paha
(colloquial: midwestern USA) commonly an erosional remnant modified by depositional processes consisting of a low, elongated, rounded ridge or hill consisting mainly of drift, rock, or windblown sand, silt, or clay capped with a thick cover of loess; found especially in northeast Iowa. height varies between 10 and 30 m. GG

pahoehoe lava
a type of basaltic lava (material) with a characteristically smooth, billowy or rope-like surface and vesicular interior. compare - a'a lava, block lava, pillow lava. GG & MA

pahoehoe lava flow
a type of basaltic lava flow with a characteristically smooth, billowy or rope-like surface. compare - a'a lava flow, block lava flow, pillow lava flow. GG & MA

Paleocene
the earliest epoch of the Tertiary Period of geologic time (from 56.5 to 65.0 million years ago), immediately following the Cretaceous Period and preceding the Eocene Epoch; also corresponding (time-stratigraphic) "series" of earthy materials. SW

paleosol
a soil that formed on a landscape in the past with distinctive morphological features resulting from a soil-forming environment that no longer exists at the site. the former pedogenic process was either altered because of external environmental change or interrupted by burial. a paleosol (or component horizon) may be classed as relict if it has persisted in a land-surface position without major alteration of morphology by processes of the prevailing pedogenic environment. an exhumed paleosol is one that formerly was buried and has been re-exposed by erosion of the covering mantle. most paleosols have been affected by some subsequent modification of diagnostic horizon morphologies and profile truncation. HP

paleoterrace
an erosional remnant of a terrace which retains the surface form and alluvial deposits of its origin but was not emplaced by, and commonly does not grade to a present-day stream or drainage network. compare - alluvial plain remnant. SW

palsa
an elliptical dome-like permafrost mound containing alternating layers of ice lenses and peat or mineral soil, commonly 3-10 m high and 2-25 m long, occurring in subarctic bogs of the tundra and often surrounded by water; pl. palsen. NRC

parabolic dune
a sand dune with a long, scoop-shaped form, convex in the downwind direction so that its horns point upwind, whose ground plan, when perfectly developed, approximates the form of a parabola. GG

parallel drainage pattern
a drainage pattern in which the streams and their tributaries are regularly spaced and flow parallel or subparallel to one another over a considerable area. GG

parent material
the unconsolidated and more or less chemically weathered mineral or organic matter from which a soil's solum is developed by pedogenic processes. GSST

park
(colloquial - Rocky Mountains, USA; not preferred - refer to valley)
a) an ecological term for a grassy or shrubby, wide, open valley lying at high elevation and confined between forested mountain slopes, as in a high meadow; sometimes marshy. compare - glade.
b) (refer to intermontane basin) A level valley between mountain ranges. GG & SW

parna
a term used, especially in southeast Australia and southwestern USA, for silt and sand-sized aggregates of eolian clay occurring as sheets. compare - parna dune. SW & GG

parna dune
a dune largely composed of silt and sand-sized aggregates of clay; sometimes called a clay dune or lunette. compare - parna. HP

partial ballena
(not preferred) refer to ballena.

patina
a general term for a colored film or thin outer layer produced on the surface of a rock or other material by weathering after long exposure. compare - rock varnish. GG

patterned ground
a general term for any ground surface exhibiting a discernibly ordered, more-or-less symmetrical, morphological pattern of ground and, where present, vegetation. Patterned ground is characteristic of, but not confined to, permafrost regions or areas subjected to intense frost action; it also occurs in tropical, subtropical, and temperate areas. patterned ground is classified by type of pattern and presence or absence of sorting and includes nonsorted and sorted circles, net, polygons, steps and stripes, garlands, and solifluction features. in permafrost regions, the most common macroform is the ice-wedge polygon and a common microform is the nonsorted circle. stone polygons generally form on slopes of less than 8 percent, while garlands and stripes occur on slopes of 8 to 15 percent and more than 15 percent, respectively. NRC and HP

pavement karst
areas of bare limestone, usually sculpted by solution erosion into karren of various types and where soils have been stripped off, commonly by glaciation in alpine areas (e.g. Rocky Mountains - USA) and high latitudes, and by water erosion in arid karst areas. compare - fluviokarst, sinkhole karst, karst. SW & WW

peak
sharp or rugged upward extension of a ridge chain, usually at the junction of two or more ridges; the prominent highest point of a summit area. HP

peat
unconsolidated soil material consisting largely of undecomposed, or slightly decomposed, organic matter (i.e. "fibric" in Soil Taxonomy) accumulated under conditions of excessive moisture. compare - muck, mucky peat, herbaceous peat. GSST

peat plateau
a generally flat-topped expanse of peat, elevated above the general surface of a peatland, and containing segregated ice that may or may not extend downward into the underlying mineral soil. controversy exists as to whether peat plateaus and palsen are morphological variations of the same feature. NRC

pediment
a gently sloping erosional surface developed at the foot of a receding hill or mountain slope. the surface may be essentially bare, exposing earth material that extends beneath adjacent uplands; or it may be thinly mantled with alluvium and colluvium, ultimately in transit from upland front to basin or valley lowland. in hill-foot slope terrain the mantle is designated "pedisediment." the term has been used in several geomorphic contexts: Pediments may be classed with respect to
a) landscape positions, for example, intermontane-basin piedmont or valley-border footslope surfaces (respectively, apron and terrace pediments (Cooke and Warren, 1973));
b) type of material eroded, bedrock or regolith; or
c) combinations of the above. compare - Piedmont slope. HP

pedisediment
a layer of sediment, eroded from the shoulder and back slope of an erosional slope, that lies on and is, or was, being transported across a pediment. FFP

pedoturbation
the mixing of soil materials by natural processes. compare - cryoturbation. BHM

peneplain
(not recommended; obsolete) a low nearly featureless, gently undulating land surface of considerable area, which presumably has been produced by the processes of long-continued subaerial erosion. GG

peninsula
a) an elongated body or stretch of land nearly surrounded by water (e.g., on three sides) and connected with a larger tract of land area, usually by a neck or an isthmus.
b) a relatively large tract of land jutting out into the water, with or without a well-defined isthmus; e.g., the Italian peninsula. GG

perennial stream
a stream or reach of a stream that flows continuously throughout the year and whose surface is generally lower than the water table adjacent to the region adjoining the stream. compare - Ephemeral stream, Intermittent stream. GG

periglacial
(adjective) pertaining to processes, conditions, areas, climates, and topographic features occurring at the immediate margins of glaciers and ice sheets, and influenced by cold temperature of the ice. the term was originally introduced to designate the climate and related geologic features peripheral to ice sheets of the Pleistocene. HP

permafrost
ground, soil, or rock that remains at or below 0o C for at least two years. It is defined on the basis of temperature and is not necessarily frozen. compare - continuous permafrost, discontinuous permafrost, sporadic permafrost, thaw-stable permafrost, thaw sensitive permafrost. NRC

physiographic province
a region of which all parts are similar in geologic structure and climate and which has consequently had a unified geomorphic history; a region whose pattern of relief features or landforms differ significantly from that of adjacent regions. examples: the Valley and Ridge, Blue Ridge, and Piedmont provinces in the eastern U.S.A., and the Basin and Range, Rocky Mountains, and Great Plains provinces in the western U.S.A. GG

piedmont
(adjective) Lying or formed at the base of a mountain or mountain range; e.g., a piedmont terrace or a piedmont pediment. (noun) an area, plain, slope, glacier, or other feature at the base of a mountain; e.g., a foothill or a bajada. in the United States, the Piedmont (noun) is a low plateau extending from New Jersey to Alabama and lying east of the Appalachian Mountains. GG

piedmont slope
(colloquial - western USA) the dominant gentle slope at the foot of a mountain; generally used in terms of intermontane-basin terrain in arid to subhumid regions. main components include:
a) an erosional surface on bedrock adjacent to the receding mountain front (pediment, rock pediment);
b) a constructional surface comprising individual alluvial fans and interfan valleys, also near the mountain front; and
c) a distal complex of coalescent fans (bajada), and alluvial slopes without fan form. piedmont slopes grade to basin-floor depressions with alluvial and temporary lake plains or to surfaces associated with through drainage(e.g., axial streams). compare - bolson, fan piedmont. HP

pillow lava
a general term for lava displaying pillow structure (discontinuous, close-fitting, bun-shaped or ellipsoidal masses, generally < 1 m in diameter); considered to have formed in a subaqueous environment; such lava is usually basaltic or andesitic. compare - a'a lava, block lava, pahoehoe lava. SW, GG, & GS

pillow lava flow
a lava flow or body displaying pillow structure and considered to have formed in a subaqueous environment (underwater); usually basaltic or andesitic in composition. compare - a'a lava flow, block lava flow, pahoehoe lava flow. SW & GS

pimple mound
(colloquial: Gulf Coast U.S.A.) low, flattened, approximately circular or elliptical features composed of sandy loam that is coarser than, and distinct from, the surrounding soil; the basal diameter ranges from 3 m to more than 30 m, and the height from 30 cm to more than 2 m. compare - mima mound, patterned ground, shrub-coppice dune. GG

pingo
a large frost mound; especially a relatively large conical mound of soil-covered ice (commonly 30 to 50 meters high and up to 400 meters in diameter) raised in part by hydrostatic pressure within and below the permafrost of Arctic regions, and of more than 1 year's duration. GG

pinnacle [geomorphology]
a tall, slender, tapering tower or spire-shaped pillar of rock, either isolated, as on steep slopes or cliffs formed in karst or other massive rocks, or at the summit of a hill or mountain. compare - erosional remnant, hoodoo. SW, GG, & WW

pit and mound topography
(not recommended) use tree-tip pit and mound topography.

pitted outwash
outwash deposits with surficial pits or kettles, produced by the partial or complete burial of glacial ice by outwash and the subsequent thaw of the ice and collapse of the surficial materials. compare - pitted outwash plain. GG

pitted outwash plain
an outwash plain marked by many irregular depressions such as kettles, shallow pits, and potholes which formed by melting of incorporated ice masses; much of the gradient and internal structures of the original plain remain intact; many are found in WI, MN, MI, and IN. compare - collapsed outwash plain, outwash, pitted outwash. GG

pitted outwash terrace
a relict glaciofluvial terrace that retains its original attitude, composed of undistorted outwash sediments and depositional structures and whose surface is pock-marked with numerous potholes or kettle depressions. compare - collapsed outwash plain. SW

plain
a general term referring to any flat, lowland area, large or small, at a low elevation. specifically, any extensive region of comparatively smooth and level gently undulating land. a plain has few or no prominent hills or valleys but sometimes has considerable slope, and usually occurs at low elevation relative to surrounding areas. where dissected, remnants of a plain can form the local uplands. a plain may be forested or bare of trees and may be formed by deposition or erosion. compare - lowland, plateau. GG

plateau
[geomorphology] a comparatively flat area of great extent and elevation; specifically an extensive land region considerably elevated (more than 100 meters) above adjacent lower-lying terrain, and is commonly limited on at least one side by an abrupt descent, has a flat or nearly level surface. a comparatively large part of a plateau surface is near summit level. compare - hill, foothill, mountain, mesa, plain. GG

playa
the usually dry and nearly level lake plain that occupies the lowest parts of closed depressions, such as those occurring on intermontane basin floors. temporary flooding occurs primarily in response to precipitation-runoff events. playa deposits are fine grained and may or may not have high water table and saline conditions. HP

playa dune - (colloquial - Southern High Plains) A linear or curvilinear ridge of windblown, granular material (generally sand or parna) removed from the adjacent basin by wind erosion (deflation), and deposited on the leeward (prevailing downwind) margin of a playa, playa basin, or salina basin. The dune may be barren or vegetated. Compare - dune. SW