Africa

The Silurian was followed by the Devonian, Mississippian, and Pennsylvanian periods (408-286 million years ago), the time interval when insects, reptiles, amphibians, and forests first appeared. A continental collision between Africa (Gondwanaland) and the North American plate formed a super-supercontinent (Pangaea) and raised the ancient Mauritanide mountain chain which once stretched from Morocco to Senegal. During the late Pennsylvanian period, layer upon layer of fossilized plants were deposited, forming seams of coal in Morocco and Algeria.

When Pangaea and later Gondwanaland split apart in the Cretaceous period (144-66 million years Zebras grazing at the foot of Mount Kilimanjaro, the highest point in Africa at 19,340 ft (5,895 m). © Gallo Images/Corbis. Reproduced by permission.

ago), a shallow sea covered much of the northern Sahara and Egypt as far south as the Sudan. Arabia, subjected to many of the same geological and climatic influences as northern Africa, was thrust northward by tectonic movements at the end of the Oligocene and beginning of the Miocene epochs (around 30 million years ago). During the Oligocene and Miocene (5-35 million years ago; segments of the modern Cenozoic Era) bears, monkeys, deer, pigs, dolphins, and early apes first appeared.

Arabia at this time nearly broke away from Africa. The Mediterranean swept into the resulting rift, forming a gulf that was plugged by an isthmus at present-day Aden on the Arabian peninsula and Djibouti near Ethiopia. This gulf had the exact opposite configuration of today's Red Sea, which is filled by waters of the Indian Ocean.

As the Miocene epoch drew to a close about five million years ago, the isthmus of Suez was formed and the gulf (today's Red Sea) became a saline (salty) lake. During the Pliocene (5-1.6 million years ago) the Djibouti-Aden isthmus subsided, permitting the Indian Ocean to flow into the rift that is now the Red Sea.