Magma genesis, migration, and eruption have played prominent roles in the chemical differentiation of the Earth. Plate tectonics has provided the framework of tectonic environments for different suites of igneous rocks and the dynamic mechanisms for moving masses of rock into melting regions. Petrology is rooted in geophysics. Petrological and geophysical processes are calibrated by the phase e...

Harrison et al. (Reports, 23 December 2005, p. 1947) proposed that plate tectonics and granites existed 4.5 billion years ago (Ga), within 70 million years of Earth's formation, based on geochemistry of >4.0 Ga detrital zircons from Australia. We highlight the large uncertainties of this claim and make the more moderate proposal that some crust formed by 4.4 Ga and oceans formed by 4.2 Ga.

Whereas cohesin cleavage alone did not produce any detectable effects on engaged centrioles, Cdk inhibition, in contrast, was sufficient to induce centriole disengagement even in the absence of proper chromosome disjunction. Upon p27 injection, centriole disengagement was observed with a similar kinetics to the disengagement observed in the TEV+p27 experiments (Figure 1). Our previous experimen...

Vicariance hypotheses of Gondwanan fragmentation have been the prevailing explanation for the distributions of plant and animal taxa in the Southern Hemisphere since the widespread acceptance of plate tectonics in the late, 1960s (Bauer, 1993; Sanmartı́n & Ronquist, 2004). Recently, several molecular studies comparing the timing of cladogenic and vicariant Conservation Biology Graduate Program, ...

Until the arrival of the theories of plate tectonics and seafloor spreading in the 1960s, the Earth’s mantle was generally believed to consist of peridotites of uniform composition. This view was shared by geophysicists, petrologists, and geochemists alike, and it served to characterize the compositions and physical properties of mantle and crust as “Sial” (silica-alumina) of low density and “S...