Natural England - Geology glossary (P to R)
Geology glossary (P to R)
This page of the glossary covers P to R. You can navigate to the next section from the links at the bottom of this page.
Palaeogene The name given to the period of geological time dating from about 65 to 25 million years ago.
Palaeozoic An era of geological time, dating from about 545 to 248 million years ago (comprising the Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian periods).
Palaeontology The study of fossils.
Periglacial Cold climates often bordering and associated with glaciers (with average annual temperatures of -15 to -1°C and seasonally snow-free ground). May also relate to the surface features created under those climates.
Permian A period of geological time dating from about 290 to 248 million years ago.
Peat Compressed, partially decomposed vegetation formed in a waterlogged environment. Dried peat can be burned as fuel.
Period The most commonly used unit of geologic time, representing one subdivision of an era.
Pillow Lava When basalts erupt underwater, they commonly form pillow lavas. These elongate mounds or "pillows" are formed by the repeated squeezing out (extrusion) and quenching of hot basalt masses.
Plate The Earth’s crust and part of the underlying mantle are divided into several rigid plates which glide over the underlying, viscous mantle. The movement of the plates (plate tectonics) is due to convection currents in the mantle.
Plate tectonics The theory that the Earth's crust consists of large, rigid plates that move horizontally in response to the flow of the asthenosphere beneath them. Interactions among the plates at their borders cause most major geologic activity, including the creation of oceans, continents, mountains, volcanoes, and earthquakes.
Plateau An elevated flat area.
Plesiosaur A marine reptile with a long neck and four flippers that lived in the Jurassic and Cretaceous seas.
Pliosaur A large marine reptile with a short neck and four flippers that lived in the Jurassic and Cretaceous seas.
Pluton An extremely large body of intrusive igneous rock (e.g. the Dartmoor Granite).
Precambrian The interval of geological time, dating from the consolidation of the Earth's crust around 4600 million years ago to about 545 million years ago.
Pterosaur A flying reptile of the Mesozoic related to the dinosaurs.
Quartzite An extremely durable, metamorphic rock derived from pure sandstone and consisting primarily of quartz.
Quaternary The period corresponding to the last 1.8 million years of the earth’s history, corresponding approximately to the time of the most recent and extensive glaciation. Also referred to as the Pleistocene.
Ripple marks A pattern of ripples formed along the top of a bed by wind, water currents, or waves.
River Terrace A flat, step-like surface standing above the floodplain of a stream and representing an erosional remnant of an older floodplain.
