Dates	Period (System)	Epoch (Series)	Age (Stage)	Physical/Biological Features
10,000	QUATERNARY	HOLOCENE	(Present Time)	Continental glaciers restricted to antarctica and Greenland; extinction of giant mammals; development and spread of modern human culture.
Years Ago
1,800,000		PLEISTOCENE	Wisconsinan
			Sangamonian	Continental glaciers covered much of Northern North America and Northwestern Europe; volcanoes along the west coast of the U.S.; many giant mammals; appearance of modern man late in Pleistocene.
			Illinoian
			Yarmouthian
			Kansan
			Aftonian
			Nebraskan
			Blancan
5,000,000	TERTIARY	PLIOCENE
			Hemphillian	Western North America uplifted; most recent uplift of Sierra Nevada, much modernization of mammals; first possible apelike humans appeared in Africa.
22,500,000		MIOCENE	Clarendonian
			Barstovian	Renewed uplift of Rocky Mountains and Sierra Nevada; great lava flows in Western U.S.; mammals began to acquire modern characteristics; dogs, modern type horses, manlike apes appeared.
			Hemingfordian
38,000,000		OLIGOCENE	Arikareean
			Whitneyan	Many older types of mammals became extinct; mastodons, first monkeys, and apes appeared.
			Orellan
			Chadronian
54,000,000		EOCENE	Duchesnean
			Uintan	Mountains raised in Rockies, Andes, Alps, and Himalayas; continued expansion of early mammals; primitive horses appeared.
			Bridgerian
			Wasatchian
65,000,000		PALEOCENE	Clarkforkian
			Tiffanian	Great development of primitive mammals
			Torrejonian
			Dragonian
			Puercan