A survey of the Earth's magnetic field in the vicinity of the Mid-Atlantic Ridge south of Iceland shows magnetic anomalies aligned as paired stripes in the direction of the ridge. The youngest material is found at the ridge axis. A change in colour indicates a reversal of polarity in the magnetic field. Different colour indicates different age since rock formation, age increasing away from the Mid-Atlantic Ridge. The 100 m and 1000 m depth contours are also shown.
adapted from Heirtzler, J. R., X. LePichon and J. G. Baron (1966) Magnetic anomalies over the Reykjannes Ridge. Deep-Sea Research 13, 427; based on http://www.gly.fsu.edu/~salters/GLY1000/Chapter5/Slide12.jpg (accessed 30 August 2004)