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Science 8 September 2006:
Vol. 313. no. 5792, p. 1360
DOI: 10.1126/science.313.5792.1360f
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This Week in Science

Volcanism on Earth occurs at plate boundaries (such as mid-ocean ridges and island arcs) and within plates above mantle plume hot spots. Hirano et al. (p. 1426, published online 27 July; see the Perspective by McNutt) report finding another type of volcano that is far from any of these primary sources. In submersible dives in the western Pacific Ocean, far from the plate edge, they saw the tops of small volcanoes that were partly buried in sediment and surrounded by pillow lavas and exploded shards. Geochemical analysis suggests the resulting basalts are young and formed at depths greater than 100 kilometers in the asthenosphere, which would imply that this layer contains a few percent melt. The authors argue that these "petit spot" volcanoes have grown along cracks where the asthenosphere has flexed and squeezed out its melt.




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Science. ISSN 0036-8075 (print), 1095-9203 (online)