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Plagioclase
Plagioclase, or plagioclase feldspar, is a group of rock-forming feldspar minerals forming a continuous solid solution between the sodium end-member albite and calcium end-member anorthite.
Planchon-Peteroa
Planchon-Peteroa, a complex of Azufre, Planchon, and Peteroa stratovolcanoes with overlapping calderas on the Chile-Argentina border, 3,977 m, frequently erupting ash; largest historical eruption VEI 4 in 1762; binational monitoring.
Planetary boundary layer
The planetary boundary layer, or atmospheric boundary layer, is the turbulent layer of the atmosphere adjacent to Earth's surface, typically about 1 km deep, where friction affects wind and temperature.
Plankton net
A plankton net is a cone- or cylinder-shaped device of fine mesh towed through water to filter and concentrate plankton, which collect in a bucket at the cod end.
Plate tectonics
Plate tectonics is the scientific theory that Earth's lithosphere is broken into moving plates whose interactions explain most earthquakes, volcanoes, and mountain building; it was widely accepted after 1968.
Playa
A playa is a dry, vegetation-free flat at the lowest part of an undrained desert basin, underlain by clay, silt, or sand, where ephemeral lakes form during wet periods.
Pleistocene
The Pleistocene, often called the Ice Age, is the geological epoch from 2.58 million to 11,700 years ago, spanning Earth's most recent repeated glaciations before the Holocene.
Plinian eruption
A Plinian eruption, also called a Vesuvian eruption, is the most powerful class of explosive volcanic eruption, named for Pliny the Younger's account of Vesuvius in A.D. 79.
Pliocene
The Pliocene Epoch spans 5.333 to 2.58 million years ago, following the Miocene and preceding the Pleistocene, with warm early climates and growing Northern Hemisphere ice sheets.
Plymouth Marine Laboratory
Plymouth Marine Laboratory (PML) is an independent marine research charity in Plymouth, England, formed in 1988 by NERC, known for ocean acidification research and long-term ocean monitoring since 1903.
Poco Mandasawu
Poco Mandasawu (Gunung Poco Mandasawu, Poco Likang) is a lava dome of the Ranakah volcanic complex in south-central Flores, Indonesia, near Ruteng; elevations 2,109-2,370 m are published, and the 1987 Anak Ranakah dome eruption ended 400 dormant years.
Point bar
A point bar is a sediment deposit built on the inside of a river bend where slower water drops its load, a defining feature of meandering rivers.
Polar amplification
Polar amplification is the phenomenon in which the polar regions warm faster than the global average; Arctic amplification has warmed nearly four times the global rate.
Polar cell
The polar cell is the smallest and weakest of the three atmospheric circulation cells in each hemisphere, where air rises near 60–70° latitude and sinks over the pole.
Polar climate
A polar climate, Köppen group E, is a climate where no month's mean exceeds 10 °C, roughly the limit of tree growth, subdivided into tundra and ice-cap climates.
Polar front
The polar front is the semi-permanent boundary between cold polar air and warmer low-latitude air in each hemisphere's midlatitudes, along which most extratropical cyclones form.
Polar low
A polar low is a small but intense maritime cyclone that forms over high-latitude oceans in winter, producing gale-force winds, heavy snowfall, high waves, and icing.
Polar night
Polar night is the winter period north of the Arctic Circle and south of the Antarctic Circle when the Sun does not rise for more than 24 hours.
Polar night jet
The polar night jet is a strong westerly wind current in the stratosphere, encircling the winter polar vortex in each hemisphere and acting as a barrier that isolates cold polar air.
Polar stratospheric cloud
The polar stratospheric cloud, also called a nacreous or mother-of-pearl cloud, forms in the winter stratosphere at 15 to 30 km and drives Antarctic ozone depletion.
Polar vortex
The polar vortex, also called a polar cyclone, is a band of westerly winds encircling each pole in the stratosphere, forming each winter and breaking down in spring.
Polar WRF
Polar WRF (PWRF) is a polar-optimized version of the Weather Research and Forecasting model, developed at Ohio State University in 2008 for Arctic and Antarctic simulations.
Polarite
Polarite is a rare palladium bismuthide mineral with the formula Pd(Bi,Pb), first described in 1969 from copper-nickel sulfide ores at the Talnakh deposit, Norilsk, Russia.
Polarization analysis (seismology)
Polarization analysis in seismology characterizes the direction and shape of ground particle motion recorded by three-component seismic stations, supporting event detection, direction finding, and filtering.
Poleta Formation
The Poleta Formation is an Early Cambrian sedimentary unit of limestone and siltstone exposed in the White and Inyo Mountains of California and western Nevada, named by C. A. Nelson in 1962.
Polish Hydrobiological Society
The Polish Hydrobiological Society (Polskie Towarzystwo Hydrobiologiczne, PTH) is a Polish scientific association founded in 1959 that supports research in hydrobiology, the study of aquatic organisms.
Pollutant
A pollutant is any substance introduced into the environment that may harm human health or ecosystems, typically from human activities; some, like ground-level ozone, form in the air.
Pollution
Pollution is the introduction of contaminants, whether substances or energy, into the environment at rates that harm health, living systems, or air, water, and soil quality.
Polynya (полынья)
A polynya (полынья), from Russian, is an opening of persistent or recurring open water within sea ice; coastal polynyas produce about 10% of Antarctic sea ice.
Pore-scale imaging
Pore-scale imaging is the microscopy and tomography techniques that resolve individual pores in rocks, chiefly X-ray CT, so pore geometry can be tied to fluid flow and transport.