The expanding Earth or growing Earth hypothesis asserts that the position and relative movement of continents is at least partially due to the volume of Earth increasing. Conversely, geophysical global cooling was the hypothesis that various features could be explained by Earth contracting.
Although it was suggested historically, since the recognition of plate tectonics in the 1970s, scientific consensus has rejected any significant expansion or contraction of Earth.
The hypothesis had never developed a plausible and verifiable mechanism of action. During the 1960s, the theory of plate tectonics—initially based on the assumption that Earth’s size remains constant, and relating the subduction zones to burying of lithosphere at a scale comparable to seafloor spreading —became the accepted explanation in the Earth Sciences.
The scientific community finds that significant evidence contradicts the Expanding Earth theory, and that evidence used in support of it is better explained by plate tectonics:
Measurements with modern high-precision geodetic techniques and modeling of the measurements by the horizontal motions of independent rigid plates at the surface of a globe of free radius, were proposed as evidence that Earth is not currently increasing in size to within a measurement accuracy of 0.2 mm per year. The lead author of the study stated “Our study provides an independent confirmation that the solid Earth is not getting larger at present, within current measurement uncertainties”.
The motions of tectonic plates and subduction zones measured by a large range of geological, geodetic and geophysical techniques supports plate tectonics.
Imaging of lithosphere fragments within the mantle supports lithosphere consumption by subduction.
Paleomagnetic data has been used to calculate that the radius of Earth 400 million years ago was 102 ± 2.8 percent of today’s radius. However, the methodology employed has been criticised by the Russian geologist Yuriy Chudinov.
Examinations of data from the Paleozoic and Earth’s moment of inertia suggest that there has been no significant change of Earth’s radius in the last 620 million years.