Dianne Stubbs, age 14, of Mize, Miss., for her question:

What was the Tertiary Period

We are living in the Cenozoic Era, the most recent chapter of earth’s  age old history. This era opened with the Tertiary Period, some 61 million years ago and the Tertiary came to a close about one million years ago, A t the start of the Tertiary Period, we would hardly recognize our planet. The young Rockies seethed with volcanoes and much of our west was swamped by shallow seas. There were no Great Lakes, and no Grand Canyon. Central America had only recently risen from the sea to make North arid South America a single land mass.

The climate was very warm. Magnolias bloomed in Alaska and crocodiles flourished in the Dakotas. There were still giant reptiles stalking the earth, but the Day of the Dinosaurs was coming to a close. One branch of their family, the crocodiles: was to survive, though on a smaller scale. Another offshoot of the ancient reptile family which was to survive was the birds. When the Tertiary Period opened, the birds had already become warm¬blooded animals and most of them had already lost the teeth they once had.

A new type of animal, the mammal, had crept into the scene. Some of these furry, warm blooded little animals were meat eaters and some were vegetarians These mammals brought the greatest change to animal life in the history of the world. Until now, all baby animals had hatched from eggs. Their parents left them to fend for themselves as soon as they hatched. The mammal babies were born alive and at first mothers and later fathers learned how to become protective and devoted parents.

Another new factor brought by the mammals was intelligence, though not the kind of intelligence we think of in school. The mammals had more brain and were generally smarter than the dull dinosaurs.

And, almost always in a contest between brains and muscles, the brainy fellow wins out. Certainly the little mammals were better able to cope with life than the clumsy dinosaurs who were soon to perish.

When the Tertiary Period was about ten million years old, herds of collie sized horses and small humpless camels roamed North America. They were the ancestors of our modern horses and camels. Soon the world climate became cooler. The busy little Colorado River began to dig Grand Canyon and the west seethed with volcanoes. Oaks, elms and other trees that shed their leaves began to spread. In Europe, the Alps and the Pyrenees began to lift up their heads and the lofty Himalayas began to hump up from a shallow ditch.

When the Tertiary Period closed, the face of the old earth was much as we know it, though many animals were strangers to us. These and other animals perished in a dramatic event which began as the Tertiary Period closed. This was about a million years ago when the glaciers of the Ice Age crept down from the north.