what evidence is there for the mass extinction?

Question

apparently there was a mass extinction that killed 95% of life on Earth, (not the one that did in the dinosaurs) what evidence is there for this conclution? is there any theories on what caused it?

Answer 1

I thgink they studied Mitochondrial DNA (DNA inherited from the mother) from a large sample of people around the world. they found a bottleneck event. There wasn't as much genetic difference as there should have been. The reason the experimenters theorised for this, was a global catastrophic event that resulted in mass extinction.

It could have been many number of things, I think the eruption of a large volcano was mentioned (sorry i can't remember the name of it for sure, it might have been kracatoa). As you know a large enough eruption can block out the sun for years afterwards causing the onset of an nuclear winter. There are also supervolcanos like the one directly under Yellowstone national park in the States. if that blows were all pretty much as screwed as our distant ancestors were.
With geological events like this there are always knock-on events to deal with as well, earthquakes, tsuanami, mega tsunami. which could have explained the death figures (as if a nuclear winter/mini ice age wasn't enough).

Some suggested an asteroid impact but it is alsways hard to get evidence for such theories.
some researchers suggested a global flooding event.

Answer 2

Which one? There have been many!

Evidence supporting the Devonian mass extinction suggests that warm water marine species were the most severely affected in this extinction event. This evidence has lead many paleontologists to attribute the Devonian extinction to an episode of global cooling, similar to the event which is thought to have cause the late Ordovician mass extinction. According to this theory,the extinction of the Devonian was triggered by another glaciation event on Gondwana, as evidenced by glacial deposits of this age in northern Brazil. Similarly to the late Ordovician crisis, agents such as global cooling and widespread lowering of sea-level may have triggered the late Devonian crisis.

Meteorite impacts at the Frasnian-Famennian boundary have also been suggested as possible agents for the Devonian mass extinction. Currently, the data surrounding a possible extra-terrestrial impact remains inconclusive, and the mechanisms which produced the Devonian mass extinction are still under debate.

Answer 3

I believe there is also a layer of sooty material way underground showing evidence that there was a large impact causing lots of debris and dust to gather in the air. I'm sure that there is also an isotope of uranium wtihin this layer which is not abundant within Earth naturally so must have been brought here by an impacting body. Within this layer there would also be fossil evidence showing mass excinction of species.

Answer 4

The fossil record, which is really quite extensive and getting bigger every day.
The dinosaurs were in a millions of years period of decline anyway, but the last of them, plus about 70% of species on earth were thought to have been destroyed by a massive asteroid impact. There's various theories though and suggest you google it and check out some of the theories on this massive scale of extinction.
These are quite good sites to visit:

http://web.ukonline.co.uk/a.buckley/dino.htm
http://www.ucmp.berkeley.edu/diapsids/extinction.html

Your best bet will be scientific or university websites for accurate information. Fascinating subject though... :)

Answer 5

Fossils in sedimentary rocks laid down before the extinction date ( around 550 million years ago) do not exist in rocks laid down shortly after.
This is called the Permian Extinction event and is often blamed on very very high co2 levels due to insufficient stirring of the oceans around Gondwanaland. Gondwanaland was the large land mass that existed before the present day continents moved apart.

Answer 6

Which mass extinction? There have been five mass extinctions during the Phanerozoic Eon: at the end of the Cambrian Period, at the end of the Ordovician Period, in the middle of the Devonian Period, near the end of the Permian Period, or at the end of the Cretaceous Period.

Answer 7

I think your referring to the Permian/Triassic mass extinction ~250 Ma ago when ~95% of all living things died and ~75% of speicies became exstinct. Check out the link below it explains it better than I could.


http://en.wikipedia.org/wiki/Permian-Triassic_extinction_event

Answer 8

Apart from fossils, just the faith and 'theory' that scientists hypocritically denounce and yet at the same time rely on as the basis for most of their work.

The only science worth worrying about is medical science. Best thing to do is not worry about it at all, you're here now so make the most of it.

Answer 9

the burgess shale. there are hundreds of marine fossils that appeared to die all at once. those that survived are what led to us, in a manner of speaking.

Answer 10

The fossil record says it all.