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M -- top --
Magma: (Gk: magma/ masso= to knead) fluid or semifluid material deep inside the earth from which igneous rock is formed.
Magnetite: (Magnesia= an island in Asia Minor, from which magnetic rock was obtained) black, unhydrated magnetic iron oxide.
Marble: (L: marmor; Gk: marmaros= shining stone) limestone in a metamorphic crystalline (or granular) state, and capable of taking a polish. Used in sculpture and architecture.
Mass movement: erosion of soil or rock by gravity-induced collapse. Usually triggered by groundwater pressure after heavy rain, but can also have other causes, notably streams undercutting the base of a slope, or earthquakes. Movement can either be rapid and near-instantaneous (landslides, avalanches, debris flows) or slow and intermittent (earthflows, slumps).
Metamorphic/ metamorphism:  (Gk: meta= with/after; morphe= form) rock that has undergone transformation by natural agencies such as heat and pressure.
Mica: (L: mica=crumb) any of a group of silicate minerals with a layered structure, especially muscovite.
Mica-schist: a fissile rock containing quartz and mica.
Mineral: (L: minera=ore) a solid, inorganic substance, found in nature, which has  an orderly internal structure and a specific chemical composition.
Mohorovicic discontinuity (Moho): (named after Mohorovic) the boundary between crust and mantle, marked by a sharp decrease in earthquake wave speed.
Mollisols: (L: mollis=soft; solum=ground) grassland soils, mostly rich in calcium; also forest soils developed on calcium-rich parent materials. They are characterised by a thick surface layer, rich in organic material.
Montmorillonite: (Montmorillon= a place in the south of France) a three-layer clay (smectite group), capable of high cation exchange and holding large amounts of water. Sticky when wet.
Mudstone: a sedimentary rock composed of silt and clay particles, compacted and weakly cemented together by a small quantity of lime.
Muscovite: (L: Muscovia= moscow) a silver-grey form of mica with a sheetlike crystalline structure that is used in the manufacture of electrical equipment, etc.
N -- top --
Nitrogen volatilisation: (volatile= evaporative. L: volare= to fly) conversion of soil nitrogenous matter to NO and NO2 gas, by high-temperature reaction when overlying vegetation is burned, or by bacteria in the soil.
Nontronite: (?) an amorphous smectite clay formed from weathered volcanic ashes, basalt. Na(0.33)Fe2(Al(0.33)Si(3.67))O10(OH)2.nH2O.
O -- top --
Octahedron: (Gk: okto=eight; hedra= seat) a body (crystal) contained within eight triangular planes of equilateral triangles.
Olivine: (Say: "olivene") (olive-green colour) a naturally occurring form of magnesium-iron silicate, usually olive-green and found in igneous rocks. Other names: peridot, chrysolite. (Mg,Fe)2SiO4.
Organic load: the quantity of organic matter passing a stream reach in the course of a year. Usually expressed in terms of biological oxygen demand, i.e the amount of oxygen consumed by micro-organisms as they break it down.
Orogeny: (Gk: oros=mountain; genes=born, of a specified kind; gignomai=be born, become) mountain building, involving deformation, metamorphism, uplift and intrusion of igneous rock. It happens when continents collide.
Orthoclase: (Gk ortho=straight; klasis=cleavage) a common alkali feldspar usually occurring as variously coloured crystals, used in ceramics and glassmaking.
Orthorhombic: (Gk: orthos= straight; rhombos= a parallelogram with oblique angles and equal sides, a rhombus ) a crystal, characterised by three mutually perpendicular axes, which are unequal in length, such as in topaz and talc.
Outwash: alluvial sand and gravel deposited by rivers, draining glaciers during the last ice age. Widespread on terraces and floodplains in areas near ancient glaciers.
Oxysols: (Gk oxus=sharp) Soils that are more weathered than the ultisols, including most laterites.
P -- top --
Pair planting: plantation of trees in pairs on either side of a hill slope watercourse, to prevent gully incision.
Parent material: the bedrock underneath the soil, from which the soil originated.
Ped: (Gk: pedon=ground) a crumb of soil.
Pedalfer: () soil of humid climate.
Pedocal: () soil of arid climate.
Pedology: (Russian: pedologiya: soil study; Gk: pedon= ground) the scientific study of soils, especially its formation, nature and classification.
Peridotite: (Old-French: peritot) A heavy intrusive igneous rock mainly consisting of olivine and 5-15% pyroxene. Peridot: A green variety of olivine, used especially as a precious stone.
Perlite: (French: perle=pearl) a vermiculite volcanic glass with the composition of rhyolite. When heated, it pops, to form a light-weight aggregate for construction.
Permafrost: (from permanent + frost) subsoil which remains below freezing point throughout the year, as in the polar regions.
Phreatic: (Gk: phreatos= well) driven by (ground) water. Phreatic eruptions throw out old, previously cooled rock as a result of sudden violent interaction between hot rock or gas and groundwater. This kind of eruption is also called pyroclastic surge or base surge, resulting in base surge deposits.
Plagioclase: (Gk: plageos= oblique; klasis=cleavage) a series of feldspar minerals forming glassy crystals.
Planosol (or solod): (L: planus= flat; solum= ground) calcium- or hydrogen-saturated soils with considerable difference in clay content between the eluviated surface (top) and the clay illuvial horizon (below).
Plutonic: (L/Gk: Plouton= god of the underworld) formed as igneous rock by solidification below the surface of the earth.
Podsol/isation: also podzol/isation (Russian: pod=under; zola= ashes) weathering in a strongly acid medium eluviatesthe iron and aluminium oxides, causing the formation of amorphous clays with high CEC. The soil gets an upper horizon rich in sand and an illuvial horizon rich in amorphous clays (spodic horizon). These soils are called podsols. Best developed under pine forests.
Precipitate: (L: prae=before; caput=head; praecipitare= to head before) causing to be deposited onto a surface; moisture condensed from vapour.
Profile: (L: pro= for, on behalf of, infavour of; filare=to spin; filum= thread) an outline, a cross-section. A soil profile is a cross- section through the soil.
Pumice: (L: pumex/ pumicis= pumice stone) a light-weight and light-coloured, cellular glassy rock with the composition of rhyolite. Pumice forms when lava from a volcano flows onto the earth's surface or erupts violently into the air.  The hot, gas-filled lava then cools quickly to form glass.  Many tiny holes remain after the volcanic gases escape from the cooling lava.  Pumice floats on water because it contains many air bubbles. Used as light-weight aggregate and for scouring. Also see tephra.
Pyrite (Fool's Gold). (Gk: pyr=fire) A yellow lustrus (shiny) form of irondisulphide.
Pyroclastic: (Gk: pyr=fire; klastos= broken in pieces) debris ejected from volcanoes.
Pyroclastic flow: also called glowing cloud or burning cloud. An explosive volcanic eruption accompanied by rapidly expanding gas and particles, travelling as a fluid gas down hill. Such flows are hot (up to 1000ºC) and move at speeds of several hundred km per hour. They are extremely dangerous.
Pyroxene: (Gk: pyr= fire; xenos= stranger) any of a group of minerals commonly found as componenets of igneous rocks, composed of silicates of calcium, magnesium and iron.
Q -- top --
Quartz: (Gk: Quarz) a mineral form of silica that crystallises as hexagonal prisms.
R -- top --
Regolith: (Gk: rhegos= rug, blanket) Unconsolidated solid material (residue) covering the bedrock of a planet. The basal layer of soil, composed of material that is still recognisable as weathered rock or other geological deposits (such as alluvium). It grades upwards into overlying subsoil.
Regression: (L: re/red=back/again; gradi=step; regressio=backward movement) a seaward shift of the shore, due to a fall in sealevel, a rise of the land or sedimentation.
Resource consent: permit issued by a district or regional council, allowing a change in the use of land (or other resources). Consents are only required if a district or regional plan identifies the proposed use as capable of causing adverse environmental effects.
Retirement: (Fr: rétirer= to withdraw) fencing of land to exclude grazing by stock. It may entail rank grass and weed, or reversion to scrub, or plantation of timber trees on the land that is no longer grazed.
Reversion:  spread of indigenous scrub across land that is lightly grazed or retired from grazing.
Rhyolite: (Gk: rhyax= lava stream; lithos= stone) a fine-grained volcanic rock of granitic composition.
Rift: (of Scandinavian origin) a cleft or fissure; a trough between two fault zones, with a down-dropped central block. It is often the beginning of continental breakup and also occurs on mid-ocean ridge axes.
Rilling: erosion of surface soil particles by rainwater running off across the ground as distinct rills after heavy rain.
Riparian: (L: ripa= bank) pertaining to river banks.
Rock: rock  is an aggregate of one or more minerals.
Rubification: (L: rubidus=red) when soil is thoroughly dried from time to time, precipitates of iron and organic matter cannot accumulate and the organic matter disappears by decay, causing irreversibly dehydrated iron sesquioxides to form. Soils are called cinnamonic (red).
Runoff: water flowing across or through soil after rain. The term is sometimes also applied for water flowing in ephemeral channels.
S -- top --
Sandstone: a sedimentary rock composed of sand grains, compacted and weakly cemented by a small quantity of lime.
Saturation: (L: satur= full) penetration of all the pores and fissures in soil by water, so that air is excluded.
Schist: (L/Gk: schistos=split) a metamorphic rock that tends to split into sheets or slabs, showing glistening or speckled surfaces. It often has white bands of quartz alternating with bands of fine-grained minerals, coloured silvery grey, greenish or pinkish.
Scour: erosion of channel beds and banks by stream flow.
Sediment: (L: sedere=to sit) matter that settles to the bottom of a liquid.
Sediment load: the quantity of sediment passing a stream reach in the course of a year.
Sedimentary rock: (L: sedere=to sit) rock laid down by erosion. Matter that is carried by water or wind and deposited on the surface of the land, and may in time be consolidated into rock. Under heat and pressure, sedimentary rock may metamorphose.
Segregation of iron in soil: (L: segregare= to set apart) in soils rich in iron but poor in two-layer clays that retain it, iron tends to segregate, forming irregular concretions and nodules that become hard as stone. See also ferrugination.
Serpentine: (L: serpentinus= serpent) a soft rock mainly of hydrated magnesium silicate (Mg,Fe)3Si2O5(OH)4. Antigorite, a flaky variety, is found in massive rocks. It is usually dark green and sometimes mottled or spotted like a serpent's skin, taking a high polish (greasy/silky lustre and a slightly soapy feel) and used as a decorative material. Such serpentine is used as ornamental stone called verd antique or serpentine marble.  Chrysotile, a fibrous variety of serpentine, is the most important type of asbestos. Serpentine is also used as an additive in making magnesium superphosphate fertiliser.
Sesquioxides: (L: semi=half; qui=and; one and half unit, 1.5) the hydrated oxides of iron, aluminium, manganese and titanium. Three oxygen atoms for two metal atoms, like Fe2O3.
Shale: (German: schale=scale, plate) a fine-grained sedimentary rock formed from silt and clay, tending to separate in thin sheets along depositional bedding planes. Often contains organic matter like oil.
Sheetwash: erosion of surface soil particles by rainwater running across the ground as thin sheets after heavy rain.
Shield: A large rigid area of the earth's crust, usually of Precambrian rock (basement rock), which has been unaffected by later orogenic (mountain building) episodes.
Shield basalt: A basaltic lava flow that erupted from numerous small closely spaced vents, and coalesced to form a single unit. It is generally of smaller extent than a plateau basalt (flood basalt).
Shield volcano: A broad, gently sloping volcanic cone of flat domical shape, built chiefly of overlapping and interfingering basaltic lava flows.
Silica: (L: silex=flint) silicon dioxide (SiO2) occurring as quartz, etc. and as a principal constituent of sandstone and other rocks.
Silicate: (L: silex=flint) any of the many insoluble compounds of a metal combined with silicon and oxygen, occurring widely in the earth's crust.
Silviculture: (L: silva= a wood) management of timber trees to improve their quality and yield, principally by pruning, and thinning. It also entails seedling selection, fertilising, spraying or disease & weed control.
Sillimanite: (Named after B Silliman, an American chemist, who died in 1864) an aluminium silicate occurring in orthorhombic crystals or fibrous masses.
Smectite: an amorphous clay formed from easily weatherable volcanic ashes, lava or basalt.
Soil conservation: measures which protect soil from excessive erosion, structural breakdown, nutrient loss or pollution, thereby minimising soil decline in its capacity of supporting plant and animal life.
Soil nutrients: minerals in the soil that are beneficial for plant growth, principally the elements N, P, S, Ca, Mg, K and their derived compounds.
Soil structure: the arrangement of soil particles and inter-particle spaces (pores and fissures). Good soil structure is beneficial for aeration, percolation of water, penetration by plant roots, resistance to stock treading and for load-bearing (tractor) when cultivated.
Solid solution: composed of various components such that the chemical formula of the rock is not unique and any combination is possible. Two or more elements can substitute for each other completely. For example, the anions Mg++ and Ca++ , which are similar in size and function, can combine CaSiO3 and MgSiO3 to (Ca,Mg)SiO3 as if the rock components were dissolved into one another. The fact that silicate rocks allow for substitution makes them easy to take apart through weathering.
Solonisation: (?) sodium-saturated soils (solonetz) having a richer clay horizon at depth than at the surface.
Solum: (?) the horizons of the soil which have been changed from the parent material by the soil forming process. Subsoil+top soil.
Solute load: (solute= a dissolved substance) the quantity of dissolved chemicals passing a stream reach in the course of a year.
Spaced planting: plantation of trees, sufficiently apart that a close canopy cannot form. Depending on species, mature trees at a density of 50 to 100 stems a hectare are widely enough spaced for pasture or other vegetation to grow in between.
Spar: (Old-English: sparen= plaster; sparstan=gypsum) any crystalline, easily cleavable and non-lustrous mineral, e.g. calcite or fluorspar.
Spinel: (?) MgAl2O4 a magnesium-aluminium oxide.
Spodosols: (?) see gleisation.  Soils with a light, ashy gray A horizon, and a B horizon containing inorganic matter and clay leached from the A horizon.
Stadial: (Gk: stadion=stage) a colder phase within a glacial interval.
Staurolite: (?) an iron-aluminium silicate Al4Fe[O/OH/SiO4]2.
Stone line: ? the layer of stones found underneath the A-horizon, caused by worms and other soil organisms rotating the soil above it.
Strata/stratum: (L: sternere= to strew; stratum= something laid down) a layer or set of successive layers of any deposited substance.
Stratovolcano: (L: stratum=layer) These are steep volcanic cones built by both pyroclastic (thrown by fire) and lava-flow eruptions. They are composed of volcanic rock types that vary from basalt to rhyolite, but their composition is generally andesite. Stratovolcanoes may erupt many thousands of times over life spans of millions of years. A typical eruption would begin with ash explosions and end with extrusion of thick viscous lava flows. The cone-shaped form begins gradually and becomes steeper (up to 35°) toward the summit, which generally contains a crater. At the end of its activity, lava may gently pur out to form a shield of rock (shield volcano).
Streamflow: water flowing through premanent channels.
Strike-slip fault: a fault along which the displacement of rock bodies is horizontal.
Subduction: (L: sub=under; ducere= to lead, bring) the process by which an oceanic plate slips underneath another plate.
Subsaturite: ?
Subsoil: (L: sub=under; solum= ground) the mineral-rich layer of the soil, lying underneath the topsoil and above the regolith, from which it is derived. It is weathered to a stage where the parent material (rock or sediment) is no longer recognisable.
Superphosphate: the most common form of phosphate fertiliser. Ca(H2PO4)2
Suture: (L: sutura=a stitch; suere= to sew) a join or weld left from a former collision of two continents.
T -- top --
Talc: (L: talcum; Arabic: talk) any crystalline form of magnesium silicate that occurs in soft flat plates, usually white or pale green in colour and used as a lubricator.
Tectonics: (Gk: tektonos= carpenter) originally, the art of producing pleasing buildings. The study of large-scale structural features. The study of the movement and deformation of the earth's crust and mantle.
Tephra: (Gk: tephra= ash) loose material, e.g. ash and pumice, deposited by volcanic eruptions. Tephra is subdivided into three main particle sizes: less than 2mm = ash; 2-64mm= lapilli; over 64mm= blocks or bombs. Consolidated ash is also known as tuff. Scoria is dark-coloured tephra, which has been erupted but not in a molten condition. It is permeated by holes from which gas has escaped, and in colour resembles cinders or slag from a furnace. Pumice is a light coloured equivalent. Tephra is usually dispersed widely during an eruption, depending on particle size. Tephra can be accompanied by emissions of poisonous chlorine and fluorine gases.
Terrace: (L: terra= earth) a flat to gently sloping alluvial surface, elevated above floodplain level.
Tetrahedron/tetrahydral: (Gk: tetra=four; hedron= seat) substance (crystal) contained within four equilateral triangles.
Tholeiite basalt: A basalt resembling that found in Tholey, Germany. It is characterised by the presence of orthopyroxene and/ or pigeonite in addition to clinopyroxene and calcic plagioclase. Olivine may be present.
Till: (origin unknown) chaotic mix of stiff clay, sand and boulders deposited by glaciers during the last ice age.
Topaz: (L: topazus; Gk: topazos) a transparent or translucent aluminium silicate mineral, usually yellow, used as a gem.
Topsoil: the uppermost layer of soil, rich in organic matter, incorporated from the decay of plants and the activities of micro-organisms, intermixed with mineral material derived from the underlying subsoil.
Tor: (Old-English: torr= broken hill) a broken hill or rocky peak.
Torrent: (L: torrens= scorching, boiling, roaring) a steep, permanently flowing channel, incised on a mountain slope.
Transform fault: a fault with horizontal movement connecting two segments of a mid-ocean ridge. More broadly, a plate boundary along which plates move horizontally past one another without either convergence (coming together) or divergence (moving apart).
Transgression: a landward move of the shore, produced by a sea level rise or sinking of the land. Erosion of the shore does not normally cause significant transgression.
Translocation: movement from one place to another.
Tuff: (L: tophus; Italian: tufo) a volcanic sediment, made of compacted debris from old volcanic ash showers. See tephra.
Tundra: (of Lappish origin) a vast, level, treeless Arctic region  with a marshy surface and underlying permafrost.
Tunnel (Under-runner): a natural sub-surface cavity formed by runoff flowing downslope through sub soil in heavy rain.
U -- top --
Ultisols: (?) soils similar to alfisols, but with weathering more advanced. They include some lateritic (highly leached) soils. See rocktable/soils.
Unconformity: a surface separating two beds of sedimentary rock and representing a gap in time during which sedimentation ceased or erosion removed the rock record.
Underthrusting: a process pushing one rock body underneath another along an inclined fault plane. It is usually accompanied by intense deformation and some metamorphism, and is common at the collision edge of two plates.
V -- top --
Vermiculite: (L: vermiculari= be full of worms; vermis=worm) a hydrous silicate mineral occurring as layered flakes.  It resembles the mineral mica.  Vermiculite consists mainly of the chemical elements aluminium, iron, magnesium, oxygen, and silicon.  It may be brown or yellow. When expanded by heat, vermiculite becomes a lightweight, fireproof substance with good heat insulating properties.  It is used chiefly in building materials for insulation and soundproofing.  It is also used as a soil conditioner and potting material.
Vertisols: (?) soils with upper layers mixed or inverted because they contain expandable clays (that swell when wet and crack when dry). See rocktable/soils.
Volcanic: (L: Volcanus= Vulcan, Roman god of fire) produced by a volcano.
W -- top --
Weathering: breakdown of rock or other geological materials (e.g. alluvium) into soil, by physical disintegration and chemical reaction.
Windblow: erosion of surface soil particles by strong wind blowing across sparsely vegetated or bare ground.
Wollastonite: a calcium silicate CaSiO3.
X -- top --
Xerophytic: (Gk: xeros=dry; phyton=plant) drought resisting plants, able to survive water shortage.
Y -- top --
Zircon: a zirconium silicate ZrSiO4 of brown to grey colour. Some translucent varieties are used as gemstones.
Z -- top --
Zeolite: (Gk: zeo= boil; lithos= stone) is any of a group of crystalline mineral compounds whose framework of atoms forms microscopic tunnels and rooms.  The internal structure of zeolites, consisting of equal-sized channels, makes them useful as filters (molecular sieves) and catalysts. Zeolites, one of the most abundant kinds of minerals, are made of silicon, oxygen, and aluminium and other metals. Used for oil refining, adsorbents, water softening, cosmetic additives.