physical characteristics of a rock unit visible at outcrop, in hand or core samples or with low magnification microscopy, such as colour, texture, grain size, or composition.Loess - fine, silty, pale yellow or buff in color, windblown (eolian) type of unconsolidated deposit.Lowland - broad expanse of land with a general low level.M[edit]Ma - 1,000,000 yearsMafic - a silicate mineral or rock that is rich in magnesium and iron. A mnemonic term for the ferromagnesian and other non-felsic minerals actually present in an igneous rock rich in dark (ferromagnesian) minerals (>60% by volume). Basic [alkali gabbro (alkali basalt), syeno-gabbro (trachybasalt), gabbro (basalt and dolerite)]Magma - molten rock that sometimes forms beneath the surface of the earth (or any other terrestrial planet) that often collects in a magma chamber.Magnetite - An oxide of iron which crystallises in the cubic system It is attracted by a magnet but does not attract iron itself.Malmesbury group - 830 to 980 Ma basal group of the Western Cape comprising at least eight formations including Tygerberg, Piketberg, Porterville, Berg river, Klipplaat, Moorreesburg, Franschhoek and Bridgetown formations.Mantle - highly viscous layer directly under the crust, and above the outer core.Marble - Fine to coarse-grained granoblastic calcium carbonate that effervesces in dilute hydrochloric acid. Often banded with various colours and sometimes veined.Marine terrace - narrow flat area often seen at the base of a sea cliff caused by the action of the waves.Marl - calcium carbonate or lime-rich mud or mudstone which contains variable amounts of clays and aragonite.Massive - a description applied to a homogeneous rock, lacking internal structure or layers.Melange - large scale breccia formed in the accretionary wedge above a subduction zone.Melanocratic - A term applied to rocks which are abnormally rich in dark and heavy ferro-magnesium mineralsMesocratic - A term applied to igneous rocks which in respect of their content of dark silicates are intermediate between those of leucocratic and melanocratic type, and contain 30 to 60% of dark heavy minerals.Mesozoic - The era of geological time including Triassic, Jurassic and Cretaceous agesMetamorphism - the solid state recrystallisation of pre-existing rocks due to changes in heat and/or pressure and/or introduction of fluids i.e. without melting.Metapelite - A metamorphosed pelite rockMetasilicate - A salt of metasilicic acid H2SiO3.Metatexis - Low grade anatexis: partial or differential melting of rock components with low melting point.Mica - A group of minerals which crystallise in the monoclinic system: They have similar chemical compositions and highly perfect basal cleavage.Micropaleontology - branch of paleontology which studies microfossils.Mid-oceanic ridges - underwater mountain range, typically having a valley known as a rift running along its axis, formed by plate tectonics.Migmatite - A composite rock composed of igneous or igneous looking and/or metamorphic materials which are generally distinguishable megascopically.Mineralization - hydrothermal deposition of economically important metals in the formation of ore bodies or "lodes".Miogeosyncline - A geosyncline in which volcanism is not associated with sedimentation. The non-volcanic part of the orthogeosyncline located near the craton.Molasse - A partly marine, partly continental or deltaic sedimentary facies consisting of a very thick sequence of soft ungraded cross-bedded fossiliferous conglomerates,