Dekkan Trapp
The Dekkan-Trapp in the Dekkan region in western India is one of the largest volcanic regions on earth. It consists of a stair-like formation ( Trapp ) made of flood basalt and today extends over an area of more than 500,000 square kilometers. In the basalt of the Deccan Traps the cave temple of were Ellora and Ajanta erected, the World Heritage Site of UNESCO count.
Volcanic activity
The remaining volume of basaltic lava cover is around 500,000 km³. Estimates of the original extent are more than 1.5 million square kilometers. The basalt layers are still partly up to 2,000 m thick. Due to its extent and its relatively rapid geological formation, the Dekkan-Trapp is an outstanding example of a magmatic large province .
The volcanic activity that gave rise to the Dekkan Trapp took place about 66 million years ago. Along with the Trapp, extensive Dyke swarms occur in the Deccan . The Trapp consists almost exclusively of tholeiitic basalt and basaltic andesite .
The duration of the formation of the Dekkan-Trapps is controversial, periods between 500,000 and 9,000,000 years are given. The passage of the Indian plate over a mantle plume is said to be responsible for the ejection of the basalts . However, this theory is also controversial. As the cause of the mantle plume out of the question that the time in today's Reunion - hotspot feeding.
The Dekkan Trapp as the reason for the extinction of the dinosaurs
Some scientists blame the climate change associated with the deposition of the Dekkan Trapps for the great extinction of species at the Cretaceous-Tertiary boundary (cf. the Verneshot hypothesis ), contrary to the widespread meteorite theory of dinosaur extinction . This view was further supported by the discovery that the typical deposition of iridium at the Cretaceous-Tertiary boundary around 65 million years ago, not only caused by meteorite impacts , but also by volcanism. This theory remains controversial. It is argued that the abrupt decline in fossil species after the increase in iridium concentration can hardly be explained by constant volcanic activity, but better by a one-off, brief event such as a meteorite impact. The non-terrestrial isotopic composition of iridium, palladium and osmium within the chalk-paleogene boundary layer as well as the fact that both the thickness and concentration of the boundary layer and of the iridium are distributed almost identically around the world speak against the Deccan traps as a source of iridium . Only in the area of the Caribbean, i.e. the location of the Chicxulub impact , a significant increase in the iridium concentration and the thickness of the boundary layer can be observed. All of this speaks in favor of the Caribbean as the place of origin of the iridium contained in the boundary layer and of the boundary layer itself, since of course there must always be an accumulation of material around the point of origin. However, the fact that the activity in India could have been triggered by the impact in Yucatan is also considered. Seen in this way, the volcano would have increased the effects of the meteorite.
Web links
Individual evidence
- ↑ Hetu C. Sheth: “Large Igneous Provinces (LIPs)”: Definition, recommended terminology, and a hierarchical classification. Revised version of the article of the same name in Earth-Science Reviews, Vol. 85, pp. 117 - 124, 2007 ( original article as pdf )
- ↑ a b The Deccan beyond the plume hypothesis (engl.)
- ^ B. Steinberger: Plumes in a convecting mantle: Models and observations for individual hotspots. Journal of Geophysical Research , Vol. 105, pp. 11127-11152, 2000
- ↑ The mass extinction at the end of the Cretaceous , article at www.Terra.Planeten.ch ( Memento of the original from December 14, 2007 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ Mass Extinction - Catastrophic "Accidents" of Evolution? , Article by Nadja Podbregar at the knowledge magazine www.scinexx.de, February 21, 2002
- ↑ Geology - The End of the Dinosaurs , article in Focus magazine from March 5, 2010
- ↑ At the «Ground Zero» of the Chicxulub crater
