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Fraser
2003-Sep-26, 04:27 PM
SUMMARY: Most paleontologist believe that a gigantic asteroid struck Mexico 65 million years ago and killed all the dinosaurs; end of story. But a minority believe that the Earth's environment was already uncomfortable for dinosaurs because of a series of asteroid strikes and volcano eruptions - the asteroid was just the straw that broke the camel's back. By studying the life spans of colonies of one-celled organisms, paleontologist Gerta Keller has uncovered that the Cretaceous period might have lasted 300,000 years after the asteroid impact.


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SCHNECK
2003-Sep-27, 09:43 AM
:blink:

--Ocean floor becomes negatively buoyant as it cools 50 million years ago(1).Andrew Hynes.

(1)BUOYANCY OF THE OCEAN FLOOR
HYNES, Andrew, Earth and Planetary Sciences, McGill Univ, 3450 University Street, Montreal, QC H3A 2A7 Canada, andrew@eps.mcgill.ca.
Estimates of the age at which ocean floor becomes negatively buoyant as it cools range between 50 Ma and as little as 10 Ma. The buoyancy of the ocean floor - how much lighter the ocean floor is than the underlying mantle - may be calculated from the composition of the crust and its underlying mantle, by calculating the mineralogy of the crust and mantle and determining the density from the oceanic geotherm. I have used a variety of parameterizations of the chemistry of melting of the mantle as it rises at mid-ocean ridges to determine the bulk chemistry of the crust and the chemistry of the residual depleted mantle as a function of depth. I have then used the mineralogy derived from this chemistry to determine the density as a function of age of the ocean floor. Regardless of whether the oceanic crust is considered to be derived from uniform melting of a column of mantle, or from greater melting at shallow depths than at deeper ones due to greater overstepping of the peridotite solidus, calculations indicate that typical ocean floor does not become negatively buoyant, even if it cools at the surface for 200 Ma. The mean density of the ocean floor at 200 Ma is still 10-30 kg/m3 less dense than the underlying mantle. The range in estimates of its buoyancy is more affected by the choice of thickness for the oceanic plate than by the choice of melting parameterization. The positive buoyancy of the ocean floor does not preclude subduction, since older ocean floor is always less buoyant than young ocean floor that would replace it, but it suggests that ocean floor would not subduct spontaneously, even if it did not strengthen as it cooled, and that slabpull forces may typically have been overestimated.

GSA Annual Meeting, November 5-8, 2001
General Information for this Meeting
Session No. 162
Tectonics III: Wrench Systems- Oceanic and Global Tectonics
Hynes Convention Center: 210
8:00 AM-12:00 PM, Thursday, November 8, 2001


--The pleiades are thought to have formed 60-80 Million years ago, perhaps at the same time or just before the K-T event
http://www.ras.ucalgary.ca/~gibson/pleiades/

imported_Draco
2003-Sep-28, 03:36 AM
I saw a documentary once about how the dinosaurs died.
This was a few weeks ago.
And i think the documentary incorporated some of the stuff that you said Schneck.
Yes an asteroid collided with the earth, but i think it hit Greenland or somewhere, becuase thats where this type of rock or something was mainly found.
And the dinosaurs didn't die instantly, but over a period of like 40thousand years.There were something like geysers i think underneath the water, and if something penetrates them, its causes them to like explode, heating the water or something....
I forgot most of the impportant points. But i did remember something highly intriguing part, this mammal....the name was weird, something like Listoarus or something...all other creatures died, but this one mammal managed to cling to life, and it is becuase of this mammal that we are alive today....supposedly!

I'm sure that there are people that would disagree with me if they believe in god....so yeah!

Abbey Finnigan
2004-Jan-15, 03:57 PM
Originally posted by fraser@Sep 26 2003, 04:27 PM
SUMMARY: Most paleontologist believe that a gigantic asteroid struck Mexico 65 million years ago and killed all the dinosaurs; end of story. But a minority believe that the Earth's environment was already uncomfortable for dinosaurs because of a series of asteroid strikes and volcano eruptions - the asteroid was just the straw that broke the camel's back. By studying the life spans of colonies of one-celled organisms, paleontologist Gerta Keller has uncovered that the Cretaceous period might have lasted 300,000 years after the asteroid impact.


Comments or questions about this story? Feel free to share your thoughts.
[FONT=Times][SIZE=7][COLOR=blue] I, for one, do not believe that the earth exisisted 65 million years ago. However, if this world did exsist then, then the possibility of the asteroid hitting the world, targeting mexico, would have most likely caused extinction of dinosaurs. To reach this conclusion i studied on what scientist had hypothesised. If the the Asteroid hit, MILLIONS of TONS of debris flew into he atmosphere and block the heat from the sun. Plants depend on the energy of the sun for photoseinthesis to produce it's food. Plant eaters depend on the plants for their survival, so without the plants those animals that were dependant on plants, would die out. Also, the carnivores that depend on the other dinosaurs to survive would start losing the plant eaters therefore having to turn onto their own species. Since dinosuars most likely did not consider other dinosaurs feelings, they woujld eat when they were hungr. Eventually, the species in themselves would collapse, leaving 1 dinosaur alive at the end. While that dinosaur displayed Jack London's theory of Survival of the Fittess, it would soon die of starvation. All together, the asteroid's massive destruction of the earth caused death among dinosaurs and all other animals who could not adapt to the changing enviroment.

damienpaul
2004-Jan-15, 04:02 PM
In a recent edition of Scientific American, the suggestion that a prolonged period of wild fires, continental sized wild fires swept across most landmasses immediately after the Chixculub impact...perhaps as thestory goes, there were a continuous reign of fire so to speak.

Chook
2004-Jan-15, 09:02 PM
Gee Alice - I reckon that swarms of the Giant Carnivorous African Ants chased the dinosaurs and ate 'em all up. ;)