Volcanism:
Image 43
Eruptive activity for the Snake River Plain began in the middle Miocene. The Plain itself is bound in each direction by distinctive features. The western edge is composed of a "complex of graben bounded by a system of normal faults." The eastern edge is characterized by both faulting and downwarping while the northern extent reveals folded Paleozoic-Mesozoic rock types (*1). Downwarping is the most common and significant type of structural activity found in the Snake River area (*6). The southern boundary of the Snake River Plain is "basin-and-range fault-block mountains and Tertiary rhyolitic and basaltic rocks." The Snake River Plain was created from "plains" volcanism which is characterized by: small low shield volcanoes, fissure flows and large tube fed lava flows (*1). The Snake River Plain runs approximately 400 miles from east to west with widths ranging from 50 to 125 miles across (*6). Image 43 illustrates the formation of a shied volcano as found in Craters of the Moon.
Volcanic Stages:
Image 23 above illustrates a cross section of the Snake River Plain and the associated types of tectonic activity and volcanism (*4).
Four stages of development along the North American Plate characterize the development and timeline of the Snake River Plain. Stage one, approximately 8 mya, beneath what is now Craters of the Moon, an eruptive hotspot spewed rhyolite in a series of massive eruptions. Beginning 6 mya to 15,000 years, basaltic eruptions occurred in the Snake River Plain area. More recently, 15,000 to 2,100 years ago, eight eruptive events created the landscape of Craters of the Moon. Today, Yellowstone occupies the area above the mantle hotspot and produces geysers, pools and other activity park visitors enjoy (*7).
Geology:
Inside lava tubes, one can see lava stalactites, remelt features, and lava curbsEntrance to a large lava tube (Image 56) in the Craters National Monument produced by an "inflation" of lava at the surface creating a cavern area. "Inside lava tubes, one can see lava stalactites, remelt features, and lava curbs". Sample of a lava bomb or lava meteor created when explosive eruptions occur splattering hot lava into the air where it cools to produce different varieties of lava bombs. Below is an example of the "breadcrust" lava bomb (*17).
Park Imagery:
Below: Intrance to the Craters of the Moon National Monument. Image 10 shows an arm of the lava flow and relief associated with the Monument. Image 5 is a close up of lava tubes called pahoehoe or "ropy" lava (in a more fluid state prior to hardening) from the hawaiian language. Most lava tubes in Craters Monument were formed and fed through tube systems while others were formed from sheet flows (*7).
Processed Imagery:
Below: Image 32 is a false color composite obtained from Digital Geology of Idaho. The large dark mass in the middle of the screen is Craters of the Moon National Monument. The second smaller mass to the bottom right is Wapi Lava Fields; Both are a part of the larger Great Rift area in the Snake River Plain. Vegetation shown in red.
Historic Photos & First Nations:
Shoshone Indians and Robert Limbert: Through archeological evidence and oral traditions, it is well known that early Indian tribes explored and utilized the Snake River Plain as well as some of the micro-communities found within the Craters landscape. Early pioneers such as Robert Limbert traced the paths on early inhabitants and created his own mythology surrounding his exploration of the Craters area (*10). Image 42 captures the early Shoshone-Bannocks people. Image 41 of Robert Limbert in the early 1920's. Images 8 and 40 show early settlers of the Snake River Plains.
Moon Mission:
In 1969 Apollo 14 astronauts visited The Craters of the Moon to explore a similar lunar landscape and gain a deeper knowledge of volcanic geology prior to their flight. It was noted that most of the astronauts were "pilots and not geologist" so the trip was designed to aid in the identification of "significant" rock samples on Earth as well as for when they arrived on the moon (*8).