The Apollo astronauts visited this stark lunar landscape for a preview of what they might find when they landed on the moon.
To Washington Irving, this bleak and barren moonscape in southern Idaho was “a desolate and awful waste, where … nothing is to be seen but lava.” To tourists by the tens of thousands who visit the area, which is preserved as a national monument, it is an awesome showcase of volcanic forces. Extending from horizon to horizon is an unearthly panorama of lava flows, cinder cones, and craters.
This eerie setting resulted from volcanic activity, but not in the form of a single explosive eruption. Instead, a great crack, or fissure, about 50 miles (80 kilometres) long developed in the earth’s crust. Through this zone of weakness, known as the Great Rift, lava welled up to the surface time and again over the course of thousands of years. With each successive series of eruptions, older volcanic formations were buried and new ones were superimposed on their surfaces. The barren black lavas, which are so prevalent throughout the general area, were all emitted during the most recent eruptions, which probably occurred approximately 2,000 years ago.
The most prominent volcanic features are the numerous cinder cones aligned along the Great Rift. Steep-sided and conical, they were built up of ash and eruptive debris that accumulated where fiery fountains of lava shot high into the air. The finest and tallest cinder cone in the area, Big Cinder Butte, rises about 600 feet (185 meters) above its surroundings.
There are also many spatter cones, which are much smaller—up to about 50 feet (15 meters) high—and have steeper sides. The creation of less powerful fire fountains, they were built up of lava that shot up into the air and then piled up in the form of viscous clots or blobs.
Volcanism, including lava bombs, craters, molds of tree trunks engulfed by lava, and especially massive lava flows. Some of the lava flows are so-called pahoehoe (a Hawaiian term). Their wrinkled, ropy texture resulted from hardening of the surface crust while fluid lava within the flow continued to push the mass forward and heap it up in billowy cascades and festoons. In contrast the many as lava flows (also known by their Hawaiian name) have jagged surfaces and were formed by the movement of less fluid streams of lava.
Penetrating many of the flows are lava tubes. These tunnel like caves were formed when the surface of the molten material cooled and hardened, while a river of lava underneath gradually drained out, leaving an opening. Some of them are even decorated with lava stalactites where hot lava dripped down from the ceiling. This is one of the great places for a holiday full of adventure.