Kansas Geological Survey, Public Information Circular (PIC) 13
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Glossary

Bedrock: General term for the solid rock that underlies the soil.

Block slide: A mass of soil and rock that moves along a straight failure surface without rotation or internal deformation in the landslide mass.

Clay: A group of submicroscopic silicate minerals related to mica. Clay-sized particles are less than 0.0039 mm in diameter.

Competent rock: Hard rock layers that resist weathering.

Creep: Slow, imperceptible movement of soil and rock downslope.

Earth flow: A mass of soil that moves downslope and undergoes internal deformation. During an earth flow, the landslide mass breaks apart.

Expansive soil: Soil containing clay minerals that increase in volume when wet and decrease when dry.

Failure surface: A planar surface at the base of the landslide along which motion has occurred; it separates the material that has moved from the stationary material.

Head: The upslope portion of a landslide.

Hydraulic conductivity: Capability of water to move through soil or rock.

Landslide: A mass of soil and rock that moved downslope by gravity.

Lobe: A bulge in the ground surface where soil and rock mounds at the toe of a landslide.

Rock fall: Free-fall of rock blocks from a cliff or rock outcrop.

Scarp: Steeply dipping region of exposed soil and rock that marks the upslope end of a landslide.

Slump: A mass of soil and rock that moves along a curved failure surface with rotation but without internal deformation of the landslide material.

Soil (engineering usage): All loose (unconsolidated) material between the ground surface and the underlying bedrock, including stream, river, and glacial sediments.

Subsidence: Sinking or settling of the ground surface caused when soil or rock collapses into a void. Subsidence can be natural (a sinkhole) or human induced (due to underground mining or pumping of petroleum or water).

Tension gashes: Cracks in the ground surface caused by stretching or buckling of the landslide mass during failure.

Toe: The downslope portion of a landslide.

Water content: The amount of water by weight in the soil. Water content is found by dividing the weight of water in the soil by the weight of dry soil.

Weather, Weathering: Physical and chemical processes that disintegrate bedrock and form soil.

Geologists

What is an engineering geologist?

An engineering geologist is an individual with a degree in geology who has taken specialized courses and has work experience in evaluating the effects of geology and geologic processes on structures (buildings, roads, dams, etc.).

What should I expect from an engineering geologist?

Engineering geologists begin by collecting background data on the site and surrounding area, including published reports of geologic problems in the vicinity, geologic maps, geologic hazard maps, and soils maps. They will then inspect the site and surrounding area. Based on the background search and the site inspection, they may want to drill or trench the site to better define the problem and to collect soil and rock samples for testing. Additionally, they may suggest placement of instruments to monitor ground-water flow and movement of soil and rock. Finally, engineering geologists will provide a written report on the extent of geologic problems and may make recommendations on suitable remedial methods.

Where can you find an engineering geologist?

Generally, engineering geologists work for civil, geotechnical, and environmental engineering firms. Some own their own companies or work independently. Check the Yellow Pages under geologists or engineers for local companies. You can also use Internet yellow pages or search engines (such as Yahoo or Excite) to find geologists and engineering firms. Local governments should also be a good source of information.

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Additional Reading and Internet Sites

Kansas Geological Survey, Public Outreach
Web version April 1999
http://www.kgs.ku.edu/Publications/pic13/pic13_glossary.html