Available online
Description
For several years oceanographers have suspected that seawater leaks into the Earth's crust and re-enters the sea as hot brine. These suspicions were vindicated when a manned submersible explored th...e bottom of the Pacific near the Galapagos Islands in 1977. At one point they were travelling through near freezing water and then suddenly the temperature jumped to 17°c. Out of the portholes they saw hot water plumes rising out of the ocean floor amid rocks teeming with life. This programme explores these plumes and describes the chemical modifications that seawater undergoes when it percolates deep into the hot crust. It also considers what happens when these hot brines meet the cooler overlying seawater and deposit metal-rich sediments.
For several years oceanographers have suspected that seawater leaks into the Earth's crust and re-enters the sea as hot brine. These suspicions were vindicated when a manned submersible explored th...e bottom of the Pacific near the Galapagos Islands in 1977. At one point they were travelling through near freezing water and then suddenly the temperature jumped to 17°c. Out of the portholes they saw hot water plumes rising out of the ocean floor amid rocks teeming with life. This programme explores these plumes and describes the chemical modifications that seawater undergoes when it percolates deep into the hot crust. It also considers what happens when these hot brines meet the cooler overlying seawater and deposit metal-rich sediments.
| Module code and title: | S334, Oceanography |
|---|---|
| Item code: | S334; 07 |
| First transmission date: | 1978 |
| Published: | 1978 |
| Rights Statement: | |
| Restrictions on use: | |
| Duration: | 00:24:00 |
| + Show more... | |
| Producer: | Roger Jones |
| Contributors: | David Cronan; Andy Fleet; John Wright |
| Publisher: | BBC Open University |
| Keyword(s): | Galapagos rift; Hydrothermal plumes; Manganese nodules; Red Sea brine pools |
| Footage description: | Film of the ocean floor at Galapagos Rift Valley showing a hydrothermal plume and some of the animal life which depends on its warmth. Commentary by John Wright introduces the programme. Andy Fleet, with a topographical model of a cross section of the Rift, explains how the plumes rise and affect the water around them. Fleet goes on, using the same model, to explain how the sea water gets into the oceanic crust before it is released as a plume. Film of an apparatus which uses dyes to model the flow of a hydrothermal plume. Commentary by Andy Fleet relates this model to what is happening on the ocean floor. David Cronan, using a model of the Galapagos Rift and still shots of a core taken from this area, explains how the transformation of sea water to brine in the crust and its circulation as plumes precipitates out various minerals which form sediments on the ocean floor. Cronan goes on, with the aid of a model and an animated diagram, to explain the fractionation process by which various metals are precipitated out of the brine in hydrothermal plumes. He points out that a definite sequence of precipitation can be recognised (metal sulphides, iron oxides and manganese dioxide). Cronan examines several cores from the Red Sea to illustrate how complicated the sequence of sedimentation is. Finally, Cronan speculates on the existence of conditions in areas of midocean ridge similar to those found in the Red Sea. He points to a model of ocean crust as he talks. Andy Fleet discusses the contribtition made by manganese precipitates from hydrothermal plumes to the general manganese content of sea water. Animated diagrams help illustrate his points. John Wright sums up the programme with a look at film of the biological environment provided by hydrothermal plumes. |
| Master spool number: | 6HT/72808 |
| Production number: | 00525_1299 |
| Videofinder number: | 878 |
| Available to public: | no |
