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This programme looks at some of the techniques which enable scientists to reconstruct the size of oceans in the geological past. The development of new ocean current systems in the Atlantic are als...o examined.
Metadata describing this Open University video programme
Module code and title: S334, Oceanography
Item code: S334; 13
First transmission date: 28-09-1978
Published: 1978
Rights Statement:
Restrictions on use:
Duration: 00:24:00
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Producer: P. L. Firstbrook
Contributors: Ian Gass; Hugh Jenkyns; Dan McKenzie; Graham Jenkins
Publisher: BBC Open University
Keyword(s): Basaltic magma; Black shales; Cretaceous; Magma; Magnetic anomalies; Ocean currents; Paleo-winds; Red Sea; Seafloor spreading; Triassic
Footage description: Animated map of the world showing the development of the Atlantic Ocean from the Triassic to the present day. Animated diagram illustrates the mechanism of sea floor spreading. Commentary by Ian Gass explains the process. He points out particularly how the phenomenon of magnetic reversal creates magnetic anomalies in the crust. Dan McKenzie, using a still of the animated diagram above and a map, explains that these magnetic anomalies can be used to reconstruct the shape of oceans in the past. Film of a rock sample being drilled from volcanic rock. McKenzie discusses the use of paleomagnetic techniques to establish paleolatitudes of continents. Shot of a map of the world during the Triassic and then an animation showing the movements of continents since the Triassic. Graham Jenkins discusses ways in which the ocean circulation patterns in the geological past can be reconstructed. He starts by reconstructing the overall wind patterns as determined from an examination of fossilised sand dunes. Shots of a map of the world during the Triassic. Film shots of a rotating tank at Woods Hole Institution of Oceanography which models ocean circulation patterns. The tank is set up to simulate paleocirculation in the Atlantic as it formed. Animated map of the world shows movements of continents since the Triassic. Commentary by Jenkins points out how ocean circulation changed over this period. Ian Gass (voice over graph) and Hugh Jenkyns discuss changes in the sea level over the past 200 million years. Jenkyns discusses the evidence from ocean core samples which show that at some periods there existed anoxic conditions in the bottom waters of the Atlantic. He tries to correlate this with a rise in sea level on a global scale by invoking an 'enclosed basin model' but finds this inadequate. With the aid of a graph and an animated cross section of the Atlantic and Pacific Oceans, Jenkyns elaborates the model to include variations in shallow water organic production. The model now seems to predict a correlation between sea level changes and oceanic anoxic events. Dan McKenzie, using a graph and diagrams of the ocean crust, suggests that the younger, shallower ocean basins such as the Atlantic which formed since the Triassic may have been responsible for the general rise in sea level predicted by the model above. Ian Gass, with the aid of maps and animated diagrams, looks at the sequence of events which led to the formation of the Red Sea (a new ocean in the process of formation). He suggests that the rifting of continents as has happened here may have been similar to that of the rifting which formed the Atlantic.
Master spool number: 6HT/72839
Production number: 00525_1305
Videofinder number: 883
Available to public: no