Field Trip to Mars

Glossary A-G

Terms and Definitions

Here are some basic terms used in the tour. At the bottom of each page in the tour is a short list of terms used on that page and their definitions. Find more science terms in the Kid's Cosmos Astronomy and Science Glossary.

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A
Anastomosing: Branching and rejoining. Geologists describe the braided channels of the Channeled Scabland as "anastomosing."
Andesite: Volcanic igneous rock related to granite.
Ares Vallis: Area of Mars where the Mars Pathfinder and Sojourner Rover landed.
Ash: Fragments of less than 2 millimeters in diameter of lava or rock blasted into the air by volcanic explosions.
B
Bar: A mound of gravel and sand deposited by flowing water. Bretz and other geologists identified many large bars in the Channeled Scablands.
Basalt: Volcanic rock caused by partial melting of the Earth's crust.
Bedrock: Solid layers of rock in the Earth's crust beneath soil.
C
Caldera: A large volcanic depression, commonly circular or elliptical when seen from above, caused by a volcano collapsing into itself.
Caliche: One or more layers of calcium carbonate deposited as water holding the carbonates in suspension evaporates. This is similar to hard water deposits on drying dishes.
Cataract: A waterfall with a single, sheer drop. Usually with a large volume of water flowing over the falls.
Catastrophic Principle: A concept proposing that all geological features were formed by sudden, catastrophic events like volcanoes, earthquakes, floods and even asteroid hits. Most geologists today believe that certain catastrophic events may form features but most are formed by slow processes that happened in the past just as they do today (uniformitarianism). Also, Catastrophism.
Channel: The deepest part of a river or bay.
Channeled Scabland: Area in Washington state where huge floods made channels in a large, deep basalt flow. Named by J Harlan Bretz during the 1920's in various publications. See also Channeled Scabland and Glacial Lake Missoula.
Composite Volcano: A steep-sided volcano composed of many layers of volcanic rocks, usually made from high-viscosity (thick like honey) lava, ash and rock debris (broken pieces).
Cinder Cone: A circular or oval cone made up of small fragments of lava from a single vent that have been blown into the air, cooled and fallen around the vent.
Coulee: Long winding channel cut through lava formations. A term primarily used in the northwestern United States.
Current Ripple: Mark left on streambed from water current usually less than an inch high and a few inches between the tops (crests) of each ripple. The giant ripples from Lake Missoula floods are as much as 35 feet high and several hundred feet between. See also Ripple Mark.
D
Dome: A steep-sided mound that forms when viscous (thick like honey) lava piles up near a volcanic vent (opening at the surface).

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E
Epicenter: The spot on the surface of the Earth directly above the area where an earthquake took place.
Erosion: Lifting and removal of rock, dirt, sand and the like caused by wind, water, or glacial ice.
Erratic: Large rock or boulder carried by water or glaciers and left behind.
Esker: A narrow, winding ridge made of gravel usually formed by streams flowing on a glacier or in a tunnel below the glacier or ice sheet.
F
Fault: A split or fracture between two blocks of rock in the Earth's crust that have slipped, slid or pushed against each other. An area where earthquakes commonly occur.
Floodplain: A smooth plain covered by deposits of sand, gravel and rocks from floods. Sharp-edged rocks have only been carried by floodwaters a short distance while smooth, rounded rocks have traveled long distances.
Focus (Earthquake): The area inside the Earth where an earthquake happened. Also known as the Hypocenter.
Fumarole: A vent that releases volcanic gases and steam.
G
Geomorphology: The study of the changes in landforms due to volcanoes,
earthquakes, weather, floods, etc.
Gneiss: A type of metamorphic rock formed as older rocks recrystallize under heat and stress from pressure characterized by a layering of light and dark bands or streaks.
Graben: An area between two parallel faults that is lower than that on the other side of the faults.
Granite: Coarse-grained igneous rock usually without obvious bands or markings.
Gravel: Rounded rock fragments larger than sand.

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