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Offline AlphBravo

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Dinosaur Extinction
« on: 08/05/2007 11:32:21 »
Having read some articles and of course TV and radio on the subject how the dinosaurs became extinct, Apparently caused by a Meteorite, but suppose that the Meteorite was part of a comet, and the Comet collided with Earth, would not the proximity of the Comet also cause a heating effect by reflecting it's "mass" onto the Planet, this would effectively make the surface temp to rise but also affect the plant life causing drought etc.


 

another_someone

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Dinosaur Extinction
« Reply #1 on: 08/05/2007 13:33:56 »
As I understand it, there would have been local short term heating due to the impact itself, but after that, the longer term consequence would have been a cooling effect caused by the blocking out of sunlight.

There is no doubt that if the theory is correct, it would have had a major impact on plant life in general - but plants don't leave bones behind, so their extinction is less obvious (that is not to say that there can be no research into plant extinction, particularly with regard to pollen found in ice cores, but historically it has not been as easy to research as simply tripping over bones when you dig down into the ground).

There is no doubt that the extinction events of 65 million years ago did effect many species of living organism, not only dinosaurs; although I don't know exactly which groups of living organisms were more or less effected than which other groups.

There is still a lot of debate even about the exact time period over which the extinctions happened, and as such, whether the comet impact itself actually directly caused the extinction, or whether it triggered a series of events that began on a small scale and over the succeeding thousands of years had ever greater impact, or even whether the comet impact was merely coincidental and something else caused a decline in populations over thousands of years; or if there was indeed a dramatic effect over maybe a decade in the direct aftermath of the comet impact.

What is clear is that, whatever happened, although we know that time best as the time that the dinosaurs became extinct, it was not only dinosaurs that became extinct at that time.
 

Offline JimBob

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« Reply #2 on: 08/05/2007 21:59:50 »
There is no doubt that if the theory is correct, it would have had a major impact on plant life in general - but plants don't leave bones behind,

Plants do leave fossils.

Petrified forests, amber (petrified pine sap), leaf impressions, actual flowers preserved in mud (how we know flowering plants first appeared during the Late Cretaceous) cones from Permian conifers, lots more. The evidence for the meteorite is enhanced by fossil charcoal of the late Cretaceous, but fossil charcoal is some of the oldest evidence of something other than ferns, which came in a vast spectrum of types, even tree-like analogs. I can drive 30 minutes from my house and pick up fossil palm tree bits that have been burned from the impact of the Yucatan meteorite less than a thousand miles SE of here, that supposedly ended the dinosaurs.

I say supposedly because the evidence strongly suggest that the end of the Cretaceous was not a single event but a series of events, lasting 10's of thousands of years, that cause their extinction. Same for all the major extinction events. Climactic change, size and the low availability of oxygen at the Cretaceous-Eocene boundary due to oxygen fixing in limestones (only one of several theories put for to explain this) combined to cause the "extinction" of the dinosaurs. We really do not know the reason and change theories to accommodate new data.

But dinosaurs are not extinct. If you own a budgie or have eaten chicken you have had a close encounter of the dinosaur kind.

(Why do I do this, post to this site while I am working trying to figure out the paleo-stress of NW New Mexico's San Juan basin. I'm daft. That's why!  [:-'(])
 

another_someone

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Dinosaur Extinction
« Reply #3 on: 09/05/2007 01:28:44 »
Plants do leave fossils.

I did not say otherwise.  I was very deliberate in saying they do not leave bones.  Our ability to understand some of the subtler reamins of the past (e.g. leaf impressions) is a relatively modern development, and people were being taught about the extinction of the dinosaurs 100 years ago; thus the extinction of the dinosaurs has become pretty much folklore, while the wider extinction is still something discussed mainly in scientific circles.

I say supposedly because the evidence strongly suggest that the end of the Cretaceous was not a single event but a series of events, lasting 10's of thousands of years, that cause their extinction. Same for all the major extinction events.

Again, consistent with what I said about the uncertainty of the time period.  The main difference is that while I was more agnostic, you have come down to saying a longer time period is the more probable, but both of us have agreed that actually we have no certainty at all about the time period, and it is still just a matter of assigning probabilities to answers that we have no certainty in.

But dinosaurs are not extinct. If you own a budgie or have eaten chicken you have had a close encounter of the dinosaur kind.


Again, it does not invalidate anything that I have said, since it is clear that many dinosaurs did become extinct, and so is perfectly valid to talk about the extinction of the dinosaurs, so long as we are aware that it is not the extinction of all the dinosaurs (but it does, I agree, make a correction to the implied assumption in the question itself).

(Why do I do this, post to this site while I am working trying to figure out the paleo-stress of NW New Mexico's San Juan basin. I'm daft. That's why!  [:-'(])

Don't ask me ;)
 

Offline ukmicky

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Dinosaur Extinction
« Reply #4 on: 09/05/2007 02:08:37 »
Quote

(Why do I do this, post to this site while I am working trying to figure out the paleo-stress of NW New Mexico's San Juan basin. I'm daft. That's why!  [:-'(])
No your not daft its because your a nice guy who love's to share his knowledge, either that or your one of these people who just likes to show off. ;) ;D
 

Offline DoctorBeaver

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« Reply #5 on: 15/05/2007 11:25:13 »
Quote

(Why do I do this, post to this site while I am working trying to figure out the paleo-stress of NW New Mexico's San Juan basin. I'm daft. That's why!  [:-'(])
No your not daft its because your a nice guy who love's to share his knowledge, either that or your one of these people who just likes to show off. ;) ;D

He likes to show off  ;D


Anyway, dinosaurs died out coz they started a fight with beavers!
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Offline tony6789

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« Reply #6 on: 15/05/2007 16:38:05 »
im not complaining about their extinction!
 

Offline DoctorBeaver

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« Reply #7 on: 16/05/2007 10:45:25 »
im not complaining about their extinction!

Nor me. I wouldn't much fancy coming face to face with a T Rex in Burger King!
 

Offline Bass

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« Reply #8 on: 04/06/2007 05:22:13 »
Same for all the major extinction events. Climactic change, size and the low availability of oxygen at the Cretaceous-Eocene boundary...
JimBob, you rascal!!
You've managed to do away with the Paleocene! :o

and I'm barely old enough to remember those good old days.
 

Offline losguy

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« Reply #9 on: 19/12/2008 21:36:03 »
I was watching a program on television called Time Warp, a great visual oriented program that slows down different events with a high speed camera. Last night they were photographing a drop of water falling into a pan of water. The water drop carves out a depression, and then the cornet comes up and then the pillar of water and finally the concentric rings emanating from the center of the event. This is also the basics of the Chixalub impact. Time Warp also did other demonstrations and one was dropping a drop of water into very shallow water. Everything was the same as the first demonstration, until the pillar of water raise from the center which was not much higher than the coronet and then the concentric rings occurred. The Scientist that was assisting the demonstration team also had a high speed camera and had been experimenting with the drops of water. He made the statement that when the water was shallow you would get the depression being carved out and the cornet but because of the shallowness of the water the pillar of water was never much higher than the coronet. Without the tall column of water and debris raising up from the Chixalub event there would not be the world wide firestorm that would have burned up everything (there has been no world wide charcoal layer associated with the KT boundary or the Chixalub Impact Event) as well as the acid rain which would have killed all the frog species that have come survived the extinction event. The layer of iridium could have come from a portion of the asteroid being burned off as it blasted through the atmosphere (as well as from the burning up of sucker asteroids moving along with the main asteroid), wind patterns would have spread much of the dust, plus from the actual impact. A group of small sucker asteroids following the main asteroid might also account for the irregular distribution of iridium as each of their trajectories might have differed. One must also remember that with all the plate tectonics, weather, erosion, volcanism, and other large natural disasters (including seas being created and destroyed) the iridium layers and spherules may have been displaced which can account for any discrepancies in the dating and the closeness of the continents would have allowed the dispersion to look larger than it would if looking at the present continent arrangement.
The Chixalub impact was not in the same environment that is always displayed when they do an animation of the Chixalub event. The Continents had not really separated very much and the sea that the Chixalub asteroid fell into was a shallow continental shelf sea in the far west of the continents. The Chixalub impact is actually on continental shelf and possibly did not even disturb the Methane Hydride layers. Maybe the Chixalub event was not the whole cause of the dino extinction or even a major effect at all.
If the scenario that is put forth where the Impact was in deep sea bed, which caused the Carbonate Layers to heat turning them into Carbon Dioxide (Which is heavier than air) which circled the earth and killed only the Dinosaurs and a few other plants, and some of the fish and animals I think is a little off base. This is like expecting the extinction event to pick and choose who will live and who will die. If we look at the Lakes in Africa, that released Carbon Dioxide and killed every animal in the area above and below ground, then the Chixalub Impact Event would have killed everything but plant and fish.
    According to paleontologist the Dinosaurs had been in decline for at least 3 million years prior to the Chixalub Impact Event when most of the animals and many plants and fish became extinct. If the Methane Hydride layer at the bottom of the ocean was release as methane (methane is lighter than air) it could have left a layer of good air close to the surface. Bubbling out of the oceans, along with an ocean temperature rise, it would have killed most of the ocean species except for the few that lived in areas of the ocean that did not release the Methane Hydride (where water still had a cooler temperature) or fresh water where no Methane Hydride occurs (as a side note various fish species that go to sea then return to fresh water may have been caused due to escaping the Methane Hydride residual in the sea water). If enough of the Methane Hydride is released all at once it could have filled the atmosphere up to a heavy cloud layer which would have been created by the global warming that was occurring at this time. Some data point to an average rise in temperature of 8 C (14 F) in the last half million years before the impact at Chicxulub. In refering to a program that was presented that 6 C raise in temprature would cause the extinction of the human race what would 8 C (14 F) do compounded by lowered oxygen levels and climatic changes? Most of the animals that lived close to the surface or below would have been mostly left alone while the ocean fish and plants, land plants and animals that were large and/or up in the area where the methane hydride had collected would have died and the few that might have been left alive would have probably died soon after the event, even if the methane hydride would have been washed out of the air because of the climate change that was occurring.
    The fact that, many other large object impacts events have occurred on earth without an extinction event occurring, makes this event suspect. The fact that an Impact event occurred near the same time as an extinction event occurred does not necessarily link it.  The likely hood of an impact event that caused the mass extinction even the size of the Chixalub event seems not very likely or at least not with fire raining down then acid rain, I feel that it is very unlikely to have occurred, especially the issue of Carbon Dioxide as the killer released by the Impact Event. I believe the heating up of the atmosphere due to the Caribbean large igneous province flood Basalt from 139 to 69 million years ago with a volume which has been estimated as on the order of 4 x 106 km, Brito-Arctic province the first which occurred ~61 million years ago was of 2 x 106 km in total volume and Deccan Trapps right at the 65 million year mark with a present volume of directly observable lava flows is estimated to be around 512,000 km. (None of these Flood Basalt Events are Antipode to the Chixalub Event their for probably not related) which occurred at the same time the extinction event occurred which probably heated the atmosphere releasing large quantities of fresh water into the Ocean Conveyor stopping it and allowing the deep sea water to heat enough to release the Methane Hydride layers. It is estimated that the original area covered by the lava flows was as large as 1.5 million km, approximately half the size of modern India. The possibility that an extinction event occurring and only picking and choosing its victims is a little far fetched. The extinction event has to be tailored around the outcome and not the event itself. If everything else has been ruled out no matter how improbable what is left is the answer.


 

Offline m40

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Dinosaur Extinction
« Reply #10 on: 19/02/2011 18:15:01 »
Some notes on the KT extinction case...

   Early mammals seem to have survived and thrived after whatever event 'wiped out the dinosaurs'. It is well established that a catastrophic meteor fall had a lot to do with the final die out of many early species, though it does not explain the whole story. It is also well established that many dinosaur species were already either extinct, or on their way out when the event occurred.

   The obvious factor that is often overlooked is that NOT all dinosaurs became extinct. We still have all manner of reptilian life from the smallest lizards to alligators, crocodiles and Kimodo dragons. We have sharks, birds, snakes, and many other creatures that have survived quite successfully. They are modern descendants of dinosaur species that have thrived, relatively unchanged since the time of dinosaurs. However, we know that many dinosaur species DID go extinct. What separates those species that died out from those that survived? What separates them from the mammalian species that also survived? Hint: SIZE MATTERS!

   A couple questions that are often asked on the subject of dinosaurs are, "Why did they grow so big?", and "Why aren't there lots of large animal species today?". The answer is OXYGEN. Oxygen is used by almost all species on earth as a catalyst to break down food into fuel. Every cell in our bodies requires a constant supply of oxygen in order to survive. The larger the species, the more oxygen that is required, and the distribution system for that oxygen becomes more and more complex. 

   It is nearly inconceivable that dinosaurs could have led any kind of active lifestyle in today's world because they simply couldn't get enough oxygen distributed throughout their huge bodies to live. They would have needed lungs that comprised 75% of their body. It is well known that there was a lot more oxygen in the atmosphere in the age of dinosaurs (about 35%). A warmer planet (and thus far more ample plant life) provided for an oxygen rich environment. This allowed the largest dinosaurs to make good use of the rich atmosphere that was available without having overly large lungs to process it.

   As the planet cooled over many millions of years from a tropical climate to something approaching that which we see today, plant life waned to a large extent, both on land and at sea. The atmosphere changed significantly as oxygen levels began dropping, and by the tome it stopped, there was only about half the oxygen as had been there (about 20%). This depletion would have been devastating to the largest dinosaurs, and it began a process of thinning out or even weeding out many species.

   Again, it's well established that many dinosaurs were already extinct when the meteor event occurred, and that those that remained were already in serious trouble. The meteor event cooled the planet further with a blanket of atmospheric dust that blocked sunlight from warming the earth's surface. This likely lasted a good many years, and acted as a sort of 'nuclear winter' scenario. The effect would be a sudden and catastrophic reduction in plant life within the first few years, and this goes hand in hand with greatly reduced oxygen levels. It is likely that oxygen levels dropped even lower than today's levels, possibly down to 10 or 15% (about a third of what had existed in the age when dinosaurs ruled the land).

   Mammals and smaller reptiles would have suffered during this time as well, but the major effect would be similar to a human at higher altitudes. We can still run, jump, and do the things we need to, but we need to stop and catch our breath a little more frequently. However, the effects would be FAR more pronounced in larger species. Any species that can only take a few steps and then has to stop to catch its breath... is doomed to extinction.

   There is no other mode of extinction (fire, flood, climate, famine or drought) that is so selective between large and small creatures. If you look at the 'dinosaurs' and even the mammals that survived, they just happen to be those that most efficiently process oxygen. Birds have a large lung capacity, as do alligators, crocodiles and other reptiles that live in and around water. The largest mammals are whales, and they just happen to have a huge lung capacity (the size of a small car) and their lungs are incredibly efficient.

   To me the 'final straw' seems rather obvious, but now we have a lot of 'junk scientists' arguing otherwise.
 

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Dinosaur Extinction
« Reply #10 on: 19/02/2011 18:15:01 »

 

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