| IN THE YELLOWSTONE AREA | YEARS AGO | IN THE WORLD |
| 4.6 bya |
Earth and all the planets are formed. |
| Formation of the Precambrian gneiss of the Beartooth Range, seen in Lamar Canyon. | 3.2 to 2.7 bya | |
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| Limestones are formed from the shells of sea-dwelling animals, as seen at Pebble Creek.
| 360 to 320 mya | |
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| | 200 mya | The motion of earth's tectonic plates is beginning to bring the continents
into today's positions. First dinosaurs appear; small mammals live among them. |
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| Shale and sandstone from silts laid down in shallow seas will make up Mt. Everts at Mammoth Hot Springs.
| 150 to 70 mya | Sierra Nevada forms in California. |
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| | 68 mya | Dinosaurs become extinct, probably as a result of a gigantic meteorite impact in Yucatan, Mexico. |
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| Absaroka Range volcanoes form, and their eruptions cover the area with lava, mudslides,
and ash. In the subtropical climate, forest growth and lava flows alternate many times, creating the petrified trees of Specimen Ridge and the Gallatin Range. | 53 to 44 mya | |
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| Tetons begin to rise and Jackson Hole begins to sink along a fault; displacement continues today. | 13 mya | |
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| | 4.1 to 3 mya | Hominids (Australopithecus anamensis and A. afarensis) live in East Africa. |
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| First caldera eruption occurs; Huckleberry Ridge tuff accumulates, seen at Golden Gate near Mammoth. | 2.2 mya | Glaciers cover parts of Europe and North America. Ice covers the land and recedes in cycles of 50,000 to 100,000 years' duration. |
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| | 1.8 to 1 mya | Man-like apes (Australopithecus africanus) live in Africa. |
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| Second caldera eruption occurs; Mesa Falls tuff accumulates west of Yellowstone's Bechler Region. | 1.3 mya | |
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| 800,000 to 200,000 ya | Direct ancestors of today's humans (Homo erectus) use fire and perfect tools but then are transcended by Homo sapiens. |
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| Third caldera eruption occurs; Lava Creek tuff accumulates, as at Tuff Cliff between Madison Junction and Gibbon Falls. | 640,000 ya | |
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| Glaciers cover Yellowstone (the Bull Lake Glaciation, evident in the Madison Valley near West Yellowstone). | 160,000 to 130,000 ya | |
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| Lava continues to flow from the magma chamber, filling the caldera and spilling over its rim. Most is rhyolite lava, as at Firehole Falls, but some is basaltic lava, as at Sheepeater Cliffs. | up to 70,000 ya | |
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| Glaciers again cover Yellowstone intermittently (the Pinedale Glaciation,
evident throughout the lower Lamar Canyon). Hot areas that will become geyser basins
are under some 2000 feet (more than 0.5 km) of ice. | 110,000 to 12,000 ya | |
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| | 35,000 ya | Oldest known cave art is created in Ardeche region of southern France. |
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| Artifacts found in and near Yellowstone prove Paleo-Indian humans were here from the end of the last glaciation. | 13,000 to 9000 ya | Clovis and Folsom cultures live in southern and western present-day U.S. |
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| | 12,000 to 10,000 ya | Latest ice sheet retreats northward from midwestern and northeastern U.S. |
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| | 5000 to 4500 ya | Man begins to create written records (Sumerian language). |
