mpollock September 26th, 2016
Denver, CO – The Association for Women Geoscientists (AWG) held their annual breakfast at #GSA2016, where they recognized those people who make exceptional contributions to their mission. AWG seeks to encourage the participation of women in the geosciences, exchange information (technical, educational, professional), and enhance professional growth and advancement. After this morning’s inspirational stories, who wouldn’t want to become a member? One notable part of the program was the recognition of women geoscientists from the Mongolian Chapter of AWG.
This year’s Outstanding Educator Award winner was Barbara Dutrow, a renowned mineralogist.
mpollock July 25th, 2016
Wooster, OH – The summer portion of the Keck Iceland project is officially over, but our research isn’t finished. We’ll be working together throughout the academic year and will synthesize our final results at the Keck Symposium at Wesleyan University in April 2017. Along the way, we’ll be presenting at GSA in Denver, Colorado. We wrote and submitted 4(!) abstracts based on our work this summer. Here they are:
NEW INSIGHTS ON THE FORMATION OF GLACIOVOLCANIC TINDAR RIDGES FROM DETAILED MAPPING OF UNDIRHLIDAR RIDGE, SW ICELAND
HEINEMAN, Rachel1, LEMBO, Cara2, ENGEN, Carl-Lars3, KOCHTITZKY, William4, WALLACE, Chloe5, ORDEN, Michelle4, THOMPSON, Anna C6, KUMPF, Benjamin5, EDWARDS, Benjamin R.4 and POLLOCK, Meagen5, (1)Department of Geology, Oberlin College, 52 West Lorain St, Oberlin, OH 44074, (2)Department of Geology, Amherst College, 11 Barrett Hill Dr, Amherst, MA 01002, (3)Department of Geology, Beloit College, 700 College Street, Box 777, Beloit, WI 53511, (4)Department of Earth Sciences, Dickinson College, 28 N. College Street, Carlisle, PA 17013, (5)Department of Geology, The College of Wooster, 944 College Mall, Wooster, OH 44691, (6)Department of Geology, Carleton College, One North College Street, Northfield, MN 55057, email@example.com
Undirhlíðar ridge on the Reykjanes Peninsula in southwest Iceland is a glaciovolcanic tindar formed by fissure eruptions under ice. Previous work in two quarries along the ridge shows that this specific tindar has had a complex eruption history. Here we report new results from investigations along the length of the ridge (~3 km) between the quarries. We have identified aerially significant fragmental deposits and a potential vent area on the ridge’s eastern side. The newly mapped tephra deposits are dominated by lapilli- and ash-size grains that are palagonitized to some degree (~20-60%) but locally contain up to ~75% fresh glass. Basal units are tuff breccia to volcanic breccia with basaltic and rare gabbroic lithic clasts. Upper units are finely bedded with few large clasts and some glassy bombs. Locally, lapilli-tuff units show repetitive normally graded bedding and cross bedding. Measured bedding attitudes suggest that present exposures represent a moderately eroded tephra cone that was subsequently intruded by basaltic dikes. Extending north and south of the tephra cone, the upper surface of the ridge comprises pillow rubble with outcrops of massive basalts showing radial jointing and concentric vesicle patterns. All of the outcrops appear to be similar coarse-grained, olivine- and plagioclase-bearing basalts; ongoing petrographic and geochemical analysis will determine if the bodies represent “megapillows” or if they are related to intrusions that are present in both quarries. Along the western side of the ridge, lapilli tuff and/or volcaniclastic diamictites overlie pillow lava (or volcanic breccia made of pillow fragments) that is locally intruded by dikes. In northern gullies, at least two stratigraphically distinct units of pillow lava are present. In order to communicate the implications of our detailed research to a broad audience, we are constructing two “map tours” of the ridge: one that is centered on the abandoned and accessible Undirhlíðar quarry, and another that describes features along the upper part of the ridge between the quarries. Stops along the tour include exposures of dikes, pillow lavas, and erosional alcoves within the tephra cone. The goal of these tours is to compare similar units across the ridge and quarry and to show the general anatomy of a glaciovolcanic ridge.
PHYSICAL CHARACTERISTICS OF GLACIOVOLCANIC PILLOW LAVAS FROM UNDIRHLIDAR, SW ICELAND
THOMPSON, Anna C1, ORDEN, Michelle2, LEMBO, Cara3, WALLACE, Chloe4, KUMPF, Benjamin4, HEINEMAN, Rachel5, ENGEN, Carl-Lars6, EDWARDS, Ben2, POLLOCK, Meagen4 and KOCHTITZKY, William2, (1)Department of Geology, Carleton College, One North College Street, Northfield, MN 55057, (2)Department of Earth Sciences, Dickinson College, 28 N. College Street, Carlisle, PA 17013, (3)Department of Geology, Amherst College, 11 Barrett Hill Dr, Amherst, MA 01002, (4)Department of Geology, The College of Wooster, 944 College Mall, Wooster, OH 44691, (5)Department of Geology, Oberlin College, 52 West Lorain St, Oberlin, OH 44074, (6)Department of Geology, Beloit College, 700 College Street, Box 777, Beloit, WI 53511, firstname.lastname@example.org
GEOCHEMICAL CONSTRAINTS ON THE MAGMATIC SYSTEM AND ERUPTIVE ENVIRONMENT OF A GLACIOVOLCANIC TINDAR RIDGE FROM UNDIRHLíðAR, SW ICELAND
WALLACE, Chloe1, KUMPF, Benjamin1, HEINEMAN, Rachel2, LEMBO, Cara3, ORDEN, Michelle4, THOMPSON, Anna C5, ENGEN, Carl-Lars6, KOCHTITZKY, William4, POLLOCK, Meagen1, EDWARDS, Ben4and HIATT, Alex1, (1)Department of Geology, The College of Wooster, 944 College Mall, Wooster, OH 44691, (2)Department of Geology, Oberlin College, 52 West Lorain St, Oberlin, OH 44074, (3)Department of Geology, Amherst College, 11 Barrett Hill Drive, Amherst, MA 01002, (4)Department of Earth Sciences, Dickinson College, 28 N. College Street, Carlisle, PA 17013, (5)Department of Geology, Carleton College, One North College Street, Northfield, MN 55057, (6)Department of Geology, Beloit College, 700 College Street, Box 777, Beloit, WI 53511, email@example.com
Glaciovolcanic tindar ridges are landforms created by the eruption of magma through fissure swarms into ice. The cores of many of these ridges comprise basaltic pillow lava, so they serve an accessible analogue for effusive mid-oceanic ridge volcanism. Furthermore, similar landforms have been identified on Mars, and thus they may also serve as models for planetary volcanic eruptions. To better understand pillow formation and effusive glaciovolcanic eruptions, we are investigating Undirhlíðar ridge, a pillow-dominated tindar on the Reykjanes Peninsula in southwest Iceland. Our detailed mapping and sampling in two rock quarries along the ridge and in the ~3 km area between the quarries show that this specific tindar ridge has had a complex eruption history. In the northern quarry (Undirhlíðar), Pollock et al. (2014) demonstrated that at least two geochemically distinct magma batches have erupted. Further trace element and isotope analyses in the southern quarry (Vatnsskarð) suggest that the ridge is fed by a heterogeneous mantle source. Isotopic Pb data show a spatially systematic linear array, which is consistent with a heterogeneous mantle mixing between depleted and enriched endmembers. The occurrence of multiple magma batches in dikes and irregular intrusions suggests that these structures are important to transporting magma within the volcanic edifice. Glassy pillow rinds were sampled for volatile analysis by FTIR in order to determine how paleo-water pressures vary along the ridge. In Undirhlíðar quarry, paleo-water pressures decrease with stratigraphic height (1.6-0.7 MPa). In Vatnsskarð quarry, paleo-water pressures show evidence of two separate eruptions, where pressure values decrease with an increase in stratigraphic height from 1.1 to 0.7 MPa over ~30 m, at which point pressure resets to 1.1 MPa and continues to decrease with elevation. When comparing the two quarries, paleo-water pressures in the upper units of Undirhlíðar and all the units in Vatnsskarð have similar values (0.7-1.1 MPa), and these are lower than the basal units of Undirhlíðar (1.2-1.6 MPa). Overall, compositional variations correlate with stratigraphy and spatial distribution along axis, suggesting that glaciovolcanic eruptions and their resulting landforms show a higher level of complexity than previously thought.
MAPPING OF QUARRY WALLS TO CONSTRAIN THE INTERNAL STRUCTURE OF A GLACIOVOLCANIC TINDAR, SW ICELAND
EDWARDS, Benjamin R.1, POLLOCK, Meagen2, KOCHTITZKY, William1 and ENGEN, Carl-Lars3, (1)Department of Earth Sciences, Dickinson College, 28 N. College Street, Carlisle, PA 17013, (2)Department of Geology, The College of Wooster, 944 College Mall, Wooster, OH 44691, (3)Department of Geology, Beloit College, 700 College Street, Box 777, Beloit, WI 53511, firstname.lastname@example.org
Documentation of the internal structures of volcanoes are critical for understanding how edifices are built over time, especially for glaciovolcanoes, which have rarely formed historically and are inaccessible during eruptions. We have been unraveling the internal structure of a complex glaciovolcanic ridge (tindar) in southwestern Iceland for the past 5 years in order to better understand the sequence of events that built the ridge. Undirhlidar ridge is ~5 km long, and has been dissected by two different aggregate mines along its axis. The northern mine (Undirhlidar quarry) is inactive and has walls up to 40 m in height that fully expose several critical stratigraphic relationships including multiple sequences of separate pillow lava flows, cross-cutting dikes that locally feed overlying pillow flows, and ridge parallel, continuous massive jointed basaltic units that may be the remnants of internal lava supply networks. The second quarry, ~3 km to the southwest (Vatnsskard quarry) is presently active and continually has new exposures. This quarry only penetrates halfway through the width of the ridge but has ~500 m of exposure along strike. It also has remnants of what appears to be the internal magma distributary system, and many components clearly show evidence that they were (and some still are) open lava tubes. While both quarries contain excellent exposures, many of the structures are difficult to safely access or are inaccessible due to mining activity. In order to overcome access issues, we have used Structure-from-Motion techniques to make 3-D maps of the quarry walls. A series of overlapping pictures were taken from points constrained with D-GPS using a Trimble GeoXH data logger and external antennae. The image locations with corrected positions were imported into Photoscan software to create a point cloud representative for each quarry and to derive a Digital Elevation Model with a reported vertical resolution of less than 1 m. Field testing of a preliminary, low resolution DEM shows that measurements of dyke widths on the DEM have errors of ~5% relative to measurements on the ground. Measurements made from the field-generated DEM will provide significantly better constraints on deposit thicknesses and volume estimates compared to traditional methods of estimating unit thicknesses on vertical faces.
mpollock July 21st, 2016
Wooster, OH – If you’ve been following our summer research adventures, you know that Amineh AlBashaireh (’18) has been hard at work studying the compositions of soils around abandoned mines in Black Mountain Open Space Park in San Diego, CA. She wrote the following abstract for the Geological Society of America Annual Meeting in Denver, Colorado this September.
Evaluation of Arsenic Extent and Mobilization in Soil and Vegetation surrounding abandoned, ultra-enriched Arsenic Mines in Black Mountain Open Space Park, San Diego, California to GSA
ALBASHAIREH, Amineh B.1, JOHNSTON, Elizabeth2, O’SHEA, Bethany2 and POLLOCK, Meagen1, (1)Department of Geology, The College of Wooster, 944 College Mall, Wooster, OH 44691, (2)Environmental and Ocean Sciences, University of San Diego, 5998 Alcala Park, San Diego, CA 92110
Black Mountain Open Space Park in San Diego, CA is part of the Santiago Peak Volcanic Formation, a heterogeneous meta-volcanic unit that is locally ultra-enriched in arsenic (As). Small scale, artisanal-type As mining occurred during the early 1920s. Mines were abandoned with little documentation and no obvious remediation efforts. Initial field study by portable XRF yielded As concentrations up to 480,000 ppm in abandoned mines and rock outcrops throughout the park. This study is a first step towards understanding As fractionation in soils surrounding the mines. Twelve samples from the surface 5 cm of soil were collected in a ~48 m2 grid between two of the abandoned mines to determine how As concentration varies spatially, the degree of As mobilization during rain events, and how plants sequester As and affect soil As. Soils were pressed into pellets for analysis via WDXRF, and LOI was used to distinguish between organic and mineral-rich soils. To simulate transport by precipitation, 1:5 DI water leaches were performed on soils for 1 h, 24 h, and 7 day periods. Vegetation (miner’s lettuce, lemonade berry, and fern) was collected from the grid and will be analyzed by SEM-EDS for the extent of As throughout plant roots and bodies. While the crustal average for As is 1.5 ppm, soil concentration of As varies from hundreds of ppm to tens of thousands of ppm between the two mines. Consistent with hypotheses, the two greatest As concentrations occurred in rocky soils, possibly due to the presence of waste rock in the naturally occurring San Miguel-Exchequer rocky silt loam. Vegetation in the area appears healthy, but is not growing consistently across the grid, so SEM data will be compared with soil organic matter content and As concentration. San Diego’s semi-arid climate causes low precipitation and increased rates of soil erosion, making aeolian dispersion a likely mode of As transport. Consequently, there’s a potential health risk for those traveling off trail to visit the mines, hiking along the trails, and living in the canyon outlet. This is the first soil-plant arsenic study in a broader project aimed at understanding potential impact to public health. Additionally, this project has implications for the geologic occurrence of extreme As concentrations in igneous rocks from island arc settings.
After the prescribed leach time, samples are centrifuged and filtered using a syringe fitted with a nylon filter to separate leachate (amber to red liquid above) from soil.
mpollock July 18th, 2016
Wooster, OH – Keck Iceland 2016 by the numbers:
- Scientists in Keck Iceland: 10
- Time in the field: 14 days
- Pillows described in detail: >40
- Samples collected: 71
- Structural measurements made: 94
- Photos taken: >2000
- GPS data recorded: ridiculous
With a few extra charges for baggage fees, and a lot of help from the airport luggage carts, we successfully returned to Wooster to begin processing our samples and photos.
mpollock July 1st, 2016
Reykjavik, Iceland – Guest Blogger Ben Kumpf (’18)
Carl-Lars Engen (Beloit ’17), among thousands of Islanders gathered in the capital, Reykjavik. Fans were cheering on the national team in the Euro Cup round of 16 against England. We were fortunate enough to see one of the biggest upsets of the year as a country with more volcanoes than professional soccer players defeated England 2-1.
mpollock June 26th, 2016
Hafnafjörður, Iceland – Cara Lembo (Amherst), official Keck Iceland 2016 Guest Blogger.
Greetings from rainy Iceland! After spending 4 full days in the field we are spending a rainy day inside discussing projects and compiling our data.
We spent our first day and a half in Iceland inside the Undirhlíðar quarry – an ideal place to observe cross sections of pillow lavas and other volcanic deposits.
After getting a feel for many different types volcanic deposits in the quarry, we headed out to survey the ridge South of the quarry and observe these deposits “in the wild.”
We surveyed the ridge for the next day and a half. Highlights include discovering an unexpected tephra cone and learning how to tell the difference between goats and sheep. According to Ben you say, “Goaty, Goaty raise your tail!”
Once we surveyed the whole ridge, we started our mapping project with a gully on the southwest side of the ridge.
We’ve also sampled some local Icelandic cuisine such as Skyr, chocolate covered licorice and, to Dr. Pollock’s dismay, Harðfiskur (dried fish).
Overall it has been an exciting first week in the field. More to come as we continue working in the field and trying to adjust to the never-ending daylight.
mpollock May 25th, 2016
San Diego, CA – If you’ve been following our adventures, you know that we’ve started a project on Black Mountain with our collaborators at the University of San Diego. We’ve dedicated a significant portion of our time in California to sample preparation, and today we see the results of all of our hard work.
In order to address our research questions, we need to understand the compositions of the minerals, rocks, and soils that are present at the field site. To analyze mineral compositions, we are using a scanning electron microscope equipped with an energy-dispersive detector (SEM-EDS). The electron beam interacts with a polished rock specimen to produce characteristic X-rays. The detector separates those X-rays by energy, correlates the energy to specific elements, and maps the distribution of elements in the sample. This technique allows us to determine the compositions of individual minerals in our rocks.
To analyze the bulk compositions of our soil samples, we’re using a benchtop X-ray fluorescence spectrometer (XRF). The XRF uses an X-ray beam to generate X-rays from the samples. The generated X-rays are characteristic of specific elements, which the XRF measures and compares to a calibration curve to calculate a concentration. This XRF model is equipped with several modes for analyzing soil or ore samples and allows us to analyze bulk compositions without destroying the sample.
mpollock May 24th, 2016
San Diego, CA – Thinking like a scientist is a challenging and important learning goal for the Wooster Geologists, and one of the primary reasons that we engage our students in undergraduate research. Although science is often portrayed as a collection of facts or as a series of exercises designed to prove something that is already known, our research students learn that science is a way of thinking. It is a method of inquiry that involves creativity, examining a question from multiple perspectives, and understanding uncertainty. Science requires hypotheses that are testable, data that can be collected and interpreted, and explanations that are supported by evidence. Today, our Black Mountain research group focused on these aspects of science as we developed our research goals and plans for the rest of the summer.
Eventually, we developed a couple of research questions that Amineh will be able to address this summer. We formulated hypotheses for the answers to these questions and designed a research strategy that will generate the data necessary for testing our hypotheses. In the end, we created a research plan that is both achievable (given the constraints of time, expertise, resources, etc.) and flexible enough to allow the research to evolve as Amineh discovers new findings and develops new questions.
For an excellent resource on the process of science, check out the Visionlearning module by Anthony Carpi and Anne Egger. It’s an incredible resource for teachers and students alike.
Carpi, A., and Egger, A.E. 2009. The process of science. Visionlearning POS-2 (8).