In the 1950s, surprising links were proposed between cosmological theory and the geological and paleontological sciences. These links were mainly provided by Paul Dirac's hypothesis of 1937 that the gravitational constant G decreases with cosmic time. Pascual Jordan, famous for his pioneering contributions to quantum theory, took up Dirac's hypothesis; after the end of World War II, Jordan developed its geophysical consequences, concluding that the Earth is expanding. Much of Jordan's later scientific work focused on the expanding Earth and other aspects of the earth sciences relating to the varying- G hypothesis. This chapter in the history of science has received almost no attention from either scientists or historians. The article analyzes Jordan's cosmo-geological work in relation to the somewhat similar efforts of other "expansionists" in the period that led to the plate tectonic revolution in the earth sciences.