Glossary and Links

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Basin and Range
A regional topographic structure that is characterized by parallel fault-block mountain ranges separated by broad valleys filled with alluvium. Movement is along normal faults accommodating crustal stretching.

caldera eruption
A large, more or less circular volcanic crater usually resulting from the collapse of underground lava reservoirs, and having a diameter many times greater than that of the vent.

central peak
A mountain or group of mountains lying inside a crater usually near the center of the crater. Most likely produced by elastic rebound of the target rocks immediately after the crater-forming impact.

Cernan, Eugene
Eugene A. Cernan walked in space on Gemini 9, orbited the moon on Apollo 10 and walked on the moon as commander of Apollo 17. He was born March 14, 1934, in Chicago. He received a Bachelor of Science degree in Electrical Engineering from Purdue University in 1956 and a Master of Science degree in Aeronautical Engineering from the U.S. Naval Postgraduate School. Cernan received his commission through the Navy ROTC program at Purdue and entered flight training upon graduation. He was assigned to Attack Squadrons 26 and 113 at the Miramar Naval Air Station in California and later attended the Naval Postgraduate School. NASA selected him as an astronaut in 1963.

He flew as pilot on Gemini 9 with Tom Stafford as commander in June 1966. Cernan and Stafford returned to space together aboard Apollo 10 on May 18, 1969. Together with John Young, they orbited the moon, and Cernan and Stafford separated the Lunar Module and approached to within 10 miles of the surface, paving the way for the Apollo 11 crew to make the first moon landing two months later. He had his own Apollo command when Apollo 17 blasted off on Dec. 7, 1972. With him were Ronald Evans and geologist-astronaut Harrison H. (Jack) Schmitt. Cernan and Schmitt landed in a mountain-ringed valley named Taurus-Littrow. They set up a science station and then assembled their moon buggy for three seven- hour excursions over as many days. They launched themselves back to the Command Module, and the astronauts spent to additional days in lunar orbit to gather more information and then headed home. They splashed down on Dec 19 to conclude the final flight in the Apollo moon program.

Cernan later acted for the program manager as the senior U.S. negotiator in direct discussions with the Soviets on Apollo-Soyuz, the 1975 joint American-Soviet space mission. He retired from the Navy and left NASA in 1976 to enter business.

Clovis point
A long, leaf-shaped projectile point type characteristic of the early Paleo-Indians often found in association with mammoth bones. Named for Clovis, New Mexico, where it was first found.

cinder cone
A conical hill or mountain formed by the accumulation of cinders, lappili, and other volcanic debris around a vent.

Columbia River Basalts
The Columbia River Flood Basalt Province forms a plateau of 164,000 square kilometers between the Cascade Range and the Rocky Mountains. In all, more than 300 individual large lava flows cover parts of the states of Idaho, Oregon, and Washington. The total volume of the volcanic province is 175,000 cubic km. with some locations covered by as 3,500 m of lava.


A pattern of movement of subcrustal mantle material, vertically and horizontally, due to heat variations in the earth. This circulation of mantle material is thought to be responsible for the movement of plates or plate tectonics.

convergent zone
The boundary between two plates of the Earth's crust that are pushing together. The plates are moving in opposite directions and one is dragged down (or subducted) beneath the other. Convergent plate boundaries are also called subduction zones and are typified by the Aleutian Trench, where the Pacific Plate is being subducted under the North American Plate.

A stable region of the continental crust that has not undergone active deformation for an extensive period of time, probably the last 2 billion years. Made predominantly of granite and metamorphic rocks.

dark mantling deposit
A thin layer of dark ash and cinder that has been erupted on the surface.

divergent zone
The boundary between two crustal plates that are pulling apart. These adjacent plates pull apart at places like the Mid-Atlantic Ridge, where the North and South American Plates are separated from the Eurasian and African Plates. This pulling apart causes "sea-floor spreading" as new material is added to the oceanic plates.

Engle, Joe
Born August 26, 1932, Dickinson County, Kansas, Engle was one of the 19 astronauts selected by NASA in April 1966. He was back-up lunar module pilot for the Apollo 14 mission. He was commander of one of the two crews that flew the Space Shuttle approach and landing test flights from June through October 1977. The Space Shuttle Enterprise was carried to 25,000 feet on top of the Boeing 747 carrier aircraft, and then released for its two-minute glide flight to landing. Engle and Dick Truly flew the first flight of the Space Shuttle in the orbital configuration. He was the back-up commander for STS-1, the first orbital test flight of Space Shuttle Columbia. He was spacecraft commander on STS-2 and STS-51I, and has logged over 225 hours in space. He served as Deputy Associate Administrator for Manned Space Flight at NASA Headquarters from March 1982 to December 1982. He retained his flight astronaut status and returned to the Johnson Space Center in January 1983. Joe retired from the United States Air Force on November 30, 1986. On December 1, 1986 he was appointed to the Kansas Air National Guard and subsequently promoted to the rank of Brigadier General. He is currently an Aerospace and Sporting Goods Consultant, and continues an active flying career in high performance aircraft.

fire fountain
A plume of incandescent molten lava sprayed vertically into the air from a volcanic vent or fissure.


fissure eruption
A volcanic eruption occurring along a fracture or crack in the earth's surface rather than from a central vent. A row of coalescing lava fountains along a fissure; a typical feature of a Hawaiian-type eruption and at Craters of the Moon.

Fort Hall
Built by Nathaniel Wyeth in 1834. It later became an important trading post on the Oregon Trail.

Goodale's Cutoff
A spur of the Oregon Trail. It left Fort Hall to the south and led around the north edge of Craters of the Moon. In 1852, John Jeffrey began promoting the route, but it was not until 1862 when an emigrant party asked guide Tim Goodale to lead them, that a large percentage of Oregon Trail traffic chose the>

An elongated, relatively depressed crustal block lying between two more or less parallel faults. The down-dropped block of a normal fault.

A region of high heat flow beneath the Earth's surface. The volcanic center can be 60 to 120 miles across and persist for at least a few tens of million of years. Geologists are still trying to determine the cause of the hotspots.


impact crater
A crater formed by the impact of an unspecified object, especially on the surface of planets or their moons.

mare ridge
An uplift produced when the surface of the Moon buckles due to the emplacement of a load of basalt. It is not uncommon to see a series of these ridges together. Same as a wrinkle ridge.

Large, relatively uncratered expanses of dark basalt, nearly all of which are on the moon's near side and most of which fill impact basins. Similar to the flood basalt provinces of the Earth including the Snake River Plain, Columbia River Basalts, and the Deccan Plateau of India.

The geologic era found between the Paleozoic and Cenozoic eras, dating from approximately 225 to 65 million years ago; includes the Triassic, Jurassic, and Cretaceous periods.

Mitchell, Edgar
Mitchell entered the Navy in 1952 upon graduation from college. After completing basic training, he attended Officer Candidate School and was commissioned an Ensign. He then attended flight training at Hutchinson, Kansas and a year later, in 1954, was assigned to Patrol Squadron 29, deployed to Okinawa. From 1957 to 1958, he flew the Douglas A3 Skywarrior. He then served as a Research Project Pilot, attended MIT where he earned his Ph.D. in 1964, and became Chief of the Project Management Division of the Navy's field office for the Manned Orbiting Laboratory. In 1965, Mitchell attended the Aerospace Research Pilot School at Edwards AFB, California. After completing the course the following year, he became an Instructor at the school, and was working there when selected as an astronaut.

Mitchell was selected by NASA for astronaut training in April 1966. He had one spaceflight, aboard the Apollo 14 lunar landing mission, and served as Support and Backup Crew on several other missions. Mitchell's first assignments at NASA were as Support Crew for Apollo 9, the second manned Apollo flight, and as the Backup Lunar Module Pilot for Apollo 10. His sole spaceflight was as Lunar Module Pilot for Apollo 14, the third lunar landing mission launched January 31, 1971. On this mission, Alan B. Shepard (Spacecraft Commander) and Stuart A. Roosa (Command Module Pilot) joined him. He resigned from NASA and retired from the Navy in October 1972.

normal faults
A fault in which the hanging wall as been displaced downward in relation to the footwall. The down-dropped block is called a graben. The mechanism responsible for the formation of the Basin and Range.


A black or dark-colored volcanic glass characterized by conchoidal fracture, usually of rhyolite composition. This volcanic glass, which was highly prized in prehistoric stone toolmaking, was often used for projectile points and knife blades. See Clovis points

The geologic era between the Precambrian and Mesozoic eras, dating from about 600 to 230 million years ago. Includes the Cambrian, Ordovician, Silurian, Devonian, Mississippian, Pennsylvanian, and Permian Periods.

plate boundaries
The zones of seismic activity long which plates are in contact. These may coincide with continental margins, but usually do not. Movement between plates is predominately horizontal, and may be divergent, or convergent, or side-by-side.

plate tectonics
A modern geological theory of tectonic activity, proposed by Alfred Wegner in 1960, according to which the earth's crust is divided into a small number of large, rigid plates whose independent movements relative to one another cause deformation, volcanism, and seismic activity along their margins. The plates, about 50 miles thick, move in relation to one another, shifting continents, forming new ocean crust, and stimulating volcanic eruptions. Most of the world's active volcanoes are located along or near the boundaries between shifting plates and are called "plate-boundary" volcanoes.

The era that includes all geologic time from the formation of the earth to the beginning of the Paleozoic era (from about 4.6 billion to 570 million years ago

rayed features
A term for the "splatter" pattern of ejecta (surface material) after a crater impact. It is the bright material surrounding large fresh craters.

reversed shadowing
Shadows will fall on opposite sides of a depression and an uplift. If the light source is from the right, the shadow on a depression will fall on the right where the shadow on an uplift will fall on the left.

A narrow fissure or other opening in a rock, caused by cracking or splitting. This fissure may allow magma to erupt on the surface as a lava flow.

Long, narrow, trench-like valleys on the surface of the moon most likely produced by the movement of lava; may be straight or winding. Have been compared to lava tubes or channels on Earth.

A volcanic mountain on the seafloor with either a peaked or flat top. If flat-topped, it is called a guyot, and was probably eroded by ocean waves.

Rock formed from the accumulation of sediment, which may consist of fragments and mineral grains of varying sizes from pre-existing rocks. The particles are generally cemented with calcite or silica.

Shepard, Alan
Born Alan Bartlett Shepard, Jr. on Nov. 18, 1923, in East Derry, NH, he received a Bachelor of Science degree from the United States Naval Academy in 1944. Upon graduation, he married Louise Brewer, whom he met while at Annapolis. Shepard received his wings as a Naval aviator in 1947 and served several tours aboard aircraft carriers. In 1950, he attended Naval Test Pilot School at Patuxent River, MDS, and became a test pilot and instructor there. He later attended the Naval War College at Newport, RI, and after graduating, was assigned to the staff of the commander-in-chief, Atlantic Fleet, as an aircraft readiness office. Named as one of the nation's original seven Mercury astronauts in 1959, Shepard became the first to carry America's banner into space on May 5, 1961, riding a Redstone rocket on a 15-minute suborbital flight that took him and his Freedom 7 Mercury capsule 115 miles in altitude and 302 miles downrange from Cape Canaveral, FL. He was a member of the Apollo 14 crew and is one of only 12 Americans ever to step on the Moon. He died on July 21, 1998.

Snake River Plain
The Snake River Plain forms a broad arch across the southern part of Idaho extending 600 kilometers eastward from the Oregon border to the Yellowstone Plateau. Its width ranges from 65 to 100 kilometers. The western part is a complex graben bounded by a system of normal faults.


spatter cone
A low, steep-sided mound or cone of small pyroclastic fragments built up on a fissure or around a volcanic vent. Lava is generally spit out in blobs.

summit crater
A bowl-shaped, generally steep-walled surface depression found on the top of a feature with positive relief (an uplift) It may be formed from the impact of a falling body or the eruption and subsequent collapse of a volcano.

The first geologic period of the Cenozoic era between the Mesozoic and Quaternary periods, covering a time span from about 63 million to 2 million years ago.

transform zone
A plate boundary where one plate slides horizontally past another. The best known example is the earthquake-prone San Andreas fault zone of California, which marks the boundary where the Pacific and North American Plates are moving in opposite directions.

wrinkle ridges
Long, low, prominent ridges, perhaps offset by faults, which are seen on all the lunar maria. Same as mare ridge.

Yellowstone Snake River Plain hotspot
The Snake River Plain extends 400 miles (650 km) westward from northwest Wyoming to the Idaho-Oregon border. The Snake River Plain is a broad, flat arcuate depression, which is concave to the north and covers one quarter of the state of Idaho. The geysers, hot springs, and bubbling mud pots of Yellowstone National Park indicate there is extra heat beneath this corner of Wyoming. Geologists and volcanologists think the heat is from a hot spot beneath Yellowstone. A long line of features that extends to the west from Yellowstone are interpreted to be the track left in the continent as it passed over the hotspot. Most of these features are part of the Snake River Plain.


Last updated: February 28, 2015

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Craters of the Moon National Monument and Preserve
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Arco, ID 83213


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