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Craters of the Moon Timeline
Craters of the Moon National Monument in Idaho exhibits some of the most recent volcanic activity in the United States. It hides, possibly, some of the oldest rocks beneath its dark cloak of lava. It has a complicated history that begins some 4.6 billion years ago.

(View Glossary definitions by clicking on the tan words).


4.6 Billion Years Ago

In Precambrian time, 4.6 billion years ago (Ga), as the earth began to take shape, small continents called cratons formed. Craters of the Moon was located along the western edge of one of these cratons.

540 Million Years Ago

Paleozoic time, starting about 540 million years ago (Ma), saw an increase in sea levels, possibly from an increase in temperatures and melting glacial ice. Gondwanaland and Pangea formed during this time. What is now southern Idaho was covered in hundreds of feet of water, sand, silt, mud, plants, and animals. Many of the fossils and sedimentary rock of southern Idaho were formed during this time.

245 Million Years Ago

All of that sedimentary rock was crushed and uplifted into mountains in Mesozoic time, about 245 Ma. The collision of the Earth's plates and the resulting subduction zones caused long chains of mountains to form along the edge of the plates. Idaho is right in the middle of all that commotion.

65 Million Years Ago

The mountain building continued into Tertiary time, 65 Ma. Because of the stretching of the crust, Basin and Range faulting begins. These large normal faults allowed huge blocks of land to rise forming more mountains. Also at that time the stationary Yellowstone-Snake River Plain Hotspot begins blowtorching a volcanic path across Southern Idaho as the North American plate moves over it. During this same time period the Columbia River Basalts of Oregon, Washington, and Idaho begin erupting. Is there some connection between all of these events? Geologists think so, but aren't sure how.

10 Million
Years Ago

Approximately 8-10 Ma, in Miocene time, the Yellowstone Hotspot erupted beneath the area that is now known as Craters of the Moon.

Years Ago

The Great Rift, stretching over 50 miles, began erupting 15,000 years ago in a chain of fire fountains or a curtain of fire, later concentrating to form cinder cones and spatter cones at Craters of the Moon. The last eruptions along the Great Rift occurred 2000 years ago. Scientists believe the first humans moved into Idaho about the same time the Great Rift began erupting. Evidence of habitation was found in a lava tube or cave 30 miles west of Craters of the Moon. There, archaeologists found bones carbon dated at 13,000 B.C. and a spear point dated at 12,500 B.C. These spear points, mostly made of obsidian, were later called the Folsom and Clovis points. These people probably witnessed some of the first eruptions at Craters of the Moon.


These early nomadic hunters evolved into the more stationary hunter/gatherers who were the ancestors of the Shoshone-Bannock Indian Tribe. They obtained horses about 1650 and then were able to range far and wide in search of game, plants, and trade. The Shoshone often passed through Craters of the Moon on annual migrations.


Lewis and Clark passed through Idaho in August on their way to the Pacific Ocean and in May and June (1806) on the return trip. Although they came in contact with a band of the Shoshone (Sacagawea's tribe) near Salmon they never came as far south as the Snake River Plain.


Fort Hall was established in August by Nathaniel Wyeth to aid the fur trade. Several mountain men passed through Craters of the Moon as they moved between the Big Lost and Wood River Valleys.


The migration of the pioneers to the west begins with the opening of the Oregon Trail. Jeffrey's or Goodale's Cutoff, an alternate route of the Oregon Trail, was opened in 1852 by John Jeffrey and was used frequently by Tim Goodale starting in 1862. This cutoff passed through Craters of the Moon as it ventured around the north side of the Snake River Plain.


A Geological Survey led by Israel Russell explored the area of Craters of the Moon and provided the first geologic description of what he called the Cinder Buttes.


In May, Robert Limbert, W.L. Cole, and a dog left Minidoka, Idaho on the south edge of the Snake River Plain and headed north to the "Lava Beds of Idaho." This was the first time anyone had explored the entire length of the Great Rift. His exploration was related in the March, 1924 issue of National Geographic Magazine.


Geologist Harold Sterns describes the area as the most recent example of a fissure eruption in this country, coins the name "Craters of the Moon", and recommends it be preserved as a national monument.


President Calvin Coolidge signs a proclamation creating Craters of the Moon National Monument.


NASA astronauts Alan Shepherd, Edgar Mitchell, Eugene Cernan, and Joe Engle explore the monument while training to visit the moon.


Congress creates the Craters of the Moon Wilderness, the first such designation within the National Park Service.


President Clinton signs a bill that increases the size of the monument 13-fold, from slightly less than 55,000 acres to over 750,000 acres.


Next Eruption!?!?

Last updated: February 28, 2015

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Mailing Address:

Craters of the Moon National Monument and Preserve
P.O. Box 29

Arco, ID 83213


(208) 527-1300

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