This is the last of three geologic eras squeezed into the Phanerozoic ("Evident Life") Eon that covers the last 10% of Earth's whole geologic history. This is the "Age of Mammals" in which whales took over the oceans, saber-tooth cats shared the land with elephants and giant sloths, and humans finally appeared.
The Cenozoic period began about 65 million years ago with the extinction of the dinosaurs and continues through the present. The Cenozoic is divided into just two time periods: the Tertiary, and the Quaternary. We can only summarize the many events of these periods. You can learn more by going to your library or searching the Internet for words like "Cenozoic" or the names of each of the periods.
The view of Earth above is that of today. During the last 65 million years, Pangea has broken up into the continents, and they have moved into the positions which we see them in now. The Atlantic Ocean has opened from a narrow valley to a vast ocean. India has moved across the Indian Ocean and collided with Asia to make the Himalaya Mountains. North and South America have moved westward over part of the Pacific Ocean. The pressure has crumpled the western coasts of both continents to form the Rocky and Andes Mountains. Part of the Pacific sea floor has been forced into the warm interior under the American continents, causing melting and the formation of the Cascade and Andes volcanoes on the surface.
The global climate has turned somewhat colder, and the last few million years have seen the return of giant glaciers and ice caps to North America, Eurasia, and Antarctica.
After the disappearance of the dinosaurs, there were suddenly many empty places on Earth where animals could live. Mammals, which were small, mouse-like animals at the beginning of the Cenozoic, quickly spread out, diversified in kind, and grew in size. Soon the plains and forests of Earth were occupied by giant rhinos and elephants, lions and saber-tooth cats, horses and deer. The skies filled with bats and birds, and the seas filled with whales and porpoises, as well as with fish and octopi. There have been mass extinctions during the Cenozoic as there were during the Mesozoic and Paleozoic, but not as many animals and plants have disappeared.
Finally, humanity appeared during the last two million years. In the last 10,000 years, a blink of the eye in geologic time, humanity has spread across the lands and seas of Earth, altering the face of Earth with cities and farms, destroying some plants and animals and domesticating others. Humans have become the dominant terrestrial life form: more numerous than any other large animal, and more fearsome than the most terrible of dinosaurs.