Copy of `BGS - Geological terms`

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BGS - Geological terms Category: Sciences > Geology Date & country: 27/12/2017, UK Words: 324

S wave
The second arrival on a seismogram, the S wave, is slower than the P-wave. It is a shear wave and cannot travel through liquids.

U-shaped valley
The term given to a valley when it has been eroded by glaciers. Its cross-section is U-shaped.

Yorkshire Dales
An upland area of central northern England, the Yorkshire Dales are the central part of the Pennine chain and are made of hard and resistant fossiliferous limestones overlain by shales and hard gritstones and sandstones.

Zinc ore
A rock sufficiently rich in zinc to make it worth while mining.

P wave
The first and faster of the body waves which moves by a series of compressions and dilatations, similar to a sound wave. They can travel through both solid and liquid.

Web Map Service
(WMS) Web Map Service (WMS) - Is a standard interface for the querying of geospatial data and for the serving of that data as georeferenced images (such as png, gif or jpeg) over the web.

Web Feature Service
(WFS) Is a standard interface for the querying and manipulation of geospatial vector data and for the serving of that data as georeferenced features, using Geography Markup Language (GML), over the web.

Weathering
(chemical) The process by which rock is broken down by changes in the mineral composition, mainly as a result of acidic rainfall.

Weathering
(mechanical/physical) Rock is broken up into small pieces by wind, water or ice.

Web Coverage Service
(WCS) Is a standard interface for the querying and manipulation of geospatial coverage data, and for the serving of that data as georeferenced objects, over the web. Coverages can be a set of data points; a regular grid of points (or pixels); a set of segmented curves (eg. road paths); a set of Thiessen polygons; or a TIN triangulated irregular network (eg. terrain models). These data locations can also carry range information data - eg. a terrain model would include height information.

Weathering
The processes (chemical or physical) by which rock is broken down.

Web Map Service (WMS)
Web Map Service (WMS) - Is a standard interface for the querying of geospatial data and for the serving of that data as georeferenced images (such as png, gif or jpeg) over the web.

Weald
Lowlands area of south east England, composed of impermeable clay.

Web Feature Service (WFS)
Is a standard interface for the querying and manipulation of geospatial vector data and for the serving of that data as georeferenced features, using Geography Markup Language (GML), over the web.

Web Coverage Service (WCS)
Is a standard interface for the querying and manipulation of geospatial coverage data, and for the serving of that data as georeferenced objects, over the web. Coverages can be a set of data points; a regular grid of points (or pixels); a set of segmented curves (eg. road paths); a set of Thiessen polygons; or a TIN triangulated irregular network (eg. terrain models). These data locations can also carry range information data - eg. a terrain model would include height information.

Wavelength
The distance between two successive crests or troughs of a wave.

Weather
The physical conditions of the atmosphere (mainly the troposphere) with regard to wind, temperature, cloud cover, fog and precipitation (rain, hail, snow) at a specific time and place. It is highly variable and can be unpredictable. Compare with climate.

Weathering (chemical)
The process by which rock is broken down by changes in the mineral composition, mainly as a result of acidic rainfall.

Weathering (mechanical/physical)
Rock is broken up into small pieces by wind, water or ice.

Walbury Hill
One of the highest hills in the south east of England (297 m).

Water table
The level below which the pore spaces of the soil or rocks are completely saturated with water. The horizon under the ground, below which all the pores, fissures and joints are filled with ground water. Above this horizon, the pores, fissures and caves are free draining (vadose zone) and below it they are permanently saturated (phreatic zone). Where the water table comes to the surface of the ground, spring lines, resurgence and exurgence occur.

Vruljas
Underwater springs formed when high hydrostatic pressure forces rivers to flow out of the ground below the water table.

Volcanic earthquake
Earthquakes associated with volcanic activity.

Vale of York
Lowlands area of north east England, comprising soft mudstone.

Vale of the White Horse
Lowlands area in the west of the Marlborough, Berkshire and Hampshire Downs.

Vale of Evesham
Lowlands area of England, near the Cotswolds.

Vadose
(adjective) Describing a passage or cave above the water table that is free draining or dry (although it may have a river flowing through it, the passage is not entirely flooded

Valley mires
Elongate in form, developed on the lower slopes and floors of small valleys and channels with a through-flow of water along the main drainage axis. The water table is maintained, at least partly, by springs and seepage along the valley sides.

Vale of Aylesbury
Lowlands area of England, composed of impermeable clay.

Vale of Belvoir and Trent Valley
Lowlands area of central England, composed of impermeable clay.

Tsunami
A huge sea wave caused by earthquakes. (Referred to by many as a tidal wave.)

Tufa
A fine grained, porous limestone formed by chemical precipitation, often around springs.

Unconsolidated
A sediment is unconsolidated if the particles are not attached together at all. As a sediment becomes more rock like it becomes more consolidated.

Uvalas
Enclosed depressions with uneven floors that are formed by solution of the limestone. They may be where several dolines are joined together or they form when small dolines form within a larger one.

Topogenous mires
Have a high-water table maintained by the generally low lying ground.

Topography
Description on maps, etc, of natural features (hills, rivers, etc) and features made by humans (e.g. buildings, roads and railways).

Travertine
A coarsely crystalline limestone that forms by chemical precipitation. It is often translucent and banded.

Triassic
The period of time between 205.7 and 248.2 million years ago.

Travel time
The time required for a wave train to travel from its source to a point of observation.

Till
(called 'boulder clay' in the past) Formed as moraine that was dumped from a glacier when the ice retreated. It comprises muds, silts and sands mixed with pebbles and boulders.

Thames Valley
Lowlands area in the Greater London area.

The Fens
Lowlands area in eastern England.

Thurrock ASCII grids
This folder contains the export of the Thurrock Sample Model data as a non-proprietary ascii (ESRI) grid with a cell size of 20 metres. Each geological unit is represented by its top, base and thickness.

Thurrock ESRI shells
This folder contains the export of the Thurrock Sample Model data as a proprietary (ESRI) multipatch shapefile. Each geological unit is represented by a shell or skin created from triangles.

Thurrock Gocad surfaces
This folder contains the export of the Thurrock Sample Model data to Gocad as tsurf files.

Temperate forests
Forests in the temperate (mild, not extreme) climate zones.

Terminal depth borehole
Boreholes that record terminal depth (TD) are boreholes that end before going through the base of the superficial deposits. These boreholes can't prove the base of the superficial deposits, but can provide a minimum value for thickness.

Teleseism
An earthquake that is distant from the recording station.

Suffosion
The process of washing soil down an underlying fissure (in massive limestone areas this is usually a joint).

Surface waves
Seismic waves with motion restricted to near the ground surface (Love and Rayleigh)

Swallow hole
A type of doline into which a river or stream descends.

Syncline
A downward fold of sedimentary rock put under pressure by Earth movements. (See anticline)

Subduction zone
An elongated region along which a crustal plate descends relative to another crustal block, for example, the descent of the Pacific plate beneath the Andean plate along the Andean trench.

Stratigraphy
The study and classification of rock successions.

Subpolar
Latitudes of the Earth adjacent to the Arctic and Antarctic circle.

Subtropical
Latitudes of the Earth adjacent to the tropics.

Suffusion
The process of washing soil down an underlying fissure (in massive limestone areas this is usually a joint).

Sump
A flooded cave or passage.

Structure
There are several definitions, but in Limestone Landscapes this refers to the folds and faults in rocks that have been by caused Earth movements.

Stone Age
The period of British prehistory from the earliest known inhabitation by humans to approximately 2000 BCE.

Spring mires
Often small, developed downslope of springs and seepage lines.

Stalactites
Deposits of calcite that form elongate cones at the sites of precipitation on the ceiling of a limestone cave. The word comes from the Greek stalaktos meaning dripping. Some people find it difficult to remember the difference between a stalactite and a stalagmite. It might help to remember that a 'stalactite' forms on the ceiling and that '-tites' hold tight to the cave roof.

Stalagmites
Deposits of precipitated calcite that form elongate, vertical projections on the cave floor. The word derives from the Greek stalagmos meaning 'dripped off'. Some people find it difficult to remember the difference between a stalactite and a stalagmite. It might help to remember that a 'stalagmite' forms on the ground and that ' -mites' might reach up to the '-tites'.

Spatial
The location of an object, its size, shape and relationship to other objects.

Speleothems
Precipitated calcite. It takes on many different shapes depending on local conditions and include straws, stalactites, stalagmites, columns, curtains, flowstone, etc. They are formed by the precipitation of calcium carbonate (calcite) from mineral-rich water that percolates through the limestone into a cave.

Spring
A point in the hillside where water seeps or bubbles from the limestone. It differs from a resurgence, where a stream or river emerges and it differs from exurgence, where only percolating rain water emerges.

Slate
A metamorphic rock that was originally deposited as clay, but due to intense pressure, the platy clay minerals were orientated at right angles to the direction of pressure, resulting in the characteristic 'slaty cleavage'. The rock appears to be made of many leaves, like the pages in a book. The rock can be split into thin sheets and used to roof buildings.

Soligenous mires
Have a high-water table maintained by lateral water movement.

Solution
A salt or mineral that has dissolved and held in water.

Southern Uplands
One of Scotland's mountainous areas, close to the border with England. North of the Cheviot Hills.

Shale
A laminated mudstone formed under pressure.

Sill
Intrusive igneous rocks parallel to bedding. An example is the Whin Sill in Northumberland.

Silurian
The period of time between 417 and 443 million years ago.

Sink hole
A basin in limestone areas down which water disappears. Other names include swallow hole, swallet or doline.

Signal-to-noise ratio
The comparison between the amplitude of the seismic signal and the amplitude of noise caused by seismic unrest and (or) the seismic instruments.

Seismograph
An instrument that registers the occurrence of an earthquake and the time it occurred as a written record.

Seismologist
A scientist who studies earthquakes.

Seismometer
An instrument that not only measures the time of the arrival of earthquake waves, but also allows the exact motion of the ground to be computed from the record.

Seismoscope
An instrument that registers the occurrence of an earthquake, but not the time.

Seismogram
A record of an earthquake or ground vibration. The wave trace is made up of P-waves, S-waves and surface waves, the pattern of onsets of the first two arrivals help to determine the location. The seismogram can be either a paper record or a digital record that is analysed by computer.

Sea level
Sea level or mean sea level as it is sometimes known, is the average height of the ocean's surface between high and low tide. Changes in tides and wave conditions over time are averaged out to determine a 'still water level' that can be used to identify a real change in sea level or a change in the height of the land that a tidal gauge is measuring. In the UK, height above sea level is defined as 'Ordnance Datum' and this is the mean sea level at Newlyn Bay in Cornwall.

Secondary porosity
Porosity that results from processes that occur after the rock has formed , such as fracturing or the more soluble grains dissolving.

Sedimentary rock
Rocks that originated from the broken up or dissolved and reprecipitated particles of other rocks. Examples include clay, mudstone, siltstone, shale, sandstone, limestone and conglomerate.

Sea level
Sea level or mean sea level as it is sometimes known, is the average height of the ocean's surface between high and low tide. Changes in tides and wave conditions over time are averaged out to determine a 'still water level' that can be used to identify a real change in sea level or a change in the height of the land that a tidal gauge is measuring. In the UK, height above sea level is defined as 'Ordnance Datum' and this is the mean sea level at Newlyn Bay in Cornwall.

Schwingmoor
Floating rafts of peat.

Scree
A pile of rubble along the base of a steep valley, crag or cliff composed of small pieces of rock and gravel that have fallen down from above due to weathering. The rock usually becomes detached as a result of freezing and thawing. (The word 'talus' is sometimes used instead of scree, but strictly speaking, talus is made of large pieces of rock).

Scarp slope
see escarpment.

Salisbury Plain
Lowlands area of southern England.

Scar
A vertical cliff of limestone that form along the sides of valleys.

Sandstone
As the name implies, sandstone is formed of sand that has been turned to stone. The grains of this sedimentary are mainly quartz or feldspar and cemented together with minerals such as calcite, silica or iron to form a rock. The grains are as small as 0.06 mm (1/16th mm) and as large as 2.0 mm in size. Colour varies from white to orange, red, brown, green and grey depending on the minerals present. The original sand that makes up the sandstone may have been deposited in deserts, lakes, rivers, deltas or shallow seas. Different names are given to sandstones depending on variables such as the shape, size and composition of the grains.

Ridge and corridor
A karstic feature in hot, arid regions, comprising a series of low ridges (up to 6 m high) separated by flat-floored basins (up to 1 km wide and several kilometres long).

Richter scale
A popular name for the local magnitude scale (See Magnitude).

Relative dating
Determining the age of a rock relative to another, rather than its absolute age in millions of years.

Refraction
The change in direction of a wave on reaching a boundary of different density and velocity.

Reflected wave
A wave that has turned back from a boundary or discontinuity in the earth's crust.

Respiration
The breakdown or organic compounds which releases energy and produces carbon dioxide and water.

Resurgence
Where a river or stream that has fallen into a cave system, returns to the surface. (Exurgence is where only percolated water returns to the surface and the term 'spring' refers to the point where any underground water returns to the surface.)

Reduced porosity
The porosity in rocks can decrease after burial. Pores are closed when the rock is squeezed and compacted underground. Porosity is also decreased by the precipitation of silica or calcite in pore spaces from percolating fluids.

Recharge
The natural process in which aquifers are replenished by rainwater reaching the water table.

Reduced
The loss of oxygen or gain of electrons in a chemical reaction. See oxidised.