Craters of the Moon National Monument and Preserve, located in southern
Idaho is a vast ocean of lava flows with scattered islands of cinder cones
and sagebrush. This bizarre landscape covers some 715,000 acres of geologic
wonderland that provides views of volcanic craters, lava tubes, deep
cracks, and vast lava fields on Idaho's
Snake River Plain.
Rocks from relatively recent volcanic eruptions dominate the landscape
created by "fissure eruptions" that occurred along cracks in the earth's
crust beginning some 15,000 years ago. Though volcanic eruptions have
occurred on the Snake River Plain for many millions of years, Craters of
the Moon was formed by eruptions that represent the last period of active
volcanism in this area. The most recent activity occurred 2,100 years ago.
Unlike other ancient
lava flows, visitors will not see a large volcano with steep slopes
and a summit crater, as these volcanic fissures are quite different.
Each cone is a small volcano, from which eruptions were of very fluid
basaltic lava from which gases could easily escape. Without high gas
pressure, eruptions tended to be very mild, but produced extensive
The National Monument
encompasses the entire Great Rift, which contains a huge concentration
of volcanic landforms and structures along the more than a 50-mile
zone of fractures and eruptions. A composite field made up of about 60
lava flows and 25 cones, it is the largest lava flow type in the lower
Plants and animals began occupying the
area while the once molten lava fields were still cooling. Some
animals, like the big horned sheep and grizzly bear have been gone for
almost 100 years, but many other animals continue to thrive here.
Difficult access due to rugged terrain and a lack of water discouraged
people from altering the landscape with roads, buildings, farms, and
power lines which occupy much of the present day Snake River Plain.
Though people never made permanent homes in the
lava flows due to the harsh conditions, numerous Northern
artifacts, temporary shelters, and hunting blinds have been found in
the monument, indicating that they hunted and gathered tachylite (a
very dense form of basalt) for arrow points.
In the late spring, tiny wildflowers adorn the cinder
slopes of the monument. Because they are so evenly spaced, they appear
to have been planted in neat rows. However, this is not the case --
plants here must compete for a very limited amount of water;
consequently, they cannot grow too close together and survive. The
plants space themselves naturally according to the availability of
Unique natural features at Craters of the Moon include
lava tubes caves such as Indian Tunnel, which is passable for 800
feet; Big Cinder Butte, at 700 feet, one of the largest purely
basaltic cinder cones in the world; and the Blue and Green Dragon
flows, which are named for their striking lava colors. The monument
also contains large areas of sagebrush steppe as well as numerous
kipukas. Kipukas are isolated islands of remnant vegetation protected
by surrounding lava flows that act as small, virtually undisturbed
havens for native plants and animals.
Craters of the Moon is a dormant rather than an extinct
volcanic area. The volcanoes here are not dead, only sleeping. Indications
of impending eruptions -- earthquakes, the opening of steam vents, and
ground swelling -- have not occurred recently. However, geologists believe
that the area will become active again within the next 1,000 years.
Today, visitors can explore the isolated landscape on a
number of hiking trails which provide unique opportunities to encounter
plants and animals in various lava habitats. A driving tour is also
available called Seven-mile Loop Road. A Visitor’s Center provides
additional information and exhibits and a campground is available during
the summer months.
The visitor center is
located approximately18 miles southwest of Arco, Idaho on Highway 20 and
50 miles northeast of Shoshone on Highway 26.