The wind has begun to blow and is cooling us off a bit, which is welcome. The seas have picked up too, so the ship is moving around under our feet for the first time this trip.
After a false start this morning due to a hydraulic leak, ROV dive D398 set out to explore more old/young flow relationships further northeast yet on Alarcón Rise. We began the dive on a feature that looked very strange in the autonomous underwater vehicle (AUV) map. Rather than a smooth shield or rounded mound as produced during low-effusion-rate pillow eruptions, or the flatter and collapsed or channeled terrain of lobate pillows or sheet flows, which are the eruptive styles usually produced at mid-ocean ridges, it is a broad, lumpy, irregular pile 500 meters by 320 meters by 55 meters tall (1,640 feet by 1,050 feet by 180 feet tall). It is unlike anything we have mapped on the mid-ocean ridges of the Northeast Pacific or Lau Basin, and it is not distinguishable in the ship-based bathymetric map of the Alarcón Rise. It looks a lot like cones we have mapped on the summit of Davidson Seamount off California, which are composed of viscous, trachyte (silica-rich) lavas.
The steep slope of this dome is rounded boulders of talus and intact outcrops of lava that resemble the ragged surface of 'a'a (rough, rubbly, or blocky lava) flows. The gravel we collected contains extremely pitted, clear glass, which is probably rhyolite pumice. Rhyolite is the same silica-rich chemistry of granite before the crystals have a chance to grow. Silica-rich lavas are commonly erupted by volcanoes on the continents but extremely unusual for mid-ocean ridges! It is possible that the feature is a viscous, silicic dome, which shed talus that tumbled—possibly glowing—as it built. This would be analogous to the dome that grew in the crater of Mount Saint Helens in the Cascades.
A four-kilometer-long series of narrow, steep ridges extends to the northeast and southwest of the dome, and may be related to it. We found the ridges to contain shattered pillow lavas. Some of the pillows are round as if emplaced on flat ground but are now on 60 degree slopes, and matching halves of pillow mounds lie on either side of ridges. They have been pushed upward and apart, and tilted. These ridges may be from dike intrusions that buckled up the crust above but may not have reached the surface.
This feature is less than 10 kilometers (6.2 miles) from the northern transform fault and only about 100 kilometers (62 miles) from the continent, either of which may influence the eruptions here. It is also 25 kilometers (15 miles) northeast from the center of the most volcanically robust part of the ridge. Perhaps lavas that feed along dikes that far cool so much that the residual melt becomes viscous and enriched in silica, so it behaves differently than the basaltic lavas normally found on mid-ocean ridges.
- Jenny Paduan
The wind started blowing Thursday afternoon, as a result small waves were formed and as time went by the waves started to get bigger. All night the ship was moving around quite a lot, but nothing to worry about. On Friday we still were having big waves. The dive started and a few minutes later the remotely operated vehicle (ROV) stopped its descent. The technicians brought the ROV up to the ship to determine the problem. Once the technicians finished doing their thing with the ROV, the ROV was on its way again.
But today I’m not telling you about what the ROV saw at the bottom, I will let someone else tell you about it. Today I’m going to tell you the story of the “Rock Crusher”. It all began when I heard Jenny Paduan talking to another person about the “Rock Crusher”. It is an oceanographic instrument used to obtain rock samples from the seafloor. I got interested in knowing how this instrument works.
There are two methods used to study the seafloor, one is indirect and the other is direct. The indirect method is used when we make suppositions of what may be found or how processes may be taking place using the information that we have in hand without actually sampling or measuring in the place of interest. Meanwhile the direct method consists of making actual measurements or observing the processes in the place on interest, like getting a rock sample to conduct a test on it in order to determine what type of rock it is. The “Rock Crusher” falls in the direct method’s category because it collects fragments of the seafloor so we can study them.
The “Rock Crusher” works this way; the collecting cups get filled with wax and are put in the tubes coming out from the head and upper ring. They get secured to the structure using some bolts. Then the instrument is lowered into the ocean (Figure 2). When it reaches the bottom, because of its weight, the rock gets crushed and the rock particles get stuck to the wax, the instrument falls on its side and more rock particles get stuck to the collecting cups that are in the upper ring. At this point we bring the instrument to the surface, and once on the ship’s deck the collecting cups are removed. Using a spatula we remove all the wax that has rock fragments and put the wax in a glass beaker with hot water and heat the beaker so the wax will melt and float to the surface (Figure 3). At this moment all of the rock fragments that were attached to the wax will settle down at the bottom and there you have it, you will have in your hands an actual sample of the rock found in the seafloor that you can analyze (Figure 4). Ingenious isn’t it?
Finally I can tell you the importance of using this instrument; when you make dives with the ROV you will be collecting rocks and sediment samples along a track in the seafloor but covering a fairly big area will be almost impossible. This is where the “Rock Crusher” comes in handy. Based upon the scientists' knowledge and what they have seen during the dives they can guess the type of rock that can be found in the area between the dives sites. The “Rock Crusher" is used to bring a sample from the bottom and verify that in fact the scientists are right (or maybe not) about the type of rock present at the seafloor.
Volcanoes & Seamounts
The R/V Western Flyer is a small water-plane area twin hull (SWATH) oceanographic research vessel measuring 35.6 meters long and 16.2 meters wide. It was designed and constructed for MBARI to serve as the support vessel for ROV operations. Her missions include the Monterey Bay as well as extended cruises to Hawaii, Gulf of California and the Pacific Northwest.
ROV Doc Ricketts is MBARI's next generation ROV. The system breaks new ground in providing an integrated unmanned submersible research platform, with many powerful features providing efficient, reliable and precise sampling and data collection in a wide range of missions.
A push-core looks like a clear plastic tube with a rubber handle on one end. Just as its name implies, the push core is pushed down into loose sediment using the ROV's manipulator arm. As the sediment fills up the core, water exits out the top through one-way valves. When the core is pulled up again, these valves close, which (most of the time) keeps the sediment from sliding out of the core tube. When we bring these cores back to the surface, we typically look for living animals and organic material in the sediments.
Niskin bottles are used to collect water samples as well as the tiny bacteria and plankton in that volume. The caps at both ends are open until the bottles are tripped, when the caps snap closed.
The box fits in a partition in the sample drawer. It is shown open, with an animal being placed into it by the ROV's manipulator. When the lid is closed, the box will hold water to protect the animals inside.
This device is used to collect volcanic glass fragments from the surface of a flow. It is made of about 450kg of lead and steel and is launched over the stern of the ship on a wire. Fragments of rock that break off of the lava flow on impact are trapped in wax-tipped cones mounted around the crusher. The wax is melted in the lab to liberate the rock particles for analysis.
The benthic toolsled is attached to the bottom of the ROV for our geology dives. Its components are the manipulator arm and the sample drawer. The sample drawer is shown open on deck, full of rocks. Normally it is closed when the vehicle is operating and is opened only when a sample needs to be stowed. Partitions in the drawer help us keep the rocks in order. The rocks often look alike, but the conditions and chemistries of the eruptions are different so it is important that we know where each came from.
This equipment is used to vacuum glass particles and larval animals from cracks and crevices. The carousel of small plastic jars fitted with wire mesh will be mounted in the benthic toolsled. The hose will be held by the ROV's manipulator and a suction will be drawn by the pump.
Canvas bags on a T-handle for collecting gravel or other materials that fall out of a push-core.
Held by the ROV's manipulator, the wire on the right is placed into the fluid emitted from a hydrothermal vent to record the temperature.
Vibracoring is a common technique used to obtain samples from water-saturated sediment. These corers work by attaching a motor that induces high frequency vibrations in the core liner that in turn liquefies the sediment directly around the core cutter, enabling it to pass through the sediment with little resistance.
R/V Western Flyer
ROV Doc Ricketts
Dave's research interests are nearly all related to the formation and degradation of oceanic volcanoes, particularly Hawaiian volcanoes, mid-ocean ridges, and isolated seamounts. Topics of interest include: compositions of mantle sources for basaltic magmas and conditions of melting; volatile and rare-gas components in basaltic magmas and their degassing history; chronostratigraphic studies of eruption sequence and evolution of lava chemistry during volcano growth; subsidence of ocean volcanoes and its related crustal flexure, plate deformation, and magmatic activity; geologic setting of hydrothermal activity; origin of isolated seamounts; and monitoring of magmatic, tectonic, and hydrothermal activity at submarine and subaerial volcanoes.
Jenny works with Dave Clague in the submarine volcanism project, processing the high-resolution MBARI mapping AUV data and interpreting the maps using ROV observations and samples from our research sites. On this cruise, she will stand watches in the ROV control room, help with rock and sediment sample workup and curation once the vehicle is on deck, and coordinate these cruise logs. She is now quite solidly a marine geologist, but her degrees are in biochemistry (Smith College) and biological oceanography (Oregon State University). She is thankful for the opportunities that have led her to study volcanoes, and loves being involved with the research and going to sea. She looks forward to discovering more about how Earth works.
On this cruise, Lonny will be in charge of biological sample collection and processing and video data management. This work entails identifying unique biological and geological features that will be seen during the dive, while using MBARI-designed software to log the observations. He is especially excited about this expedition, because no one has surveyed this particular seamount before, and he expects to find many new species on this cruise.
Julie works with the submarine volcanism group, where she currently produces high resolution maps of the seafloor that are used to identify geologic features along submarine ridges and seamounts. Her research interests also include modeling of volcanic ash from sub-aerial, large-scale explosive eruptions.
Ryan's work with the submarine volcanism project primarily focuses on the formation and distribution of volcaniclastic deposits on active and extinct seamounts and mid-ocean ridges. By categorizing the diversity in these deposits with respect to volcanic landforms he hopes to better understand the underlying controls on explosive vs. non-explosive deep marine eruptions. His background research on deep-marine gravity flow deposits preserved in sedimentary-volcanic successions exposed on land lends a comparable platform to study similar deposits of the modern oceans.
Julie is a Research Associate and Staff Scientist with the Institute for Rock Magnetism at the University of Minnesota. As a paleomagnetist, Julie studies variations in Earth's magnetic field and how those variations get recorded in rocks and sediments. One of Julie's particular interests involves using paleofield variations recorded in mid-ocean ridge lava flows to place age constraints on the flows. On this expedition, Julie is interested both in using this technique to try to date some of the young lava flows and in gaining a better understanding of how the Earth's field has varied in this particular location.
Pat is a Professor of Geology at the Scripps Institution of Oceanography, University of California, San Diego. His research interests include petrology and geochemistry of magmas produced within and along divergent and convergent boundaries of tectonic plates, magmatic and tectonic evolution of continental margins and mantle geodynamics. On this expedition, Pat is interested in the petrologic and tectonic evolution of the newly formed oceanic basement in the Gulf of California.
Brian studies the recent magmagenesis and petrology of the Juan de Fuca Ridge. His interest in mid-ocean ridges began during his postdoctoral fellowship with MBARI's submarine volcanism project; there, he utilized uranium-series disequilibria within individual lavas of Axial Seamount to clarify eruption and petrogenetic timescales. At mid-ocean ridge systems globally, Brian is interested in a) how variability in lava morphology, geochemistry, and petrology reflect deeper mantle-melting and magmatic processes and their complex interplay with tectonism and b) improving the chronological framework of the ridge magmatic plumbing systems. Brian received his Ph.D. in Earth and Planetary Science from Washington University in St. Louis in 2007.
Rigoberto Guardado is a teacher and research scientist with the Facultad de Ciencias Marinas (Marine Sciences Faculty) at the University of Baja California in Mexico. As a oceanographer, Rigoberto studies sedimentation processes in the ocean. On this expedition, Rigoberto is interested in learning more about the sediments in this area of the Gulf of California.
Ronald Michael Spelz Madero
Ronald Spelz earned his Ph.D. in earth sciences from Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE) in 2008. His research interests are mainly focused in the structural geology and tectonic geomorphology of fault bounded basins and mountain range-fronts in northern Baja California. He is also part of the multidisciplinary research team studying the origin and effects of the El Mayor-Cucapah 7.2 magnitude earthquake which struck northern Baja in April 4, 2010. Ronald presently works in the Marine Sciences Faculty at the Universidad Autónoma de Baja California.
Hiram Rivera is part of the Coastal Management group and teacher in the Faculty of Marine Science at Universidad Autónoma de Baja California. Since 2008 he has worked as a technician with geographic information systems (GIS) applied to fisheries resource management. From 2010 to now he has worked with his students in public participation geographic information systems (PPGIS) 3D models applied to the use of GIS to broaden public involvement in policymaking. His interest for this cruise is to learn about the techniques associated with digital cartography of the Gulf of California.