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Description
Several processes by which the world's granites may have been formed are postulated.
Several processes by which the world's granites may have been formed are postulated.
| Module code and title: | S333, Earth science topics and methods |
|---|---|
| Item code: | S333; 06 |
| First transmission date: | 28-03-1976 |
| Published: | 1976 |
| Rights Statement: | |
| Restrictions on use: | |
| Duration: | 00:23:50 |
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| Producer: | Peter Clarke |
| Contributors: | Peter Francis; Richard Thorpe; J. B Wright |
| Publisher: | BBC Open University |
| Keyword(s): | Animations; Chile; Constructive plate; Granite formations; Hekla; Jos Plateau; Maps; Models; Plutons |
| Footage description: | John Wright introduces the programme. He has with him a map of the world which has marked on it the known granite formations. Richard Thorpe uses models and maps to arrive at a hypothesis for origin and shape of the granites in Skye. Thorpe, with the aid of models and animations, discusses reasons for the tertiary granite centres at Skye and the British Isles region being there. He proposes that this area may have been a constructive plate in the making which was aborted. Thorpe uses a graph which shows the frequency and composition of eruptions of the volcano Hekla in Iceland since 1400 to discuss a possible method for the origin of granites. Shot of Hekla, in dormant state, starts the sequence. John Wright with a cross section geological model which shows some of the settings in which granites might form. He points out the main features of the model, particularly those which show conditions favourable to granite formation. Peter Francis uses a large geological map of Chile to point out the granite areas in that country. Shots of some granite formations in Chile, Peter Francis uses models and shots of the San Pedro volcano in Atacama to postulate an origin for granites in the plutons under active andesite volcanoes. Francis lists the interpretations of Sillitoe of Hamilton and Myers and of Cobbing and Pitcher for this type of granite formation. John Wright, using a geological map of Africa and shots of the Jos Plateau, looks at the granites in an area where there are no destructive plate margins nearby to account for their formation. Wright points out the major geological features of Jos Plateau and explains why the processes postulated for the formation of granites earlier in the programme would not apply here. Wright, using a model, goes on to examine a possible mechanism for the formation of the granites in the Jos Plateau. He points to some examples, such as the western Pacific islands, which might support this hypothesis. |
| Master spool number: | 6HT/71937 |
| Production number: | 00525_1212 |
| Videofinder number: | 1997 |
| Available to public: | no |
