The defining paradigm shift in 20th century earth science is clearly the widespread acceptance of plate tectonics. One of the most important lines of evidence helping to convince scientists were the existence of magnetic stripe anomalies in the rocks of the oceans. The above map, from the classic Vines & Matthews paper from 1964, shows two profiles [Atlantic and Indian Oceans]. The black is the bathymetry and the black line is the magnetic field anomaly
Figure 1 from: Vine, F.J. and D.H. Matthews. 1964. Magnetic anomalies over oceanic ridges. Nature 201:591-592.
Cinder cones in Iceland (with lichen)
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