May 25, 2001 GSA Release No. 01-17

International Scientists Probe Unsolved Puzzles of the Earth and Beyond at "Earth System Processes"

I. Introduction II. Session Highlights III. Support for Journalists

(II) Session Highlights

SESSION 21: Tuesday, June 26.
FEEDBACKS AND COUPLING BETWEEN THE GEOSPHERE, BIOSPHERE, HYDROSPHERE, AND ATMOSPHERE
[ View Abstracts ]

This session focuses on processes characterized by feedback interaction of two or more components of Earth's climate system. Participating scientists include geologists, biologists, astrobiologists, oceanographers, and ecologists from the US, the UK, Denmark, Germany, and Belgium.

John Shepherd of the Southampton Oceanography Centre, University of Southampton, will set the stage in the opening talk by discussing the challenges of climate modeling, given that all major components of the Earth system play important roles. A number of subsequent papers consider feedback mechanisms that regulate atmospheric oxygen and carbon dioxide levels, and several climate models are discussed. A few highlights are noted below.

James Alcock, Environmental Sciences, Penn State Abington College, will take an interesting look at tropical rainforest stability, derived in part from the ability to hold and recycle water. He will discuss positive feedback in the form of human activity that destabilizes the system, eventually leading to ecosystem collapse. Model testing suggests that a point of no return can be reached within one to two decades, resulting in unimaginable loss to global biodiversity.

André Berger from the Institut d'Astronomies et de Géophysique G. Lemaitre, Université Catholique de Louvain, will discuss how to simulate glacial-interglacial cycles with a climate model which includes, in a simplified way, the atmosphere, hydrosphere, cryosphere, and lithosphere, and their interactions. Simulations of climate over the next 130 Kyr. suggest that the present interglacial will probably be a particularly long one (50 Kyr).

Two papers will examine biotic feedback mechanisms and their implications for James Lovelock's Gaia theory of Earth as a self-regulating mechanism. Timothy Lenton of the Centre for Ecology and Hydrology, Edinburgh Research Station, has researched the evolution of vascular plants and photosynthesis. He has looked at how associated processes counteract loss of CO₂ brought about by the interaction of such variables as increased solar luminosity, increased continental area, and decline in seafloor spreading. Lenton predicts the extension of Earth's current biosphere until catastrophic warming terminates complex life in approximately 1 Gyr.

David W. Schwartzman, Department of Biology, Howard University, will address the question, "Does life drive disequilibrium in the biosphere?" Study of the carbonate-silicate geochemical cycle, or Urey reaction, has produced results counter-intuitive to a classical Gaian view.

Hiroshi Ohmoto, Astrobiology Research Center and Department of Geosciences, Penn State University, will challenge the popular geological theory that oxygen didn't reach present levels until about 600 million years ago. Simulations based on a new theory linking O₂ and CO₂ rates of production and consumption to land area, soil erosion rate, and various other geochemical parameters, suggest that atmospheric O₂ rose extremely rapidly following the emergence of cyanobacteria about 4 billion years ago. Results indicate that present levels may have been reached in less than 30 million years and produced a major divergence of aerobic and anerobic organisms. It is also probable that Earth's early atmosphere already contained appreciable amounts of ozone and methane, providing a theoretical justification for NASA programs to detect life on other planets by searching for ozone and methane in their atmospheres.

SESSION 37: Wednesday, June 27
CRITICAL TRANSITIONS IN EARTH HISTORY AND THEIR CAUSES
[ View Abstracts ]
[ View Poster Session 41 Abstracts ]

A variety of scientists from Russia, Hungary, Sudan, Australia, Canada, the US, and Britain will come together to share recent findings on such topics as plate tectonics and the growth and break-up of the Earth's supercontinents, conditions and causes for life to appear and disappear on Earth, climate system changes, and internal Earth processes.

Antony Hallam, from the School of Earth Sciences at the University of Birmingham, will explore six possible causes of the greatest of all mass extinctions in Earth's history. At the Permian-Triassic boundary, it is estimated that half of all marine invertebrate and terrestrial vertebrate families became extinct, together with a high proportion of terrestrial plants. Hallam uses results of investigations over the past 20 years in biostratigraphy, facies analysis, and geochemistry, to evaluate possible causes.

Cosmologist Charles H. Lineweaver, from the Physics Department at the University of New South Wales, will examine the creation and the nature of Earth-like planets outside of the solar system. Many of these planets are much older than Earth, and analysis provides an age distribution for life on them and a rare clue about how we compare to other life which may inhabit the Universe.

Ferenc Varadi, Institute of Geophysics and Planetary Physics at UCLA, will propose that the ultimate cause of the K-T impact (and the resultant mass extinction and the demise of the dinosaurs) may have been a chaos-induced change in Solar System dynamics. Varadi and his colleagues found that the dynamical state of the inner Solar System changed abruptly about 65 million years ago, significantly changing the orbits of Mercury and Earth. This, in turn, may also have perturbed asteroids in the asteroid belt, throwing one or more of them into Earth-crossing orbits.

Richard Ghail, from the T.H. Huxley School of the Imperial College, will address the geological debate about whether or not the early Earth behaved the same way as at present, with plate tectonics. Using evidence from Venus, Ghail will explain that the early Earth did not have modern plate tectonics, but did have something that looked similar to it, which explains the confusing evidence from the geological record. He will further argue that since this situation is unstable on Venus today (i.e., every so often Venus undergoes a cataclysmic resurfacing), early Earth did the same.

Grant M. Young, Department of Earth Sciences at the University of Western Ontario, will explore the role of plate tectonics in bringing about dramatic climate oscillations, changes in the atmosphere and hydrosphere, and setting the stage for the "explosive" evolution of life in the Cambrian. The Proterozoic eon began and ended with unbelievable climatic changes--ancient sedimentary rocks bear silent testimony to severe glaciations on every continent. The cause of these glaciations remains one of the great unanswered questions of science, but one possibility is that they were induced by plate tectonic processes. Following continental collisions, enhanced physical and chemical breakdown of minerals from resulting mountainous land-masses would have resulted in removal of CO2 from the atmosphere, and climatic cooling. The glaciations appear to be interspersed with warm climatic episodes, when atmospheric CO2 (from volcanic eruptions) built up again because during glaciations, weathering processes are inhibited.

James C. Zachos, of the Earth Sciences Department at UCLA, has found that the current warming of global climate may not be unprecedented in terms of rate and magnitude. Some 55 mya, Earth's atmosphere and oceans warmed by more than 6°C in a period of less than 20 kyrs. Geochemical evidence suggests that the warming was caused by the release of a massive quantity of methane from the destabilization of marine clathrates (frozen water and methane) in several short bursts. What remains unknown is why marine clathrates, which are common today, would suddenly destabilize 55 mya. Zachos will present geochemical evidence from deep sea sediments that indicates the event was preceded by slow warming of the ocean, which served as a trigger for destabilizing the clathrates.

A poster presentation by József Pálfy, Institut für Paläontologie at the Museum für Naturkunde in Hungary, was recently announced in a New York Times online article, "Clues to a Meteor That Aided Dinosaurs." Among the five largest extinctions documented in the fossil record, only the end-Triassic (200 million years ago) has not been previously linked to changes within the global carbon cycle. Study of rocks of that age in Hungary suggests that this extinction is also associated with environmental perturbations that are reflected in anomalous carbon isotope ratios. One scenario consistent with these results is that short-term, intensive volcanism of the Central Atlantic Magmatic Province triggered environmental changes and led to a biological crisis. Effects of volcanism at a magnitude only rarely experienced in Earth history may be similar to the current, man-made global change which also seems to drive scores of species to extinction.

Lawrence H. Tanner, Geography and Geosciences at Bloomsburg University, will question scientists' ability to test various hypotheses for the cause of large-scale extinction events of the past. The Triassic-Jurassic boundary extinction event is one of the "big five" mass extinctions of the Phanerozoic Eon. The current favorite theory to explain this event is that eruptions of flood basalts that constituted the Central Atlantic Magmatic Province released CO₂ or SO₂ aerosols. This, in turn, caused intense global warming (from the former) or cooling (the latter). New data on the isotopic composition of fossil soils of Late Triassic and Early Jurassic age fails to find evidence of any change in the CO₂ composition of the atmosphere, so other possibilities need to be investigated more fully.

SESSION 48: Thursday, June 28
THE SNOWBALL EARTH HYPOTHESIS: THEORY AND OBSERVATIONS
[ View Abstracts ] [ View Poster Session 56 Abstracts ]

Experts in geology, atmospheric science, marine geochemistry, and evolutionary biology will bring a mix of new discoveries and contrasting perspectives on this highly controversial theory of planetary glaciation, where the poles were covered by ice and the oceans were frozen. Paul Hoffman, Department of Earth and Planetary Sciences, Harvard University, will introduce the session and emphasize that any successful hypothesis must account for a unique set of geological observations. During his presentation, he will argue that the Snowball hypothesis does this better than any competing theory, but that a possible conflict with evidence for terrestrial ice streams must be resolved.

Grant M. Young is a senior geologist at the University of Western Ontario with long international experience. Twenty-five years ago, he made the important observation that the glacial deposits of the Paleoproterozoic Gowganda Formation in Canada are overlain by sediments with evidence for intense tropical weathering. The Snowball Earth hypothesis provides one possible explanation for this paradox. However, Young prefers to interpret these unusual rock associations as being due to glaciation under a CO₂-rich atmosphere, made possible by weak radiation from the faint young sun, and other radically different conditions of the Earth at that time. He proposes that the Snowball theory is really a "no-ball" theory.

Lee R. Kump, Department of Geosciences at Penn State University, will present an innovative concept based on the idea that Snowball glaciation might have caused extreme lowering of the sea level, reduced pressure at deep-sea vents, and consequently changed ocean chemistry. This may develop into another new means of testing the Snowball hypothesis.

Matthew T. Hurtgen, Penn State Astrobiology Research Center and Department of Geosciences, will take present the first results of a new class of measurements with important implications that test the Snowball Earth hypothesis. Hurtgen and colleagues' preliminary results appear consistent with predictions of the hypothesis.

Daniel P. Schrag, also from the Department of Earth and Planetary Sciences at Harvard, will propose an innovative, counterintuitive mechanism for triggering Snowball events. Evidence indicates that there was increased methane prior to glaciation. If Snowball events depended on this mechanism, a rise in atmospheric oxygen could explain why the rise of multicellular animals coincided with the end of Snowball events.

James C.G. Walker, Geological Sciences Department at the University of Michigan, will take a look at the strange weather patterns during Snowball Earth which resulted from the arid atmosphere and the solid ocean.

Bruce Runnegar, Professor of Paleontology at UCLA, will take a look at "hard" and "soft" versions of scenarios in the Snowball Earth hypothesis, emphasizing the latter in relation to the global biosphere.

Martin J. Kennedy from the University of California, Riverside, will propose that methane released from permafrost due to warming associated with post-glacial sea-level rise may explain the isotopic signature of 'cap' carbonates. Unusual sedimentary structures will be cited in support of the idea, but their interpretation will be debated. (Kennedy published an article on this topic in the May issue of GEOLOGY.)

A Snowball Earth workshop, promising lively discussion and debate, immediately follows this session.