Science Workshop: Magmatism vs. Tectonism: The key to understanding slow spreading mid-ocean ridges

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Dr. John getting ready to dive to the Mid-Atlantic Ridge in the Alvin Submersible

On Friday April 24, Dr. Barbara John from the University of Wyoming will present several aspects of her work at Science Workshop. Dr. John has done groundbreaking work in understanding extensional plate boundaries across the globe, and has most recently focused on investigating dynamics of slow-spreading mid-ocean ridges. Come and learn about how to conduct geologic research beneath several thousand meters of seawater, and what we are learning about Earth’s last frontier.

FWT – Claire Ricks in Germany

Spell check seems to think Geomicrobiology isn’t a real thing. But let me tell you, after spending six weeks totally immersed in helping research little microbes interacting with different minerals, it’s a real thing. This FWT, I was in Germany interning with the Geomicrobiology department at the University of Tuebingen, each week working with a different postdoc or PhD candidate. I also attended weekly seminars in the geosciences and took a few classes studying iron oxides (all in English).

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Collecting lake sediment samples for lab experiments – cold work in the German winter.

Although I wasn’t conducting my own primary research in Geomicrobiology, I learned a ton working with real-life scientists. Depending on the day and project, I regularly made chemical solutions for different media, worked in a nitrogen glovebox to prepare and conduct anoxic experiments, and used many different electrodes to test redox potential of different samples. I learned how to use some really neat instruments, like the Scanning Electron Microscope (SEM) along with X-ray Diffraction (XRD) and Energy Dispersive X-ray (EDX) imaging, Mössbauer Spectroscopy, and microscopes that detect fluorescence. The SEM uses electron diffraction to get ridiculously cool images on a very small scale—sometimes 1 nm!; the XRD and EDX probes on the SEM test for crystal structures and the chemical composition of specific spots on samples.  I was fortunate enough to be able to conduct basic tests and imaging on my own using these devices—with supervision, of course.

            I not only picked up some new hardware skills, but also learned so much about cutting-edge research on topics that really interest me.  For example, one week I was shadowing a PhD candidate studying biochar, charcoal used as a soil additive in compost, as a means to reduce greenhouse gases in the atmosphere by holding it in the wooden structures of the biochar pieces.  In particular, he was studying the nitrogen cycle and how microcosms living in the biochar ­— made from sewage slush and beach wood in different kilns—might reduce methane and nitrous oxide coming from the atmosphere, compost, and other agricultural processes. Another week, I worked with a new postdoc on microbially meditated reactions in the biogeochemical iron cycle.  We took a field trip to collect soil core samples and water from a lake in southern Germany to use as media to test the growth of iron oxidizing bacteria.  All of her work was anoxic to control for the chemical oxidization of ferrous iron. I also spent one week with a geology PhD student who is researching the effects that microbes had on Banded Iron Formations of the Precambrian Era and the “Great Oxidation Event”, which oxidized much of the ferrous iron in the environment.

            Overall, I’d say this was the most informative and educational experience I’ve had in science yet. I now can question certain scientific research and how it was conducted, as well as read science papers and visualize what the author is saying. I even became more certain of my studies in geology and it gave me ideas for my senior work in the future!

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Enjoying a German treat after a hard day of science

 

Public Physics Experiment – Trebuchet vs. Potato Cannon

Wednesday Oct. 29 at 2:30 PM, on the Dickinson patio, the Physics I class will attempt to resolve a long-standing scientific debate: Which device can impart more kinetic energy to a vegetable projectile?

A medieval trebuchet launching a pumpkin,

OR

A modern hairspray-powered PVC potato cannon

The trebuchet is powered by dropping a 110 kg concrete block, while the potato cannon is powered by a little bit of flammable vapor.  Which will you bet on?

Come and help us to resolve this important scientific quandary.

Geology of the Bennington region class enjoys a beautiful fall field trip

kelly_stand1The Geology of the Bennington Region class examines Precambrian bedrock along Kelly Stand Road in the Green Mountains. This road re-opened a just few weeks ago after having been completely destroyed by the Tropical Storm Irene flood over three years ago. We are very happy to have the road back with its easy access to the mountains. While the flood was tragic, we were excited to find that it scoured several new excellent bedrock exposures along the newly reconstructed road. It is always nice to take a field trip on a beautiful fall day.

 

Science Workshop Friday September 12 – Olivine carbonation and climate change

On Friday September 12 Tim Schroeder will present a part of the research that he did while on sabbatical at the University of Bremen, Germany.

Olivine is the most abundant mineral in Earth’s upper mantle. When it is exposed at Earth’s surface by faulting, it tends to be oxidized to form a number of different possible mineral species that are more stable near Earth’s surface. One possible chain of reactions consumes carbon-dioxide to form solid carbonate minerals. It may be possible to harness this reaction path to absorb much of Earth’s excess atmospheric carbon. Tim studied carbonate minerals formed during hydrothermal circulation through olivine-bearing oceanic crust in order to understand this process.

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This image was taken through a polarizing light microscope. It shows small cores of olivine (Ol) grains that have mostly been replaced by talc (Tlc) and calcite (Cal). Other minerals are present in the rock, including clinopyroxene (cpx) veins of celadonite (Cel)

 

Where is Tim?

Tim Schroeder analyzing mid-ocean ridge rocks on the University of Bremen's electron microprobe

Tim caught in the act of working on sabbatical. Here I am analyzing mid-ocean ridge rocks on the University of Bremen’s electron microprobe

 

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This is a part of a core-storage room at the Bremen Core Repository. You accumulate a lot of rock and sediment in 40+ years of scientific drilling. This room is kept at just above freezing temp. More sensitive cores are kept well below freezing in a separate room.

Greetings fellow Benningtonians. I am missing you all, but am having a happy and productive sabbatical in Bremen, Germany.

Contrary to some reports, I have been up to more than touring and sampling food & drink. Though, I have done a good amount of that. You might ask, why did Tim go on sabbatical to the drizzly, wind-swept plains of northern Germany, ~150 km from the nearest rock outcrop. This is a fair question.

About 15 years ago I began studying major faults at mid-ocean ridges, which are the centers from which new ocean crust is generated in Earth’s ocean basins. These faults very similar to faults in the regions of the southwestern US that I had previously worked. I participated in several research cruises that sampled rocks from the Atlantic seafloor, and discovered interesting parallels between fault activity at mid-ocean ridges and continental rift zones. I have subsequently become interested in how fluids and magma use these faults as conduits to exchange ions between ocean crust and seawater. This activity may be an important control on global seawater chemistry and the carbon cycling.

A logging table at the Bremen Core Repository. This is where I have been spending a good amount of time examining samples drilled at the Mid-Atlantic Ridge over the past 40 years.

A logging table at the Bremen Core Repository. This is where I have been spending a good amount of time examining samples drilled at the Mid-Atlantic Ridge.

My interests led me to my current collaboration with the “Petrologie der Ozeankruste” group at the University of Bremen. The faculty and researchers in this group study how ocean crust forms and how its composition evolves over time as it migrates away from mid-ocean ridges. The Hanse-Wissenschaftkolleg institute (HWK), which is a collaborative research center sponsored by the German states of Lower-Saxony and Bremen, awarded me a fellowship to pursue this collaboration. We are housed in an apartment on the HWK campus, and I have been riding my bike and/or trains about 20 km to the University of Bremen from here.

The University of Bremen also houses MARUM, the Germany Marine Environmental Sciences Institute, where scientific rock drill core from the Atlantic Ocean is archived. This is a wealth of rock samples drilled over a 40-year period by the international research community, including the Deep Sea Drilling Project, Ocean Drilling Program, and the Integrated Ocean Drilling Program.

I have been visiting the core repository and examining rocks sampled during several cruises that drilled holes penetrating into the deep oceanic crust. My sampling proposal allows me to collect samples from the core for detailed analyses. For me, this includes performing chemical and isotopic analyses of individual mineral grains to learn about the origins of the fluids from which the minerals precipitated, and how the history of faulting is related to fluid movement through the oceanic crust.

When not working, I have been enjoying the culture of northern Germany. Bremen is an amazing city with interesting history, architecture, and culture. There always seems to be something going on here, and the locals are always out doing things no matter how awful the weather is. Overall, my family is enjoying a change of pace from peaceful North Bennington.

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Here Karen and I are enjoying one of Bremen’s fine biergartens at the “Schlachte” promenade along the River Wesser. This was in August; Bremen looks nothing like this at the time of posting.

Science Workshop Friday March 8 – How to study processes in the lower crust

To find the right rocks, sometimes you need to go to out-of-the-way places

Xenoliths (foreign rocks) are pieces of rock that were brought from the lower crust or upper mantle by ascending magma. Xenoliths occurrences are one of the few places that we can obtain samples from this zone, and therefore provide some of the only insights into the places where a lot of the geologic phenomenon that we see at the surface actually happens. Tim Schroeder has been studying xenolith-rich lava deposits in Arizona, and will share some insights into what can be learned about the history of western North America from a few tiny little bits of rock.

Xenoliths in a lava outcrop in Chino Valley, AZ

Investigating the source of natural arsenic contamination in Vermont’s groundwater

Senior Nora LaCasse is spending her Field Work Term this year working on an independent study project that investigates the cause of natural arsenic contamination in Vermont’s groundwater.

Parts of the Taconic Mountains of Vermont have naturally elevated levels of arsenic in groundwater, which is a significant public health concern. The source of the arsenic is pyrite minerals within the the Taconic slate rock. When the pyrite is oxidized (rusts), the arsenic is liberated, and may either be absorbed onto the surface of iron oxide or clay minerals, or may go into solution with the groundwater. A study performed by Middlebury College students and the Vermont Geological survey outlined areas of highest concern. This and other studies indicate that the amount of dissolved oxygen in groundwater plays a role in determining whether arsenic ions are absorbed to mineral surfaces or released into solution.

The first step of Nora’s investigation is to perform laboratory experiments on the ability of the minerals in the Taconic slates to absorb arsenic from solution under differing oxygen concentrations. She crushed samples of Taconic slate in order to increase the available surface area for absorption, then added the rock powder to a arsenic solutions of known concentration. These are being stirred under both oxygen-rich and oxygen-depleted conditions and under a range of imposed pH conditions. After stirring for several days, the solutions will be re-analyzed to determine if the arsenic concentration has decreased. Later phases of the study will test arsenic-rich slate samples to determine under what conditions arsenic is de-sorbed and released to solution.

Nora with her experiment setup