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| Table of Contents | Enchanted Learning All About Astronomy |
Site Index |
| Our Solar System | Stars | Glossary | Printables, Worksheets, and Activities | ||||||
| The Sun | The Planets | The Moon | Asteroids | Kuiper Belt | Comets | Meteors | Astronomers | ||
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ASTEROIDS |
| Introduction | Near-Earth Asteroids (NEA) |
Asteroids and Dinosaurs | List of Some Asteroids | Composition | Activities, Web Links |
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| Dinosaurs and Asteroids |  |
There are some asteroids that have orbits outside the asteroid belt. Some have orbits that cross the orbit of the Earth, and some have hit the Earth. A large asteroid could survive the trip trough Earth's atmosphere (called a meteor during its trip through the atmosphere) and form an impact crater.
An asteroid impact with the Earth may have caused the extinction of the dinosaurs. The Alvarez Asteroid Theory explains the huge K-T mass extinction 65 million years ago by a large asteroid hitting the Earth off the Mexican Yucatan peninsula. This impact would have caused severe climactic changes leading to the demise of many groups of organisms, including non-avian dinosaurs.
, pterosaurs
, plesiosaurs, mosasaurs, ammonites, some families of birds and marsupial mammals, over half the plankton groups, many families of teleost (bony) fishes, bivalves, snails, sponges, sea urchins and others.
4-9 miles (6-15 km) in diameter hit the Earth 
about 65 million years ago. The impact would have penetrated the Earth's crust, scattering dust and debris into the atmosphere, and causing huge fires, volcanic activity 
, tsunamis
, and severe storms with high winds
and highly acidic rain 
. The impact could have caused chemical changes in the Earth's atmosphere, increasing concentrations of sulfuric acid, nitric acid, and fluoride compounds. The heat from the impact's blast wave would have incinerated all the life forms in its path.
for months, and lowered the temperature 
globally.
- Tektites are quartz grains which are vaporized under intense heat and pressure, and cool into glass beads with no crystalline structure. Tektites were probably formed during a meteorite or comet collision. Tektites are abundant in the K-T layer.
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