*What* killed dinosaurs?

Its the Gaia theory, and it was laughed it when proposed.

But I must say this, standing from a mountain girdling the city its hard not to look down and imagine the earth like a huge mammal and we like small pests scurrying through Her fur.

 

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Ice age. Has to be. The world oscillates between ice age and tropical climate. It's been proven that there has been 3 ice ages in the history of the Earth, if not more. And its always come back up to tropical. Why do you think it's getting hotter? Yep, we're climbing right now, back up to the tropical climate.

 

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--The killing of the dinosaurs wasn't caused by an ice age, though there certainly must have been a nuclear winter resultant from the impact which ultimately was the cause.

Cheers,
-Chris Grose
Geoscience Editor
Organization for Young Scientists Inquiry

 

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The Chicxulub crater found in 1990 is massive (120miles wide) and matches the time of the disappearence of fossils.
If you do a search for "Chicxulub" you can find data concerning it.

Nobody can really know what happened, it's just a matter of getting as much evidence as you can and making up your own mind on how they disappeared.

 

--Indeed, science does not work with absolutes, only degrees of plausibility between competing hypotheses. The impact theory fits the bill.

Cheers,
-Chris Grose
Geoscience Editor
Organization for Young Scientists Inquiry
http://www.oysi.promisoft.net

 

The Chicxulub crater was found while searching for oil. The way we find many of the ancient deep impact sites.

There are many guesses as to why the dinosaurs disappeared from the face of the earth. It is a wonder that there are as many fossils as there are considering the age that they lived in and the time to the present day. I would hazard the guess that if we suddenly went the way of the dinosaur and someone else came along with the same amount of time frame that we see when studing fossils, there would be precious little for them to find.

While we believe that we know the general shape of such creatures from fossils, we don't know what color that they were. It is suspected that dinosaurs may well have been warm blooded, as there have been discovered holes in their skulls that only corrospond to the passages in warm blooded creatures of the present time. While not certain exactly what sounds they produced, molds have been made of the cranial sound cavities and folks have reproduced sounds that they may well have made.

The fact that iridium can be found across the world in a rare form at a given stratus gives creedence to the idea of a massive impact event. Definately one of the massive size needed to impact the the worlds weather. This was long known before the finding of the Chicxulub crater. The crater was considered the the final piece of the puzzle in which the iridium was the smoking gun, indicating that somewhere on the face of the earth it would be found. Somewhere on the internet I have read the account of a geologist who studied this layer in Africa. Parts of his diary were published and it can be seen where he believes it supports this theory. A digilent search may well turn it back up by the determined researcher.

I tend to believe this to be the reason for the extinction event, lacking better data linking the event to another cause.

 

wet1 mentions the iridium evidence, but didn't much explain it. rayzinnz mentioned the Chicxulub crater, but w/o giving much of the back story to the meteor hypothesis.

so, here it goes.

Back in the 1800's, brontosaurs (later discovered to be a Brachiosaur body with a mis-identified diplodocus skull on top) were thought to be mainly aquatic, because there was no way that the animals could support their hugely heavy mass. T-rex's were slow moving carnivores, and their short arms were used as forks for dealing with small bits of food. All tails dragged along the ground.

During the 60 and particularly the 70's, a few people began making connections with modern reptiles and birds, and saw that the pelvic bones of the dinosaurs were made for upright, fast movement. calculations done during the late 70's suggested that a cold-blooded being the size of a large brachiosaur would produce enough heat during cellular respiration to be considered "warm-blooded". T-rex's started showing up in books as a fast-moving predator, tail in the air, running 50 mph to chase down pray. but we had no t-rex footprints to verify this speed estimate.

Then, one t-rex footprint was found in New Mexico. Unfortunately, no second prints were found, so the scientists were unable to figure out exactly how fast the t-rex was moving. based on the dig-in of the toes of the print, however, it appeared that this T rex, while crossing this stream, was not running. drat, no proof there. Further atomically study of the brain case, the fore limbs, and the vertebral column muscle attachment points have suggested that T-rex would not have made a very good live predator- it was too fat, too weak, and while it could move fast, it couldn't turn fast, which makes a land based predator very unsuccessful (which is why modern predators which turn slowly tend to attack from a water environment, for instance, crocodiles). The biggest evidence that T-Rex's were at least not predator-only? of the 30 incomplete t.rex skeletons we know of, there is a lot of evidence of healed fractures. At least one individual had cracked a lower leg bone, an injury which would have doomed an animal which had to chase down it's food on a daily basis. but this individual lived, for many more years, in fact (based on the amount of healing to the bone wound area), suggesting that even while lame, it was able to get enough food to survive. (go Bob Bakker! no, not the guy on The Price is Right

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his name is Bob Barker. you should all read Raptor Red by Bob Bakker, cool book from the perspective of a Utahraptor)

was T Rex a predator, very possible. was he a scavenger? almost definite. was he both? probably.
fossil footprints of large herbivores of the time show foot, foot, foot, and no tail drag! so it really seems that the tails were in the air, at least in part helping to balance the creature. possible as a defensive whip, and maybe even a tripoding leg for reaching high tree branches, ala Jurassic Park, the movie. vertebral measurements suggest that the brachiosaur neck could bend to very low levels, allowing a huge beast to drink from a pond w/o having to enter the pond; it could move side to side such that the head to nearly reach the hind limb joints - it was one flexible beast!!


so, on to the extinction theories. There have been many theories as to why the dino's died out, but currently, a mixture of disease and impact theories are the most accepted. Why? as for the disease theories, there is evidence of more and more individuals suffering bone level infection at the time of their deaths, suggesting there was a high level of disease at the time of extinction.
why impact theory? Well, there were a lot of theories going around in the fifties, lost of evidence, and a lot of arguing which was getting no where. Then (I forget when), two scientists suggested the impact theory. everyone laughed at them. over the last 30 years or so, more and more evidence supporting the impact idea has come to light, and the impact theory has become the prominent theory of the cause of the dino extinction 65 million years ago.

1)iridium. Iridium is not commonly found on the surface of the Earth, in fact it is not commonly found on the earth at all! It is, however, often found in asteroids which impact the earth. There is a thin layer of iridium found world wide at the same carbon dated geological level of 65 million years.
2)global fire. At this same geological level, you find a dark ash. this thin layer of ash covers the *entire planet*, as if a layer of ash was deposited all at one time, around the globe. Thus the "global fire" theory. this ash layer can also be interpreted as the ash falling back to the earth over time. ash which was ejected into the atmosphere via a large impact.
3)dino teeth. below the ash layer mentioned above, you find dinosaurs. above that layer (usually younger deposited material), you find only small dino teeth. no fossils, no large teeth. just small teeth and teeth fragments.

the above evidence points to a large fire, possible extra-terrestrial material, and some weird thing about teeth. but how can ash stay up in the air for years and years? that doesn't seem logical, does it?

4)supervolcanoes. super volcanoes which erupted in the recent past have provided evidence that ash and other material can remain in the air for long periods of time (the 535 AD eruption of a volcano in southern Europe blocked out the sun intermittently for around 18 months, according to written records, and dropped the average annual temperature a noticeable amount. ash from Mt St Helens reached all the way to Europe. Both these explosions were teeny-tiny compared to a super-volcano. The enormous environmental effect of the sulfur gas released during the Lakagigar eruption in Iceland in 1973 provided evidence of how devastating volcanoes can be, even outside of direct contact w/ really hot stuff.)
http://www.space.com/scienceastronomy/planetearth/volcano_monitor_010807-1.html

so, when the Chicxulub crater was discovered, 50% of the people shouted "asteroid!", while the other half shouted "Caldera!" (keep in mind this was just after it was realized that Yellowstone was home to one of the world's largest Calderas, and appearently it covers an actively filling lava pillow.)

then there was:

5)shocked quartz. the heat and pressure required to cause fractures in quartz are so high, that not even the force of super volcano explosions can create this "shocked quartz" (even though stuff ejected from the yellow stone Caldera during it's last explosion reached some parts of eastern Texas and further, based on chemical and visual analysis of geological material. The force is not sudden enough to properly deform the structure of the quartz). However, shocked quartz can be found at sites where know asteroid impacts have occurred, and can be found in small quantities at nuclear bomb test sites. The levels of shocked quartz found at the Chicxulub crater, together with the levels of iridium, the size, depth, and timeframe (based on estimates of everything from fill levels to C14 radio-carbon dating of surrounding strata (a currently under-fire dating method, to say the least)), in addition to this new bit of evidence:
http://www.nmnh.si.edu/paleo/blast/asteroid_hyp.htm
http://www.nmnh.si.edu/paleo/blast/the_core.htm
makes the impact theory seem very likely.

wet1: we actually have precious little to find now, so I bet you're right. Given all the fame and press that the T-rex gets, we only have 30 partial skeletons world wide! over 50% of those were found in the Wyoming/Montana area of the US. The Supersaurus is a huge behemoth based off of the partially preserved back section of one animal found in 1972. two 8' shoulder blades, some ribs, some neck vertebrae, and some of the pelvis.

some of the best preservation methods are common world wide-mudslides. too compact for air to seep through, decomposition is regulated to anaerobic bacteria, mineral replacement is rapid, fossilization is common. So as long as we are buried in mud ( and not in coffins), there should be stuff left for excavation 65 million years from now. hot, dry sand works too, but not nearly as well. wet bogs w/ huge levels of methane, and nearly no O2 (peat bogs) work pretty well, also, but there isn't a lot of evidence that they work for more than a few hundred thousand years.

ok, I'm done my dinosaur rant for now. Did I miss anything? Is anything inaccurate?


edit: oh, yeah, go Jack Horner! not as crazy as Bakker, but even more important for advancing the theory of the great mother lizard- that many dio species traveled and covered distance in herds, but also that the mothers cared for their young.

edit2: fixing little mistakes, like mis-linking my links.

edit3: don't take the above to mean that we know everything that happened! there are still a lot of holes which need filling. if you are interested, many universities sponsor summer excavation projects world-wide, and volunteers are greatly appreciated !!

edit4:spelling

 

heeheehee

topical cartoon

 

Would it be posible that a great asteroid collided the earth at the time of the dinasours that probably hits the north or the south pole, it was so huge that resulted earth to tilt and the ice on the north and south pole to entirely melt and resulted to a great flood and drowned the dinosaurs?

There are many evidence that there had been great floods that lasted for many years.

 

Have you ever read a theory that that massive asteroid impact hit either the north or the south pole causing the earth to tilt and produced a great flood that killed the dinos?

 

My impression was that the ejecta from the impact was hurled high enough to rain down across the whole Earth (more so in some places, less so in others, due to the Earth rotating beneath). The heat generated on reentry of the ejecta was sufficient to cause flash fires across the whole Earth, incinerating any animal unfortunate enough to be above ground, not protected by cloud cover, and not in one of the less affected regions.

 

Here's a link:
NationalGeographic.com

 

Interesting discussion here (from June 2001):

Do We Know What Killed the Dinosaurs? (NASA Astrobiology Institute)

 

Very interesting essay. I start to agree that it may help explain the problem to examine the (what's that called again?) non-heterotrophic creatures.....