The Wood River Valley’s Fourth of July fireworks displays are nothing like the pyrotechnics that created the Snake River Plain over the past 15,000 years.
Craters of the Moon National Monument, east of Carey, Idaho, is one of the best places in the world to see the awesome effects of volcanoes at work, the National Park Service says. The monument is on the western Snake River Plain, which spans most of southern Idaho. In places, it is 60 miles wide, and lava deposits are more than 10,000 feet deep.
Eruptions at the national monument 2,000 years ago are the most recent volcanic activity on the plain.
“Lava eruptions have created a landscape there that has forced animals and plants to adapt, and people to endure or detour, and to ponder,” says the National Park Service.
The twisted, jagged lava landscape includes cinder cones, spatter cones, lava tubes and several varieties of lava flows. Cinder cones provide the greatest vertical relief of the monument’s volcanic features. The highest cinder cone, Big Cinder Butte, stands more than 700 feet above the surrounding plain.
The monument is home to a vast array of wildflowers, birds and 48 species of mammals. Wildflower blooms typically peak in June, but could last into early July.
Scientists explain the formation of the Snake River Plain and the Craters of the Moon lava fields using a “mantle plume theory.” According to the theory there’s a “hot spot,” or focused heat source beneath the crust of the Snake River Plain. Periodically, this hot spot consists of a “plume” of molten rock called magma that rises to the earth’s surface. The hot spot doesn’t move, but the earth’s crust does. As the North American plate slides southwest over the hot spot, volcanic eruptions occur on the surface.
Initially the eruptions are very violent and produce rhyolite lavas. Huge calderas 30 miles in diameter can be formed when the devastating eruptions occur.
A more fluid basaltic lava later flows onto the surface and covers rhyolitic flows. Yellowstone National Park, the area where the hot spot is believed to be now, is where catastrophic rhyolitic eruptions last occurred 600,000 years ago. Craters of the Moon represents the second stage of the eruptions where fluid basaltic lava flowed over the plain just 2,000 years ago.
Much of the volcanism of the Snake River Plain was confined to volcanic rift zones. A volcanic rift is a concentration of volcanic land forms along a line of cracks in the earth’s crust. The 62-mile-long Great Rift volcanic zone is an area of cracks running northwest to southeast across nearly the entire eastern Snake River Plain.
Before leaving office, former President Bill Clinton signed a proclamation expanding the monument 600,000 acres to include the Great Rift and sagebrush habitats in between. The former monument, established in 1924, consisted of 54,000 acres.
Craters of the Moon facts
l Craters of the Moon National Monument includes a 618-square- mile lava field, the largest young basaltic lava field in the contiguous United States.
l More than 370 species of plants, 48 species of mammals and 160 different birds call Craters of the Moon home.
l Former President Clinton expanded the monument 12 times its former 54,000-acre size when he signed an Antiquities Act proclamation in November 1999.
l Some of Craters’ lava flows traveled as far as 43 miles from their vents, and some flowed around areas of higher ground and rejoined downstream to form islands of older terrain that were surrounded by new lava. These areas are called “kipukas,” Hawaiian for windows.
l Craters boasts an informative visitor center, a 7-mile loop road and numerous hiking opportunities ranging from quarter-mile to 11-mile loops.
l To get there, go to Carey and continue east on state Highway 20. The monument headquarters are difficult to miss. They sit in the middle of a black, jagged lava field. Turn to the right at the top of a hill in the middle of the difficult-to-miss lava field.