Souvenirs magnétiques
Bernard David-Cavaz
1996 - 14 min - Betacam - Couleur - France

The study of the earth's magnetic field and its evolution through geological periods thanks to fossil rocks provides a wealth of information on the history of the earth. The paleomagnetician, Vincent Courtillot, presents his research on this subject. The inclination of the earth's magnetic field compared with the equator at any point on the globe depends on its latitude. Samples of rock are removed at various points on the globe, and the directions of the fossil magnetizations are determined : they reveal the place the rocks originally came from. These measurements have made it possible to simulate on a computer the movement of the continents in time. According to the measurements carried out on the fossilized lava of the traps of the Deccan, India has migrated from latitude 30° South to 30° North in 65 million years. A volcanic phenomenon dated by the paleontology of the limit between the secondary era and the tertiary could account for the extinction of dinosaurs.