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ixty-five
million years later, the extinction of the dinosaurs remains a
great mystery. Scientists think that dinosaurs existed on Earth for
almost 200 million years. How could these great beasts, some of which
weighed thousands of pounds and stood 100
feet tall, suddenly disappear?
The most popular theory is that dinosaurs were killed off when an asteroid
crashed into southern Mexico. The asteroid’s collision caused earthquakes, fires,
and tidal waves. Volcanoes erupted, spewing poisonous gases into the sky and
lowering the oxygen level in the oceans.
Plants died, removing the food source
for plant-eating dinosaurs. As these dinosaurs died, there was no food for
meat-eating dinosaurs. In a short period of time, the dinosaurs were gone, and
the first mammals began to appear.
Many
scientists note that, while the asteroid had a major impact, the Earth’s
climate had already begun to change. The planet was cooling, and the colder
temperatures were likely killing plants. Some scientists claim that mammals already
on Earth before the asteroid might have facilitated the
extinction by eating dinosaur eggs.
We may never know for certain what caused the
extinction of dinosaurs. But it
was most likely the result
of a combination of the asteroid, colder climates, disease,
and egg-stealing mammals rather than the single event of
the asteroid hitting the Earth.
