Sonntag, 3. Januar 2010

Did volcanoes kill the Mammoth?

The cause(s) of the Pleistocene Megafauna extinction is(are) still unclear. Various explanations were proposed, ranging from human activity (hunting or disease spreading) to climate change or sea level rise, and since the last year, a possible extraterrestrial impact. But an important factor until now was less considered - volcanism. Volcanoes can have an impact on climate and ecosystems, for example ash can block the sunlight, and poison large territories.
A short, but intriguing paper by Dmitry A. Rubam summarizes and analyze the idea that intensified volcanism at the end of the last glacial period maybe triggered the biotic crisis. The volcanic activity of the last 50.000 years can be reconstructed by ash layers and geochemistry of ice cores, and compared to extinction patterns on the different continents.


The data show a higher frequency of eruptions near the end of the Pleistocene, but the demise of the fauna doesn’t coincide exactly with this period, especially the extinction in Australia happened previously. However it is possible that only a certain "sum" of volcanic events finally triggers a biotic response.

Fig. 1 - Temporal relationships between the volcanic eruption frequency and extinction events. Volcanism intensifications are highlighted by grey circles (from RUBAN 2009).

The preliminary results show that intensified volcanism cannot provide a better explanation of the crisis than other triggers; however none of the possible triggers alone provide an ultimate explanation.

The evidence makes it plausible, that an intensification of volcanism just before the end of the Pleistocene was able at least to contribute to the extinction of megafauna in America and Eurasia.

References:
RUBAN, D.A. (2009): A possible contribution of volcanism to the end-Pleistocene megafaunal etinction. Natura Nascosta 39:26-32

Kommentare:

Jessica hat gesagt…

Another great extinction that is not well explain is the Permo-Trias one. My geological professor (I'm a geography student from Canada) made us do a research on it. Sooo interesting!

David Bressan hat gesagt…

And like all mass extinctions it is still not solved, work for future earthscientists ;)

Here you can find some interviews and opinions about the problem:
http://www.cbc.ca/quirks/archives.htm

And two papers I came across:
SAHNEY & BENTON (2008): Recovery from the most profound mass extinction of all time. Proc. R. Soc. B (2008) 275, 759-765
http://rspb.royalsocietypublishing.org/content/275/1636/759.abstract

WARD (2005): Abrupt and Gradual Extinction Among Late Permian Land Vertebrates in the Karoo Basin, South Africa."
www.gps.caltech.edu/~jkirschvink/pdfs/WardKarooScienceFinal.pdf