structure).exfoliationexfoliaceThe stripping of concentric rock scales to slabs from the outer surface of a rock mass.extrusive rocksvylevne vyvrele horninyAny igneous rocks that form at the earth s surface, whether it soldifies directly from a lava flow or is pyroclastic.fallskalni riceniThe situation in mass wasting that occurs when material free-falls or bounces down a cliff. See rockfall.faultzlomA fracture in bedrock along which movement has taken place.feldsparszivceGroup of most common minerals of the earth s crust. All feldspars contain silicon, aluminium, and oxygen and may contain potassium, calcium, and sodium. Pink, white to dark grey, rarely green in colour. Hardness is around 6. Perfect cleavage, vitreous luster when fresh, dull when weathered. Attention: According to luster on cleavage planes are feldspars very often confused with muscovite.felsic rockssvetle vyvrele horninySilica rich igneous rocks with silica content more then 65%.fine-grained rocksjemnozrnne horninyA rocks (except clastic sediments) in which most of the mineral grains are between 0,33-0,01 mm in size.fiordfjordA coastal inlet that is a glacially carved valley, the base of which is submerged.firnfirnA compacted mass of granular snow, transitional between snow and glacial ice.fissured clayspotrhane jilyClays with a lot of small, irregular fissures.flexureohybBending of beds (without rupture) as a result of long lasting and slow tectonic pressure.flintpazourekA dense, fine-grained form of silica which is very tough and breaks with a conchoidal fracture and cutting edges. It occurs in cretaceous cliffs.flood erosionErosion caused by the high velocity and large volume of water in a flood.flood plaininundacni uzemiA broad strip of land built up by sedimentation on either side of a stream channel.flowteceniA type of movement that implies that a descending mass is moving downslope as a viscous fluid.fluidal structureproudovita texturaStructure of igneous rocks, where rock particles have preferred direction in orientation.fluoritefluoritMineral with formula CaF2. It is a basic raw material for fluor and fourth member of Moh s scale. Purple, green, yellow in colour. Perfect cleavage, vitreous luster.focusohnisko zemetreseni (hypocentrum)The point within the earth from which seismic waves originate in an earthquake.foidszastupci zivcuGroup of minerals formed instead of feldspars within the process of magma crystallization, when amount of SiO2 in magma is reduced. Main members of this group are: leucite, nepheline, analcime, sodalite, nosean, hauyne.foldvrasaBend in layered bedrock of sinusoidal shape.foliationfoliaceParallel alignment of structural features of a rock.foliation planefoliacni plochaPlane with parallel alignment to structural features of a rock.fossiliferous limestoneorganogenni vapenecLimestone composed of fossil shells or skeletons.fossilsfosilieTraces or fragments of skeletons of plants or animals preserved in rock.fracturezlomThe way a substance breaks where not controlled by cleavage.fracture planelomna plochaCurved plane formed by fracture, often conchoidal.fragments of rocksulomky horninPieces of rock decoposed by mechanical or chemical weathering.fresh rocknezvetrala horninaRock not affected by weathering.frost actionucinek mrazuMechanical weathering of rock by expanzion of freezing water.frost heavingThe lifting of rock or soil by the expansion of freezing water.frost wedgingA type of frost action in which the expansion of freezing water pries a rock apart.gabbrogabroA mafic, coarse-grained igneous rock composed predominantly of ferromagnesian minerals and with lesser amounts of calcium-rich plagioclase feldspar.gaining streamA stream that receives water from the zone of saturation.garnetgranatReddish brown, yellowish tan in clolour, vitreous to pitch luster. Hardness