Thickness of a submarine lava flow determined from near‐bottom magnetic field mapping by autonomous underwater vehicle

Magnetic field surveys obtained near the seafloor can map the boundaries of recent volcanic eruptions and can provide thickness estimates of these lava flow units independent of bathymetry differencing methods. Magnetic thickness estimation requires knowledge of the intensity of magnetization of the new lava and surrounding terrain, but this can be satisfactorily obtained by representative sampling of the various volcanic units. While bathymetry differencing requires pre‐existing data to assess the thickness of new lava eruptions, magnetic surveys can be obtained after an eruption has occurred. In this study, near‐bottom magnetic surveys were obtained using an autonomous underwater vehicle (AUV), which operates without a tether or human intervention. AUV technology offers rapid deployment and an efficient surveying approach for remotely mapping recent lava eruption sites on the seafloor.

[1]  H. Bigelow.  Woods Hole Oceanographic Institution , 1930, Nature.

[2]  R. Parker,et al.  The inversion of magnetic anomalies in the presence of topography , 1974 .

[3]  K. Macdonald,et al.  A 220 km2 recently erupted lava field on the East Pacific Rise near lat 8°S , 1989 .

[4]  E. Baker,et al.  Geology of the northern Cleft segment, Juan de Fuca Ridge: Recent lava flows, sea-floor spreading, and the formation of megaplumes , 1991 .

[5]  W. Chadwick,et al.  Detection of changes in ridge‐crest morphology using repeated multibeam sonar surveys , 1992 .

[6]  W. Chadwick,et al.  SeaBeam depth changes associated with recent lava flows, Coaxial Segment, Juan De Fuca Ridge: Evidence for multiple eruptions between 1981–1993 , 1995 .

[7]  M. Tivey,et al.  Alvin magnetic survey of zero‐age crust: CoAxial Segment Eruption, Juan de Fuca Ridge 1993 , 1995 .

[8]  R. Dziak,et al.  The June‐July 1993 seismo‐acoustic event at CoAxial segment, Juan de Fuca Ridge: Evidence for a lateral dike injection , 1995 .

[9]  M. Tivey,et al.  Magnetic properties of zero-age oceanic crust; A new submarine lava flow on the Juan de Fuca Ridge , 1995 .

[10]  E. Baker,et al.  Initial results of the rapid response to the 1993 CoAxial event: Relationships between hydrothermal and volcanic processes , 1995 .

[11]  Robert P. Dziak,et al.  Acoustic detection of a seafloor spreading episode on the Juan de Fuca Ridge using military hydrophone arrays , 1995 .

[12]  M. Tivey.  Vertical magnetic structure of ocean crust determined from near‐bottom magnetic field measurements , 1996 .

[13]  D. Fornari,et al.  Rapid emplacement of a mid-ocean ridge lava flow on the East Pacific Rise at 9° 46'-51'N , 1996 .

[14]  Dana R. Yoerger,et al.  Autonomous underwater vehicle maps seafloor , 1997 .

[15]  J. M. Rhodes,et al.  Researchers Rapidly Respond to Submarine Activity at Loihi Volcano, Hawaii , 1997 .

[16]  W. Chadwick,et al.  Graben formation associated with recent dike intrusions and volcanic eruptions on the mid‐ocean ridge , 1998 .

[17]  T. Shank,et al.  The 1996 Gorda Ridge eruption: geologic mapping, sidescan sonar, and SeaBeam comparison results , 1998 .