EXTINCTIONS There have been five great mass extinctions of life forms caused by volcanic activity or meteorite strikes. A great extinction in the Permian/Triassic time, 250 million years ago, destroyed 95% of life forms. EXTINCTION OF THE DINOSAURS Scientists think a giant meteor struck earth about 65 million years ago. It caused the extinction of the dinosaurs and two-thirds of the world’s species. The energy of the explosion heated the atmosphere to furnace temperatures. Animals roasted and forests burned. Then dust and smoke blocked out the sunlight creating a world-wide freeze.

You look up in the sky and see something un- usually bright. An hour later it appears even more brilliant. The object grows larger and brighter until three hours later it enters Earth's at- mosphere. It is an asteroid, and

it ignites into a blinding fire- ball that strikes the surface of our planet seconds later. Ground zero is a shallow sea; the impact generates enormous tsunamis that flood coastal regions for thousands of kilo- metres. Dust and gas fly into

the sky. The energy released as the dust and gas rain back down to Earth heats the atmo- sphere to the temperature of a kitchen grill. Land animals roast and forests burst into flames. Dust particles and smoke block out the sun. In

the darkness, plants perish and animals starve. Earth plunges into a deep freeze. Sulphur gases released from vapourised rock mix with water in the atmosphere to form acid rain, which falls to Earth, killing any tiny marine plants.