Publication Date:
2022-05-25
Description:
Author Posting. © American Geophysical Union, 2006. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 7 (2006): Q05001, doi:10.1029/2005GC001086.
Description:
A 2002 multibeam sonar survey of Mauna Loa’s western flank revealed ten submarine radial vents and
three submarine lava flows. Only one submarine radial vent was known previously. The ages of these vents
are constrained by eyewitness accounts, geologic relationships, Mn-Fe coatings, and geochemical
stratigraphy; they range from 128 years B.P. to possibly 47 ka. Eight of the radial vents produced degassed
lavas despite eruption in water depths sufficient to inhibit sulfur degassing. These vents formed truncated
cones and short lava flows. Two vents produced undegassed lavas that created ‘‘irregular’’ cones and
longer lava flows. Compositionally and isotopically, the submarine radial vent lavas are typical of Mauna
Loa lavas, except two cones that erupted alkalic lavas. He-Sr isotopes for the radial vent lavas follow
Mauna Loa’s evolutionary trend. The compositional and isotopic heterogeneity of these lavas indicates
most had distinct parental magmas. Bathymetry and acoustic backscatter results, along with photography
and sampling during four JASON2 dives, are used to produce a detailed geologic map to evaluate Mauna
Loa’s submarine geologic history. The new map shows that the 1877 submarine eruption was much larger
than previously thought, resulting in a 10% increase for recent volcanism. Furthermore, although alkalic
lavas were found at two radial vents, there is no systematic increase in alkalinity among these or other
Mauna Loa lavas as expected for a dying volcano. These results refute an interpretation that Mauna Loa’s
volcanism is waning. The submarine radial vents and flows cover 29 km2 of seafloor and comprise a total
volume of ~2 x 109 m3 of lava, reinforcing the idea that submarine lava eruptions are important in the
growth of oceanic island volcanoes even after they emerged above sea level.
Description:
This project was funded by
NSF grants OCE-97-29894 to M.G. and OCE-9818744 to
J.M.R.
Keywords:
Hawaii
;
Mauna Loa
;
Submarine volcanism
;
Radial vents
;
Bathymetry
;
Igneous petrology
Repository Name:
Woods Hole Open Access Server
Type:
Article
Format:
10619596 bytes
Format:
application/pdf
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