April 2, 2019

3:30 p.m. - 4:30 p.m.
3656 Geology

Presented By: Rob Wesson,
Scientist Emeritus - U.S. Geological Survey (USGS)

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Darwin’s First Theory: Exploring Charles Darwin’s Quest to Find a Theory of the Earth

Everybody knows―or thinks they know―Charles Darwin, the father of evolution and the man who altered the way we view our place in the world. But what most people do not know is that Darwin was on board the HMS Beagle as a geologist―on a mission to examine the land, not flora and fauna. Or about Darwin’s seminal role in demonstrating and exploring the ups and downs of the Earth’s crust. Darwin focused on what we now call tectonics. This is the story told in Rob Wesson’s book, Darwin’s First Theory, and that he will share with us. Retracing Darwin’s footsteps in South America and beyond, Rob trekked across the Andes, cruised waters charted by the Beagle, hunted for fossils in Uruguay and Argentina, and explored sites of long vanished glaciers in Scotland and Wales. As he followed Darwin’s path―literally and intellectually―he experienced the land as Darwin did, engaged with his observations, and tackled the same questions Darwin had about our ever-changing Earth. Upon his return from his five-year journey aboard the Beagle, after examining the effects of earthquakes, tsunamis, volcanic eruptions, and more, Darwin conceived his theory of subsidence and uplift‚―his first theory. These concepts and attitudes―the vastness of time; the enormous cumulative impact of almost imperceptibly slow change; change as a constant feature of the environment―underlie Darwin’s subsequent discoveries in evolution. And this peculiar way of thinking remains vitally important today as we enter the human-dominated Anthropocene age. As the New York Time Book Review wrote, Rob’s book “dares, thank goodness, to work some of the rare Darwinian territory that is actually underexplored. Tracing the young Darwin’s tracks …Wesson relates how Darwin hatched his first, favorite, and most overlooked substantive theory, on the origins of coral reefs. In both method and vision—imagining forms changing slowly over time in response to changing conditions—this precocious, even audacious idea anticipated and possibly inspired the theory of evolution Darwin would publish two decades later.”

April 9, 2019

3:30 p.m. - 4:30 p.m.
3656 Geology

Presented By: Allen Glazner,
University of North Carolina at Chapel Hill (UNC)

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A Twenty-First Century View of Plutons

Granite plutons are fundamental building blocks of the Earth’s crust, and most non-plutonic rocks descended from plutonic ancestors. The centuries-old textbook understanding of plutons, reinforced by myriad “big red blob” cartoons, is that they are the frozen remains of rapidly intruded, km-scale tanks of magma, and that such tanks underlie active volcanoes. In this talk I will argue that this central concept about the Earth is contradicted by a growing body of data from multiple fields; that big-red-blob cartoons are misleading and pernicious; and that, therefore, many of the underpinnings of petrology need to be rethought. Oh snap! Recognition that plutons are emplaced in small increments and that most are heavily modified by a metamorphic overprint reconciles pluton geology with geochemical, geochronologic, geophysical, and geodetic data and with volcanology. It is time to move beyond big red blobs.

April 16, 2019

3:30 p.m. - 4:30 p.m.
3656 Geology

Presented By: Sarah Horst,
Johns Hopkins University

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Planets in a Bottle: Exploring Planetary Atmospheres in a Lab

From exoplanets, with their surprising lack of spectral features, to Titan and its characteristic haze layer, numerous planetary atmospheres may possess photochemically produced particles of "haze". With few exceptions, we lack strong observational constraints (in situ or remote sensing) on the size, shape, density, and composition of these particles. Photochemical models, which can generally explain the observed abundances of smaller, gas phase molecules, are not well suited for investigations of much larger, solid phase particles. Laboratory investigations of haze formation in planetary atmospheres therefore play a key role in improving our understanding of the formation and composition of haze particles. I will discuss a series of experiments aimed at improving our understanding of the physical and chemical properties of planetary atmospheric hazes on Titan, Pluto, super-Earths, and mini-Neptunes.

April 23, 2019

3:30 p.m. - 4:30 p.m.
3656 Geology

Presented By: Krista Soderlund,
University of Texas in Austin

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Ocean dynamics of outer solar system satellites

The outer solar system is host to a large number of diverse satellites, many of which likely have global oceans beneath their outer icy shells. While the anticipated presence of a global liquid water ocean makes these bodies compelling astrobiological targets, ocean dynamics also play a role in promoting habitable environments. Focusing on Enceladus, Titan, Europa, and Ganymede, I use rotating convection theory and numerical simulations to predict ocean currents and the potential for ice-ocean coupling. When the influence of rotation is relatively strong, the oceans have multiple zonal jets, axial convective motions, and most efficient heat transfer at high latitudes. This regime is most relevant to Enceladus and possibly to Titan, and may help explain their long-wavelength topography. For a more moderate rotational influence, fewer zonal jets form, Hadley-like circulation cells develop, and heat flux peaks near the equator. This regime is predicted for Europa and is possible for Titan, and may help drive geologic activity via thermocompositional diapirism in the ice shell. Weak rotational influence allows concentric zonal flows and overturning cells with no preferred orientation. Predictions for Ganymede's ocean span all of these regimes.

April 30, 2019

3:30 p.m. - 4:30 p.m.
3656 Geology

Presented By: Jeremy Bloxham,
Harvard

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The Magnetic Fields of the Giant Planets: More Differences than Similarities

Jupiter and Saturn are ostensibly similar as are Uranus and Neptune, yet their magnetic fields differ. In particular, the magnetic fields of Jupiter and Saturn, as recently revealed in detail by the Juno and Cassini spacecraft, are quite dissimilar, suggesting that their magnetic fields are sensitive markers of the interior dynamics of these planets. We examine recent magnetic field observations from the Juno spacecraft, which is currently in a polar orbit around Jupiter. From the first phase of the Juno mission we find a magnetic field that is quite unlike any other: the field in Jupiter’s northern hemisphere is non-dipolar, with flux concentrated in a single band at mid-latitudes; in the southern hemisphere the field is nearly dipolar. In addition, we see a single, isolated intense flux spot at the equator. We consider possible explanations for this field morphology in terms of the interior of Jupiter, and contrast its magnetic field with that of Saturn.

May 7, 2019

3:30 p.m. - 4:30 p.m.
3656 Geology

Presented By: Stacia Gordon,
University of Nevada in Reno

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Rates, Conditions, and Scales of Mass Transfer From the Mantle to the Crust: Insights from Earth’s Youngest UHP Terrane

Ultrahigh-pressure (UHP) terranes record the subduction of crustal material to mantle depths as well as the relatively rare exhumation and return of this material to the surface. The rates, scales, and conditions under which these processes have occurred have significantly affected the geochemical evolution of Earth and have great influence on the tectonic evolution of convergent plate margins. On the D’Entrecasteaux Islands, southeastern Papua New Guinea (PNG), a series of domes contain the youngest known ultrahigh-pressure (UHP) to high-pressure eclogites and associated gneisses. The PNG UHP terrane is unique for two reasons: 1) it is exposed within an active, rapidly moving plate tectonic system that includes active extension partly due to continental rifting; and 2) of all the UHP terranes known on Earth, this area exposes—by far—the greatest volume of crystallized melt in abundant leucusomes and large granodiorite plutons. In order to understand 1) the UHP metamorphic history; 2) the timing of melt emplacement relative to the UHP metamorphism and 3) the complete exhumation and deformational history of the eclogites and surrounding gneisses, a series of leucosomes, dikes, and eclogites from the Islands were analyzed by U-Pb ID-TIMS zircon geochronology. Establishing the timing of these exhumation and melting processes has provided the framework for a larger seismic and geodetic research program geared to reveal how buoyancy drove the exhumation of subducted crustal material from mantle to crustal depths within ~ 3 myr within an active continental rift.

May 14, 2019

3:30 p.m. - 4:30 p.m.
3656 Geology

Presented By: Robert Ecke,
Los Alamos National Laboratory (LANL)

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Rotating Thermal Convection - Spin Matters

Buoyancy driven thermal convection is arguably the dominant transport mechanism in nature, driving the redistribution of heat in the Earth’s interior, in planetary atmospheres, in stellar environments, and in many other geophysical and astrophysical situations. It is also one of the most widely studied laboratory systems for the understanding of turbulent phenomena and heat transport. Adding rotation results in new and exciting phenomena, making qualitative connection to natural rotating systems such as planets and stars. I will discuss the history of this fascinating problem from its roots in the mid 20th century up to the present day. Much has been learned but puzzles remain. I will present local measurements of temperature and velocity and global measurements of heat transport that illuminate the physics of this interesting and important problem. Finally, I will outline the remaining challenges for rotating thermal convection.

May 21, 2019

3:30 p.m. - 4:30 p.m.
3656 Geology

Presented By: Sarah Stewart,
UC Davis

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The Rosetta Stones of Planet Formation: A new model for the formation of chondrules and chondrites

Meteorites are time capsules of planet formation. The most abundant meteorites types originate from primitive bodies that never heated to the point of differentiation and contain chondrules, which were transiently molten silicate spherules. These primitive planetesimals formed contemporaneously with planets over the first few million years of the solar system. There is no consensus on the physical processes that formed chondrules and assembled them into planetesimals. Impact processes have been proposed many times but have been criticized as inconsistent with observations. I will present a new physical model for the formation of chondrules and chondrites based on previously unrecognized phenomena during high-velocity collisions between planetesimals. The model links the origin of chondrites to the dynamical excitation of planetesimals from the giant planets. I propose that the uncertain history of our giant planets, their formation locations and migration distances, was recorded by planetesimals that have been preserved in the asteroid belt. Meteorites are the Rosetta stones of planet formation that can relate the history of planetesimals to the history of the giant planets.

May 28, 2019

3:30 p.m. - 4:30 p.m.
3656 Geology

Presented By: Peter Olson,
University of New Mexico

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Nebular atmosphere to magma ocean: water and other volatiles captured during Earth’s accretion.

The origin and abundance of mantle volatiles, including water, present major questions for Earth's evolution. In this talk I explorecauses and consequences of volatile capture from a massive hydrogen-helium rich atmosphere derived from the solar nebula during Earth’s accretion. I use a model of magma ocean dynamics coupled to a nebular atmosphere model adapted to Earth’s formation that includes (i) atmosphere winds based on the dynamics of deep rotating fluids; (ii) water production at the magma surface; and (iii) gas transfer between magma and atmosphere based on the systematics of air-sea gas exchange. Provided the Earth accreted to 30% or more of its final mass in the presence of the solar nebula, the mantle is expected to have ingassed one or more oceans of water along with many petagrams of helium-3 and other light noble gases. This model also predicts that thermal insulation by the nebular atmosphere led to very hot conditions in Earth's interior during accretion, with temperatures above 6000 K in the core and the possibility of an early Hadean dynamo.

June 4, 2019

3:30 p.m. - 4:30 p.m.
3656 Geology

Presented By: Nicole Sharp,
FYFluids

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From Memes to Molasses Floods: Adventures in Science Communication

Nine years ago, as a graduate student frustrated by the lack of public awareness for my field, I created FYFD (http://fyfluiddynamics.com) in order to share my enthusiasm for fluid dynamics with the world at large. Since then, I've built an audience of more than 275,000 followers and embarked on a post-academic career in science communication. In this talk, I'll discuss that journey and many of the lessons about communicating science to general audiences that I've learned along the way. From students interested in outreach to professors looking to promote research more effectively, everyone has something to gain from science communication.