Publication Date:
2022-05-25
Description:
Author Posting. © Nature Publishing Group, 2008. This is the author's version of the work. It is posted here by permission of Nature Publishing Group for personal use, not for redistribution. The definitive version was published in Nature 453 (2008): 1236-1238, doi:10.1038/nature07075.
Description:
Roughly 60% of the Earth’s outer surface is comprised of oceanic crust formed by volcanic
processes at mid-ocean ridges (MORs). Although only a small fraction of this vast volcanic
terrain has been visually surveyed and/or sampled, the available evidence suggests that
explosive eruptions are rare on MORs, particularly at depths below the critical point for
steam (3000 m). A pyroclastic deposit has never been observed on the seafloor below 3000
m, presumably because the volatile content of mid-ocean ridge basalts is generally too low
to produce the gas fractions required to fragment a magma at such high hydrostatic
pressure. We employed new deep submergence technologies during an International Polar
Year expedition to the Gakkel Ridge in the Arctic Basin at 85°E, to acquire the first-ever
photographic images of ‘zero-age’ volcanic terrain on this remote, ice-covered MOR. Our
imagery reveals that the axial valley at 4000 m water depth is blanketed with
unconsolidated pyroclastic deposits, including bubble wall fragments (limu o Pele),
covering a large area greater than 10 km2. At least 13.5 wt% CO2 is required to fragment
magma at these depths, which is ~10x greater than the highest values measured to-date in
a MOR basalt. These observations raise important questions regarding the accumulation
and discharge of magmatic volatiles at ultra-slow spreading rates on the Gakkel Ridge (6-
14 mm yr-1, full-rate), and demonstrate that large-scale pyroclastic activity is possible
along even the deepest portions of the global MOR volcanic system.
Description:
This research was
funded by the National Aeronautics and Space Administration, the National Science Foundation,
and the Woods Hole Oceanographic Institution.
Repository Name:
Woods Hole Open Access Server
Type:
Preprint
Format:
application/pdf
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