Publication Date:
2017-05-17
Description:
The spreading axis at many slow-spreading mid-ocean ridges is marked by an axial volcanic
ridge. In this study, we use a combination of high-resolution remote sensing methods to elucidate
the detailed nature of volcanoes in such a ridge. We fi nd that the “hummocks” described in
previous sidescan sonar studies are dome- or cone-shaped edifi ces, 5–150 m high with diameters
of 30–330 m. We estimate they form quickly, in single eruptions, each of which may produce
several hummocks. Hummock collapse is common and hummocks of all heights are prone to
failure. Collapses generally occur down the regional seafl oor slope, suggesting control by local
topography. Approximately 33% of hummocks lose ~40% of their volume by collapse, so ~12%
of all material erupted on the axial volcanic ridge is rapidly converted to talus. The higher porosity
of these deposits may increase average upper crustal porosity by several percent, contributing
〉0.5 km s–1 to seismic velocity decrease in the upper oceanic crust, and may be one of the
dominant mechanisms for increasing porosity in upper slow-spreading oceanic crust.
Type:
Article
,
PeerReviewed
Format:
text
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