KABOOM! Dynamite explosions have given us a detailed glimpse of a geological lubricant that aids the movement of Earth鈥檚 tectonic plates. These plates interlock like a massive jigsaw to make up the planet鈥檚 outer layer, or lithosphere, which is around 70鈥�100 kilometres deep. Their movement can trigger earthquakes, so gaining a better idea of how they move may aid our understanding of tremors, according to .
The plates sit atop a lubricating channel that separates them from the asthenosphere underneath. 鈥淭ectonic lubrication is a valid description of what we think happens in this 10-kilometre-thick channel,鈥� says Stern. The lubricating layer contains viscous melted rock that allows the plates to move independently of the layers below (see diagram).FIG-mg30074701.jpg
Stern and his colleagues directed explosions from Earth鈥檚 surface down into a zone beneath New Zealand, then captured reflections of the resulting seismic waves to build up images of the base of the tectonic plate (Nature, ). Previous studies relied on distant, low-frequency seismic waves from real earthquakes, which dramatically limited the resolution. By setting off 12 of their own mini earthquakes with dynamite buried in 50-metre-deep shafts, Stern鈥檚 team got much sharper images with a resolution of less than a kilometre.
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鈥淲hat鈥檚 so cool is that they鈥檝e really identified the base of the plate, showing it鈥檚 shallower and sharper than previous observations,鈥� says of the University of Southampton in the UK. 鈥淣o one has been able to image the channel before.鈥�
This article appeared in print under the headline 鈥淢ini quakes reveal base of tectonic plates鈥�
