteorite. Thorpe uses a blown up photograph of a section to study it in greater detail. He speculates on its origin. 4. Condrite meteorite. Thorpe uses a blown up photograph of a section to study it in greater detail. He explains why the condrite meteorite are the most important group of meteorites for study. 5. Carbonaceous meteorite. Thorpe explains the particular importance of this type of meteorite. John Wright describes one possible form of the earth's composition based on information gained in the study of meteorites. Wright uses a model of a blast furnace as an analogue for describing the formation of layers from homogeneous earth materials during its process. Shots of a diagram showing how the earth's layers may have formed from a homogeneous mass, Wright's commentary explains the process. Wright with samples of various forms of iron minerals from the earth's crust. He also examines samples of minerals which oxidise 1) more rapidly, 2) less rapidly than iron. From this he derives a simple version of the geochemical classification of the elements.
Master spool number: 6LT/70386
Production number: 00521_2160
Videofinder number: 3941
Available to public: no