Extinction events

[loganosborne]

In history there have been 5 major extinctions. They have happened during the end of the Ordovician period the late Devonian peroid, the end of the permian period the triassic period and the end of the Cretaceous period.

The Ordovician extinction was the second biggest mass extinction ever in terms of percentage of life that went extinct. This extinction happened over 444000 million years ago and it is this event that makes the boundary between the Ordovician period and the following Silurian periods. During this extinction event there were several marked changes in biologically responsive carbon and oxygen isotopes, which may indicate distinct events or particular phases within one event.

At this time in history it was only marine life that was on this planet. In this extinction about 100 marine families became extinct. This covers 49% genra of fauna (http://en.wikipedia.org/wiki/Fauna_%28animals%29).
The brachiopods (http://en.wikipedia.org/wiki/Brachiopod) and bryozoans (http://en.wikipedia.org/wiki/Bryozoan) were wiped with many others wiped out as well.

The favorite theory for what caused this extinction is a prolonged ice age perhaps the most severe glacial age of the Phanerozoic (http://en.wikipedia.org/wiki/Phanerozoic) in the Hirnantian (http://en.wikipedia.org/wiki/Hirnantian) faunal stage that ended the long, stable greenhouse conditions typical of the Ordovician time period. Then after that a fall in atmospheric CO2 which selectively affected the shallow seas where most organisms lived. As the southern supercontinent Gondwana (http://en.wikipedia.org/wiki/Gondwana) drifted over the South Pole, ice caps formed on it, which have been detected in late Ordovician rock strata of North Africa and then-adjacent northeastern South America, which were south-polar locations at the time. If you want to know more about this extinction you can Private message me.

For the late Devonian I don't know to much about so I will just quote on what Wilkipedia says about it.

The Late Devonian extinction was one of five major extinction events in the history of the Earth's biota. A major extinction occurred at the boundary that marks the beginning of the last phase of the Devonian period, the Famennian faunal stage, (the Frasnian-Famennian boundary), about 364 million years ago, when all the fossil agnathan fishes suddenly disappeared. A second strong pulse closed the Devonian period.

Although it is clear that there was a massive loss of biodiversity towards the end of the Devonian, the extent of time during which these events took place is still mooted, with estimates as brief as 500 thousand years or as extended as 15 million, the full length of the Famennian. Nor is it clear whether it concerned two sharp mass extinctions or a cumulative sequence of several smaller extinctions, though the most recent research suggests multiple causes and a series of distinct extinction pulses through an interval of some three million years [1] [2].

Anoxic conditions in the sea-bed of late Devonian ocean basins produced some oil shales. The Devonian extinction crisis primarily affected the marine community, and selectively affected shallow warm-water organisms rather than cool-water organisms. The most important group to be affected by this extinction event were the reef-builders of the great Devonian reef-systems, including the stromatoporoids, and the rugose and tabulate corals. The reef system collapse was so severe that major reef-building (effected by new families of carbonate-excreting organisms, the modern scleractinian corals) did not recover until the Mesozoic era.

The late Devonian crash in biodiversity was more drastic than the familiar extinction event that closed the Cretaceous: a recent survey (McGhee 1996) estimates that 22 percent of all the families of marine animals (largely invertebrates) were eliminated, the category of families offering a broad range of real structural diversity. Some 57 percent of the genera went extinct, and—the estimate most likely to be adjusted—at least 75 percent of the species did not survive into the following Carboniferous. The estimates of species loss depend on surveys of marine taxa that are perhaps not well enough known to assess their true rate of losses, and for the Devonian it is not easy to allow for possible effects of differential preservation and sampling biases. Amongst the severely affected marine groups were the brachiopods, trilobites, ammonites, conodonts, and acritarchs, as well as jawless fish, and all placoderms. Freshwater species, including our tetrapod ancestors, were less affected.

Reasons for the late Devonian extinctions are still speculative. Bolide impacts are dramatic triggers of mass extinctions. In 1969, Canadian paleontologist Digby McLaren suggested that an asteroid impact was the prime cause of this faunal turnover, supported by McGhee (1996), but no secure evidence of a specific extra-terrestrial impact has been identified in this case (yet see the Alamo bolide impact of Nevada).

The "greening" of the continents occurred during Devonian time: by the end of the Devonian, complex branch and root systems supported trees 30m/90 ft tall. (Carbon locked in Devonian coal, the earliest of Earth's coal deposits, is currently being returned to the atmosphere.) But the mass extinction at the Frasnian-Famennian boundary did not affect land plants. The covering of the planet's continents with photosynthesizing land plants may have reduced carbon dioxide levels in the atmosphere. Since CO2 is a greenhouse gas, reduced levels might have helped produce a chillier climate. A cause of the extinctions may have been an episode of global cooling, following the mild climate of the Devonian period. Evidence such as glacial deposits in northern Brazil (located near the Devonian south pole) suggest widespread glaciation at the end of the Devonian, as a large continental mass covered the polar region [3]. Massive glaciation tends to lower eustatic sea-levels, which may have exacerbated the late Devonian crisis. Because glaciation appears only toward the very end of the Devonian, it is more likely to be a result, rather than a cause of the drop in global temperatures.

George R. McGhee Jr (1996) has detected among the survivors, some trends that lead to his conclusion that survivors generally represent more primitive or ancestral morphologies. In other words, the conservative generalists are more likely to survive an ecological crisis than species that have evolved as specialists.

[loganosborne]

The Permian-Triassic (P-T or PT) extinction event, sometimes informally called the Great Dying, was an extinction event that occurred approximately 251 million years ago. This caused the boundary between the permian and triassic period. I find this an interesting fact it killed about 96% of all marine life and i think about 70% of life on land. This event is thought it lasted less than a million years a very brief period of time in geological terms. Organisms throughout the world, regardless of habitat, suffered similar rates of extinction, suggesting that the cause of the event was a global event.

i found this interesting after the extinction this happened

For some time after the event, fungal species were the dominant form of terrestrial life. Though they only made up approximately 10% of remains found before and just after the extinction horizon, fungal species subsequently grew rapidly to make up nearly 100% of the available fossil record.[1] However, some researchers argue that fungal species did not dominate terrestrial life, even though their remains have only been found in shallow marine deposits.[2] Alternatively, others argue that fungal hypha are simply better suited for preservation and survival in the environment, creating an inaccurate representation of certain species in the fossil record.[3]
There have been many theories about them I will just say what the theories are Plate tectonics, Antarctic impact event, Supernova,Volcanism, Atmospheric hydrogen sulfide buildup and Methane hydrate gasification or a combination of them. if you want to know why I say they caused this massive extinction PM me and I will explain why.

The Triassic extinction event occurred 200 million years ago and is one of the major extinction events of the Phanerozoic eon. It wiped out 20% of marine families. Im not to sure about the theories on what caused this one the three I know of is Climate change, Comet but a crater around this time period has not been found or a massive volcanic eruption.

The Cretaceous extinction event was a period of massive extinction of species that occurred about 65.5 million years ago. It corresponds to the end of the Cretaceous geologic period and the beginning of the Tertiary period. Not to sure of how much life died i think it was about 60% and as we know wellit wiped out the dinosaurs.

Here is Alavarez's theory

In 1980, a team of researchers led by Nobel-prize-winning physicist Luis Alvarez, his son, geologist Walter Alvarez and a group of colleagues discovered that fossilized sedimentary layers found all over the world at the Cretaceous-Tertiary boundary, 65.5 million years ago contain a concentration of iridium hundreds of times greater than normal. The end of the Cretaceous coincided with the end of the dinosaurs. It was in general a period of extraordinary mass extinction, leading to the Tertiary Period of the Cenozoic Era, in which mammals came to dominate on Earth. The paper suggested that the dinosaurs had been killed off by an impact event from a ten kilometre wide asteroid. Two facts supporting the theory are the relative abundance of iridium in many asteroids and the similarity between the isotopic composition of iridium in asteroids and K-T layers, which differs from the that of terrestrial iridium.

Iridium is very rare on the Earth's surface, but is found more commonly in the Earth's interior and in extraterrestrial objects such as asteroids and comets. Furthermore, chromium isotopic anomalies found in Cretaceous-Tertiary boundary sediments strongly supports the impact theory and suggests that the impact object must have been an asteroid or a comet composed of material similar to carbonaceous chondrites.

The blast resulting from such an impact would have been hundreds of millions of times more devastating than the most powerful nuclear weapon ever detonated, may have created a hurricane of unimaginable fury and certainly would have thrown massive amounts of dust and vapor into the upper atmosphere and even into space.

A global firestorm may have resulted as the incendiary fragments from the blast fell back to Earth. Analyses of fluid inclusions in ancient amber suggest that the oxygen content of the atmosphere was very high (30-35%) during the late Cretaceous [1]. This high O2 level would have supported intense combustion. The level of atmospheric O2 plummeted in the early Tertiary period.

In addition, the worldwide cloud would have blocked sunlight for months, decreasing photosynthesis and thus depleting food resources. This period of reduced sunlight, a "long winter", may also have been a factor in the extinctions. Gradually skies cleared but greenhouse gases from the impact caused an increase in temperature for many years.

The impact target rocks also produced acid rain that would have affected natural habitats. However, recent research suggests this effect was relatively minor. Chemical buffers would have reduced the impact and the survival of animals vulnerable to acid rain effects (such as frogs) indicate this was not a major contributor to extinction (see Kring, D.A. GSA Today v. 10, no.8).

Although further studies of the K-T layer consistently show the excess of iridium, the idea that the dinosaurs were exterminated by an asteroid remained a matter of controversy among geologists and paleontologists for more than a decade.

The main Theories for this one is Chicxulub crater, Deccan traps magma flows in India, multiple impact event and Supernova.

Hope you enjoyed reading it.

[lazserus]

There is one small discrepancy with the Cretaceous ELE. Most commonly it is accepted that the asteroid that impacted with the Yucatan Peninsula caused the death of all dinosaurs, yet there are arguments. Some scientists say that the impact could not have been enough to wipe them all out. Others in different fields say a supervolcano erupted around the same time. Now, these two combined leaves little doubt. However, I've read a few papers suggesting GRB having a significant role in that extinction. When bone samples were taken there were certain radiation levels that could only be explained from intensely energetic radiation exposure. Scientists conform to the asteroid impact, but I think it's possible that there is more than meets the eye.

I'll have to do more research, but it's widely accepted that a GRB caused one of the first extinctions on Earth, killing all sea life. The interesting factor is that I've heard that sea water can create a better buffer from high energy radiation than solid rock can. I'll have to look into it again, it's been years.

[loganosborne]

However, I've read a few papers suggesting GRB having a significant role in that extinction. When bone samples were taken there were certain radiation levels that could only be explained from intensely energetic radiation exposure. Scientists conform to the asteroid impact, but I think it's possible that there is more than meets the eye.

I'll have to do more research, but it's widely accepted that a GRB caused one of the first extinctions on Earth, killing all sea life. The interesting factor is that I've heard that sea water can create a better buffer from high energy radiation than solid rock can. I'll have to look into it again, it's been years.
Im still researching i found an article on it and before you whinge I know it's only a bbc article best I can come up with at the moment. http://news.bbc.co.uk/2/hi/science/nature/4433963.stm

[Scrapyard Ape]

Logan, the volcanism that is theoried to be a cause of extinction events is known as Basalt Flooding. The Deccan Traps are a famous example of such flooding. It is the rarest known type of volcanic eruption which makes it the least understood form of volcanic activity. The most recent episode occurred about 16 million years ago in what is now the US pacific northwest.

Here is an article that goes into many of the past extinction events and some possible causes. Note the table they have provided which lists occurences of extraterrestrial impacts, basalt flooding, and radical sea level changes and how they correlate to extinctions.
http://www.firstscience.com/SITE/articles/macleod.asp

[loganosborne]

Logan, the volcanism that is theoried to be a cause of extinction events is known as Basalt Flooding. The Deccan Traps are a famous example of such flooding. It is the rarest known type of volcanic eruption which makes it the least understood form of volcanic activity. The most recent episode occurred about 16 million years ago in what is now the US pacific northwest.

Here is an article that goes into many of the past extinction events and some possible causes. Note the table they have provided which lists occurences of extraterrestrial impacts, basalt flooding, and radical sea level changes and how they correlate to extinctions.
http://www.firstscience.com/SITE/articles/macleod.asp
Thank you Scrapyard Ape for that awesome link.

[Ningishiddza]

Here is an article that goes into many of the past extinction events and some possible causes. Note the table they have provided which lists occurences of extraterrestrial impacts, basalt flooding, and radical sea level changes and how they correlate to extinctions.
http://www.firstscience.com/SITE/articles/macleod.asp

I like the correlation factors, I've not seen that before. What are the odds and locations of continental flood basalt eruptions in this time period?

[loganosborne]

Here are some links on Basalt Flooding if anyone is intrested
Link 1 (http://www.auburn.edu/academic/science_math/res_area/geology/camp/McHone_Puffer.html) and Link 2 (http://www.otago.ac.nz/geology/students/mcclintock/mcclintock.htm)

I also found this interesting article (http://www.staff.livjm.ac.uk/spsbpeis/CCNet-21-07-06.htm) on how global warming did not cause the K/T extinction.


However, I've read a few papers suggesting GRB having a significant role in that extinction. When bone samples were taken there were certain radiation levels that could only be explained from intensely energetic radiation exposure. Scientists conform to the asteroid impact, but I think it's possible that there is more than meets the eye.
On that I have got this link (http://www.aas.org/publications/baas/v29n5/aas191/abs/S119001.html). Im finding it difficult to find bits on it. I will do somemore research and see what I can find.

[loganosborne]

I Found this (http://www.space.com/scienceastronomy/planetearth/extinction_sidebar_000907.html) on Space.com it gives a simple explanation on the 5 major extinction events.

[Ningishiddza]

However, I've read a few papers suggesting GRB having a significant role in that extinction. When bone samples were taken there were certain radiation levels that could only be explained from intensely energetic radiation exposure. Scientists conform to the asteroid impact, but I think it's possible that there is more than meets the eye.

I'll have to do more research, but it's widely accepted that a GRB caused one of the first extinctions on Earth, killing all sea life. The interesting factor is that I've heard that sea water can create a better buffer from high energy radiation than solid rock can. I'll have to look into it again, it's been years.

Honestly, I don't see how gamma-ray bursts could possibly come into play. Although simplified, a gamma ray is nothing more than a photon with a certain amount of energy imparted on it.

The energy imparted on a gamma ray determines its life span. When a gamma ray comes to the end of its life span, it decays into an electron-positron pair (at least in theory).

Granted, space is virtually a vacuum, but it would still require enormous energy to travel from a nova/supernova to Earth, then penetrate through the magnetosphere, radiation belt, and through the atmosphere to sea level.

It requires about 6.6 cm of (sea) water to reduce the gamma ray intensity by half. The hydrogen atom in water (and concrete) is very effective (and cheap).

That depth in the sea were no light penetrates is were 100% of the gamma rays would be effectively attenuated more or less, so I can't see how all sea creatures could be affected. Even at depths above that, that level of radiation should not be sufficient to kill all sea life.

If the GRB was intense enough with sufficient energy, could it ionize the seas? Afterall, ionizing radiation begets ionizing radiation, but still, you'd be talking about beta radiation which might be a problem at levels near the surface, but not at the lower depths.

I don't know, maybe I'm missing something.

As far as higher levels of radiation in fossilized bone samples, there are a few things to look at. First, the natural background radiation of the planet in the distant past was much higher than it today. The Earth did not come stocked with lead, rather lead was formed from the decay of Uranium isotopes. With a half-life of 4,468,000,000 years, figure there was twice as much U238 4.5 billion years ago as there is today. For U235 at 703,800,000 years, figure there was 64 times as much 4.5 billion years ago and so on for all radionuclides. Second, the possibility that the fossilized bones were contaminated at a later time is very real. Consider that an animal dies then is covered by alluvial deposits containing Thorium from a nearby mountain (just like the beaches of southern India today).
Finally, since life existed, we have to assume that it was adapted to higher radiation levels, so higher levels of radiation may be irrelevant.

[uki]

the interesting thing about gamma rays and other energy frequencies is the fact that if one's own personal energy is strengthened and in tune, it will be more receptive to the energies of the cosmos that bombard us constantly every day. this energy can be absorbed by us and changes us on a molecular level. this is my personal belief thru experience using energy-work systems(tai chi, qigong, yoga, physical exercise). the human body is an energy receptor and a energy generator... the physical will be nothing more than a manisfestation of the mental, which of course is affected by the spiritual... there is much to be learned from observing the natural way... in this case... become like the plants... and grow!!. :scatter:

[loganosborne]

For people who are unsure on what a gamma ray burst is heres a good piece (http://en.wikipedia.org/wiki/Gamma_ray_burst) on it.

[Skynet12]

Thanks, logan-some good links!

[Doomer]

Logan, the volcanism that is theoried to be a cause of extinction events is known as Basalt Flooding. The Deccan Traps are a famous example of such flooding. It is the rarest known type of volcanic eruption which makes it the least understood form of volcanic activity. The most recent episode occurred about 16 million years ago in what is now the US pacific northwest.

Here is an article that goes into many of the past extinction events and some possible causes. Note the table they have provided which lists occurences of extraterrestrial impacts, basalt flooding, and radical sea level changes and how they correlate to extinctions.
http://www.firstscience.com/SITE/articles/macleod.asp

Wow, what an eye opener. This should be required reading for everyone here at AO. Thanks. :2thumbs:

[loganosborne]

By Hillel J. Hoffmann
"Welcome to the Black Tri-angle," said paleobiologist Cindy Looy as our van slowed to a stop in the gentle hills of the northern Czech Republic, a few miles from the German and Polish borders. The Black Triangle gets its name from the coal burned by nearby power plants. Decades of acid rain generated by power-plant emissions have devastated the region's ecosystems. Yet the treeless hills looked healthy and green.

I tried to hide my surprise. For months I'd been on the trail of the greatest natural disaster in Earth's history. About 250 million years ago, at the end of the Permian period, something killed some 90 percent of the planet's species. Less than 5 percent of the animal species in the seas survived. On land less than a third of the large animal species made it. Nearly all the trees died. Looy had told me that the Black Triangle was the best place today to see what the world would have looked like after the Permian extinction. This didn't look like apocalypse.

We saw the first signs of death as we walked into the hills—hundreds of fallen timbers lay hidden in the undergrowth. A forest once grew here. Half a mile uphill we found the trunks of a stand of spruce, killed by acid rain. No birds called, no insects hummed. The only sound was the wind through the acid-tolerant weeds.

"The forest that grew here a few decades ago contained dozens of species of plants," said Looy. "Now there are only a few grassy species."

Looy picked up a spruce cone. Pollen from the trees around us might be preserved inside. She believes that the Permian extinction was caused by acid rain following a massive release of volcanic gases. She wants to compare tree pollen from a modern forest killed by acid rain with fossil pollen found in Permian rocks.

Like a homicide detective at a crime scene, Looy sealed the cone in a plastic bag for later lab work. "You could say we're working on the greatest murder mystery of all time," she said.

Looy is one of many scientists trying to identify the killer responsible for the largest of the many mass extinctions that have struck the planet. The most famous die-off ended the reign of the dinosaurs 65 million years ago between the Cretaceous and Tertiary periods. Most researchers consider that case closed. Rocks of that age contain traces of an asteroid that struck Earth, generating catastrophic events from global wildfires to climate change. But the Permian detectives are faced with a host of suspects and not enough evidence to convict any of them.

To understand this extinction, I wanted first to get a sense of its scale. That's difficult—sediments containing fossils from the end of the Permian are rare and often inaccessible. One site that preserves the extinction's victims lies about a half day's drive inland from Cape Town, South Africa, in a scrubland known as the Karoo.

"The Karoo is the kind of place where people fall asleep at the wheel," said Roger Smith, a paleontologist at the South African Museum, as we drove across the treeless land. "But it may be the best place to see the terrestrial realm's transition from the Permian to
the Triassic period."
You can read more at this Link http://www.nationalgeographic.com/ngm/0009/feature4/fulltext.html
What do you think of this article?

[loganosborne]

I found this on the web. This article is saying that wobbles and varations are asscoiated with extinctions of rodent and mammalian species. Heres the article.

Earth wobbles linked to extinctions

LONDON, England (Reuters) -- Wobbles or variations in the Earth's orbit and tilt are associated with extinctions of rodent and mammalian species, Dutch scientists said on Wednesday.

They studied rodent fossil records in central Spain dating back 22 million years and found that the rise and fall of mammal species was linked to changes in the Earth's behavior which caused cooling periods.

"Extinctions in rodent species occur in pulses which are spaced by intervals controlled by astronomical variations and their effects on climate change," Dr Jan van Dam, of the Utrecht University in the Netherlands, said.

Read More (http://edition.cnn.com/2006/TECH/science/10/11/extinction.mammals.reut/index.html)

[loganosborne]

Found this on Livescience where new studies about the permian extinction didnt just wipe out 95% of sea creatures and 70% of land creatures but it also gave the oceans a face lift as reported here.

Greatest Mass Extinction Gave Oceans a Face Lift

The largest extinction in Earth's history not only wiped out 95 percent of sea creatures and 70 percent of land animals, it also gave the oceans a fundamental "face lift," according to a new study.

Read More (http://www.livescience.com/animalworld/061123_sealife_shift.html)

Found this intresting.

[TC]

I think the climate shift that took place in the early Holocene had more of an impact than was previously thought, along with what caused it. The mammoth remains in eastern Siberia show an almost instant death by freezing without tissue decay, even the grass in their mouths prevalent to that region was still intact.

At the time this took place, the area was a grass step, heavily populated by Mammoth, what took place is still being debated, but the evidence shows that these animals died chewing green grass (temporal 40-75F) and were suddenly thrown into arctic conditions, more or less killing them where they stood, even as late as WW1, people of that area had actually eaten this meat, which shows just how quickly the animal perished.

One interesting theory is that the earth actually shifted in its position due to an imbalance in polar ice, throwing temperate regions into arctic conditions. Needless to say, this would have an enormous impact on anything living on the planet.

[Anarch]

bumped for your reconsideration.

[Ningishiddza]

bumped for your reconsideration.

What do you have an issue with? It's quite interesting because some of the extinctions are bizarre in that they were very selective. Most people are familiar with the 5 Big Ones but there were a lot of minor extinction events in the interim periods, probably related to the effects of climate change.

The Permian was the worst and probably the only real true extinction event, as that wiped out about 95% of the planet.

[lazserus]

What do you have an issue with? It's quite interesting because some of the extinctions are bizarre in that they were very selective. Most people are familiar with the 5 Big Ones but there were a lot of minor extinction events in the interim periods, probably related to the effects of climate change.
The K/T extinction is given the most attention, but as far as extinctions are concerned it is the mildest. The Ordovician extinction was at least twice as nasty as the Cretaceous, and the Permian extinction the worst known to occur on our planet.

I'm not sure, Ningishiddza, what you mean by these major extinctions being "selective." There are a number of factors to keep in mind when considering these extinction events, such as continental movement, appearance of new predators, change in food sources (both meat and veggie), and even climate.


The Permian was the worst and probably the only real true extinction event, as that wiped out about 95% of the planet.
An extinction event is an extinction event. There is no "true" version. The classification deals in magnitude. The disappearance of large land mammals in North America (mammoths, giant sloths, saber-cats, etc.) is classified as a minor extinction, but not an event. It's classified as minor because it did not affect the entire globe, and there was no event causing the extinction.

We have to remember that the majority of life on this planet has been and is in the oceans. The Permian extinction was particularly devastating because 95% of marine species were wiped out. This is an upgrade from the Ordovician extinction. Moreover, something on the nature of 70% of terrestrial vertebrates were vanished at this time. The P/Tr boundary is significant in that it led to the rise of land-beasts.

Extinctions are quite common. There are currently more living animals on this planet than we have classifications for. If you take the number of today's classified species and multiply it by itself, you still won't equal the number of living organisms that have lived here in the last 4 billion years. *shrugs*