Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) An erratum has been published Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Gilbert, L. A. Articles by Paul Johnson, H. Search for Related Content GeoRef GeoRef Citation

Porosity of the upper edifice of Axial Seamount

¹ Maritime Studies Program, Williams College and Mystic Seaport, 75 Greenmanville Avenue, Mystic, Connecticut 06355, USA
² School of Oceanography, University of Washington, Seattle, Washington 98195-7940, USA

Seamounts are not solid basalt structures, but have relatively high porosities in their upper crustal sections. At Axial Seamount, off the coast of Oregon, United States, we used on-bottom gravity measurements with a Bell gravity meter within deep-sea submersible Alvin to determine a porosity of 31% for the uppermost 100 m of the edifice. The southwestern caldera wall has a porosity of 22% and the caldera floor has a slightly higher porosity of 33%. Seafloor observations and models indicate that these high porosities result from large-scale structural features such as lava tubes and cracks, large lava drain backs, or regions of open pillow basalts in the near subsurface. These high-porosity zones can affect the subsurface permeability, and models of hydrothermal upflow zones explain observed localized gravity anomalies. The variety of hydrothermal alteration, hydrothermally active areas, and open porous features appears to be related to the high porosity that is inferred from geophysical measurements on this active seafloor volcano.

Key Words: crustal density • seamounts • gravity anomalies • porosity • Axial Seamount • Juan de Fuca Ridge • submersible Alvin