The Arabian Plate was part of the African Plate during much of the Phanerozoic Eon (Paleozoic-Cenozoic), until the Oligocene Epoch of the Cenozoic Era. Red Sea rifting began in the Eocene, but the separation of Africa and Arabia occurred approximately million years ago in the Oligocene, and since then the Arabian Plate has been slowly moving toward the Eurasian Plate. The opening of the Red Sea rift led to extensive volcanic activity. There are large volcanic fields called the Older Harrats, such as Harrat Khaybar and Harrat Rahat, cover large parts of the western Arabian Plate. Some activity still continues especially around Medina, and there are regular eruptions within the Red Sea.