Extinction events

Experiments confirm this mechanism. It was observed that before the extinction events set in, the speed of a limit flame propagating downward falls and the flame partially loses contact with the walls (Figure 3.1.14). In a square tube, local extinction starts in the corners, where heat loss to the walls is expected... 

Figure 7.2.5 provides a visualization of a localized extinction event in a turbulent jet flame, using a temporal sequence of OH planar LIF measurements. The OH-LIF measurements, combined with particle image velocimetry (PIV) reveal that a distinct vortex within the turbulent flow distorts and consequently breaks the OH front. These localized extinction events occur intermittently as the strength of the coupling between the turbulent flow and the flame chemistry fluctuates. The characteristics of the turbulent flame can be significantly altered as the frequency of these events increases. 

Temporal sequence of OH-LIF measurements captures a localized extinction event in a turbulent nonpremixed CH4/H2/N2 jet flame (Re 20,000) as a vortex perturbs the reaction zone. The time between frames is 125 ps. The velocity field from PIV measurements is superimposed on the second frame and has the mean vertical velocity of 9m/s subtracted. (From Hult, J. et al.. Paper No. 26-2, in 10th International Symposium on Applications of Laser Techniques to Fluid Mechanics, Lisbon, 2000. With permission.)... 

Section 8.6.2, the Permian period ended with the largest mass extinction event that has yet occurred on planet Earth. As the ocean began a sustained recovery at the beginning of the Mesozoic era, opportunities likely abounded for the survivors to take over empty ecological niches through evolutionary adaptation. Prior to the advent of planktonic... 

One implication of Earth - degassing models of metallogenesis is that there should be links between the formation of the Earth s resources, secular changes in architecture and geochemistry of the planet over some 4.5 billion years of evolution and phenomena such as mass extinction events, global anoxia, and atmospheric evolution. 

In physics, the late Danish physicist. Per Bak, and his colleagues Tang and Wiesenfeld startled the field in the late 1980s by producing a widely quoted paper on self-organized criticality. Bak and others applied this model widely - to the size distribution of earthquakes and the distribution of clusters of matter in the universe, to the size distribution of extinction events in the biological record. Self-organized... 

These phenomena were accompanied by an extinction event that resulted in the demise of 26% of all known genera (Sepkoski, 1986). Although the overall extinction rate is much lower than that at the Cretaceous-Tertiary boundary, deep water marine invertebrates fared much worse in the CTB event (Kaiho, 1994). This difference supports the view that anomalous oceanic volcanism around the CTB may have played a significant role in the environmental and biotic crisis at this time (Kerr, 1998). 

HaUam A. (1987a) End-Cretaceous mass extinction event argument for terrestrial causation. Science 238, 1237-1242. 

Kaiho K. (1994) Planktonic and benthic foraminiferal extinction events during the last 1(X) m.y. Palaeogeog. Palaeoclim. Palaeoecol 111,45-71. 

Leary P. N. and Rampino M. R. (1990) A multicausal model of mass extinctions increase in trace metals in the oceans. In Extinction Events in Earth History, Lecture Notes in Earth Science, 30 (eds. E. G. Kauffman and O. H. WaUiser). Springer, Berlin, pp. 45—55. 

McGhee G. R., Jr (1982) The Frasnian-Famennian extinction event a preliminary analysis of Appalachian marine ecosystems. In Geological Implications of Impacts of Large Asteroids and Comets on the Earth. Geological Society of America Special Paper (eds. L. T. Silver and P. H. Schultz). Geological Society of America, Boulder, 190, pp. 491-500. 

The largest extinction event of the Phanerozoic occurred in the latest Permian, a time when both shallow and deep marine environments appear to have experienced widespread anoxia. As a result, anoxia has figured prominently into proposed extinction mechanisms for this time, although models for extinction that invoke multiple causality are currently in favor (e.g., Erwin, 1993, 1995 Kozur, 1998). 

A Paleozoic oceanic impact at a time of widespread anoxia would instantaneously replace the surface ocean with anoxic, sulfidic, high pco deep waters. CO2 and H2S would degass to the atmosphere CO2 would equilibrate, and H2S would oxidize. However, an H2S-rich plume could last days to weeks, and spread across the land surface (A. Pavlov, personal communication). Such a scenario may explain the F-F and P-Tr extinction events if the impactor was a comet, a smaller iridium anomaly would result and may have escaped detection. If so, only the Late Ordovician extinction remains as a likely candidate for a purely terrestrial extinction mechanism (glacio-eustatic sea-level fall causing shallow-marine habitat loss). 

Hart M. B. (1996) Biotic Recovery from Mass Extinction Events. Geol. Soc. London, Spec. Publ. 102, pp. 265-277. 

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