fine-grained sediment as it dries.mudflowbahnotokA flowing mixture of debris and water, usually moving down a channel.mudpotbahenni sopkaSpecific type of hot spring that contains thick, boiling mud.mudstoneslinovecA fine-grained sedimentary rock that lacks shale's laminations and fissility.muscovitemuskovitTransparent or white mica that lacks iron and magnesium. Properties see micas.nacreous lusterperle?ovy leskSee pearly luster.natural glassvulkanicke skloAmorphous form of silica formed by very fast cooling of lava.nematoblastic texturenematoblasticka strukturaMetamorphic texture formed mostly of columnar or spicular minerals.NeogeneneogenniYounger epoch of Tertiary period (from 1.8 to 25 mil. of years ago).oblique-slip faultA fault with both strike-slip and dip-slip components.obsidianobsidianVolcanic glass black in colour with typical conchoidal fracture.oceanic crustoceanska kuraThe thin, basaltic crust under oceans.oceanic trenchhlubokomoosky poikopA narrow, deep through parallel to the edge of a continent or an island arc.olivineolivinA ferromagnesian mineral with the formula (Fe, Mg)2SiO4. Yellowish green to green in colour, conchoidal fracture but not obvious cleavage, with vitreous luster. Hardness is 6.5 to 7. Most olivine occurs in a form of accumulations of small crystals in dark-coloured igneous rocks (e.g. basalt).oolitic limestoneooliticky vapenecA limestone formed from a small spheres of calcite precipitated from seawater.open foldotevoena vrasaA fold with gently dipping limbs (angle between limbs 70-120).orbicular structurekulovita texturaSpecial type of structure of plutonic rocks where feldspars are in concentric arrangement.OrdovicianordovickyPeriod in lower Paleozoic (from 435 to 500 mil. of years ago).orerudaNaturally occuring material that can be profitably mined.organic sedimentary rocksorganogenni sedimentarni horninyRocks composed mostly of the remains of plants and animals.organic sedimentsorganogenni sedimentSediments composed mostly of the remains of plants and animals.orogenyorogenAn episode of intense deformation of the rocks in a region, generally accompanied by metamorphism and plutonic activity.orthoclaseortoklasA potassium feldspar with the formula KAlSi3O8. Properties see feldspars.orthogneissortorulaType of gneiss formed from igneous rocks.outcropvychozA surface exposure of bare rock, not covered by soil or vegetation.outer corevnijsi jadroA thick shell of rock between inner core and lower mantle.overturned foldpoekocena vrasaA fold in which both limbs dip approximatelly in the same direction.oxbow lakeslepe ramenoA crescent-shaped lake occupying the abandoned channel of a stream meander that is isolated from the present channel by a meander cutoff and sedimentation.P-wavesp-vlnyCompressional waves (seismic waves) in which rock vibrates parallel to the direction of wave propagation.PaleogenepaleogenOlder epoch of Tertiary period (from 23.7 to 66.4 mil. of years ago).PaleozoicpaleozoikumGeological era that followed the Precambrian and during which began with the appearance of complex life, as indicated by fossils (from 245 to 570 mil. of years ago).paragneisspararulaType of gneiss formed from sedimentary rocks.parent rockmateena horninaOriginal rock before being metamorphosed.pearly lusterperle?ovy leskA luster that gives a substance pearly appearance.pebbleoblazekA sediment particle with a diameter of 2 to 64 mm.pegmatitepegmatitExtremely coarse-grained igneous rock formed mainly of feldspars and quartz together with micas and other minerals. It has zonal structure. In czech classification it belongs to dike rocks, in english classification to plutonic rocks.pelagic sedimentpelagicke sedimentSediment made up of fine-grained clay and skeletons of microscopic organisms that settle slowly down through the ocean water to the sea bottom.pelitespelityWithin the clastic subgroup of sediments and sedimentary rocks the most fine-grained category (<0.002 mm).pencil structurestebelnata texturaRare type of structure of metamorphic rocks characterized by mineral grains which are extremly elongated along