This has been a great cruise with almost all of our initial goals met and some new discoveries added on top. As Rob Zierenberg noted yesterday, numbers sometimes tell a story and here are some more from this cruise. We collected 191 lava samples, 14 samples of hydrothermal deposits, 3 mudstone samples, 82 short (30 centimeters) push cores…
The number for today seems to be 33—the current wind speed in knots. Waves are pounding into the ship and we cannot launch the ROV in this weather. Everyone was really looking forward to today’s dive, which was in Pescadero Basin, the next spreading segment north of the Alarcón Rise.
As previously mentioned, the Alarcón Rise is the northernmost segment of the East Pacific Rise spreading center. The Alarcón Rise is roughly 50 kilometers long. It is the axis along which new ocean crust is forming as a rocky ridge, compared to the short spreading segments within the Gulf of California that are sediment-filled basins.
Today was like traveling back in time! Our goal was to establish an approximate eruptive history at this location, so we started our dive about three kilometers to the west of the active Alarcón Rise axis.
Today’s dive was, as the Wisconsinites on board (Julie Bowles, Knute Brekke, and Patrick Mitts) would say, a smorgasbord! There were new and very impressive hydrothermal chimneys, mounds of lovely elongate basaltic pillows, and a vast flood of a relatively young, jumbled sheet-like lava flow, which will be discussed in tomorrow’s cruise log.
Today’s dive targeted the southernmost end of the Alarcón Rise, where it transitions from oceanic spreading center to what is called a transform fault.
Today’s dive on the Alarcón Rise started in a newly discovered active hydrothermal field, a vent through which hot fluids emerge from the seafloor. The tall chimney edifices, along with their peculiar deep-sea inhabitants, and their jetting hot fluids, literally gave us a “very warm” welcome.
A primary goal of today’s dive was to explore the extent of high-silica lava flows at Alarcón Rise. These flows are common on land volcanoes but rare at oceanic spreading centers—sites where two tectonic plates move away from one another.
The purpose of our expedition today was to determine if volcanic rocks containing silica occurred along the spreading ridge south of the previously identified rhyolitic lava dome.
Today we dove on the Alarcón Rise mid-ocean ridge. With few exceptions, mid-ocean ridges typically lie very deep beneath the sea surface. They are a locus of active volcanoes, hydrothermal vents and chimneys, and an abundance of life.
The R/V Western Flyer departed last evening from Pichilingue Harbor near La Paz, Mexico. The weather was clear and warm and the sea was smooth as glass. We steamed through the night and arrived in time to do a full day’s ROV dive on the eastern-most volcano of the Alarcón Seamounts.
Research programs at the Monterey Bay Aquarium Research Institute (MBARI) encompass the entire ocean, from the surface waters to the deep seafloor, and from the coastal zone to the open sea. The need to understand the ocean in all its complexity and variability drives MBARI's research and development efforts.