Africa

Present-day Africa, occupying one-fifth of Earth's land surface, is the central remnant of the ancient southern supercontinent called Gondwanaland, a landmass once made up of South America, Australia, Antarctica, India, and Africa. This massive supercontinent broke apart between 195 million and 135 million years ago, cleaved by the same geological forces that continue to transform Earth's crust today.

Plate tectonics are responsible for the rise of mountain ranges, the gradual drift of continents, earthquakes, and volcanic eruptions. The fracturing of Gondwanaland took place during the Jurassic period, the middle segment of the Mesozoic era when dinosaurs flourished on earth. It was during the Jurassic that flowers made their first appearance, and dinosaurs like the carnivorous Allasaurus and plant eating Stegasaurus lived.

Geologically, Africa is 3.8 billion years old, which means that in its present form or joined with other continents as it was in the past, Africa has existed for four-fifths of Earth's 4.6 billion years. Africa's age and geological continuity are unique among continents. Structurally, Africa is composed of five cratons (structurally stable, undeformed regions of Earth's crust). These cratons, in south, central, and west Africa are mostly igneous granite, gneiss, and basalt, and formed separately between 3.6 and 2 billion years ago, during the Precambrian era.

The Precambrian, an era which comprises more than 85% of the planet's history, was when life first evolved and Earth's atmosphere and continents developed. Geochemical analysis of undisturbed African rocks dating back 2 billion years has enabled paleoclimatologists to determine that Earth's atmosphere contained much higher levels of oxygen than today.