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Spring 2016 Colloquia

March 3rd, 2016
Kathy Licht, Indiana University
Title: Where did it all come from? Exploring the Origin of Glacial Till
Host: John Isbell

Deciphering the origin of glacial till turns out to be really challenging, yet it is essential because the information it provides about past ice flow paths is critical to ice sheet reconstructions. These reconstructions, in turn, are essential to numerical modeling efforts that try to quantify the ice sheets contributions to global sea levels. In this talk I will explore examples of till provenance studies in Antarctica and Indiana that aim to reconstruct ice flow paths in two very different modern environments. We have found that not all provenance methods applied to Antarctic tills yield the same answer about the origin of debris. Fortunately we know the ice flow paths, so these studies provide a valuable test case to understand what conditions may produce such ambiguity. I will also present results from our work on detrital zircons in Indiana till to highlight some opportunities and challenges in applying this method to Midwestern tills.

March 10th, 2016
Daniel Horton
, Northwestern University
Title: Late Paleozoic Climate Dynamics; Generating Cyclicity in an Icehouse World
Host: John Isbell

The late Paleozoic era witnessed the vegetated Earth’s only known transition from an icehouse to a greenhouse climate. This transition brought Earth from the Phanerozoic’s most severe glaciation, the late Paleozoic ice age (LPIA), into a greenhouse climate that would dominate the next 220 million years of Earth history. Developing an understanding of the late Paleozoic icehouse climate and the mechanisms that drove Earth into a protracted greenhouse state are fundamental to the study of climate dynamics in both the distant past and the near future. The traditional understanding of late Paleozoic climate contends that massive continental-scale ice sheets formed when the southern hemisphere land masses were located near to the austral pole and repetitively waxed and waned due to orbital insolation variations. Recent re-analysis of the temporal and geographic distribution of glacial deposits, in conjunction with a re-examination of glacioeustasy records, indicates that LPIA climate was much more dynamic. In addition to ice sheets waxing and waning on orbital time-scales, the emerging view of LPIA climate contends that icehouse conditions were episodic, interrupted by multiple intervals of ice-free greenhouse conditions. This newfound variability in the LPIA climate state has been hypothesized to result from fluctuations in atmospheric pCO2 concentrations. To constrain the climatic dynamics discussed in these disparate LPIA views, I present numerical climate-modeling results that explore the interactions of the late Paleozoic atmosphere, biosphere, cryosphere, hydrosphere, and lithosphere.

March 24, 2016
George Coyne, Lemoyne University
Title: Our Cosmological Ignorance: Dark Matter and Dark Energy
Host: Megan Barlow

Brief description or abstract of talk: Gravity is responsible for structure in the universe: planets, stars, galaxies, the universe itself. There is strong evidence from many independent astrophysical observations that much of the gravitating mass in the universe does not radiate like ordinary matter. It is called “dark matter” both because it does not radiate and because our brains are dark as to what it is. But, of course, we have some ideas. Furthermore, there is overwhelming evidence that the universe is accelerating in its expansion. There must, therefore, be a repulsive force in the universe which is working against gravity. This is called “dark energy” which reveals again our ignorance. Our ignorance thus far in these two cases is an excellent example of how science progresses through “educated ignorance.”

March 31, 2016
Rachel Headley, UW-Parkside
Title: TBA
Host: Julie Bowles

April 7, 2016
Sandra Passchier, Montclair State University
Title: TBA
Host: John Isbell

April 21, 2016
Shangping Xu, UW-Milwaukee
Title: TBA
Host: Shangping Xu

May 5th, 2016
Ken Bradbury, UW-Madison
Title: TBA
Host: Elmo Rawling