Today, our first dive was on the Alarcón Seamount volcanic chain, 36 kilometers (22 miles) northwest of Alarcón Rise in the entrance to the Gulf of California. The Alarcón Seamount volcanic chain is comprised of near-axis seamounts that formed on or very close to the currently active Alarcón Rise mid-ocean ridge, where we will be diving over the next several days. The seamounts are estimated to be about one to 1.5 million years old. Aside from a couple of dredges in the late 1990s, these seamounts have not been studied in any detail.
Our dive today used a high resolution map recently collected by MBARI's autonomous underwater vehicle (AUV). Our geologic objectives today were: 1) to make detailed observations of some interesting channel-like features seen on the map; 2) to sample lava flows; and 3) to find volcanic sand on the top of the seamount.
We started the dive in the central crater of a large dome structure and took a meter-long push core of sediment for the record of past climates, or paleoclimatology, it might contain. We ascended the crater's steep inner wall collecting talus—rock fragments lying at the bottom of a steep slope from which they have broken off. The outer flanks of the crater have numerous channel-like features that radiate outward. Features such as these have not been documented from a near-axis seamount before. They have relatively flat, sediment-covered floors and bowl-shaped headwalls—a nice place to pitch a tent if it wasn't covered by 1,300 meters (4,265 feet) of water! The lateral margins of the channels contain large blocks that seem to fit together like puzzle pieces. We collected one of these large blocks and it was a jumbled, chaotic assemblage of contorted and blocky basalt lava chunks. Many of the chunks have pockets filled with sediment. The toe of the channel exhibits a bulbous “speed-bump” morphology very similar to slump features we see on land. A more in-depth analysis of the features and the substances of which these features are composed will hopefully reveal how they form.
Upon exiting the channel-like feature, we moved across the relatively flat, lava-covered terrain surrounding the crater. We took samples of numerous basalt flows having pillow, lobate, and sheet flow morphologies. Some very beautiful contacts between flows were observed, which will give us a very good indication of "who's on first," so to speak.
We crossed the ends of a few more channel-like structures. The flat lava terrain abruptly stopped at a very prominent fault scarp, a steep slope which may have formed from a sector collapse of the volcano. There are enormous blocks and boulders along its base, up to four cubic meters (141 cubic feet), or about the volume of a car, and they represent the lava beds exposed higher up in the fault scarp. After some hunting we managed to collect several smaller samples that will be analyzed later in the laboratory for geochemistry.
After sampling the blocky talus pile we ascended the steep vertical face of the fault scarp to the top of the seamount. We collected several samples of bedded glassy volcanic sand. This material is the fallout from an explosive style of eruption and is quite common on the tops of many near-axis seamounts, but it is generally not found anywhere else on the seamount.
Another common feature of many seamounts including the one we dove on today is the presence of large calderas. The caldera just below where we sampled the glassy volcanic sand is 350 meters (1,150 feet) deep and 1.5 kilometers (one mile) wide (just north of the west end of our dive track, see first map above). Calderas are thought to form by collapse as molten magma is withdrawn from the interior of the seamount. Where the withdrawn magma goes is uncertain as we do not find large eruptions on flanks or the tops of the seamounts. Perhaps this withdrawn magma retreats to deeper parts of the oceanic crust, intrudes into the nearby mid-ocean ridge, or helps to start the next seamount. This question and the ubiquitous occurrence of glassy volcanic sand on the tops of many of these seamounts keep us coming back to try to understand how these amazing underwater volcanoes form and evolve.
During today's dive we saw numerous sea urchins and sea cucumbers making a living in the sedimented areas adjacent to geologic targets. On rocky outcrops we observed several species of cold-water coral, including antipatharians (black corals) and gorgonians (sea fans). These suspension feeders use their small polyps (tentacles) to capture and consume small planktonic organisms which drift past them in the currents. Sponges, which filter plankton from the water, were also quite common on rock outcrops and talus slopes.
We observed and collected numerous clams which will prove useful in an ongoing project that MBARI scientists are working on that uses genetic markers to understand the relationship between populations living here in the gulf and elsewhere, like seamounts in southern California.
Rattail fishes were quite common, as they are one of the most abundant families of fishes in the deep. Other fishes were also observed including small batfishes, many long and slender eel-like fishes, and a small cat shark.
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.