Bob Welter, age 11, of Des Moines, for his question:

When was the Jurassic Age?

The Jurassic was a Period of earth's history, a mere paragraph in the chapter called the Mesozoic Era. The era lasted about 125 million years. The Jurassic Period was the middle paragraph in the chapter and. lasted about 25 million years. The experts estimate it opened about 155 million years ago and closed about 130 million years ago.

The dinosaurs were at their prime and. the first birds took to the air during this period. An invasion of the sea swamped eastern California and, perhaps, made the coastal region into a long, offshore island. The Rockies as we know them were unborn. But the proud Sierra Nevada grew to their full height during the: ancient Jurassic Period.