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The programme is in two parts. The first part discusses granites and their origin. Miss Pat McCurry, a Research Assistant in the Department of Earth Sciences at the Open University, examines outcr...ops of granite in the field at Dartmoor and other places in South West England. In places the contact between the granite and the country rocks can be seen, and the contact metamorphism is observed. A piece of speeded up film showing the re arrangement of crystals in a polished block of steel as it is heated, is used to show the way in which solid state recrystallisation occurs in a metamorphic rock. Professor Ian Gass introduces geophysical evidence for the granite batholith in South West England and uses a model to show its subsurface shape. He goes on to discuss the origin of granite, and illustrates how intrusion might occur. A model with two layers of immiscible liquid is heated at depth; the lower layer rises in granite like plumes up into the overlying layer. In the second half of the programme Dr. Chris Wilson, Senior Lecturer in Earth Sciences at the Open University, looks at examples of folds seen on geological maps. He explains how to interpret their shape and how to date the age of the folding.
Metadata describing this Open University video programme
Item code: S23-; 07
First transmission date: 22-04-1972
Published: 1972
Rights Statement:
Restrictions on use:
Duration: 00:24:26
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Producer: Peter Clarke
Contributors: Ian Gass; Pat McCurry
Publisher: BBC Open University
Keyword(s): Contact metamorphism; Dartmoor; Geological maps; Intrusion; Metamorphic rock; Outcrops of granite; Solid state recrystallisation; South West England; Subsurface shape
Footage description: Part 1. Title; Granite and the plutonic association, presented by Ian Gass and Pat McCurry. Ian Gass introduces the programme with a brief discussion on the importance of field relationships when studying the origins of granites. Pat McCurry with a relief map of southwest England. Granite areas are marked and she points out each area. Several still shots of granite tors (surface outcrops) at Dartmoor. Pat McCurry points out the main features. She next examines the contacts of granite with country rocks near Tremethen, Cornwall. A series of still photographs accompany her commentary. She then discusses xenoliths and proposes that they are good evidence that granite crystallized from magma. Pat in the studio with specimen of rocks, discusses further the effect of the granite on country rocks. Ian Gass examines the shape of granites at depth with the aid of a map of the area showing gravity anomalies. He then shows a 3-D model of the granite formation at depth. Gass uses diagrams to explain how this granite formation may have been formed. He also uses a granite specimen (migmatite) to aid. More diagrams. Gass with a model which demonstrates the formation of migmatite. Part 2. Mapwork: looking at faults, presented by Wilson. Chris Wilson uses a simple model constructed from a sheet of foam rubber to demonstrate the folds depicted on the Cheddar sheet. Wilson next describes the folding shown on the Church Stretton sheet. He uses the same model. Wilson then explains how the age of the folding is worked out.
Master spool number: 6LT/70461
Production number: 00521_2156
Videofinder number: 1714
Available to public: no