Tracing Competing Paradigms - Mapping Scientific Frontiers: The Quest for Knowledge Visualization - page 213

Fig. 6.10 A year-by-year animation shows the growing impact of articles in the context of relevant
paradigms. The top-row snapshots show the citations gained by the KT impact articles ( center ),
whereas the bottom-row snapshots highlight the periodicity cluster ( left ) and the Permian extinction
cluster ( right )
In the KT impact theory debate, the impact theory eventually emerged as an
increasingly predominant paradigm, opposed to the more traditional gradualism
views held by many paleontologists. The study of the PT mass extinction convinced
scientists from the impact theory camp that they should take the volcanism more
seriously. At the time of the KT boundary, there was a big outpour of volcanic lava
from the Deccan Traps. At the time of the PT boundary, there was the eruption of
the largest ever volcanoes - the Siberia Traps.
The 1996 article in Science by Knoll et al. ( 1996 ) suggested that the overturn
of anoxic deep oceans during the Late Permian introduced high concentrations of
carbon dioxide into surficial environments. Wignall's 1996 Science article (Wignall
and Twitchett 1996 ) was on a similar topic, suggesting anoxic oceans might have
caused the Permian extinction.
Just below the 30-citation threshold in the visualization of the PT cluster there
was the 1995 Science article by Paul Renne and his colleagues ( 1995 ). They argued
that the Siberian plume changed the environment and climate, which in turn led to
the mass extinction. It was believed that 2-3 million cubic kilometers of Siberian
volcanic flood lasted less than million years. Erwin's 1994 article in Nature (Erwin
1994 ) is among the most highly cited articles in the Permian cluster. He listed causes
such as intense climatic, tectonic and environmental change.
Figure 6.10 shows a few frames from a year-by-year animation of the growing
impact of articles in different paradigms. The citation skyline indicates that the
volcanism paradigm is one of the pioneering ones in the study of mass extinctions
and that the KT impact paradigm rapidly became the most prevalent paradigm more
recently. The animated growth of citation counts allows us to identify the role of a
particular landmark article in a broad context of the mass extinction debate. The co-
citation network provides a powerful context for us to understand the implications
of rises and falls of paradigms. In Fig. 6.11 , we outline the citation profiles of the
three major clusters.