||May 25, 2001
GSA Release No. 01-17
International Scientists Probe Unsolved Puzzles of the Earth and Beyond at
"Earth System Processes"
(II) Session Highlights
- SESSION 21: Tuesday, June 26.
FEEDBACKS AND COUPLING BETWEEN THE GEOSPHERE, BIOSPHERE, HYDROSPHERE, AND ATMOSPHERE
- 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
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
- 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
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
- 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
- A Snowball Earth workshop, promising lively discussion and debate, immediately
follows this session.