G : The death of the dinosaurs is a great mystery.
About 65 million years ago, dinosaurs lived all
over the Earth. They had existed for nearly 200
million years. Suddenly, they all became extinct.
Many scientists believe that the dinosaurs
were killed by a large meteor. They think that
this meteor was about six to twelve miles wide.
It crashed into southern Mexico and made a
hole about 130 miles wide. The crash threw dust
and dirt into the sky. Dust clouds darkened the
Earth’s atmosphere. The crash caused fires,
earthquakes, and tidal waves. The plants were
killed. The oceans were poisoned. Very soon,
there was no food left for the plant-eating
dinosaurs. When they died, there was no food
for the meat-eating dinosaurs. The meteor killed
almost 70 percent of all plants and animals on
Earth. The only animals that could survive were
small ones that could eat many different kinds
of food.
Some scientists say the meteor alone did not
cause dinosaurs to become extinct. They think
that dinosaurs were already getting weaker.
They are not sure why. One reason might be
disease. Another might be climate change. A big
part of the mystery is why some types of animals
survived. If climate change killed dinosaurs, it
should also have killed frogs. If the meteor killed
most sea reptiles, it should have killed crocodiles.
Yet frogs and crocodiles still exist in the world
today.