Geology Timeline

2.7 billion to 570 million years ago

Precambrian History: The most ancient rocks in North America form during the Precambrian era. Huge mountain ranges form and erode away, until Yellowstone is a relatively flat plain.

600 million to 75 million years ago

Floods alter the Landscape: The region is periodically flooded by shallow seas. Lush jungles slowly evolve. The area that is now Grand Teton National Park looks like the Everglades in Florida!

75 million to 55 million years ago

Formation of the Rocky Mountains: The Rocky Mountains form, creating intense stresses within the earth, followed by a period of violent volcanic activity.

55 million to 40 million years ago

Volcanic Period: During the Tertiary period, the Absaroka and Washburn ranges are formed by molten magma that covers most of the area that is now Yellowstone.

40 million to 2 million years ago

Climatic Changes: Yellowstone's climate grows hot and dry. Camels, elephants and primitive horses roam the land. Eventually, mountain building begins again in the region.

2 million to 640,000 years ago

Yellowstone Caldera Formed: Three tremendous volcanic blasts occurred. The last, the Yellowstone Caldera, formed a crater more than 45 by 30 miles in size.

300,000 to 14,000 years ago

The Ice Ages: Three glacial ages sweep through Yellowstone. When the last one subsides, it leaves behind the changed landscape that we see today.