Magma rising in the rifts between diverging ocean plates renews ocean basins about every 200 million years. These rifts snake around the globe for 75,000 km, the globe’s longest physical feature.
Age of ocean floor (millions of years) 0
180 Fig. 12 The location of the Mid-Atlantic Ridge Plate Tectonic Theory - Vine and Matthews (late 1960s)
Vine and Matthews mapped the distribution of earthquakes and volcanoes across the world. These maps revealed how the crust is broken up into large and small plates. Hess’s sea-floor spreading and Wegener’s theory of continental drift were now combined and formed the basis of the plate tectonic theory we know today.
Note the relationship between plate boundaries and the location of earthquakes and volcanoes. See Fig. 13.
Fig. 13 Map to show the distribution of earthquakes and volcanoes 8