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Earth Institute at Columbia University
January 17, 2003

Contact:
Mary Tobin
845-365-8607

Columbia University Research Finds Correlation Between Meteorite and 
Comet Impacts and an Increase in Volcanic Activity Development

10 Major Episodes of Extraterrestrial Impacts Found to Correlate with 
9 Major Episodes of Volcanism

Supporting the theory that catastrophic events significantly influence 
major Earth processes, researchers have determined that comet and 
meteorite impacts on Earth occurring over the last 4 billion years 
have directly correlated with the activity of strong and normal mantle 
plumes - heated mantle rock causing volcanic eruptions (e.g. Hawaii, 
Iceland). 

Dr. Dallas Abbott, of the Lamont-Doherty Earth Institute, and Ann 
Isley, of SUNY Oswego, assembled an expanded database of terrestrial 
impacts over the last 4 billion years. They used clues from known 
craters such as impact spherules created from impact melt, and from 
impact breccias that are created from shattered debris fused under 
high temperatures and pressures. They also examined the activity of 
normal and strong mantle plumes over geological time. Time series 
derived from this data showed that 10 major peaks in terrestrial 
impact activity were seen on Earth over this time period. Nine out of 
10 of these impact peaks are directly matched by peaks in normal to 
strong mantle plume volcanism. In addition, there are two prominent 
lulls in impact activity, also corresponding to periods of lower 
activity of mantle plume volcanism. 

The biggest mystery remaining is the mechanism by which large impacts 
might intensify volcanism. Abbott and Isley propose three 
possibilities: impacts may cause cracking and de-stressing of the 
crust, allowing melts that had been trapped due to tectonic stress 
and/or impermeable boundaries to rise more easily to the surface; 
impacts may produce large cracks in the surface of the Earth allowing 
new plate boundaries to form with consequent thinner lithosphere and 
longer melt columns; or impacts may produce microdikes at the core 
mantle boundary, which, if very thin, would allow molten core and 
mantle material to mix, increasing the amount of heat available for 
melting the mantle and producing a rapid intensification of existing 
mantle plumes.

Another question raised by the correlation between impacts and 
volcanism concerns widely adopted theories that meteorite and comet 
impacts were the cause of mass extinctions of life on Earth. Was it 
the impact alone or could major episodes of mantle plume volcanism 
have contributed to these extinctions? 

Dallas Abbott is an adjunct research scientist at The Lamont-Doherty 
Earth Observatory. Her primary research focus is the thermal history 
of the earth, and the manner in which heat transport through the crust 
and upper mantle influences geological processes, both ancient and 
present-day.

Abbott and Isley"s research paper, "Extraterrestrial Influences on 
Mantle Plume Activity," is appearing in Earth and Planetary Science 
Letters this month. 

The Lamont-Doherty Earth Observatory, a research unit of the Earth 
Institute, is one of the world"s leading research centers examining 
the planet from its core to its atmosphere, across every continent and 
every ocean. From global climate change to earthquakes, volcanoes, 
environmental hazards and beyond, Observatory scientists continue to 
provide the basic knowledge of Earth systems that must inform the 
future health and habitability of our planet. 

The Earth Institute at Columbia University is the world"s pioneer 
academic center for mobilizing the sciences and public policy in 
pursuit of a sustainable future, especially for the world's poor.  Its 
director is international economist Jeffrey D. Sachs. More than 800 
scientists with strength in Earth science, ecology, health, social 
science or engineering are working together to reduce poverty, hunger, 
disease and environmental degradation. The Institute brings their 
creative knowledge to bear through teaching, research and outreach in 
dozens of countries around the world. In all it does, the Earth 
Institute remains mindful of the staggering disparities between rich 
and poor nations and the tremendous impact that global-scale problems 
-- from the AIDS pandemic to climate change to extreme poverty in much 
of the developing world -- will have on all nations.

http://www.earthinstitute.columbia.edu/news/2003/story01-17-03.html

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