Available online
Description
This programme shows two contrasting ways in which information is gathered about the evolution of the Earth. The first is filmed in the area of Achmelvich, .N.W.Scotland. Here Dr. Steve Drury exam...ines some of the oldest rocks in Britain to search for records of past geological events. In the second part of the programme Dr. Chris Hawkesworth shows how Rubidium and Strontium isotope analysis data can be used to test models for the evolution of the continental crust, oceanic crust and upper mantle.
This programme shows two contrasting ways in which information is gathered about the evolution of the Earth. The first is filmed in the area of Achmelvich, .N.W.Scotland. Here Dr. Steve Drury exam...ines some of the oldest rocks in Britain to search for records of past geological events. In the second part of the programme Dr. Chris Hawkesworth shows how Rubidium and Strontium isotope analysis data can be used to test models for the evolution of the continental crust, oceanic crust and upper mantle.
| Module code and title: | S237, "The Earth, structure, composition and evolution" |
|---|---|
| Item code: | S237; 15 |
| First transmission date: | 26-09-1981 |
| Published: | 1981 |
| Rights Statement: | |
| Restrictions on use: | |
| Duration: | 00:24:00 |
| + Show more... | |
| Producer: | Barrie Whatley |
| Contributors: | Stephen Drury; C. J. Hawkesworth |
| Publisher: | BBC Open University |
| Keyword(s): | Destructive margin; Dyke; Gneiss; Isochron diagram; Isotope; Lewisian; Metamorphism; Rubidium; Strontium; Underplating |
| Footage description: | Over film shots of landscape at Achmelrich in N.W.Scotland, Steve Drury introduces the programme. Drury examines the banded, coarsely crystalline Lewisian rocks at one of the outcrops in the area. Close up shots show some of the minerals. Drury goes on to examine an animated triangular variation diagram which illustrates the variation of mineral content of the three main minerals found in Lewisian rocks. He explains what this tells about the early evolution of these rocks. Over animated diagrams showing Rubidium and Strontium isotope ratios, Drury explains what these tell about the age and early evolution of Lewisian rocks. Drury continues to examine the rocks at the above outcrop and points out some of their distinguishing features. He points out a banded mass of rocks which may well represent the original crust in this area. More shots of coastal Lewisian rocks. Drury points to the evidence that a tremendously large amount of chemically bound water was active in the rocks during the Archaeic. He shows evidence of shearing in many places and also evidence that, as a result, the Lewisian layer began to melt. Chris Hawkesworth discusses similarities and differences of rock formation in the Archaean with those of present day rock formation. Shots of Archaean rock samples as well as diagrams are used to illustrate his points. Hawkesworth spends the remainder of the programme discussing the gross evolution of the continental crust by looking at strontium isotope evolution in the rocks. He shows a series of strontium isotope evolution diagrams to try to distinguish between two rival models for crust evolution. Hawkesworth ends the programme by pointing out that variation in radiogenic isotopes as shown in the data above reflect stabilisation of the contintal crust rather than its formation. |
| Master spool number: | DOU00525 |
| Production number: | FOUS201X |
| Videofinder number: | 1604 |
| Available to public: | no |
