Pagina's

The Siberian Traps

About 65 million years ago a meteorite crashed into what is now the Mexican shoreline. The immediate result was the Chicxulub crater, the impact crater that is now buried beneath the Yucat√°n Peninsula in Mexico. The crater is more than 180 kilometers in diameter and 20 kilometers in depth. Scientists have calculated that the impacting rock was at least 10 kilometers in diameter.
It is now an accepted theory that the discovery of the Chicxulub crater lends support for the extinction of numerous animal and plant groups, including non-avian dinosaurs, may have resulted from a meteoric impact. In scientific circles this great dying is called the Cretaceous–Paleogene (K–Pg) extinction event, because its boundary clearly marks the end of Cretaceous Period and the beginning of Paleogene Period (K–Pg boundary).

Still, science isn't a religion and new theories and facts may add to our knowledge. Now new evidence is appearing that the extinction was not only the result of the impact of the meteor, but also of the also simultaneous eruption of the Deccan Traps in India[1].

But there were many more extinction events in the troubled history of our earth.
[Part of the Siberian Traps]

Around 250 million years ago, at the end of the Permian geologic period, there was another mass extinction so severe that it is the largest known species die-off in Earth's history. This time it wasn't a meteorite that created havoc, but a volcanic event of unimaginable scale[2]. For about a million years large floods of lava produced the Siberian Traps and covered over 2,000,000 square kilometers.
The continuous eruption of the Siberian Traps may have caused worldwide dust clouds and acid aerosols, which would have blocked out sunlight and thus disrupted photosynthesis both on land and in the ocean, causing food chains to collapse. The eruptions may also have caused acid rain when the aerosols washed out of the atmosphere. That may have killed plants on land. In the sea, shellfish would die because their calcium carbonate shells would simply have dissolved by the acid. More than 90 percent of marine species and more than 75 percent of terrestrial species disappeared from the face of the earth[3]. This is called the Permian–Triassic (P–Tr) extinction event, the Great Dying or the Great Permian Extinction.

[1] Petersen et al: End-Cretaceous extinction in Antarctica linked to both Deccan volcanism and meteorite impact via climate change in Nature Communications - 2016
[2] Campbell et al: Synchronism of the Siberian Traps and the permian-triassic boundary in Science – 1992
[3] Burgess et al: High-precision geochronology confirms voluminous magmatism before, during, and after Earth's most severe extinction in Science Advances - 2015

Geen opmerkingen:

Een reactie plaatsen