Gaines Wins Wig Award
We are delighted to announce that Associate Professor of Geology Robert Gaines was selected to receive a 2013 Wig Award for Exceptional Teaching, the highest form of teaching accolade that the College bestows. Wig Award winners are selected each year by the college’s Junior and Senior classes, and receiving the award is a cherished honor. Heartfelt congratulations Bob!
Majors Earn Fulbright & Goldwater
March 2013 brought the wonderful news that two of our majors won prestigious awards!
Lorelei Curtin (PO’13, from Edina, MN) was awarded a Fulbright Fellowship for 2013-2014. For her graduate project, she will spend the year at the University of Otago in Dunedin, where she will study sediment cores from lakes in the Fjordlands region of the South Island, to assess the effect of the Southern Hemisphere westerly winds on the hydrology of New Zealand.
Kyle Metcalfe (PO’14, from Santa Rosa, CA) was awarded a Goldwater Scholarship for 2013-14 to study the process of microbial extraction of iron from clay minerals in seafloor sediments. Kyle’s award makes it two consecutive years that a Geology major has earned a Goldwater award, with Ben Murphy (PO’13) earning one to study volcaniclastic sedimentology in the Long Valley Caldera.
Congratulations to Lorelei and Kyle on their outstanding accomplishments!
Geology Department Colloquium, April 4th
Speaker: Alexandra Davatzes (’99), Temple University
Title: “The Earth During the Extended Late Heavy Bombardment”
Please join us: Thursday, April 4th @ 11AM in Edmunds 130
Abstract: Three processes fundamentally shaped the early Earth: the Late Heavy Bombardment, the onset of plate tectonics, and the early evolution of life. During this time, these three processes overlapped and influenced each other in fundamental ways that are ultimately responsible for the transition to the modern environment. They have largely been studied through models, but analyses of Archean rocks preserved on Earth document the results and interplay of these processes.
I will discuss evidence of large meteor impacts, in the form of what are termed spherules, preserved on the Earth from 3.5 to 2.5 billion years ago. The frequency, scale and geochemistry of these spherule layers indicate that the Late Heavy Bombardment was longer than initially believed, extending all the way through the Archean. In addition, the geochemistry of these layers retains a record of crustal and atmospheric chemistry at the time, giving us a window into what the early Earth was like.
Geology Department Colloquium, March 5th
Speaker: Anita Grunder, Oregon State University
Title: “Cause and effect of High Lava Plains volcanism, Oregon: Modification of the crust in an enigmatic tectonic setting”
Please join us: Tuesday, March 5th @ 11AM in Edmunds 130
Abstract: The High Lava Plains of Oregon are an enigmatic volcanic province spanning from Miocene to Recent. Rhyolites of this bimodal province are successively younger to the west and so make a mirror image to the volcanic track of the Yellowstone hotspot. The High Lava Plains lie at the northwestern boundary of the Basin and Range extentensional province and in the back arc of the Cascades, further complicating the tectonic setting. Although located in a continental setting, basalts of the High Lava Plains have affinity with oceanic rift basalts.
Exploration of the compositional variation of basalts and rhyolites in and around the High Lava Plains reveals evidence for creation of an increasingly mafic continental crust. Rising basalts modify the overlying crust by intrusion and by leaving mafic residua of differentiation as inferred from petrologic modeling. Protracted mafic intrusion also leads to crustal melting and more mafic crust yields more iron-rich rhyolites. The basaltic magmatism is driven by shallow melting of the mantle welling up in the wake of the Juan de Fuca Plate as it rolls back and steepens beneath Cascadia.
33rd Woodford Eckis Lectureship, Feb 13-14
The Geology Department is pleased to announce that the 33rd annual Woodford Eckis lectureship will be held on February 13th and 14th, 2013. This year’s honored guest, Dr. E. Bruce Watson, is the Institute Professor of Science at Rensselaer Polytechnic Institute, a geochemist and materials scientist whose experiments have helped shape our current understanding of conditions deep within the Earth.
Please join us!
FEBRUARY 13th
At 8:15 PM in the Rose Hills Theater (Smith Campus Center), Dr. Watson will deliver a lecture entitled “The environment of earliest Earth: decoding the oldest zircons.” This talk is intended for a general audience, and is open to the public.
FEBRUARY 14TH
At 11AM in the Rose Hills Theater (Smith Campus Center), Dr. Watson will deliver a lecture entitled “Growth-rate effects on crystal composition: from phenocrysts to climate proxies.” This talk, while intended for a somewhat more technical audience, is also open to the public.
Full abstracts for both talks are provided below. For more information about Dr. Watson’s research and illustrious career, please visit his home page.
The environment of earliest Earth: decoding the oldest zircons
The time period in Earth history between 4.0 and 4.55 billion years ago is referred to as the Hadean Eon. Little is truly known about this interval of Earth history, but it is widely regarded as an energetic and defining period in our planet’s history. In recent decades, researchers have inferred that during this time period the Earth collided with a Mars-sized-object, formed a deep magma ocean, grew the first continents, suffered cataclysmic bombardment from space, and nurtured the emergence of life. However—given the limited geochemical record from this time—we must acknowledge that our perception of these events may be inaccurate and/or incomplete. The challenge is that we have essentially no rock record from this interval from which to gain direct insight into these processes (the oldest firmly dated terrestrial rock is “only” 4.06 billion years old).
Prof. Watson will provide a summary of the evidence gleaned over the past decade from 4+ billion-year-old zircons from Western Australia supporting the view that continental crust was already fully developed, plate tectonic-style recycling was well underway, and liquid water was present on Earth’s surface during the Hadean. The “zircon thermometer” developed at Rensselaer has led to the understanding that most Hadean zircons crystallized at temperatures consistent with those achieved during water-saturated melting of crustal rocks in processes not unlike those of more modern times. Zircon “oxygen barometry” suggests, further, that magmatic gases streaming into the Hadean atmosphere were much like today’s H2O-CO2-SO2-dominated volcanic emanations¾and unlike the methane-dominated, reduced assemblage hypothesized by earlier researchers. These findings may bear on the suitability of earliest Earth for complex organic molecules and life itself.
Growth-rate effects on crystal composition: from phenocrysts to climate proxies
The equilibrium compositions of minerals provide the principal means of gaining insight into the environment of mineral formation (T, P, fO2, pH, PCO2) and, indirectly, the conditions and dynamics of Earth systems. Applications cut across many disciplinary boundaries in the geosciences, including high- and low-T geochemistry, petrology, tectonics, paleoceanography and paleoclimate studies. In some instances, however, there is reason to be cautious in our assumptions about equilibrium. Rapid crystal growth can result in significant deviations from equilibrium between a crystal and its growth medium with respect to trace elements and isotope ratios. There are multiple potential causes of this “failed equilibrium” that do not require growth that is rapid in an absolute sense. Broadly speaking, the causes of non-equilibrium growth are traceable to dynamical phenomena occurring at or near the interface between the growing crystal and its surroundings. Prof. Watson will discuss these causes in the context of experimental measurements and theoretical considerations, emphasizing the need for fundamental understanding, as well as the optimistic view that minerals will continue to serve us well in illuminating natural processes.
Grosfils Ponders Pit Chain Patterns
– pit crater chains in Iceland (from Fig 3. of Ferrill et al., 2011)
In a 2013 Canadian Journal of Earth Sciences paper Prof. Grosfils — with colleagues Sarah Davey (first author), Richard Ernst, and Claire Samson (all at Carleton University) — presents an analysis of pit crater chain clustering in selected areas of Venus in an effort to improve our understanding of the volcanic and/or tectonic conditions under which pit crater chains form. After comparing pit crater chain morphologies and clustering characteristics with mapped structures and geomorphological units in areas such as the Ganiki Planitia (V-14) quadrangle, mapped previously with the aid of Pomona College geology students and other colleagues (Grosfils et al., 2011), we propose that pit craters form above extensional graben covered with friable, most likely volcaniclastic material. While this hypothesis requires further testing, our results are quite exciting as it is difficult to detect such materials on Venus using available Magellan radar data. If the proposed link between surface materials and pit crater chains can be confirmed, it would yield a powerful new tool for advancing our understanding of Venusian volcanism and contribute to our general understanding of pit crater chains: an enigmatic feature observed on numerous planets and moons in the inner and outer solar system.
For more information: Hierarchical clustering of pit crater chains on Venus
Students: Want to get involved in planetary research? Please stop by!
Geology Department Colloquium, Jan. 31st
Speaker: Maria Prokopenko, Pomona College and USC
Title: “Being a walrus in the warming oceans – Using oxygen triple isotopes and O2/Ar ratios to determine factors controlling carbon export production in spring blooms on the Bering Sea shelf”
Please join us: Thursday, January 31st @ NOON in Edmunds 130
Abstract: The ongoing climate change and decline in sea-ice cover observed over the last few decades have been implicated in driving large scale changes in high-latitude ecosystems. It has been proposed that on the eastern Bering Sea shelf, which hosts one of the world’s most productive biological ecosystems, the decline in the winter ice extent and duration weakens benthic-pelagic coupling, driving the decline of benthic biomass, and affecting bottom dwelling communities. However, mechanistic understanding of environmental factors driving the observed changes is currently lacking.
To address this issue, we constrained the rates of Net Community and Gross Photosynthetic Production in spring phytoplankton blooms in the marginal ice zones on the Bering Sea shelf using O2/Ar supersaturation and oxygen triple isotope composition of the dissolved O2. Linking the observed rates of biological production to water column hydrography we found that the depth of the mixed layer exerts direct control on the biological carbon export efficiency of the algal blooms on the Bering Sea shelf.
The depth of the mixed layer has been previously linked to the extent of winter ice cover and the timing of ice retreat, thus the relationship between the rates of Net and Gross biological production and the mixed layer depth observed in our study provide a possible missing link between the seasonal ice dynamic and the carbon flow through the eastern Bering Sea shelf ecosystem.
Geology Department Colloquium, Nov. 15th
Speaker: Glenn Kroeger ’77, Trinity University
Title: “Great Earthquakes and Great datasets”
Please join us: Thursday, November 15th @ 11AM in Edmunds 130
Abstract: Great and mega-earthquakes have been arguably more prevalent in the last decade than in the preceding few decades. This coincides in time with the near real-time availability of high quality and densely sampled seismic data from arrays such as the USArray Transportable Array Observatory are shedding new light on the spatial and temporal characteristics of earthquake rupture processes. The ability of the seismological community to rapidly and accurately characterize such events has consequently improved over the same period of time, and geoscientists are now regularly served with detailed source characteristics of a recent earthquake within several hours of the event occurring.
Magnitude is a commonly known but limited way of characterizing the size of an earthquake. Seismic moment and fault rupture models are physical quantities that better characterize the tectonic significance and societal hazards of earthquakes. I will review these and other characterizations of earthquake source processes and discuss some of the fascinating results from the Mw9.0 Tōhoku Japan earthquake on 11 March 2011 and the remarkable Mw8.6 and Mw8.2 Northern Sumatran earthquake pair of 11 April 2012.
How can you avail yourself of these results? Raw seismic data as well as an ever-expanding portfolio of end user data products are made available by the IRIS Consortium Data Management System. I will demonstrate some of the tools available to access this data and some of the exciting data products that are now available to the geoscientific community.
Geology Department Colloquium, October 18th
Speaker: Len Eisenberg
Title: “Giant Stromatolites, Mass Flows and Fluid Escape Structures, Navajo Sandstone, Capitol Reef National Park, Utah”
Please join us: Thursday, October 18th @ 4PM in Edmunds 130
Abstract: Thick interdune sections at three separate but co-genetic outcrops are characterized by the presence of large (to 6m) stromatolites, and an overlying mass flow (to 28m), which contains clasts of interdune dolomite up to 12m long. Huge fluid escape structures (to 20m) extend upward from the interdune section to near the top of the mass flow.
A depositional model for these spectacular outcrops envisions 1) a high water table associated with a dune-dammed paleodrainage in a stabilized Navajo erg, 2) growth of large stromatolites on sunny south-facing sides of interdune lakes, 3) creation of a mass flow by catastrophic failure of a dune dam, 4) loading of saturated interdune sediments by the sudden arrival of the mass flow and creation of large fluid escape structures.
A good modern analogue exists in the Namib sand sea. The Navajo outcrops suggest that 1) terrestrial floods played a significant role in Navajo depositional history, 2) dam breach events and consequent rapid changes in water table may have engendered some forms of convoluted bedding and 3) widespread, isolated but co-genetic flood deposits could be useful for correlation within the Navajo Sandstone.
2012 Dept. Fieldtrip: Pinnacles NM to Morro Bay
GEOLOGY DEPARTMENT ANNUAL FIELD TRIP: PINNACLES NM TO MORRO BAY, SEPTEMBER 21-23, 2012
Geology students and faculty enjoyed a two night excursion, exploring The Pinnacle National Monument and the central Californian coastline. The group drove through the central California Valley, examining geomorphology, tectonics and economic geology on the way to the Pinnacle National Monument. Students took a spectacular walk through the talus caves and volcanic breccias before reaching the summit, seeing California Condors in their native habitat. Driving down the coast the group was treated to blueschist exposures, amazing scenery and sedimentary deposits at Point Lobos State Reserve, along with stunning views along the Pacific Coast Highway before setting up camp in Morro Bay and heading home via exposed pillow lava ophiolite sequences in Point San Luis.