Earth history: A journey in time and space from base to top

Abstract

The invention of a robust and accurate sea-going chronometer transformed navigation in the mid-eighteenth century. The calibration of longitude against the prime meridian at Greenwich, in combination with latitude derived from the positions of celestial bodies gave mariners for the first time confidence that they could calculate their position on the Earth's surface. Until recently, Earth scientists have been in a comparable position of having no way of calculating the longitudes of continents before the Cretaceous. Here I discuss Phanerozoic polar wander and paleogeographies and describe ways of quantitatively establishing ancient longitudes which also establish how the Earth's interior can be linked to its surface in geological time. The first method makes use of the fact that longitudinal uncertainty of continents that were assembled in Pangea can, for subsequent times, be eliminated, if longitude motion is known for only one of these continents. The best assumption is zero-longitude motion for Africa and with this assumption we can show that large igneous provinces (LIPs) and kimberlites almost exclusively erupted above the margins of TUZO and JASON in the lower mantle. This remarkable observation, also considering the effect of true polar wander, has led to a second method the plume generation zone reconstruction method unlocking a way forward in modelling absolute plate motions before Pangea and exploring links between plate tectonics, intra-plate volcanism and Deep Earth dynamics. Conceptually, that link can be viewed as a simple mass-balance: subducted lithosphere slabs restore mass to the mantle and trigger the return flow toward the surface including mantle plumes rising from the margins of TUZO and JASON. The surface manifestations of plumes are hotspot lavas, kimberlites and LIPs.