Environmental Geology Glossary

A fan-shaped deposit of sediment formed where a fast-flowing stream emerges from a confined valley onto a flat plain, common in arid and semi-arid regions.

A geologic formation of permeable rock, sand, or gravel saturated with groundwater that can yield water to wells in useful quantities.

A low-permeability geologic layer that restricts groundwater flow, such as clay or unfractured shale.

A fine-grained, dark-colored volcanic rock formed from rapid cooling of low-viscosity lava, the most common type of volcanic rock on Earth's surface.

A body of contaminated groundwater extending from a pollution source in the direction of groundwater flow.

An equation describing groundwater flow through porous media: Q = KiA, where Q is discharge, K is hydraulic conductivity, i is hydraulic gradient, and A is cross-sectional area.

A systematic process evaluating the potential environmental effects of a proposed project before construction begins.

The point on the Earth's surface directly above the focus (hypocenter) of an earthquake.

The flat area adjacent to a river channel that is subject to periodic inundation during high-water events.

The study of landforms and the processes that shape the Earth's surface, including erosion, weathering, and deposition.

A measure of the ease with which water can move through pore spaces in soil or rock, expressed in units of length per time.

A terrain with distinctive features such as sinkholes, caves, and underground drainage, formed by dissolution of soluble bedrock like limestone.

A volcanic mudflow consisting of water-saturated volcanic debris that travels rapidly downslope from a volcano.

The transformation of saturated, loose sediment into a fluid-like state during seismic shaking due to increased pore water pressure.

The rigid outer layer of the Earth comprising the crust and upper mantle, broken into tectonic plates.

The gravity-driven downslope movement of rock, soil, and debris, including landslides, rockfalls, and mudflows.

Actions taken to reduce the severity or impact of a natural hazard or environmental problem.

The measure of how easily fluids can flow through the interconnected pore spaces of rock or soil.

The percentage of a rock or sediment's total volume that consists of open pore space, whether or not those pores are connected.

A fast-moving, superheated mixture of volcanic gas and fragmented rock that flows downslope from a volcano during explosive eruptions.

The process of restoring land that has been disturbed by mining or other activities to a usable and environmentally stable condition.

The cleanup of contaminated soil, groundwater, or sediment to reduce pollutant concentrations to acceptable levels.

An instrument that detects and records ground vibrations caused by earthquakes, explosions, or other seismic sources.

The sinking or settling of the ground surface due to underground material removal, compaction, or dissolution.

The upper surface of the zone of saturation in an unconfined aquifer, below which all pore spaces are filled with groundwater.