Permian–Triassic extinction event

At the Permian-Triassic boundary or PT boundary, or Permian-Triassic event or the great extinctions million years ago, 251.4, at the turn of Permian to Triassic (which at the same time the Paleozoic from the Mesozoic is different ), found the largest known mass extinction of earth's place ..

It is the only mass extinction that was started insects. About 75% of terrestrial species and about 95 % of marine invertebrates died out ( large Foraminifera, Paleozoic corals, trilobites, Eurypteriden and others); were decimated bryozoans, brachiopods, crinoids, and ammonoids. Mollusks were affected by the extinction of species less. For a time, it seems mainly to have been fungi on land and in shallow water. Another interpretation of the fossil record, however, is that the hyphae of the fungi being more suitable for fossilization, especially since they were already living in the sedimentary substrate. But flow and cause of the PT event are still unclear. Studies proceed from one to three different causes. Also over the duration of the " Great Dying " at the top Perm vary the ideas of geologists between a single event to several extinction highlights every few million years.

Possible Causes

Supercontinent Pangea

Because of the association of most of the former continents at the Permian-Triassic turn of the supercontinent Pangea regressions of the sea were widespread and the surface of the shelves around the world declined significantly. In addition to the negative impact on the biodiversity of Flachwasserfaunen also prevented the now very limited number of possible migration routes in west-east direction in the lower latitudes the exchange of marine faunas and limited biodiversity further. With climate change the organisms Dodge was very difficult, so that the risk of extinction of entire species of animals was very high.

Volcanism

Another cause of the extinction of species, a number of volcanic eruptions over a period 165000-600000 years is assumed. Evidence of this is up to 3,000 m thick lava deposits of the Siberian Traps which have arisen in the period in question. Due to the volcanic activity reached a large amount of gases in the atmosphere that have changed the climate sustainable. Through these climate changes large amounts of methane were released into the oceans, which drove the climate change continues. Sulfur-containing and oxygen-poor, dark ocean sediments from this period are a further indication of the climate changes.

Recent studies of the layer sequences on the western Blind Fjord on Ellesmere Iceland in the Canadian Arctic showed that there siliceous sponges began to die out already 100,000 years before the extinction in the Tethys. It was concluded that this as well as the chemical traces of increased land erosion and nutrient leaching was initially limited to the northern hemisphere effects of volcanic activity in Siberia were. Research from 2013 suggest that volcanic eruptions may not have been solely responsible for the extinction of species.

Meteorite

In summer 2006, a possible impact crater was in Antarctica in Wilke discovered country with a diameter of up to 500 km, which was also dated to this time period, the so-called Wilke country meteorite. Against the cause of a meteor impact at the end of the Permian, however, is often the lack of in meteorites about 1000 times more frequently than on Earth occurring iridium in the corresponding geological layers (as opposed to species extinction 65 million years ago at the Cretaceous - Tertiary boundary ) cited. Impact researchers give out, however, that not all meteors the same high proportion of iridium with it. Above all comets have, because of their history, very little of this precious metal, so it must be demonstrated by the impact of a comet, consequently, hardly in the then emerging impact layer. In addition, it must be remembered that it is the biggest strikes put so much energy is released that a large part of the ejected out of the crater material is being hurled into space and thus is lost. It is the largest impacts would thus be characterized by an increasing lack of iridium in the forming impact layer. The impact of a meteorite is also discussed as a possible cause of the volcanism above. The Australian Bedout structure comes as (co -? ) Trigger in question.

Gamma-ray burst

Another theory speaks of the effects of a so-called cosmic gamma-ray burst (english gamma -ray burst, GRB ) on Earth. Such enormously high energy gamma-ray bursts occur at the birth of black holes, an event that is within our galaxy is extremely rare and occurs also very concentrated, would just so happens that focused on our solar system need to be.

The character of the Permian-Triassic mass extinction, with an emphasis on marine species and temporally distributed events over a period of up to one million years includes a gamma-ray burst as a decisive cause. Moreover, there is no evidence of an event that would come for such a gamma-ray burst in question.

Halocarbons

Another possible cause of the release of metabolic products of individual learning is finally considered. Bacteria in the salt lakes of the Zechstein Sea could according to a published 2008 theory have blame for the extinction of species in which they issued halocarbons into the atmosphere. These substances attack the ozone layer and cause damage to plants.