Craters of the Moon National Monument—a little bit of Hawai’i in Idaho

If you ignore the arid climate and sagebrush vegetation in the Snake River Plain of Idaho, and just look at the landscape of lava, you can imagine yourself on the Big Island of Hawai’i. This photograph shows basalt-type lava in pahoe’oe and a’a flows, with cinder cones in the background. The area is still considered to be volcanically active, with the basalt flows at the surface ranging in age from 15,000 to 2,000 years. Although the youngest flows are 2,000 years old, they appear younger because of the arid climate. Flows this old in Hawai’i would have long ago turned into soil and would be hosting a luxuriant vegetative cover (especially on the rainy Hilo side of Hawai’i).


Like Hawai’i, these volcanoes are the result of a hot spot located deep beneath Earth’s surface that is causing rock to melt and rise to erupt above ground. Movement of a plate over the hot spot results in a chain of volcanoes—in Hawai’i, the above-surface chain on the Pacific Plate extends from Kauai (about 5 million years old) to the Big Island (currently active). Unlike Hawai’i, the hot spot that has created Craters of the Moon is beneath continental crust rather than oceanic crust. As the North American plate has moved southwest over this hot spot, the chain of volcanoes has extended from SE Oregon (about 16 million years old) to Yellowstone (currently active; the most recent eruption was 600,000 years ago). The hot spot was located beneath the Snake River Plain, where Craters of the Moon is located, about 10 million years ago.


When the hot spot first begins breaking through continental crust, it produces silica-rich magmas that erupt explosively and are very dangerous. This is because the magma picks up more silica-rich materials as it travels through the continental crust. Yellowstone is called a “super volcano” because of its propensity to produce huge eruptions—estimated at about 2,000 times the amount of material that was erupted at Mt St Helens in 1980! This explosive type of volcano erupted here about 10 million years ago, but it has now been buried by lavas of the relatively silica-poor type of lava (basalt) that creates less explosive volcanoes. It appears that the conduit for the magma has now been cleared of continental material and is coming directly from greater depths. The quantity of lava is augmented by rifting of the continental crust, as the extensional province of the Basin and Range (think Nevada) has extended northward.


Other features in Craters of the Moon that resemble features found in Hawai’i are lava tubes and tree molds. In the photo below, a tree fell as a result of the hot flow and left an impression in the lava.


In June, the wildflowers were blooming—they created a beautiful carpet on the pumice plains.


While a geology student at San Francisco State University, John Niles mapped volcanic features in the National Monument as a Geocorps summer intern. It was exciting to see his map for sale in the visitors center. Although many others contributed to the work, his contribution was deemed largest—he is listed as first author. The different colors outline cones and flows of different ages and compositions.


The monument has enough interesting features to fully occupy visitors for a day or two. It is possible to camp within the monument; for other types of lodging, it is necessary to drive to a nearby town. The nearest is Arco, a small town with its small piece of fame. Adjacent areas of open space were used for bomb testing by the federal government, and the Idaho National Laboratory is still operating between Arco and Pocatello, but it now focuses on “changing the world’s energy future”.


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  1. Larry Alden on July 8, 2018 at 8:13 pm

    Hi Karen,

    I went there a few years ago. Amazing landscape. Hope you are doing well.


    • Landscapes Revealed on July 8, 2018 at 10:48 pm

      Hope you drive back through Oregon again soon. We have wonderful,landscapes too!

  2. Karen S. Smith on July 9, 2018 at 7:08 pm

    Another very fine blog entry, Karen. I’m grateful you share your blog with friends!!

  3. John Johnson on October 26, 2020 at 12:47 pm

    The site of the INL was never used for bomb tests. During WWII is was used to test Naval guns being built in Pocatello. After the war Rickover and the Navy used the area for testing navel nuclear reactors and fuel. Training for sailors on nuclear submarines took place their until about 1985, leading to the joke about having a submarine base on the desert. Later, other commercial reactor types were developed and tested there, including Experimental Breeder Reactors I and II. Other specialized reactors were built to test safety systems for nuclear reactors. When I retired in 2001, the main emphasis appeared to be changing to clean up of the waste accumulated over the 70-year history.

    • John Johnson on October 26, 2020 at 12:51 pm

      I should have said almost 50-year history instead of 70-year history, up to 2001

    • Landscapes Revealed on October 26, 2020 at 1:39 pm

      Good to know – thanks John.

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