Today is another beautiful day in the Gulf of California, the sky is blue and the sea is calm. However, in the afternoon a few clouds appeared in the sky; hope that is not a sign of bad weather coming our way.
Today we are conducting our remotely operated vehicle (ROV) dive D395, just northeast of the dive we did yesterday. That means that we are going north in the Gulf of California. Our chief scientist Dave Clague, as in all the dives, is very excited about this dive because we may find some active chimneys, but deep in our heart we know that we may not find activity on these chimneys because yesterday we didn’t find active ones, and now we are to the north of that dive in a less active area of the Alarcón rise.
The first images that we received reveal a seafloor similar to the one we found yesterday; a seafloor covered with lava flows, but there are some differences. In the first part of the journey we didn’t see as many irregularities—big fault scarps, big submarine mounts, big talus deposits, and fissures—as we did yesterday, which suggests a less active area. As we expected, we also found some chimneys that were inactive.
When the journey was coming to an end, we found several more inactive chimneys. When the ROV approached a chimney, we noticed something shining on the surface. It was a mineral called pyrite. The presence of this mineral indicates that the temperature was very high when it precipitated.
As in the rest of the dives, we collected lava samples and sediment push cores. These samples will be analyzed in specialized labs, and the information will help to get a better understanding of processes taking place in the Gulf of California. For example, some of the microfossils contained in the sediment can be used to; a) try to detect changes in water productivity, b) determine how far the California Current penetrates the Gulf of California, c) observe how oxygen concentrations in the water vary over long spans of time, d) see how the climate has changed in this area, and many more interesting and useful things.
As several people have mentioned by now, one of the things we do with the ROV at the bottom of the ocean is collect and bring back rocks. To some people they all look the same: black, volcanic rocks—great for paperweights! But to us, each rock has a story to tell, and when we put all those stories together, we hope to be able to answer some bigger questions that others have been describing here. How often do eruptions occur? How big are they? Where do they come from? Does the same batch of magma feed both Volcano A and nearby Volcano B? Or did they come from different sources? What processes deeper in the Earth’s mantle led to that batch of magma? In order to answer some of these questions, we need to know something about the composition and age of the rocks.
Part of the story can be told just by the observations we make at the seafloor combined with the high-resolution sonar maps. As discussed by Ryan Portner on Day 1 and by Ronald Spelz and Brian Dreyer on Day 3, if we can tell that flow A is on top of flow B, or has a thinner sediment cover, we know that flow A is younger. As Rigoberto mentioned above, today’s dive explored several extinct hydrothermal vent regions. Although active vents are exciting and beautiful, inactive vents tell a useful story as well, because if there is no heat to drive the vents, then the lava flows are probably not very young.
These observations all tell us relative age—in other words, we can sometimes tell if one flow is older or younger than another. But we can’t say one is 40 years old and the other is 350 years old—we can’t tell absolute age. And we can’t say anything about how magma composition varies.
To do this, we need rocks! (And mud, as noted by Brian on Day 3.) Several scientists on the cruise will be working with the rocks back at home, using different techniques to extract different bits of the rocks’ stories. Some will be looking at the different minerals in the rocks and the overall composition of the rocks: How much iron, magnesium, silicon, etc. are in the lava rocks? Variations in rock composition can tell us how similar or different the magma source is. Minerals in the lavas might also tell us how deep the magma chamber was, how much time the magma spent in the magma chamber before erupting, or how old the rock is. The compositions of the minerals in the sulfide rocks may also tell us how long it has been since the venting ceased. Even the magnetic properties of the rocks can tell us something useful. When lava cools after eruption, it records the direction and strength of Earth’s magnetic field, which varies over time. By extracting this “paleomagnetic” information we can try to place absolute or relative dates on the flows.
Rocks can tell us many things. We just have to know what and how to ask, and then listen carefully to the answers!
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.