154 The History of the Earth: Supplemental Guide 8A | Dinosaurs
Show image 8A-10: Meteor
For years, many scientists believed that extraordinary geologic
events, such as super volcanoes, must have had something to
do with it. These days, however, many scientists believe that the
dinosaur extinction was caused by a giant meteorite from outer
space.^13 There are billions of meteors, or burning chunks of debris
in outer space. Some meteors are quite large, but most are tiny,
between the size of a sand grain and a baseball. Meteors are
whizzing around all over the place in outer space. Occasionally, a
meteor crashes toward Earth. When this happens, the meteor hits
the atmosphere at an incredible speed and usually burns up as it
enters the uppermost parts of earth’s atmosphere.^14 Occasionally,
bits and pieces of meteors survive their trip through the
atmosphere and actually fall to earth. This is very rare, but it does
happen from time to time, and it is possible to fi nd pieces of them
on the ground. When part of a meteor survives the trip through the
atmosphere and lands on Earth, the meteor becomes a meteorite,
or space rock that has landed on Earth.
Show image 8A-11: Recovered meteorite
Now, let’s go back to dinosaur extinction. Some scientists think
that the dinosaur extinction was caused by a giant meteorite from
outer space. When the meteorite struck the earth, it sent massive
plumes of debris up into the atmosphere.^15 This debris would
have blocked out the light and energy of the sun, causing much of
the earth’s plant life to die and severely lowering the temperature.
Most creatures at the time would have been unable to adapt, and
they would have died out before the skies had a chance to clear.
Whether this is true or not remains to be seen, though
geologists have discovered at least one very large crater that
was caused by a meteorite impact about the time the dinosaurs
became extinct. Whatever the case, we know that dinosaurs
became extinct, making way for new kinds of life on earth. I, for
one, will continue to study the earth’s fossil record, and I am sure13 A meteorite is a piece of rock that
falls from space to the earth.
14 [Remind students that they learned
in the Astronomy domain that this
creates a streak of light in the night
sky that some people think is a
shooting star.]
15 It sent large amounts of bits and
pieces of objects from the earth up
into the atmosphere.