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Pacific–North American pattern
The Pacific–North American pattern (PNA) is a prominent teleconnection pattern of atmospheric circulation variability over the North Pacific and North America, tracked by a NOAA index since 1950.
Packstone
Packstone is a limestone in the Dunham classification of carbonate rocks, defined in 1962 as grain supported but containing carbonate mud between the sand-sized grains.
PAGASA
PAGASA, the Philippine Atmospheric, Geophysical and Astronomical Services Administration, is the national weather service of the Philippines under the Department of Science and Technology, issuing forecasts, typhoon warnings, and flood bulletins.
PAGASA name lists for tropical cyclones
PAGASA name lists are four rotating sets of 25 Filipino names, each with a 10-name auxiliary list, that PAGASA assigns to tropical cyclones entering the Philippine Area of Responsibility.
Palaeoclimate Modelling Intercomparison Project
The Palaeoclimate Modelling Intercomparison Project (PMIP) coordinates standardized simulations of past climates in many climate models, testing them against palaeoclimate reconstructions since the early 1990s.
Paleoarchean
The Paleoarchean is the second era of the Archean Eon, spanning 3,600 to 3,200 million years ago, defined by fixed ages and hosting many of the oldest claimed records of life.
Paleocene
The Paleocene is the first epoch of the Paleogene Period, lasting from 66 to 56 million years ago, when mammals diversified after the extinction that ended the dinosaurs.
Paleocene–Eocene Thermal Maximum
The Paleocene–Eocene Thermal Maximum, or PETM, was a geologically rapid global warming and carbon release event about 56 million years ago, at the Paleocene–Eocene boundary.
Paleoclimate proxy
A paleoclimate proxy is a measurable property of a natural archive, such as ice cores, tree rings, or corals, that stands in for climate measurements made before instruments existed.
Paleoclimatology
Paleoclimatology, the study of Earth's ancient climate history, reconstructs conditions before instrumental records by reading natural archives such as tree rings, corals, ice cores, and sediments.
Paleogene
The Paleogene Period is the first period of the Cenozoic Era, spanning 66 to 23 million years ago and divided into the Paleocene, Eocene, and Oligocene epochs.
Paleogeography of the India–Asia collision system
The paleogeography of the India–Asia collision system reconstructs the continents and oceans that preceded India's collision with Asia, which closed the Neo-Tethys Ocean and built the Himalayas.
Paleointensity
Paleointensity is the study of Earth's ancient magnetic field strength, recovered from rocks and fired clays by comparing their natural magnetization with one induced in a known laboratory field.
Paleolimnology
Paleolimnology is the study of lake and wetland sediments, using physical, chemical, and biological proxies in dated sediment cores to reconstruct past lake, catchment, and climate conditions over decades to millennia.
Paleomagnetism
Paleomagnetism is the study of the Earth's past magnetic field, recorded in rocks, sediments, and fired materials; it underpins the geomagnetic polarity timescale and continental reconstructions.
Paleosol
A paleosol is a fossil soil that formed on a landscape of the past and is preserved in the geological record; its study is called paleopedology, and buried soils define geosols in stratigraphy.
Paleostress analysis
Paleostress analysis is a branch of structural geology that reconstructs past stress fields from deformation structures, most commonly fault-slip data and calcite twins, using inversion methods developed since the 1970s.
Paleozoic
The Paleozoic Era, spanning 541 to 251.9 million years ago, saw fish diversify and life colonize land, ending with the greatest mass extinction in Earth's history.
Palisades Fire
The Palisades Fire, a wind-driven wildfire, ignited on January 7, 2025 in Pacific Palisades, Los Angeles, burning 23,448 acres, destroying 6,845 structures, and killing 12 civilians.
Palmer Drought Severity Index
The Palmer Drought Severity Index (PDSI) is a standardized drought index developed by Wayne Palmer in 1965 that uses temperature and precipitation data to estimate relative dryness.
Palmer Station
Palmer Station is a U.S. year-round Antarctic research station on Anvers Island, off the Antarctic Peninsula, operated by the National Science Foundation and commissioned in 1968.
Palsa
A palsa, from the Lappish and Finnish word for a bog hummock, is a peat-covered permafrost mound with an ice core, rising above mires in subarctic regions of the Northern Hemisphere.
Palygorskite
Palygorskite, also known as attapulgite, is a fibrous magnesium aluminum phyllosilicate clay mineral valued as a salt-tolerant thickener, absorbent, and suspending agent in drilling fluids and cat litter.
Palynostratigraphy
Palynostratigraphy is the branch of biostratigraphy that dates and correlates sedimentary rocks using fossil pollen, spores, and other organic-walled microfossils, especially where marine index fossils are absent.
Pan American Silver
Pan American Silver is a Canadian precious metals mining company headquartered in Vancouver, founded by Ross Beaty in 1994, producing silver and gold from mines across the Americas.
Pan-African orogeny
The Pan-African orogeny was a protracted series of tectonic, metamorphic, and magmatic events between about 725 and 500 million years ago, forming mobile belts during the assembly of Gondwana.
Pangaea
Pangaea, also spelled Pangea, was the supercontinent that assembled most of Earth's land about 300 million years ago and broke apart beginning about 201 million years ago.
Pangaea Proxima
Pangaea Proxima, originally named Pangea Ultima, is a hypothesized future supercontinent in which the Atlantic closes and the continents reassemble, projected to form 200 to 250 million years from now.
Pannonian Basin
The Pannonian Basin, also called the Carpathian Basin or Kárpát-medence, is a large sedimentary basin centered on Hungary, formed as a back-arc basin during the Miocene.
Pannotia
Pannotia, also known as the Vendian supercontinent, is a hypothetical supercontinent that may have formed around 600 million years ago, with Gondwana at its core and Laurentia, Baltica, and Siberia attached.