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The programme examines volcanoes, both ancient and modern. The speakers are Professor Ian Gass, Professor of Earth Sciences at the Open University, and Dr. Peter Francis, lecturer in Earth Sciences... at the Open University. Professor Gass shows on a world map the distribution of active volcanoes, and comments on the 'ring of fire' around the Pacific. Several volcanoes are seen on film to show features of their activity; they include Popacatepetl and Paricutin in Mexico, then highly fluid lavas giving rise to fire fountains in Hawaii, and the recent eruptions of Etna in Sicily, where the lava was much more viscous. Several volcanic rocks - such as bombs, vesicular lavas and tuffs are examined in hand specimens. The uniformitarian approach is used to examine volcanoes long since extinct, and now found as part of the stratigraphic record. Dr. Peter Francis shows how the rocks of Arthur's Seat in Edinburgh can be interpreted as as ancient volcano. The vents, the lava flows and an intrusive sill, known as Salisbury Crags are examined in detail, and their positions are drawn on an aerial photograph; and their field relationships are also visualised in a cross-section. A demonstration in which liquid is injected into a jelly model of a volcano is used to show the formation of radial dykes, and the results are compared with a map of Tristan da Cuhna. But the uniformitarian approach cannot explain everything. No one has witnessed pillow lavas or ignimbrites forming. Professor Gass concludes by discussing the mode of origin of these last two products of vulcanicity.
Metadata describing this Open University video programme
Item code: S23-; 06
First transmission date: 08-04-1972
Published: 1972
Rights Statement:
Restrictions on use:
Duration: 00:23:48
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Producer: Peter Clarke
Contributors: Peter Francis; Ian Gass
Publisher: BBC Open University
Keyword(s): Etna; Fire fountains; Fluid lavas; Hawaii; Mexico; Pacific; Paricutin; Popacatepetl; Ring of fire; Sicily
Footage description: Ian Gass with a map of the world showing the seismic zones. He points out the areas of volcanic activity. Shots of Mt. Popocatepetl. Comnentary by Ian Gass gives details. Shots of Mt. Paricutin. Commentary by Ian Gass gives details. Shots of a fire fountain in Hawaii. Commentary by Gass gives details. Shots of Mt. Etna. Commentary by Gass gives details. Ian Gass in the studio with lava specimen from various volcanoes. He discusses a variety of features such as bombs, spatter, pahoehoes, vesicles and amydales. Gass shows a specimen of ancient sedimentary volcanic rock. He explains why old volcanoes have to be examined to discover the processes which occurred within them. P.W. Francis visits the ancient volcano of Arthur's Seat in Edinburgh. He describes various famous landmarks in and around Edinburgh and demonstrates their volcanic origin. Francis uses a set of photographs of the area and of thin sections of the volcanic rock. Francis with an aerial photograph of the area, draws up a geological map. He then examines a cross section diagram of the same area. Film shots of a jelly model of a volcano. A coloured liquid "magma" is pumped into the model. The model illustrates the intrusion of dykes into a central-vent volcano and the formation of parasitic vents on the flanks of the major cone. The random distribution of these dykes is plotted and compared with dykes of an actual volcano (on Tristan da Cunha). Gass with pictures and specimen of pillow lavas discusses the type of volcanic activity which cannot be demonstrated by invoking uniformitarianism. Activity such as that which occurs on the ocean floor and cannot be seen. Finally Gass discusses a form of volcanic activity the production of ignimbrites through the process of nuee ardente eruptions. He uses a thin section of North Wales volcanic rock to speculate on how it was formed.
Master spool number: 6LT/70429
Production number: 00521_2155
Videofinder number: 1713
Available to public: no