EESA10H3 Lecture : EESA06 Lecture 1
19 Mar 2019
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Lecture 2: formation of planet earth: 4,500 million years before present, continental drift and pangea: 1912 (alfred wegener, sea floor spreading: 1962 (harold hess, magnetic stripes on ocean floor and wander paths for continents: 1965. Epicentre: where the earthquake occurs on the earth"s surface. Use hot spots (volcanoes) to measure the movement of plates. Important point: these are the surface expressions of hot rock drilling its way up to the mantle. There is continuous volcanic activity along mid-ocean ridges and rifts. Magnetometer: measures how magnetic rocks are on the sea floor and small variations in the earth"s magnetic field (normal polarity and negative reversed polarity) Paleomagnetic changes through time (geomagnetic polarity timescale: magnetic reversals occur on average of every 500,000 years, takes approximately 10,000 or less years for a reversal to occur (you won"t notice if it occurs, called magnetic epochs. Rocks produced by ocean ridges are of higher density than usual 2. 7 g/cm3.
