We know waterfalls.

Glossary of related terms

Accessibility
A term used to describe the relative ease or difficulty in reaching a waterfall.

Angle of Repose
The steepest slope in which a particular sediment will lie motionless without falling or sliding.

Arroyo
A flat-floored, often vertically walled channel of an intermittent stream typical of semiarid climates. Commonly observed in the southwestern United States. Synonymous with Wadi and Wash.

Basalt
A fine-grained igneous (volcanic) rock, dominated by dark-colored minerals, consisting of plagioclase feldspars (over 50 percent) and ferro-magnesian silicates. Basalts and andesites represent about 98 percent of all extrusive rocks on earth. Commonly seen in regions synonymous with volcanic activity (Iceland, New Zealand, Northwestern North America, Japan).

Base
The bottom of a waterfall formation.

Bedrock
The solid rock substrate beneath which lies beneath more permeable materials (such as soil, gravel or water). Often the term is used to describe the rock formation which a waterfall descends over.

Block
A form of a waterfall. A waterfall in a Block form occurs over a wide breadth of the stream. The waterfall must be wider than it is tall. A waterfall with this form does not have to be a solid sheet of water across it’s entire width.

Boulder Cascade
A term used to describe a steep section of a stream where the water cascades over, under and between large boulders piled on top of one another. Boulder Cascades usually occur within constricted areas of a stream’s course such as canyons and gorges and are usually associated with bedrock cleaving off of an adjacent cliff. Boulder Cascades are generally not thought of as waterfalls because the boulders are not considered to be part of the underlying bedrock, but rather lie on top of the bedrock.

Boulder Garden
A section of a larger stream where a river flows around and through many large boulders fallen into a river. Differing from a Boulder Cascade in that it is significantly less steep and the river usually flows around said boulders instead of over them. A term often associated with rivers which see usage by the whitewater kayaking community.

Brink
The top of a waterfall. Also referred to as the Crest.

Bushwhack
To clear a path through thick vegetation. More commonly, this term is used to describe any off-trail, or cross country travel, which involves navigating heavily forested ground, in which a large, sharp blade (ex. machete) would aid in travel.

Butte
A steep sided and flat topped hill formed by erosion of flat laying strata where remnants of a resistant layer protect the softer rocks underneath. Also applied to small, usually dormant or extinct volcanoes known as Cinder Cones, which usually stand less than 1000 feet above the outlying plain.

Canyon
A deep, narrow, steep-sided (often vertical-walled) valley, usually with a watercourse flowing through it.

Caprock
An overlying rock layer that is more resistant to weathering than formations located beneath it. Waterfalls dropping over cap rock formations tend to be classified as a Plunge, Block or Curtain form.

Cascade
A form of a waterfall. A waterfall of a Cascade form descends over, gradually sloping rocks, a series of small steps in quick succession, or a rugged sloping surface of some kind. Cascades can be both gradual and steep.

Cataract
A terms used to describe vertical waterfalls which possess a large volume of water. Often used synonymously with “Plunge”.

Cirque
A steep-walled hollow, shaped like a half-bowl or amphitheater, formed by glaciation and frost wedging. Cirques are found in mountainous regions populated with glaciers, or which have had a history of being glaciated. The term Headwall can often be used interchangeably with Cirque, but not vice versa.

Conglomerate
Detrital sedimentary rock made up of compressed, poorly sorted dust, sand, pebbles and small stones. Conglomerate rock looks like sandstone with large pebbles and small stones infused throughout.

Contour Lines
A line on a topographic map representing a certain elevation at a certain location. Space between two contour lines represents a change in elevation by the interval the contour lines represent.

Contours
Contours represent the vertical, or third, dimension on a topographic map. They show the shape and size of physical features such as mountains, hills and valleys.

Crest
See “Brink”.

Current
A term used to describe the movement of water in a stream.

Curtain
A form of a waterfall. Curtain waterfalls occur along a wide breadth of stream where the falls must be taller than it is wide.

Discharge
The amount of water to pass a given point on a stream, per unit of time. Usually expressed in cubic feet or cubic meters of water per second.

Erosion
Movement of earthen material from one place to another on earth’s surface. Natural causes of erosion include gravity, water movement, glaciation, and wind.

Escarpment
An often vertical, or near vertical, slope or cliff at the edge of a plateau or ridge, which often stretches for several miles. Usually formed by erosion.

Face
The vertical surface of a cliff. In this case, the rock surface where the water is falling. Also known as Cliff Face.

Fan
A form of a waterfall. Waterfalls of a Fan form occur when the breadth of the water in the waterfall increases during it’s decent, causing the base of the falls to appear much wider than the top of the falls.

Fjord
A deep, steep-walled, U-shaped valley formed by glaciation, which has been flooded by seawater. Typically, waterfalls in this formation drop from hanging valleys. Fjords are commonly found in New Zealand, Canada, southern Argentina and Norway.

Glacier
A large mass of ice which persists throughout the year, and moves slowly downslope in a liquid manor by it’s own weight. Glaciers are formed in areas where the winter snow doesn’t have a chance to melt, and consecutive snowfalls accumulate and compress into ice.

Gneiss
A coarse-grained regional metamorphic rock that shows compositional banding and parallel alignment of minerals.

Gorge
A deep, usually narrow ravine, or canyon, often with vertical walls, usually with a watercourse running through it.

Gradient
The slope of stream bed or land surface within a given distance. Expressed in percentage, feet per mile, meters per kilometer, or in degrees.

Granite
A coarse-grained, intrusive igneous (volcanic) rock composed of quartz, orthoclase feldspar, sodic plagioclase feldspar, and micas. Waterfalls flowing over granitic bedrock are often characterized by water sculpture and polishing.

Greywacke
A variety of sandstone generally characterized by hardness, dark color, and angular grains of quartz, feldspar, and small rock fragments set in a matrix of clay-sized particles. Also known as Lithic Sandstone.

Hachures
A depression indicated on a topographic map by short dashes, which point towards the center of the depression. Often used to mark rock quarries or volcanic craters.

Hanging Valley
A valley most often formed as a result of glaciation, where a large glacier erodes a valley, at a perpendicular angle to the hanging valley, to a deeper extent. The result is that of a small valley intersecting a larger valley at an elevation noticeably above the bottom of the larger valley. Hanging valleys can be, but are not always, eroded by a glacier.

Height
The measurement of a waterfall from it’s brink to it’s base. Often not an exact science, as placing the brink and base of a waterfall is sometimes ambiguous and arbitrary.

Horsetail
A form of a waterfall. Horsetail waterfalls are characterized by the constant or semi-constant contact the water keeps with the bedrock as it falls. Horsetail waterfalls can be almost vertical, as well as very gradual.

Igneous Rock
An aggregate of interlocking silicate minerals formed by cooling and solidification of magma or lava. Igneous rocks are formed by volcanic processes.

Joints
Breaks in rock mass with no relative movement of rock on opposite sides of the break.

Karst Topography
Irregular topography characterized by sink holes, caves, streamless valleys, and underground streams; all developed by the actions of surface and underground water in soluble rocks, such as limestone or soapstone.

Knickpoint
A distinct point of sudden or abrupt steepening in the gradient of a streambed, often indicating the presence of a waterfall.

Limestone
Sedimentary rock composed largely of the mineral Calcite (CaCO3), formed by either organic or inorganic processes. Most limestones have clastic texture, but nonclastic, particularly crystalline, textures are common.

Marble
Metamorphic rock of granular texture, with no rock cleavage, and composed of Calcite (Marble), Dolomite, or both.

Metamorphic Rock
Any type of rock which changes in texture or composition, after it’s original formation, as a result of extreme heat, pressure, or chemically active fluids.

Meters of Head
A term used by the hydropower industry to describe the elevation change between two points on a watercourse, often above and below a large waterfall, which would result in the production of a given amount of electricity. Measurements of Meters of Head are often not a true representation of the actual height of a waterfall, but are commonly, and incorrectly used as such.

Orientation
The direction a waterfall faces, or the direction in which a watercourse flows over a waterfall.

Plateau
A typically extensive land area, having a relatively level surface raised sharply above adjacent land on at least one side.

Plunge
A form of a waterfall. The classic and overly cliched waterfall form, where the water drops vertically, losing most, or all contact with the rock face. This waterfall form has also been referred to as a “Cataract” and a “Vertical” form waterfall.

Plunge Pool
A pool at the base of a waterfall formed by hydraulic erosion.

Punchbowl
A form of a waterfall. Punchbowl waterfalls, coined from the famous Punch Bowl Falls in Oregon, occur where the stream is constricted to a narrow breadth and is forcefully shot outward and downward into a large pool.

Quartzite
Metamorphic rock commonly formed by metamorphism of sandstone and composed of quartz. No rock cleavage. Quartzite breaks through sand grains in contrast to sandstone, which breaks around sand grains.

Rapids
A section of a stream where the current has a moderate velocity, the surface is broken by extruding rocks and debris, producing frothy “whitewater”, and the gradient of the stream remains shallow.

Run
The horizontal distance in which the elevation change of a waterfall takes place. Also know as Runout.

Sandstone
Detrital sedimentary rock formed by cementation of individual grains of sand size and commonly composed of mineral quartz.

Schist
Metamorphic rock dominated by fibrous or platy minerals. Schist has a schistose plain of cleavage, and is product of regional metamorphism.

Scree
see Talus.

Sedimentary Rock
Rock formed from accumulations of sediment, which may consist of rock fragments of various sizes, remains or products of animals or plants, products of chemical action or of evaporation, or any mixture of these. Stratification is the single most characteristic feature of sedimentary rocks, which cover about 75 percent of earth’s land area.

Segmented
A form of a waterfall. Segmented waterfalls occur where the stream is broken into two or more channels before descending over the cliff, causing multiple falls to occur side by side.

Shale
Fine-grained, detrital sedimentary rock made up of silt and clay sized particles. Contains clay minerals as well as particles of quartz, feldspar, calcite, dolomite, and other minerals. Shale has a parallel plain of cleavage.

Sinkhole
A depression in the surface of the earth caused by the collapse of the roof of a cave or cavern.

Slate
Fine-grained metamorphic rock with well-developed slaty cleavage. Formed by low-grade regional metamorphism of shale.

Slide
A form of a waterfall. Similar to a cascade, a Slide type waterfall descends a smooth, gradual bedrock surface. Slide waterfalls maintain constant contact with the bedrock, and are often seen in areas where granitic rocks are common.

Spring
A feature where the water table intersects the land surface and water flows from underground at a more or less continuous rate.

Stream
A constantly moving body of water, confined to the lowest possible depression in the earth’s surface. The term Stream on this site refers to any size watercourse. Synonymous with Brook, Creek and River.

Talus
A slope consisting of rocks and boulders which have cleaved off of an adjacent cliff face. Talus is often found at the bottom of a waterfall. The term “talus” is also widely used to describe rock debris itself. Boulder Cascades are often associated with a slope consisting of Talus. Synonymous with Scree.

Tiered
A form of a waterfall. Tiered waterfalls are characterized by multiple distinct drops in relatively close succession to one another. Whether or not a waterfall with two visible drops counts as a tiered waterfall is up to the beholder.

Topographic Map
A schematic drawing representing landforms indicated by conventionalized symbols, such as contours and hachures. Often referred to as a Topo Map. See also: Contour Line, Contours, and Hachures.

Travertine
A terrestrial deposit of limestone formed in caves and around hot springs where cooling, carbonate-saturated groundwater is exposed to the air.

Tributary
A smaller stream which feeds into a larger stream. The size of the smaller stream is relative to that of the larger stream (the smaller stream is always the tributary).

Valley
An elongated depression of the earth’s surface, usually between ranges of hills or mountains. Also, an area drained by a stream or river and their tributaries.

Watershed
Also known as a Drainage Basin. Area from which a given stream and its tributaries receive water.

Width
The width of a waterfall formation, sometimes measured at the brink, sometimes taken as an average width of the waterfall.

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