Geology of the Mid-Atlantic Ridge

Geological Society of Minnesota 

GSM LECTURE, MONDAY, APRIL 6, 2009

At The University of Minnesota

Geology of the Mid-Atlantic Ridge

William E. Seyfried, PhD, Professor, Department of Geology and Geophysics, University of Minnesota

Date:  Monday, April 6, 2009      Lecture Begins:  7:30 PM

Location:  The University of Minnesota, East Bank, Electrical Engineering/Computer Science Bldg., Room 3-210

ABSTRACT: 

Seafloor Hydrothermal Activity in the Pacific and Atlantic Oceans:  

Geological Controls and Associated Chemical and Biological Processes

Hydrothermal activity has been known to occur on the seafloor at mid-ocean ridges, especially in the eastern Pacific Ocean where the ridge (East Pacific  Rise) is fast-spreading.  Heat from sub-seafloor magmatic activity and associated seafloor volcanism drives hydrothermal convection. This heat also supports rich faunal communities that derive their energy for life not from the sun, since at seafloor there is no light, but rather from the chemistry of the hydrothermal vent fluids.  Magmatically driven hydrothermal vent fluids in the eastern pacific can reach temperatures as high as 400 degrees C.  The relatively frequent volcanic eruptions add to the chemical, physical and biological diversity of hydrothermal vents in the eastern Pacific.

In contrast, it has been long assumed that the mid-ocean ridges in the Atlantic Ocean (Mid-Atlantic Ridge) would not be associated with hydrothermal venting, because of the slow rates of seafloor spreading and correspondingly slow and intermittent magmatic/volcanic activity.  Recently, however, our group from the Department of Geology and Geophysics at the University of Minnesota participated in a research cruise (R/V Revelle) with the submersible ROV (Remotely Operated Vehicle) Jason 2 to study the seafloor along sites on the Mid-Atlantic Ridge.  Surprisingly, numerous hydrothermal vents were recognized and explored.  The vent fluids and associated biological communities are distinct from their better studied Pacific Ocean counterparts.  The vent fluids tend to be briny, although the temperatures are still high (~400 degrees C), while the animal communities are characterized by swarms of shrimp, not the now famous tube worms at analogous vent sites in the Pacific.  Apparently, the tectonically active mid-Atlantic ridge creates fractures and cracks in the ocean crust that allow seawater-derived fluids to "mine" heat from the lower crust and mantle, before venting.  Thus, in spite of the limited magmatic activity, high-temperature hydrothermal activity is still widespread.  The lecture will compare and contrast the effects of hydrothermal activity in the Atlantic and Pacific Oceans. The types of modern exploration technologies to study the seafloor at ridges will also be discussed.

EDUCATION: 

Ph.D., 1977, University of Southern California

RESEARCH INTERESTS:

My main research interests involve assessment of geochemical processes responsible for the chemical evolution of aqueous fluids in and on the Earth. Thus, I study mineral dissolution and precipitation processes together with the reaction rates of minerals in complex aqueous fluids at a wide range of temperatures and pressures. 

Development of chemical sensors to measure dissolved gases and pH of fluids issuing from hydrothermal vents on the seafloor. 

The origin of dissolved gases and pH in hydrothermal vents in Yellowstone Lake, Wyoming. 

Experimental investigation on abiotic hydrocarbon formation with mineral catalysts in subseafloor hydrothermal systems.

Collaborative investigation on experimental controls on biogeochemical processes at deep-sea vents.

Experimental and theoretical constraints on the chemical evolution of hydrothermal vent fluids at mid-ocean ridges. Recent studies have focused on (1) Controls and heat and mass transfer in ultramafic-hosted hydrothermal systems; and (2) Solubility controls on redox and metal mobility in subseafloor hydrothermal systems. 

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Here is a short interview with Professor Seyfried, during an expedition in 2005 in the Pacific Ocean:

Where did you grow up, and how did this place influence your interest in ocean science?

I grew up in East Northport, N.Y. with easy access to Long Island Sound and the Atlantic Ocean. Certainly I enjoyed the ocean and had many great experiences sailing, swimming, and fishing.

Did a moment or event occur when you thought “a-ha, I know that I want to be a scientist?”

A single light bulb did not pop on for me. Rather, my interest in science continued to grow during college. Following graduation I had an opportunity to spend the summer at the Woods Hole Oceanographic Institution as a summer student fellow. This involved a cruise to the Indian Ocean on the long-decommissioned research vessel Chain. Working at sea on a daily basis with some great scientists motivated me to attend graduate school.

Who was most influential person in your career, and why?

I think my parents, Ann and Bill Seyfried, and my teachers had the greatest impact on my career. My parents provided the early encouragement and learning environment so critical to the development of a “scientific personality.” Science teachers, including my doctoral thesis advisor, Dr. James Bischoff at the University of Southern California, instilled in me the love of inquiry and the confidence to pursue scientific problems in need of solutions, no matter how difficult they appeared. Also, my wife Carol has been a great support person. She has contributed significantly to my scientific evolution with her encouragement and continual interest in my work.

You mentioned developing a “scientific personality.” In your view, what personality attributes should I think about developing if I am considering becoming a scientist?

I would include perseverance, motivation, and the desire to ask lots of questions about things you don’t understand.

What is your role on this cruise?

My group and I are involved with chemical measurements of hydrothermal vent fluids. An enormously challenging goal is to develop and deploy instruments that observe and monitor vent fluid chemistry over weeks and months, if not longer. Although this research is still in its early stages, we are hopeful that each opportunity to test the new instrumentation at vents will allow progress to be made in the development of better chemical sensors that are used in remote areas of the oceans.

What makes you excited to be a scientist?

I get excited about things we don’t know. You could call this being involved in opportunities for discovery. I especially enjoy figuring out new ways of testing nature.

How do you test nature?

The natural world is complex and often requires that we work on simpler parts. For example, at the University of Minnesota I often try to conceive of imaginative lab-based studies, where we can control variables of water, such as temperature and pressure, and provide new approaches to measure things in the lab and nature. This helps us to bring together the simple parts to form the complex, big picture.

What has been your most fascinating moment in the science discovery process?

I am not sure that I can point to a single moment. My 30-year journey in science has been fulfilling. I have long been fascinated by the complexities of nature and how one event, or part, can influence many others, all of which need exploration to develop an accurate picture of what is really going on. The recent discoveries at deep-sea vents (just about 30 years ago) where the worlds of geology, chemistry, biology and physics came together, not only illustrate the complexities of nature, but the need for interdisciplinary approaches for future discoveries. In other words, we researchers have to act as a team if we are going to answer some of the more challenging scientific qu