Measurements of areas of sea floor broken up into age groups show that apparent areal global sea-floor spreading rates increase exponentially from Jurassic to Holocene time, proving that subduction has taken place in that time. The sea-floor spreading phenomenon is a coordinated global process where, at a given time, high spreading rates in one ocean basin are compensated for by low rates in another. Sea-floor spreading is symmetric within 15% over periods of 60 to 165 m.y. This study shows that both global sea-floor spreading and subduction rates have increased with the passage of time. It is estimated that during the past 165 m.y. sea-floor spreading exceeded subduction by 33%. This is interpreted as an increase of the Earth's surface area by expansion, which yields a Jurassic paleoradius of 5,668 km ± 13% (0.89 of the present radius). In spite of the high error margin, due to global extrapolation of subduction and spreading in the time dimension, an expanding earth is strongly indicated.

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