Scarlet, orange, and purple stripes suddenly flashed in the sky. A terrible monster rose from the depths of the lake. How could this vision of the distant past arise in our days? What do the bones of extinct animals tell us? Why did the giant lizards, who were once the rulers of the Earth, die? Professor A. A. Malakhov tells in his science fiction book about the adventures of geology students seeking answers to these mysteries. Published in 1962.