Copy of `BGS - Geological terms`

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

Relief
The difference in height in different parts of the world's surface.

Residence time
The length of time an element spends in a storage place (sink).

Rayleigh wave
A type of surface wave having a retrograde, elliptical motion at the free surface. It is named after Lord Rayleigh, the English physicist who predicted its existence.

Raised mires
Developed from another mire type, commonly from a basin or floodplain mire to be above the general groundwater influence.

Quantock Hills
Some sedimentary rocks such as the sandstones and grits of the Quantock Hills and Clee Hills are very hard and resist weathering and erosion.

Primary porosity
Porosity a rock has when it forms.

Prediction
Predicting the time, place and magnitude of an earthquake.

Primary porosity
Porosity a rock has when it forms. Spaces (pores) between the grains of calcite, shells, sand grains etc, and within the grains themselves (shells, corals etc have pores and holes within them).

Quartzite
The rock that forms when sandstone is metamorphosed by heat and/or pressure when buried within the Earth's crust. Also sometimes used to describe very pure forms of unmetamorphosed sandstone.

Precambrian
The period of time before animals with skeletons and shells had evolved. It stretched from the formation of the Earth about 4600 million years ago to 545 million years ago.

Precession
The slow circular movement, or 'wobble', of the Earth's axis of rotation around another axis.

Precipitation
When salts or minerals, such as calcite, come out of solution and are deposited on a rock surface. (The word also has another sense, meaning rain or snow, but that is not used here.)

Porosity
The proportion of a rock that comprises spaces, voids and cracks (known as pores) between the grains.

Positive feedback
A process that is triggered by an initial change in an environmental variable which causes that variable to deviate further from the original condition. See negative feedback.

Pleistocene (Quaternary) glacial episodes
The period from 2 500 000 to 10 000 years ago, during which continental glaciers periodically expanded to cover sub-polar regions in both hemispheres.

Poljes
A very large, closed, flat-bottomed depression formed by karstic processes in temperate regions. Rivers may flow across them, and disappear down a sink hole called a ponor.

Ponor
A cave or a sink hole in the low point of a polje, down which a river or stream disappears.

Pore space
Spaces or voids between grains in the rocks in which air, water, other fluids or fine-grained mineral cements can be present.

Pleistocene
The main epoch of the last Ice Ages, between 10 000 years and 1.8 million ago, during which continental glaciers periodically expanded to cover sub-polar regions in both hemispheres.

Planning permission
Formal approval sought from a council, often granted with conditions, allowing a proposed development to proceed. Permission may be sought in principle through outline plans, or be sought in detail through full plans.

Plate boundary
The place where two or more plates in the Earth's crust meet.

Plateau
Flat-topped area of high ground.

Pinnacle karst
Karst that is characterised by remnant upstanding, blocks of limestone separated by dissolutionally enlarged joints, which may be buried by clastic sediments.

Plate
The Earth's crust is made out of a number of huge rafts of rock. Some have continents on them and others are covered by oceans. These huge slabs are called 'plates'.

Plate tectonics
The Earth's surface (crust) is divided into huge fragments called tectonic plates which carry the continents on top of them. They move very slowly over the globe, past each other, away from each other or colliding and taking the continents with them.

Phase
The onset of a displacement on a seismogram indicating the arrival of the different types of seismic wave.

Phreatic
(adjective) describes a cave, passage or cave system that formed below the water table and was consequently permanently flooded. The phreatic zone (or phreas) is the zone permanently saturated by water below the water table.

Photosynthesis
The process by which plants convert light energy to chemical energy. Carbon dioxide and water are changed into carbohydrates and oxygen in the presence of light and chlorophyll.

Permitted reserves
Mineral deposits with the benefit of planning permission for extraction.

Permian
The period of time between 252 and 298 million years ago.

Permeability
The ability of a fluid, like water or oil, to pass from one pore space to another.

Peat
A thickness of partially decayed vegetation, formed in wet anaerobic ground.

Permafrost
Permanently frozen ground in polar regions. It forms in regions close to, but not under, ice caps, ice fields and glaciers. The frozen conditions may be several tens of metres thick, but the top layer may thaw in the summer months before freezing again in the winter. During the last Ice Age, much of southern Britain was affected by permafrost.

Palaeoecology
The study of the relationship between fossil plants and animals, and the environment in which they lived in the geological past.

Palaeobiogeography
The study of the global, regional and local distribution patterns of fossil plants and animals.

Oxidised
A chemical reaction with oxygen or where electrons are lost. See reduced.

Oxidised
A chemical reaction with oxygen or where electrons are lost. See reduced.

Palaeogene
The period of time between 24 and 65 million years ago.

Ordovician
The period of time between 443 and 485 million years ago.

Ooidal limestone
A limestone that is formed of abundant ooids (sometimes called ooliths), small spheres of calcium carbonate that look like fish eggs. This is sometimes called 'oolitic limestone'

Ooids
Spherical grains that formed when aragonite is precipitated in concentric layers in gently agitated water. They usually have a sand grain or shell fragment in the core.

Open water transition mires
Developed from encroachment of vegetation around bodies of open water.

Orogeny
The process of mountain formation, especially by a folding and faulting of the earth's Crust.

North West Highlands
One of Scotland’s three large mountain ranges.

Obliquity
Earth rotates around an axis; the angle of this axis changes from 22.1 to 24.5 degrees.

Oligocene
The period of time between 23 and 34 million years ago.

Ombrogenous mires
Have a high-water table maintained by precipitation.

Mudstone
Muds and silts that have been compressed to form a hard, fine-grained rock.

Negative feedback
A process that is triggered by an initial change in an environmental variable so that the original 'normal' condition is restored. See positive feedback.

Moraine
The material eroded by a glacier and carried along by the ice, before being dumped when the glaciers retreat. Till is one type of moraine. Erratics originated as moraine.

MSK
MSK intensity is the intensity scale used in Europe before the introduction of the EMS scale. It is a 12-grade scale ranging from not felt to complete devastation.

Mogote
Like a hum, but in tropical areas. It is a residual hill sticking up through the sediment as a result of karstic processes.

Metamorphic rock
A 'changed rock', altered by heat and or pressure so that mineral grains are preferentially orientated or new types of crystals begin to grow.

Metamorphism
When a pre-existing rock is chemically or physically altered by heat, pressure or chemically active fluids.

Microseism
A motion in the Earth that is unrelated to an earthquake. It is caused by a variety of natural and artificial agents, for example wave action, wind, traffic and industrial noise.

Mesozoic
An era in which the Triassic, Jurassic and Cretaceous periods are grouped (65 to 248 million years ago).

Malvern Hills
Precambrian gneiss, a hard, highly metamorphosed rock, and schist form in these hills.

Marine regressions
Retreats of the sea over the land.

Marine regressions
Retreats of the sea over the land

Massive limestones
Limestones that are made of thick layers (called beds) of rock. In Britain, the Carboniferous Limestone is the best examples. Other limestones such as the Cretaceous chalk and Jurassic limestones of Central England are made of thin beds and can not described as massive.

Magnitude
A measure of the strength of an earthquake. There are several scales depending on which part of the seismogram is examined. These include Richter local magnitude (ML), Body wave magnitude (mb) and surface wave magnitude (Ms). Moment magnitude (Mw) is calculated from spectral analysis.

Mantle
Inside the earth, the layer below the earth's crust but above the core

Maine transgressions
Advances of the sea over the land

Love wave
A major type of surface wave having a horizontal motion that is shear or transverse to the direction of propagation. It is named after A.E.H. Love, the English mathematician who discovered it.

Lithosphere
The solid rock of the Earth’s outer layers, including the crust and the upper mantle.

Lithostratigraphy
The classification of rock successions based on rock type (otherwise known as lithology).

Limestone bench
A long narrow strip of level ground in a limestone landscape with steeper slopes above and below it.

Limestone
A hard sedimentary rock that is composed of over 50% carbonate minerals. A true limestone is over 90% calcite, but there are often other carbonates (including dolomite) and impurities in the form of sand grains, clay minerals, etc. Limestone is laid down in layers or 'beds' separated by 'bedding planes' and divided up into blocks by a series of joints (fissures created during the rock formation process) at approximately, right angles to each other.

Limestone pavement
A flat expanse of exposed limestone formed by a combination of erosion and chemical weathering.

Leith Hill
One of the highest hills in the south east of England (294 m).

Lead_ore
A rock sufficiently rich in lead that it is mined.

Lancashire Plain
Lowlands area of north west England.

Lagerstätten
Derived from a German mining term, fossil Lagerstätten are deposits that are extremely rich in fossil material and/or contain exceptionally well-preserved specimens. A well known example is the Middle Cambrian Burgess Shale of British Columbia, Canada, which contains trilobites with their soft parts preserved.

Lake District
A mountainous area, where Scafell Pike is the highest mountain in England. Igneous rocks in the Lake District vary from granite, which forms deep underground, to ancient lavas and ash ejected from volcanoes. Metamorphosis also caused slate to form in the Lake District.

Lava
Molten magma that extrudes onto the Earth's surface as a result of a volcanic eruption. The lava solidifies quickly to form a hard, very fine grained rock. Gases within the magma may form large voids, sometimes filled with minerals and crystals.

Latitude
Circles drawn around the Earth parallel to the equator; their diameters diminish as they approach the poles. These parallels have an angle provided from the angle from the equator i.e. 0 degrees at the equator and 90 degrees at the poles.

Kufeng
Towers similar to fenglin, but isolated from the other towers by a flat plain.

Karst
The term given to a distinctive landscape created by the solution and erosion of a soluble rock such as limestone. Water is an essential ingredient in the formation of the characteristic topographical features (dolines, caves, dry valleys, etc).

Karren
Small hollows on the surface of limestones (e.g. limestone pavements) caused by solution during chemical weathering.

Jurassic
The period of time between 142 and 205 million years ago.

Isotopes
Atoms of an element that have the same number of electrons and protons but different numbers of neutrons.

Isoseismal line
A line enclosing points on the Earth's surface at which earthquake intensity is the same. It is usually elliptical in shape

Joints
Fissures in rocks, often at right angles to each other and the bedding planes, formed as a result of deformation.

Ironstone
A mudstone or sandstone with a high iron content.

Iron Age
The period of British prehistory from approximately 800 BCE – 100 CE.

Isostasy
The theoretical equilibrium that tends to exist in the Earth's crust; this can alter sea level on a local scale. For example, glacial ice can push down the crust so that when it melts the crust will uplift thus causing sea level in the area to decline. Compare with Eustasy.

Intensity
A measure of the effects of an earthquake at a particular place on humans and (or) structures. The intensity at a point depends not only upon the strength of the earthquake (magnitude) but also upon the distance from the earthquake to the epicentre and the local geology at that point.

Infilitration
The downward flow of surface water into the soil.

Interglacial
A phase of relatively warm temperatures between glacials. See glacial.

Interpolated / Interpolation
The process by which software invents new data to fill gaps in an image or grid.

In spate
A river is described as being in spate during sudden flood conditions, such as flash floods.

Induced seismicity
Non-natural events induced by man's activity. These include mining induced events, events caused by loading of dams or pumping of water in geothermal areas.

Ice sheet
A glacier of more than 50 000 km2 with a flattened dome that buries the landscape.

Igneous rock
A rock that originated when a molten magma or lava cooled and solidified.

Impermeable
Rocks that do not allow water to pass through them are called 'impermeable'.

Ice age
A long period of glaciation. An informal term for a time when global temperatures were greatly reduced and glaciers, ice fields, pack ice, etc advanced. There have been several 'ice ages' during the last 600 million years or so. The last one to affect Britain occurred during the last million years (ending about 10 000 years ago). This was a time of contrasts between phases of glaciation interspersed by warmer phases (sometimes warmer than today).

Hydrostatic pressure
The weight of the water higher in the cave system, exerts a pressure on the water lower down, forcing it to flow through passages and up joints towards regions of low hydrostatic pressure, such as resurgences.

Hypocentre
The calculated location of the focus of an earthquake.

Iapetus
The precursor of the Atlantic Ocean was named after the father of Atlas.

Grampians Mountains
One of Scotland’s three large mountain ranges.