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mwestwood eNotes educator| Certified Educator

While there have been many theories on what caused the extinction of the dinosaurs--excessive size, the greenhouse effect, egg predation, non-viable eggs, replacement by mammals, disease, etc.  But, recently, scientists theorize that a meteor collided with the earth, ejected dust and debris to such thickness that the sunlight was blocked for a long time, so long that the plants died.  Without food, the herbivores died.  While the carnivores could subsist on the carcasses, once all these carcasses were gone, they, too, starved to death.

In the 1980s the father-son team of Luis and Walter Alvarez discovered a layer of iridium in the K-T Boundary.  They theorized that a hug asteroid struck the earth.  Not only would there be dust, but forest fires would create smoke as well.  The earth would be cooled as the sunlight could not penetrate it and tremendous climatic changes would occur.

Jamie Wheeler eNotes educator| Certified Educator

I once took a graduate course called "The History of the Fact." What I took away from it that "facts" are highly subjective.

All of the above responses (I believe) site "asteroids" as the likely cause of the demise of the dinos. However, just THREE days ago, NASA ruled out this theory.

The Baptistina Asteroid was thought to have crashed into another asteroid, and that impact sent "segments the size of mountains" crashing into Earth.

New techniques of measurement have been developed, and Baptistina has been dated to just 80 million years, not 160 million as previously believed.

For now, reseachers say, what killed the dinosaurs goes back to the "cold case files."

Read the entire article about this new research at the link below.



enotechris eNotes educator| Certified Educator

Iridium is a very rare element on Earth, but is plentiful in meteors.  The Alvarez discovery of a layer of iridium at the 65 million year mark all around the world had suggested that what struck the Earth was something miles wide, landing at an oblique angle in the Gulf of Mexico (if you recall the large curve between the Yucatan and Texas, that'll give you an idea of the area of impact.)  The impact was so great current theory states that North America was ablaze within minutes, and the resulting fire, ash, and debris caused by the impact brought about a "nuclear winter" which altered the climate sufficiently to wipe out much of the plant life.  It appears there have been several cataclysmic events in Earth's history, where much of what is living is killed off at once.

marycc eNotes educator| Certified Educator

Current theory is that the dinosaurs were killed by the impact of a large asteroid that struck the earth at the end of the Cretaceous period.  Evidence supports this theory.  Iridium and soot layers in rocks of this age have been found in many areas of the earth.  Magnetic studies have shown a crater like area in the Gulf of Mexico where the asteroid may have struck.  The asteroid impact would have caused widespread devastation. Fires, intense heated winds, ash, and clouds of superheated particles would have destroyed anything in their path.  The impact would be felt for many years with clouds of ash blocking out the sun and changing the climate of the earth. Many species on earth could not adapt to this and died out making one of the great extinctions on the planet,

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