The geology of Africa is defined by a stable, ancient core of Precambrian cratons surrounded by younger fold belts, a history of continental collisions and breakups (culminating in the East African Rift System), and vast mineral resources. Africa's geologic history after the Precambrian era involved several key events: Gondwana Breakup with voluminous basaltic volcanism (the Karoo System) occurred 230-200 million years ago, likely related to the initial breakup of the supercontinent Gondwana. Mountain building by the collision of the African and European plates formed the Atlas Mountains in northwestern Africa and the most prominent modern tectonic feature is the ongoing development of the East African Rift System. This is a divergent plate boundary where the continent is slowly splitting into two new plates. A process accompanied by significant seismicity, volcanism (e.g. Mount Kilimanjaro), and the formation of lakes and rift valleys. Africa's diverse geology has endowed it with vast mineral resources: The ancient cratons host world-class deposits of gold, diamonds, iron ore, and manganese. The mobile belts and layered igneous intrusions are major sources of platinum group elements, chromium, and cobalt. Younger, largely undeformed sedimentary basins overlay much of the ancient crust. They are rich in crude oil, natural gas, and coal deposits.