Driving Earth's surface motions

摘要

Density variations within Earth's mantle may be a significant driver of both horizontal and vertical surface movements. The fingerprints of such mantle processes have been found in the Mediterranean region. Horizontal and vertical motions near Earth's surface are typically stately in pace-some 0.1 to 10 centimetres per year. But their net effects over long periods can be major. After decades to centuries, velocity differences across faults in Earth's crust produce slip deficits of up to a few tens of metres, which are resolved during large earthquakes. On timescales of millions of years, surface movements result in mountain building, in the opening of ocean basins and in the separation of continents. Faccenna and Becker (page 602 of this issue)1 show that convective action in Earth's mantle, at depths extending from about 100 to 2,900 kilometres, is partly responsible for surface dynamics in one of the most complex tectonic areas in the world- the Mediterranean region.