Glossary

Soil or rock containing gypsum, which can be subject to dissolution.

A mineral composed of hydrated calcium sulfate. A common mineral of evaporites.

Any action taken to reduce or permanently eliminate the long‐term risk to human life and property and the environment posed by a hazard.

The Plan resulting from a systematic evaluation of the nature and extent of vulnerabilities posed by a hazard present in society that includes the strategies needed to minimize future vulnerability to hazards.

Multihazards; Earthquake loss estimation software using GIS databases developed by FEMA.

The upper parts of the slide material along the contact between the disturbed material and the main scarp.

Geologic epoch covering the last 10,000 years (after the last Ice Age).

Rocks formed by cooling and hardening of hot liquid material (magma), including rocks cooled within the earth (for example, granite) and those that cooled at the ground surface as lavas (such as basalt).

Materials having a texture that does not permit water to move through.

Land between two streams in the same drainage basin (Interfluve 2004).

Zone of pronounced seismicity, up to 120 miles wide and 800 miles long, extending from Arizona through central Utah to northwestern Montana.

Concerning or pertaining to lakes.

A large, ancient lake that existed 30,000 to 12,000 years ago and covered nearly 20,000 square miles in Utah, Idaho, and Nevada. The lake covered many of Utah’s valleys, and was almost 1,000 feet deep in the area of the present Great Salt Lake.

Sediments deposited by Lake Bonneville, found in the valleys, which range from gravels and sands to clays.

A general term for a mass of earth or rock, which moves down slope by flowing, spreading, sliding, toppling, or falling (see slope failure).

Lateral down slope displacement of soil layers, generally several feet or more, above a liquefied layer.

A berm or dike used to contain or direct water, usually without an outlet or spillway.

Sudden large decrease in shear strength of a cohesionless soil (generally sand or silt) caused by collapse of soil structure and temporary increase in pore‐water pressure during earthquake ground shaking.

A quantity characteristic of the amplitude of the ground motion of an earthquake. The most commonly used measurement is the Richter magnitude scale; a logarithmic scale based on the motion that would be measured by a standard type of seismograph 60 miles from the earthquake’s epicenter.

Rocks formed by high temperatures and/or pressures (for example, quartzite formed from sandstone).

The act of reducing or preventing hazards which affect society or those things deemed important to society.

The most commonly used intensity scale in the U.S.; it is a measure of the severity of earthquake shaking at a particular site as determined from its effect on the earth’s surface, man, and man’s structures.

A clay mineral characterized by expansion upon wetting and shrinking upon drying.

Native plant life existing on a piece of land before any form of development.

Fault caused by crustal extension in which relative movement on opposite sides is primarily vertical; for example, the Wasatch Fault.

Spherical grains of carbonate sand with a brine shrimp fecal pellet nucleus.

A conduit through which controlled releases can be made from the reservoir.

Developed by Wayne Palmer in 1965; measures drought severity using temperature, precipitation and soil moisture (Utah Division of Water Resources 2007).

Unconsolidated surficial deposit of partially decomposed plant remains.

A standard (world‐wide) geologic time unit.

The capacity of a porous rock or soil for transmitting a fluid.

A region whose pattern of relief features or landforms differs significantly from that of adjacent regions.

A weak incoherent layer in unconsolidated deposits that acts as a channel directing the movement of water. As the layer becomes saturated it conducts water to a free face (cliff or stream bank for example) that intersects the layer, and material exits out a “pipe” formed in the free face. Piping can occur in a dam as the result of progressive development of internal erosion by seepage.

The open spaces in a rock or soil between solid grains. The spaces may be filled with gas (usually air) or liquid (usually water).

The ratio of the volume of pore space in rock or soil to the volume of its mass, expressed as percentage.

A flood that would result from the most severe combination of critical meteorological and hydrologic conditions possible in a region.

The maximum amount and duration of precipitation that can be expected to occur on a drainage basin.

Geologic materials that are susceptible to volumetric changes, collapse, subsidence, or other engineering geologic problems.

An initiative of the Federal Emergency Management Agency intended to modify the way in which the United States handles natural disasters. The Goal of Project Impact from a Federal Government perspective is to reduce the personal and economic costs of hazard events by bringing together the private and public sector to better enable the citizens of a community to protect themselves from natural hazards.

A geologic time period covering the last 1.6 million years.

The length of time between occurrences of a particular event (an earthquake, for example).

Abrupt free fall or down slope movement, such as rolling or sliding, of loosened blocks or boulders from an area of bedrock. The rock‐fall runout zone is the area below a rock‐fall source which is at risk from falling rocks.

Forward rotation movement of a rock unit(s) about some pivot point.

Where a snow avalanche slows down and comes to rest (deposition zone). For large avalanches, the runout zone can include a powder‐ or wind‐blast zone that extends far beyond the area of snow deposition.

Deposit of sandy sediment ejected as water and sand to the surface, formed when ground shaking has caused liquefaction at depth.

A relatively steeper slope separating two more gentle slopes. Scarps can form as a result of earthquake faulting.

Material that is in suspension, is being transported, or has been moved from its site of origin by water, ice, or wind, and has come to rest on the earth’s surface either above or below the sea level.

Rocks formed from loose sediment such as sand, mud, or gravel deposited by water, ice, or wind, and then hardened into rock (for example, sandstone); or formed by dissolved minerals precipitating out of solution to form rock (for example, tufa).

A standing wave generated in a closed body of water such as a lake or reservoir. Ground shaking, tectonic tilting, sub aqueous fault rupture, or landsliding into water can all generate a seiche.

Vibrations in the earth produced during earthquakes.