2 September 2004
Californian underworld
The California Sierra Nevada is among the most spectacular mountain ranges in North America. Beneath its tranquil surface a geological upheaval is occurring on a grand scale, and new seismic images show this critical crust–mantle interaction in unprecedented detail. A large mass of mantle rock at a depth of about 50 km is flowing like a slow river into a mantle 'drip' centred under the adjacent Great Valley. The downward flow is producing an inverted mountain of crust protruding into the mantle five to six times the height of the highest peaks above the Sierra Nevada. At the surface in the wake of this subterranean flow, volcanic eruptions have been triggered and the courses of rivers are being diverted. The new images reveal surprising asymmetry in the downwelling flow.
Active foundering of a continental arc root
beneath the southern Sierra Nevada in California
GEORGE ZANDT, HERSH GILBERT, THOMAS J. OWENS, MIHAI
DUCEA, JASON SALEEBY & CRAIG H. JONES
Nature 431, 41–46 (2004); doi:10.1038/nature02847
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