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Poroelastic model
A poroelastic model is a continuum-mechanics description coupling fluid flow in a deformable porous solid to elastic stress and strain, based on Biot's 1941 consolidation theory.
Pororoca
Pororoca: the tidal bore of the Amazon River, waves up to 4 m traveling 800 km upstream during spring tides, February-March; famous for river surfing, the 37-minute record ride, and preventing an Amazon delta.
Porous media model
A porous media model is a continuum approach representing fluid flow and solute transport through soils and rocks using averaged parameters like porosity and permeability.
Porphyritic texture
Porphyritic texture is an igneous rock texture in which large crystals, called phenocrysts, sit in a distinctly finer-grained groundmass, classically formed by two stages of cooling.
Porphyry (geology)
Porphyry is an igneous rock containing large crystals, called phenocrysts, set in a distinctly finer-grained groundmass; the name also denotes the purple imperial stone of Roman Egypt.
Porphyry copper deposit
A porphyry copper deposit is a large, low-grade copper ore body formed by hydrothermal fluids above shallow intrusions, supplying about 60 percent of world copper.
Portland stone
Portland stone, formally the Portland Stone Formation, is a Jurassic limestone from the Isle of Portland, Dorset, quarried since Roman times for buildings like St Paul's Cathedral.
Portlandite
Portlandite is an IMA-approved calcium hydroxide mineral, Ca(OH)₂, first described naturally at Scawt Hill, Northern Ireland, in 1933; it makes up 15 to 25% of hydrated Portland cement paste.
Posidonia Shale
Posidonia Shale (Posidonienschiefer): early Toarcian (~183 Ma) black bituminous shale of NW Europe, major petroleum source rock and famous Holzmaden fossil Lagerstätte of the Toarcian anoxic event.
Post-glacial rebound
Post-glacial rebound, also called glacial isostatic adjustment (GIA), is the slow rise of land depressed by ice sheets, continuing thousands of years after the ice melts.
Post-perovskite
Post-perovskite is a high-pressure form of magnesium silicate, formed when bridgmanite transforms near Earth's core–mantle boundary; discovered in 2004, it explains the D″ seismic discontinuity.
Potential evapotranspiration
Potential evapotranspiration (PET) is the maximum quantity of water a well-watered vegetation cover can lose as vapor in a given climate, combining soil evaporation and plant transpiration.
Potential temperature
Potential temperature (symbol θ) is the temperature a dry air parcel would have if brought adiabatically, without heat exchange, to a standard pressure, typically 1000 hPa.
Potential vorticity
Potential vorticity (PV) is a quantity in atmospheric and oceanic fluid dynamics combining a parcel's absolute vorticity with its stratification; conserved in adiabatic, frictionless flow, it underlies the dynamic tropopause.
Potentiometric surface
A potentiometric surface is an imaginary surface representing the static head of groundwater in wells tapping an aquifer; in unconfined aquifers, it is the water table itself.
Powder River Basin
The Powder River Basin is a structural basin in northeastern Wyoming and southeastern Montana, holding the largest low-sulfur subbituminous coal resources in the United States.
Power dissipation index
The power dissipation index (PDI) is a measure of tropical cyclone destructive potential, summing maximum sustained wind speed cubed, introduced by MIT's Kerry Emanuel in 2005.
Pre-salt layer
The pre-salt layer is a sequence of Aptian-age rock salt off Brazil and West Africa, beneath which lie oil reservoirs supplying most of Brazil's oil.
Pre-stack depth migration
Pre-stack depth migration, or PSDM, is a seismic imaging technique that migrates unstacked traces into a depth image using a velocity-depth model, correctly positioning reflectors under salt and complex structure.
Precambrian
The Precambrian is the supereon of geologic time from Earth's formation about 4.6 billion years ago to the start of the Cambrian, 538.8 million years ago.
Precipitable water
Precipitable water (PW, also precipitable water vapor, PWV) is the total water vapor in a vertical atmospheric column, expressed as the depth of liquid water if fully condensed.
Precipitation
Precipitation, also called atmospheric precipitation, is water in liquid or solid form, such as rain, snow, sleet, or hail, that falls from clouds and reaches the ground, driving the water cycle.
Precipitation types
Precipitation types are the distinct forms falling water takes, such as rain, snow, sleet, freezing rain, graupel, and hail, determined by the atmosphere's vertical temperature profile.
Precise point positioning
Precise point positioning (PPP) is a GNSS technique that estimates centimeter-level positions at a single receiver using precise satellite orbit and clock corrections, without nearby reference stations.
Preferential flow
Preferential flow is the movement of water and solutes through a small fraction of the pore network, such as roots, burrows, and cracks, bypassing most of the soil matrix.
Pressure ridge (ice)
A pressure ridge is a wall of broken sea ice pushed up and down when ice floes compress, with a sail above water and a much larger keel below.
Pressure solution
Pressure solution is a geologic deformation process in which mineral grains dissolve where they touch under high stress, then reprecipitate on low-stress grain faces, reducing porosity.
Prevailing winds
A prevailing wind is the direction from which wind blows most often at a place over a period, produced by global circulation, the Coriolis effect, and local factors like sea breezes.
Priabonian
The Priabonian is the last and youngest stage of the Eocene Epoch, from about 37.71 to 33.9 million years ago, named for the Italian village of Priabona.
Primary migration
Primary migration, also called hydrocarbon expulsion, is the movement of petroleum out of its low-permeability source rock into a reservoir, the first step of the petroleum system.