Northern 2014 Expedition
Seafloor Lava Flows
August 26-September 6, 2014
Since 2007 we have been combining the 1-meter horizontal resolution maps acquired by the MBARI mapping AUV with ROV observations and sampling. We outline the boundaries of lava flows and identify old/young relationships in the maps and confirm these relationships with ROV observations and chemical compositions of collected lava samples. We can target the sampling of individual lava flows, other volcanic structures, and hydrothermal chimneys with a precision unrealized until recently. We have pioneered the use of radiocarbon dating of foraminifera shells collected with push cores from sediment on top of a lava flow to give a minimum eruption age of the underlying lava flow. These ages and sequences of flows identified in the high-resolution AUV bathymetry, have enabled us to produce a geologic map of the summit of the seamount. We have developed a two manipulator-held piston corer to more reliably collect cores up to 1.5 meter long of the thick sedimentary deposits on the flanks of the volcano. These deposits preserve another aspect of the volcano’s geologic history: explosive periods and caldera collapse.
There are three primary objectives for our ROV dives at Axial Seamount during this expedition. The first objective is to sample the thick volcaniclastic deposits (ash and volcanic glass fragments) on the upper flanks and rim of the summit caldera. The goal is to refine the timing of when the layers of the deposits formed to better understand changes in the behavior of the volcano and chemistry of the lava, which ultimately reflect changes in the magma reservoirs at depth. In previously collected cores, the top zone has thin clay and volcanic glass-shard layers with variable compositions, so deriving from multiple different, relatively mild eruptions. These thin layers overlay one or more 10-20 centimeters thick layers of almost pure glass having homogeneous compositions, suggesting that somewhat explosive eruptions generated abundant fragmental material in the past. However, the compositions of the glasses in these thick layers change as one goes around the caldera, suggesting that the eruptions were localized and clastic material was not dispersed very far. The behavior of the volcano was generally different then to have produced these thick glassy layers. Underneath these glass units is a distinctly different, bedded greenish-gray hydrothermal deposit with very fine glass shards that may have formed during phreatomagmatic (violent, steam-driven) eruptions, perhaps synchronous with or soon after the caldera collapsed. Radiocarbon dating of foraminifera shells in layers above and below suggests this material is only about 1000 years old, despite overall sediment thicknesses up to nearly two meters.
At a few locations on the caldera rims, foraminifera-rich ooze beneath the hydrothermal layer is older, dating to two, 19, and 31 thousand years old at three locations. These thicker deposits are in areas where pre-caldera summit overflows did not re-pave the sediment-covered flanks, presumably because they were elevated or shielded by faults. We will return to the oldest site with better coring equipment and techniques to sample the complete volcaniclastic sedimentary section to the underlying lava, and we will also collect cores farther away from the caldera rim where the deposits are thinner.
The second objective is to map and sample large-volume ponded and drained lava flows on the lower rift zones of Axial Seamount. We will extend our coverage on the south rift of a broad expanse of ponds that are up to 90 m deep, which we sampled in 2005 and 2013 and mapped with the AUV in 2011, and explore for the first time similar but even deeper ponds on the north rift. At other volcanoes, large-volume flows often coincide with caldera collapse events. Sediments dated so far show that one lava pond on the south rift of Axial formed about 1000 years ago—at roughly the same time as the deposition of the hydrothermal-rich deposits at the summit. This correlation is intriguing, and we hope that learning more about these ponded flows might help us understand when and how the summit caldera collapsed.
The third objective is to complete the AUV mapping (which has just been done off the R/V Rachel Carson) and observing and sampling with the ROV the flows erupted in 2011. A question remains about how the chemistry of the erupted lava changed as the fissure system extended down-rift. Another aspect of interest is the interaction of flowing lava with thick sediments. We saw during the 2013 expedition that pillows at the flow margins had exploded as water under them was heated to steam and that the sheet flows burrowed into or under the sediments. We will use push cores to sample steam-churned sediment where sheet flows burrowed under to see if sediment-lava fragmentation (peperite) occurred when the sediment was disrupted.
- News story about 2011 eruption at Axial: http://www3.mbari.org/news/homepage/2012/axial-mapping/axial-mapping.html
- YouTube video of 2011 “snowblower vent”: http://www.youtube.com/watch?v=Ki0boGH4-Kc
- Cruise log of MBARI dive on the 2011 flow: http://www3.mbari.org/expeditions/Northern11/L2/logbook/day10.htm
The 1998 Axial Seamount eruption, a collection of papers in Geophysical Research Letters, 26, No. 23 in 1999. Same sort of collection for the 1998 Axial eruption.
Chadwick, W.W., D.A. Clague, R.W. Embley, M.R. Perfit, D.A. Butterfield, D.W. Caress, J.B. Paduan, J.F. Martin, P. Sasnett, S.G. Merle, A.M. Bobbitt (2013) The 1998 eruption of Axial Seamount: New insights on submarine lava flow emplacement from high-resolution mapping. Geochem., Geophys., Geosyst., 14(10), 3939-3968. doi: 10.1002/ggge.20202
Clague, D.A., B.M. Dreyer, J.B. Paduan, J.F. Martin, W.W. Chadwick, D.W. Caress, R.A. Portner, T.P. Guilderson, M.L. McGann, H. Thomas, D.A. Butterfield, R.W. Embley (2013) Geologic history of the summit of axial seamount, Juan de Fuca Ridge. Geochem., Geophys., Geosyst., 14(10): 4403-4443. doi: 10.1002/ggge.20240
Dreyer, B.M, D.A. Clague, J.B. Gill (2013) Petrological variability of recent magmatism at Axial Seamount summit, Juan de Fuca Ridge. Geochem., Geophys., Geosyst., 14(10): 4306-4333. doi: 10.1002/ggge.20239.
Helo, C., D.A. Clague, D.B. Dingwell, and J. Stix (2013). High and highly variable cooling rates during pyroclastic eruptions on Axial Seamount, Juan de Fuca Ridge.Journal of Volcanology and Geothermal Research, 253: 54-64. doi: 10.1016/j.jvolgeores.2012.12.004.
Yeo, I.A., D.A. Clague, J.F. Martin, J.B. Paduan, and D.W. Caress (2013) Pre-eruptive flow focussing in dikes feeding historical pillow ridges on the Juan de Fuca and Gorda Ridges. Geochem. Geophys. Geosyst., doi: 10.1002/ggge.20210.
Caress, D.W., D.A. Clague, J.B. Paduan, J.F. Martin, B.M. Dreyer, W.W. Chadwick Jr., A. Denny, D.S. Kelley (2012) Repeat bathymetric surveys at 1-metre resolution of lava flows erupted at Axial Seamount in April 2011. Nature Geoscience, 5(7): 483-488. doi: 10.1038/NGEO1496. See also other papers in this volume.
Rubin, K.H., S.A. Soule, W.W. Chadwick Jr., D.J. Fornari, D.A. Clague, R.W. Embley, E.T. Baker, M.R. Perfit, D.W. Caress, and R.P. Dziak (2012) Volcanic eruptions in the deep sea. Oceanography 25(1): 142–157, doi: 10.5670/oceanog.2012.12. Overview of what is known about deep-sea volcanic eruptions and how they are studied.
Helo, C., Longpre, M.-A., Shimizu, N., Clague, D.A., and Stix, J. (2011) CO2 rich magmas from Axial Seamount – A link to explosive eruptions on mid-ocean ridges?,Nature Geoscience, doi:10.1038/NGEO1104.
Clague, D.A. and Paduan, J.B. (2009) Submarine basaltic volcanism, In: Submarine Volcanism and Mineralization: Modern through Ancient, B. Cousens and S.J. Piercey (eds.), Geological Association of Canada, Short Course 39-30 May 2008, Quebec City, Canada, p. 41-60.
Clague, D.A., Paduan, J.B., and Davis, A.S. (2009) Widespread stombolian eruptions of mid-ocean ridge basalt, Journal of Volcanology and Geothermal Research(2009) 180: 171-188. Describes the fragmental eruption products of strombolian bubble-burst activity on Pacific mid-ocean ridges, including Gorda and Juan de Fuca ridges, near-ridge seamounts, and a few back-arc basins.
Chadwick, J., Perfit, M., Ridley, I., Kamenov, G., Chadwick, W.W., Embley, R.W., le Roux, P., and Smith, M. (2005) Magmatic effects of the Cobb hot spot on the Juan de Fuca Ridge, Journal of Geophysical Research, 110, doi:10.1029/2003JB002767. Petrology of Axial Seamount, mainly based on samples from the south caldera and south rift zone.
Chadwick, W.W., Jr., Scheirer, D.S., Embley, R.W., and Johnson, H.P. (2001) High-resolution bathymetric surveys using scanning sonars: Lava flow morphology, hydrothermal vents, and geologic structure at recent eruption sites on the Juan de Fuca Ridge, Journal of Geophysical Research, 106: 16,075-16,099. Describes the North Cleft and CoAxial eruption sites.
Embley, R.W., Murphy, K.M., and Fox, C.G. (1990) High-resolution studies of the summit of Axial volcano, Journal of Geophysical Research, 95: 12,785-12,812. Best overall description of the caldera and summit of Axial volcano.