the Phanerozoic eras, and is subdivided into six geologic periods (from oldest to least old): the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian. The Paleozoic comes after the Neoproterozoic Era of the Proterozoic Eon, and is followed by the Mesozoic Era.Palagonite - an alteration product from the interaction of water with volcanic glass of chemical composition similar to basalt or from the interaction between water and basalt melt.Paralithic - a weathered layer of bedrock.Pegmatite - Exceptionally coarse grained igneous rock.Pelite - (Greek Pelos, Clay) - a descriptive name for a clastic rock with a grain size of less than 1/16 mm (originally sand or silt).Peridotite - Olive green when fresh, medium brown when weathered, saccharoidal intrusive igneous rock of mainly olivine, sometimes with pyroxene.Petrology - the branch of geology that studies the origin, composition, distribution and structure of rocks.Phenoclast - large conspicuous fragment in sediment or sedimentary rock composed of various sizes of material.Phenocryst - a relatively large crystal in an igneous rock.Phyllite - Argillaceous rocks in a condition of metamorphism between slate and mica-schistPiercing point - a feature that is cut by a fault and moved, and reconstruction of that object can show how much a fault has moved.Pitchstone - Black, opaque volcanic glass that may contain irregular, whitish clusters of minerals. Resembles pitch in appearance.Plate tectonics (from the Greek ; tekton, meaning "builder" or "mason") describes the large scale motions of Earth's lithosphere.Pleistocene - the geological epoch which lasted from about 2,588,000 to 11,700 years ago, spanning the world's recent period of repeated glaciations. The Pleistocene is the first epoch of the Quaternary Period or sixth epoch of the Cenozoic EraPliocene - the period in the geologic timescale that extends from 5.332 million to 2.588[2] million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch.Plutonic - Rocks that crystallised at depth within the crust. Slow cooling, coarse grain size and relatively low temperature of final consolidation.Plumose structure - ladder or grid patterns that occur during jointing that resemble plumes, oriented perpendicular to the stress, hence which usually form parallel to the upper and lower surfaces of the constituent rock unit.Pneumatolysis - The destructive after action of the concentrated volatile constituents of a magma, effected after the consolidation of the main body of the magma.Polymictic -Polysynthetic twinning -Porphyroblast - a large mineral crystal in a metamorphic rock which has grown within the finer grained groundmass.Porphyry - Rock that is porphyritic, containing large and small crystals, or, in mining, a specific deposit containing widely disseminated metals, typically copper.Precambrian - Earth's history before the Phanerozoic Eon, divided into several eons of the geologic time scale. It spans from the formation of Earth about 4540 Ma (million years ago) to the beginning of the Cambrian Period, about 541.0 1.0 Ma, when macroscopic hard-shelled animals first appeared in abundance.Precipitate - (In geology): A rock or mineral precipitated into solid form from an aqueous solution.Prograde metamorphism - mineral changes in rocks under increasing pressure