S e c o n d e d I t I o n 1 Reading for the Real World 1

3.
Scientists believe that an asteroid that was one or more kilometers in diameter 
may have caused the extinction of the dinosaurs.
4.
Asteroids that follow Jupiter in its orbit are called “Trojans.”
5.
The NEA in 1989 that scientists failed to detect could have been 50,000 times more 
destructive than the atomic bomb dropped on Hiroshima if it had struck the Earth.
6.
Another name for a comet is NEO or Near-Earth Object.
Asteroid Impacts on Earth
Types of Asteroids
Effects of Impact

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ifferent kinds of NEAs can produce different kinds of damage. The 
kind of damage depends first on the size and speed of the asteroid. 
However, it also depends on where the asteroid hits. An asteroid that 
hits the ocean will have a very different effect than one that strikes the land. 
An asteroid that hits the water would produce the most destruction. While 
an asteroid hitting land would cause damage in only one place, an ocean strike 
would cause a tsunami (a giant wave). This could severely damage or destroy 
cities close to the ocean over a very large area. Seventy percent of the Earth is 
covered by oceans, so an ocean impact is more likely. If a large asteroid struck 
the middle of the Atlantic Ocean, the tsunami could destroy cities on the east 
coast of North and South America, as well as western cities of Europe and Africa. 
Such an asteroid would only have to be about forty to sixty meters wide.
An asteroid strike on land would be destructive in a concentrated way. It 
would take an object of about seventy-five meters wide to destroy a city. This 
would not include all parts of the city, and suburbs might not be damaged so 
severely. To destroy an entire urban area would 
take an asteroid of around 160 meters. A 700 
meter asteroid could destroy a small country. 
However, a one or two kilometer asteroid strike 
would be deadly enough to kill millions of 
people, simply by the dust and vapor it would 
throw into the atmosphere.