March 5, 2007 (Vol. 5, No. 3)

Geology Major Wanda Vargas Researches the Sea Floor

Wanda Vargas is a senior at Lehman College, majoring in Geology and minoring in Environmental Science. Her advisor is Dr. Heather Sloan, chair of the EGGS (Environmental, Geographic and Geological Sciences) Department at Lehman. Wanda is participating as a research student in a 35-day marine geophysical expedition to the East Pacific Rise, off the coast of the Baja Peninsula, Mexico. She filed this report for Lehman E-news on March 4, 2007, from the research vessel Atlantis.

We arrived in Manzanillo, Mexico on February 11 to prepare for a 35-day cruise that began on February 13, about 1,000 miles from the west coast of Central America in the area of 9° North of the Equator.

The chief scientist Dr. Sphar Webb of the Lamont-Doherty Earth Observatory in New York and colleague Dr. Wayne Crawford of the Institut de Physique du Globe de Paris, are deploying compliance meters along the axis of the East Pacific Rise, a mid-ocean ridge.

Mid-ocean ridges occur on Earth when two tectonic plates are moving away from each other, causing material to rise from inside the Earth to fill in the new space. About 90% of the volcanic activity on Earth occurs underwater at the sea floor along the mid- ocean ridge, hidden from sight.

The study is focusing on how much of the magma is pooling below its point of eruption and how it is erupting through the open narrow fissure onto the sea floor in this particular area. These instruments measure the minute vertical motion of the Earth's sea floor under long ocean waves passing overhead. The instruments record both the height of the ocean waves (by measuring the changing water pressure) and the acceleration of the sea floor in response to the waves. Gathered data will indicate variations in the distribution of magma within the lower crust, about 1 to 4 miles below the sea floor. These spreading centers shape the ocean's floor as well as contribute to fluid and gas emissions in the deep-sea ecosystem. The goal is to deploy these compliance meters up to 50 times. They are left on the sea floor two days at a time, within these 35 days, throughout a 100 nautical mile length of the mid-ocean ridge (equivalent to 110 land miles).

A secondary study is also taking place conducted by Dr. Marie-Helene Cormier of the University of Missouri and colleagues Dr. Sphar Webb and Dr. Roger Buck of Columbia University.

They are deploying 20 Bottom Pressure Recorders (BPRs) parallel to the same ridge axis and spaced about every 7 kilometers (4.5 miles) from each other.

These devices will remain on the sea floor for a period of three years, recording the vertical motion of the sea floor as well. Vertical motion will be detected by measuring variations in the pressure of the water column above the instruments. The hypothesis is that during a volcanic eruption the sea floor moves up or down by several inches to several feet. The three-year recordings will document how often and where an eruption occurred on the sea floor during that time. These BPRs have been placed on tripods that measure four feet above the ground to keep the device from being engulfed in lava flows, should an eruption occur.

Both research projects are funded entirely by the National Science Foundation.

These experiments are taking place on board the Research Vessel Atlantis, built in 1997 and the third of her namesake. The Atlantis is geared for scientific exploration and equipped with precision navigation, bottom mapping, satellite communication systems, laboratories and working cranes to deploy and retrieve instruments. The Atlantis is operated by the Woods Hole Oceanographic Institute. There are three sister ships: the Oceanus, the Knorr and the Tiogo.

The Atlantis, however, is home to the world-famous manned submersible Alvin. Current information as well as vessel history can be viewed at the Atlantis website.

In addition to the two main surveys, we are conducting CTD Rosette surveys and dredging.

CTD stands for Conductivity, Temperature and Depth. The Rosette are a set of 23 bottles, known as "Niskin bottles," that can be triggered to close at any water depth, capturing water samples for future analysis of its properties. The instrument is also capable of measuring light attenuation in the water that may be caused by the presence of hydrothermal plumes. Light attenuation is a measure of water clarity. Strong light attenuation is expected 200 to 400 meters (600-1200 feet) above the sea floor when superheated water is escaping from hydrothermal vents. Such "hot seeps" are a sign that a magma chamber (a volume of hot molten rock) is present one to two miles below the sea floor. They also are associated with thriving ecosystems.

Two dredges were conducted at the ridge axis.

Samples of the two typical existing lava rock types were collected. The first samples are of the pillow lava type, commonly interpreted as slower lava flow. Judging from their dull appearance, the samples at this particular site may be at least a few decades old.

The second collection recovered lobate lavas, probably indicating a faster lava eruption. These samples are one year old and very "glassy" in appearance.

This is my first experience on board a cruise lasting this length of time. The research is conducted on a 24-hour basis, every day, in order to utilize the ship's time to its fullest. Four-hour shifts are maintained by the science team in order to continuously proceed to the next needed step of the operation. The day does not go by without its perks, however. We have beautiful sunrises and sunsets, Milky Way night skies, warm tropical weather and a 360° view of mesmerizing blue waters.

Adjusting to the rhythm of ship life was easy. Adjusting back to the rhythm of the #4 train will be the hard part.

On this trip, I was generally a research assistant, learning about the engineering process of the instruments as well as the hands-on process of deployment and information gathering. The real excitement for the scientist will be the interpretation of the data back home.

My first research cruise experience was on board the Research Vessel Hugh Sharp back in June 2006, when we conducted multibeam sonar, side-scan sonar and high- resolution sub-bottom profiler (CHIRP sonar) readings. We also retrieved sediment cores, water and benthic samples. The National Science Foundation (NSF) Geosciences Education Program funded this project to increase awareness in students about pursuing careers in the geosciences. I will continue to participate in the analysis of this data, along with the other eight students who worked with the five investigating scientists. More information and photos of this awesome trip can be found at www.explore-the-sound.org.

My next task will be to prepare a poster presentation of my findings on the Long Island Sound for presentation at the American Geophysical Union (AGU) conference in Acapulco, Mexico; in May 2007. Membership in AGU was made possible through my acceptance into the NSF-sponsored M.S.-Ph.D. program, "Minorities Striving and Pursuing Higher Degrees of Success in Earth System Science." This program made it possible for the newest members of AGU to participate in the AGU meeting held in San Francisco last December.

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