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Pacific Ring of Fire

The Pacific Ring of Fire refers to a region in the Pacific Ocean characterized by frequent seismic and volcanic activity.  It is a horseshoe-shaped area that stretches from the western coast of North America to the eastern coast of Asia and includes many islands in the Pacific.  The Ring of Fire is home to over 75% of the world’s active and dormant volcanoes, and it experiences about 90% of the world’s earthquakes.  The region is also prone to tsunamis, which can be triggered by undersea earthquakes or volcanic eruptions.


Pahoehoe is a type of lava flow characterized by its smooth and ropy texture.  It is a Hawaiian term that means “smooth, unbroken lava.” Pahoehoe forms when lava with low viscosity flows slowly and cools, creating a smooth and undulating surface.  The texture of pahoehoe is a result of the way the lava flows and solidifies, with the outer layer cooling and solidifying first while the still-liquid interior continues to flow.  Pahoehoe lava flows are typically associated with shield volcanoes and can be found in many volcanic regions around the world.


Paleoclimatology is the study of past climates on Earth, using evidence from a variety of sources such as ice cores, sediment layers, and fossils.  By analyzing these sources, scientists can reconstruct past climates and understand how they have changed over time.  Paleoclimatology can provide important information about the causes of climate change and the potential impacts of future climate change.  Some of the topics studied in paleoclimatology include the Earth’s temperature, sea levels, precipitation patterns, and atmospheric composition.  By studying past climate patterns, scientists can better understand how the Earth’s climate system works and how it might respond to future changes.


Paleogeography is the study of the ancient physical features of the Earth’s surface, including its landmasses, oceans, and climate.  It is an important field of study for understanding how the Earth’s surface has changed over time and how these changes have affected the evolution of life on the planet.  Paleogeographers use a variety of methods to reconstruct ancient landscapes, including analyzing rock formations, fossils, and ancient climate data.  By studying paleogeography, scientists can learn about the distribution of land and sea throughout Earth’s history and how these changes have influenced the evolution of life on the planet.


The Paleozoic era is a geologic era that began about 541 million years ago and ended about 252 million years ago.  It is known as the era of ancient life because it was during this time that the first complex multicellular organisms appeared on Earth.  The Paleozoic era is divided into six periods, each characterized by its own unique geological and biological events.  During this time, the Earth’s continents were clustered together in a supercontinent called Pangaea, and the climate was generally warm and humid.  The Paleozoic era saw the rise and fall of many different types of marine life, including trilobites, brachiopods, and crinoids, as well as the emergence of the first land plants and animals.

Paleozoic Era

The Paleozoic era is a geologic era that spanned from about 541 million years ago to 252 million years ago.  It is often referred to as the era of ancient life because it was during this time that the first complex multicellular organisms appeared on Earth.  The Paleozoic era is divided into six periods, each characterized by its own unique geological and biological events.  One of the most significant events of the Paleozoic era was the formation of the supercontinent Pangaea, which brought together all of the Earth’s continents into one landmass.  The climate of the Paleozoic era was generally warm and humid, and the era saw the rise and fall of many different types of marine life, as well as the emergence of the first land plants and animals.


Pangaea was a supercontinent that existed during the Paleozoic and Mesozoic eras, about 300 million years ago.  It was the result of the gradual merging of all the Earth’s continents into a single landmass.  The name Pangaea means “all Earth” in Greek, and it was the largest landmass in Earth’s history.  The formation of Pangaea had a profound impact on the Earth’s climate and the evolution of life on the planet. The movement of the Earth’s tectonic plates caused Pangaea to eventually break apart into the continents we know today, a process known as continental drift.  The concept of Pangaea is important in geology and paleogeography, as it provides evidence of the Earth’s constantly changing surface over time.


Pangea was a supercontinent that existed during the Paleozoic and Mesozoic eras, about 300 million years ago.  It was the result of the gradual merging of all the Earth’s continents into a single landmass.  The name Pangea means “all Earth” in Greek, and it was the largest landmass in Earth’s history. The formation of Pangea had a profound impact on the Earth’s climate and the evolution of life on the planet.  The movement of the Earth’s tectonic plates caused Pangea to eventually break apart into the continents we know today, a process known as continental drift.  The concept of Pangea is important in geology and paleogeography, as it provides evidence of the Earth’s constantly changing surface over time.


Parallax is the apparent shift in the position of an object when viewed from different angles.  It is a measurement technique used in astronomy to determine the distance of nearby stars and other celestial bodies.  By measuring the difference in the apparent position of a star when viewed from two different locations, scientists can calculate its distance using trigonometry.  Parallax is also used in other fields, such as optics and surveying, to determine the distance or size of objects.


Parallel refers to lines or surfaces that are equidistant from each other and never intersect.  In geography, parallels are a system of imaginary lines that run horizontally around the Earth, parallel to the equator.  The most well-known parallel is the equator itself, which is a line of latitude that circles the Earth at 0 degrees.  Other lines of latitude are also considered parallels, and they are numbered from 0 to 90 degrees north and south of the equator.  In mathematics, parallel lines have the same slope and will never intersect, while in geometry, parallel planes are planes that never intersect and maintain the same distance between each other.

Parent Rock

Parent rock, also known as the bedrock, is the underlying rock material that has not yet been weathered or eroded.  It is the source of soil and sediment and plays a significant role in shaping the landscape.  The type of parent rock can have a significant impact on the soil type, which in turn affects the types of plants and animals that can survive in a given area.  Parent rock is also important in the formation of minerals and ores, as well as the development of geologic features such as mountains, canyons, and valleys.


Parfleche is a type of rawhide container used by indigenous peoples of North America for storing and carrying various items, including food, clothing, and tools.  The term “parfleche” comes from the French word for “shield,” as the rawhide was often treated with various substances to make it more durable and resistant to moisture.  Parfleches were decorated with intricate designs and served both functional and artistic purposes.  They were an important part of many indigenous cultures, and examples can still be found in museums and private collections today.


A park is an area of land that is set aside for public use and enjoyment.  Parks can range in size from small neighborhood parks to large national parks, and they can be located in urban or rural areas.  Parks often feature recreational facilities such as playgrounds, sports fields, and picnic areas, as well as natural features such as trees, lakes, and hiking trails.  Parks provide a variety of benefits to communities, including opportunities for outdoor recreation, conservation of natural resources, and preservation of historical and cultural sites.

Partial Pressure

Partial pressure is a term used in chemistry and physics to describe the pressure exerted by a single gas in a mixture of gases.  In a mixture of gases, each gas exerts a partial pressure that is proportional to its concentration in the mixture.  The total pressure of the mixture is equal to the sum of the partial pressures of each gas.  Partial pressure is an important concept in many fields, including atmospheric science, where it is used to study the composition and behavior of the Earth’s atmosphere.  It is also used in medical settings, such as in the administration of anesthesia, where the partial pressure of the anesthetic gas must be carefully controlled to ensure patient safety.


A pass is a low point in a mountain range that provides a route through the mountains.  Passes are important features for transportation and trade, as they allow people and goods to move through otherwise inaccessible areas.  Passes can be natural, such as those formed by erosion or glaciation, or they can be man-made, such as tunnels or roads.  Some of the most famous passes in the world include the Khyber Pass in Afghanistan, the Brenner Pass in the Alps, and the Donner Pass in the Sierra Nevada mountains.

Passive Margin

A passive margin is a type of continental margin that is not associated with tectonic activity such as volcanism or earthquakes.  Passive margins are typically found on the trailing edge of a continent and are characterized by a broad, gentle slope that extends from the shoreline into the ocean basin. The sediment that accumulates on passive margins is often rich in organic material and can form petroleum reservoirs.  Passive margins are important in the study of plate tectonics and the evolution of continents, as they provide evidence of the movement and breakup of supercontinents such as Pangea.


A peak is the highest point of a mountain or hill.  Peaks can be found all over the world and are often used as landmarks or symbols of natural beauty. Some of the most famous peaks in the world include Mount Everest, the tallest peak in the Himalayas and the highest point on Earth, and Mount Kilimanjaro, the highest peak in Africa.  Peaks are important for outdoor recreation, including hiking, climbing, and skiing.  They also play a role in weather patterns, as they can influence the movement of air masses and the formation of clouds.


Peat is a type of organic matter that forms in wetlands and bogs.  It is composed of partially decayed plant material, such as mosses and grasses, that accumulates over thousands of years.  Peat is an important source of fuel in many parts of the world and is used for heating and cooking. It is also used as a soil amendment and for horticultural purposes, as it is rich in nutrients and can help retain moisture in soil.  Peatlands are important ecosystems that provide habitat for a variety of plant and animal species, and they play a role in carbon cycling and climate regulation.


A pediment is a gently sloping area of bedrock at the base of a mountain range or hill.  It is typically formed by erosion from wind, water, or ice and is often composed of a mixture of sediment and rock fragments.  Pediments are important features in the study of geomorphology and can provide insights into the history of a landscape.  They can also provide a habitat for a variety of plant and animal species.

Pelagic Zone

The pelagic zone is the open water region of the ocean, beyond the continental shelf and below the surface layer known as the epipelagic zone.  The pelagic zone is divided into different layers based on depth and light availability, with the mesopelagic, bathypelagic, abyssopelagic, and hadalpelagic zones extending progressively deeper.  The pelagic zone is home to a diverse array of marine life, including plankton, fish, whales, and sharks. It is an important area for commercial fishing and plays a crucial role in the global carbon cycle, as it is a major sink for atmospheric carbon dioxide.


A penstock is a pipeline or channel used to transport water from a reservoir to a power plant or other destination.  It is typically constructed of steel or concrete and can be either underground or aboveground.  Penstocks are important components of hydroelectric power generation systems, as they provide the water that drives the turbines.  They can also be used for irrigation and other purposes.

Perched Water Table

A perched water table is a localized zone of saturation above the main water table, usually located in a layer of relatively impermeable material, such as clay or shale.  It is formed when water is trapped in the pores or fractures of the impermeable layer, creating a barrier to downward flow.  Perched water tables are important in the study of groundwater and can affect the movement and availability of water in aquifers.  They can also play a role in the stability of slopes and hillsides.

Perennial Stream

A perennial stream is a stream or river that flows continuously throughout the year.  These streams are fed by a constant source of water, such as a spring, and are not dependent on rainfall or snowmelt for their flow.  Perennial streams are important for aquatic ecosystems and provide a reliable source of water for human use.


Periglacial refers to environments that are characterized by freezing and thawing cycles, typically found in regions surrounding glaciers or in high-latitude areas.  Periglacial environments can be harsh and inhospitable, with extreme temperature fluctuations, permafrost, and the formation of features such as patterned ground and solifluction lobes.  These environments are important for studying climate change and the effects of warming temperatures on permafrost and related features.


Permafrost is a layer of soil, rock, or sediment that remains frozen for at least two consecutive years.  It is typically found in high-latitude or high-altitude regions and can range in depth from a few meters to hundreds of meters.  Permafrost is an important component of the global climate system and can have significant impacts on ecosystems and infrastructure.  As permafrost thaws due to climate change, it can release large amounts of carbon and methane into the atmosphere, contributing to further warming.


Pervious refers to a material or surface that allows water to pass through it.  Pervious surfaces, such as porous pavement or permeable concrete, can help to reduce stormwater runoff and improve groundwater recharge.  Pervious materials are also used in landscaping and agriculture to help control erosion and improve soil health.  The opposite of pervious is impervious, which refers to surfaces that do not allow water to pass through, such as asphalt or concrete. Impervious surfaces can contribute to flooding and other water-related problems in urban areas.

Photic Zone

The photic zone is the uppermost layer of water in a body of water, where enough sunlight penetrates to support photosynthesis by plants and algae. The depth of the photic zone depends on factors such as water clarity and the angle of the sun.  The photic zone is an important area for marine ecosystems, as it provides the energy needed to support the growth of primary producers, which in turn support higher trophic levels.

Photo Interpretation

Photo interpretation is the process of analyzing photographs, typically aerial or satellite images, to identify and interpret features on the ground.  This technique is used in a variety of fields, including cartography, geology, and ecology, to map and study the Earth’s surface.  Photo interpretation involves using visual clues, such as colors, patterns, and shapes, to infer information about the landscape.


Photogrammetry is a technique for making measurements and creating maps using aerial or satellite photographs.  This involves taking multiple photographs of an area from different angles and using software to create a 3D model of the landscape.  Photogrammetry can be used to measure the height of buildings, the volume of stockpiles, and the contours of the land surface.


A photomap is a map that is created using aerial or satellite photographs.  Photomaps can provide detailed information about the landscape, including topography, land use, and infrastructure.  They are commonly used for planning and development purposes, as well as for environmental monitoring and resource management.  Photomaps can also be used to create 3D models of the landscape using photogrammetry techniques.

Phreatic Zone

The phreatic zone is a layer of soil or rock that is saturated with groundwater.  This zone is located below the water table and above the impermeable layer of bedrock or soil. In this zone, water is held in the pore spaces of the soil or rock and moves slowly through it by gravity or capillary action.  The phreatic zone plays an important role in groundwater recharge and storage.

Physical Map

A physical map is a type of map that shows the physical features of the Earth’s surface, such as mountains, rivers, and lakes.  Physical maps are different from political maps, which show the boundaries of countries and states.  Physical maps often use color to represent different elevations or landforms, such as green for low-lying areas and brown for mountains.  These maps are useful for understanding the topography of a region and can be used for a variety of purposes, such as planning hiking trips or analyzing the natural resources of an area.

Picnic Area

A picnic area is a designated outdoor area where people can gather to eat, relax, and enjoy the natural surroundings.  Picnic areas are often found in parks, nature reserves, and other outdoor recreation areas.  They may include picnic tables, benches, grills, and sometimes even playgrounds or other amenities. Picnic areas provide a convenient and enjoyable way for people to spend time outdoors with friends and family.


A piedmont is a type of landform that occurs at the base of a mountain range, where the mountains meet a plain or coastal area.  The term “piedmont” comes from the French phrase “pied de mont,” which means “foot of the mountain.”  Piedmonts typically have gently sloping terrain and are characterized by a transition from the steep, rugged mountains to the flat plains or coastal areas.  Piedmonts are often fertile and are used for agriculture and other forms of land use.


A pingo is a type of periglacial landform that is found in Arctic and sub-Arctic regions.  Pingos are formed by the expansion of groundwater as it freezes, which causes the soil to heave upward and form a small hill.  The hill is typically circular in shape and can range from a few meters to several hundred meters in diameter.  Pingos are important indicators of permafrost and climate change, as they are only found in regions with a permanently frozen ground.


Pinpointing is the process of determining the precise location of a point on a map or in the field.  This can be done using a variety of methods, such as GPS, triangulation, or visual sighting. Pinpointing is an important skill in navigation, surveying, and other forms of geospatial analysis.


A pipe is a long, narrow channel or conduit that is used to transport fluids, gases, or other substances. Pipes can be made from a variety of materials, including metal, plastic, and concrete. They are used in a wide range of applications, from carrying water and sewage to transporting oil and gas. Pipes can be buried underground or laid on the surface of the ground, depending on the specific application.


Pitch is a term used to describe the steepness or slope of a surface. In topography, pitch is often used to describe the angle of a roof or the slope of a hill. Pitch can be measured in degrees or as a ratio of rise to run.  The pitch of a surface can have a significant impact on its function and use, as steeper pitches may be more suitable for shedding water or providing better traction, while flatter pitches may be better for walking or driving.

Plan View

Plan view is a term used in cartography and architecture to describe a drawing or map that represents a surface as seen from above.  In a plan view, the viewer is looking down on the surface, and all features are shown in their true size and shape.  This type of view is often used in architectural drawings to show the layout of a building or in cartography to show the layout of a city or landscape.

Plane Table Surveying

Plane table surveying is a method of surveying that involves using a special type of table called a plane table.  The table is used to draw a map of the area being surveyed while taking measurements and observations in the field.  Plane table surveying is often used in areas with difficult terrain or limited access, as it allows surveyors to work quickly and efficiently without the need for complex equipment.


A planimeter is a tool used to measure the area of a two-dimensional shape on a map or drawing.  It consists of a tracing point that is moved around the perimeter of the shape, and a dial that measures the distance traveled by the point.  Planimeters are often used in cartography and engineering to accurately measure the area of land parcels or other shapes.

Planimetric Map

A planimetric map is a type of map that represents the horizontal positions of features on the Earth’s surface, without showing elevation or relief. Planimetric maps are often used in urban planning, engineering, and cartography, as they provide a detailed view of the layout and organization of features such as roads, buildings, and bodies of water.

Plate Tectonics

Plate tectonics is the scientific theory that describes the movement and interactions of the Earth’s lithospheric plates.  These plates are the large, rigid pieces of the Earth’s crust and upper mantle that “float” on the asthenosphere, a weaker, partially molten layer beneath them.  Plate tectonics is responsible for many geological phenomena, such as earthquakes, volcanoes, and mountain formation.


A plateau is a large, relatively flat area of land that is elevated above the surrounding landscape.  They can form through several processes, including uplift from tectonic activity, erosion of softer rock layers, or lava flows that cover an area and solidify into basalt.

Pleistocene Epoch

The Pleistocene epoch is a geological time period that occurred between 2.6 million and 11,700 years ago.  It is known for its series of ice ages, during which large parts of the Earth’s surface were covered in ice sheets.  The Pleistocene saw the evolution of several hominid species, including Homo erectus, Homo neanderthalensis, and Homo sapiens.


Plunge, which refers to the angle at which a geological feature, such as a fold or fault, dips below the Earth’s surface.  It is typically measured in degrees and can provide important information about the structure and orientation of rock formations.  For example, a fold with a steep plunge may indicate a more complex geological history than one with a shallower plunge.


A pluton is an igneous rock formation that forms underground from molten magma.  The magma cools and solidifies slowly over time, resulting in large and coarse-grained rock formations. Plutons are typically found deep within the earth’s crust, and can range in size from just a few meters to several kilometers in diameter.  These formations can be exposed on the surface through erosion or uplift.  Some of the most well-known plutons include Yosemite’s Half Dome and El Capitan.

Pluvial lake

A pluvial lake is a type of lake that forms during times of increased precipitation, such as during a period of glacial retreat or a wetter climate.  These lakes can cover vast areas and can last for thousands of years.  They are often found in arid regions where water is scarce, and provide important habitats for a wide range of plants and animals.  Examples of pluvial lakes include Lake Bonneville in Utah and Lake Lahontan in Nevada.


A point is a narrow and elongated piece of land that extends out into a body of water.  It can be made up of sand, gravel, or rock and can vary in size from a few meters to several kilometers.  Points are often formed by the action of waves and currents eroding the shoreline, leaving behind a protrusion of land.  They can provide important habitats for marine organisms, as well as being popular locations for recreational activities such as fishing and swimming.

Point Bar

A point bar is a curved deposit of sediment that forms on the inside of a meandering river bend. As the river flows around the bend, it erodes the outer bank and deposits sediment on the inner bank, resulting in the formation of a point bar.  These features can be several meters thick and can be composed of sand, silt, and clay.  Point bars are important habitats for a wide range of plant and animal species, and can also provide valuable sources of soil for agricultural purposes.

Point of Interest

A point of interest (POI) is a specific location or feature that is deemed noteworthy or important for various reasons.  POIs can include natural landmarks such as mountains or waterfalls, or man-made structures such as historic buildings or monuments.  POIs can be identified on maps or in guidebooks, and are often popular destinations for tourists and travelers.  They can also be used for navigation and orientation, helping people to find their way around unfamiliar areas.

Polar Front

The polar front is a boundary that separates cold polar air from warmer air in the middle latitudes.  It is a zone of low pressure where the two air masses meet, resulting in a variety of weather conditions such as storms and cyclones.  The polar front is not a fixed location and can shift north and south depending on the season and other atmospheric factors.  This boundary is an important feature of global climate patterns and plays a significant role in shaping weather systems around the world.

Polar Projection

A polar projection is a type of map projection that shows the earth from a perspective centered on either the North or South Pole.  In this projection, the meridians are straight lines that converge at the poles, while the parallels are concentric circles that get smaller towards the poles.  Polar projections are useful for visualizing the Arctic and Antarctic regions, and can be particularly helpful for navigation and research purposes.

Polar Stereographic Projection

The polar stereographic projection is a specific type of polar projection that is commonly used in cartography, particularly for mapping polar regions. This projection shows the earth as a flat surface with the North or South Pole at the center.  The meridians are straight lines that converge at the pole, while the parallels are circular arcs that intersect the meridians at right angles.  This projection is particularly useful for representing features in polar regions, such as ice sheets and ocean currents.  It is widely used in scientific research and navigation, particularly in polar exploration and mapping.


Polarity refers to the presence of opposite or contrasting qualities or directions. In geology, polarity can refer to the direction of the earth’s magnetic field, which can be used to determine the age of rocks and the movement of tectonic plates.  In biology, polarity can refer to the orientation of cells or tissues, which is important for proper development and function.  In chemistry, polarity refers to the distribution of electrical charges within a molecule, which can affect its properties and interactions with other molecules.

Political Boundary

A political boundary is a defined and recognized geographic line that separates two or more political entities, such as countries, states, or provinces. These boundaries can be based on a variety of factors, including historical, cultural, and geographical considerations.  Political boundaries can be marked by physical features such as rivers, mountains, or oceans, or they can be defined by man-made structures such as walls or fences.  These boundaries are important for regulating the movement of people and goods, and for maintaining order and stability within and between countries.


A polje is a type of large, flat plain or valley that is formed by the collapse of a karst landscape.  Karst landscapes are characterized by soluble rock formations, such as limestone or dolomite, that are eroded by water to create sinkholes, caves, and underground drainage systems.  When a large area of the underground drainage system collapses, it can result in the formation of a polje.  Poljes are often found in areas with high rainfall and porous rock formations, and can be important habitats for a variety of plant and animal species.

Polyconic Projection

The polyconic projection is a type of map projection that uses a series of cones to represent the earth’s surface.  Each cone is tangent to a line of longitude, and the cones are arranged in such a way that they intersect the earth’s surface at a series of points.  The resulting map is a combination of conical projections, which allows for more accurate representation of both shape and distance than other types of projections.  The polyconic projection is often used for mapping areas with a significant east-west extent, such as the United States, and is particularly useful for representing small-scale features such as mountain ranges and coastlines.


A pond is a small body of standing water that is usually shallow enough for sunlight to penetrate to the bottom, allowing for the growth of aquatic plants. Ponds can be natural or man-made, and can be found in a variety of settings, including forests, wetlands, and suburban areas.  Ponds can support a wide range of plant and animal species, including fish, amphibians, and waterfowl, and are important habitats for biodiversity.


Porosity refers to the amount of empty space, or pores, in a material, such as soil or rock. Porosity is an important characteristic of geological formations, as it affects the ability of materials to hold and transport water, oil, and gas.  High porosity materials, such as sandstone or limestone, can hold large amounts of water and are important aquifers, while low porosity materials, such as shale or granite, are impermeable and can serve as effective barriers to fluid flow.


The postglacial period refers to the time following the last glacial period, which ended approximately 11,700 years ago.  During this time, the earth’s climate warmed, leading to the retreat of glaciers and the emergence of new landscapes and ecosystems.  Postglacial environments are characterized by a variety of landforms, such as moraines, eskers, and kettle lakes, which were created by glacial processes.  These environments are also home to a wide range of plant and animal species that have adapted to the changing conditions.

Potential Energy

Potential energy is a type of energy that is stored in an object or system, based on its position or configuration . In the context of topography, potential energy can refer to the energy stored in a mass of rock or soil, based on its position relative to the earth’s surface.  This energy can be released in the form of a landslide or rockfall, when the gravitational force acting on the mass exceeds the holding capacity of the surrounding material.  Potential energy is an important concept in understanding natural hazards, and can be used to assess the risk of landslides and other types of slope failures.


A prairie is a large, flat grassland ecosystem characterized by tall grasses and herbaceous plants.  Prairies are typically found in North America and can be an important habitat for a variety of wildlife, including bison, pronghorn antelope, and various species of birds.  Prairie ecosystems are also important for agriculture, as the fertile soil can support the growth of crops like wheat and corn.


The Pre-Cambrian is a geological time period that spans approximately 4.6 billion years, from the formation of the earth to the beginning of the Cambrian period, around 541 million years ago.  The Pre-Cambrian is divided into several eons, including the Hadean, Archean, and Proterozoic.  During this time, the earth underwent significant geological and biological changes, including the formation of the continents, the development of life, and the emergence of complex multicellular organisms.


Precipitation refers to any form of moisture that falls from the atmosphere to the earth’s surface, including rain, snow, sleet, and hail.  Precipitation is an important part of the water cycle, as it provides the primary source of freshwater for terrestrial ecosystems.  The amount and type of precipitation can vary widely depending on a variety of factors, including latitude, altitude, and proximity to bodies of water.

Prime Meridian

The prime meridian is an imaginary line that represents the 0° longitude on the earth’s surface.  It is used as a reference point for measuring longitude and is the basis for the global system of time zones.  The prime meridian passes through the Royal Observatory in Greenwich, England, and was first established in the late 19th century as a means of standardizing global timekeeping.


A profile refers to a cross-sectional view of a landscape, typically used to illustrate changes in elevation or slope along a given line or path.  Profiles can be created using various tools, such as topographic maps or surveying equipment, and can provide important information about the shape and topography of a particular area.

Profile Leveling

Profile leveling is a surveying technique used to determine changes in elevation along a given path or line.  This method involves taking precise measurements of elevation at regular intervals along the path and then creating a profile to illustrate changes in elevation.  Profile leveling can be used to create detailed topographic maps or to identify potential changes in slope or grade along a roadway or other linear feature.

Projection Distortion

Projection distortion refers to the distortion of a three-dimensional object or surface when it is projected onto a two-dimensional plane.  This phenomenon is particularly relevant in cartography, where maps must represent the earth’s curved surface on a flat piece of paper or screen.  Different map projections can result in different types and degrees of distortion, with some projections emphasizing accurate shapes and others emphasizing accurate areas or distances.


Prominence refers to the vertical distance between the summit of a mountain or hill and its lowest contour line.  This measurement is often used to identify and rank mountains or hills based on their relative elevation and prominence.  High prominence peaks are often important landmarks and destinations for hikers and climbers, and can offer stunning views of surrounding landscapes.


A promontory is a high piece of land or cliff that extends out into a body of water.  Promontories are often formed by erosion or volcanic activity and can provide stunning views of the surrounding landscape.  They can also be important landmarks for navigators and sailors, serving as a reference point for navigation.

Propagation Velocity

Propagation velocity refers to the speed at which a wave or other disturbance moves through a medium, such as air or water.  This property is important in many fields, including acoustics, electronics, and seismology.  In seismic exploration, for example, the propagation velocity of seismic waves can be used to determine the structure and composition of the earth’s subsurface.


Prospecting is the process of searching for mineral deposits, such as gold, silver, or copper, in the earth’s crust.  This process typically involves a combination of surveying, geological analysis, and exploration drilling. Prospecting can be a challenging and risky endeavor, as mineral deposits are often found in remote or inhospitable locations and may require significant investment to extract.  However, successful prospecting can lead to the discovery of valuable mineral resources that can drive economic development and growth.


Pseudokarst refers to landforms that resemble karst terrain, such as sinkholes and caverns, but are formed through processes other than dissolution of rock by water.  Pseudokarst can be formed by various geological processes, including freeze-thaw cycles, landslides, and volcanic activity.  Although pseudokarst lacks the intricate cave systems of true karst terrain, it can still be important for its unique geological features and potential for recreation.


Pumice is a light, porous volcanic rock that forms from the rapid cooling of frothy lava.  Pumice can range in color from white to grey and is characterized by its low density and ability to float in water.  Due to its lightweight and abrasive properties, pumice is often used as an abrasive in products such as toothpaste and exfoliating scrubs. It is also used in construction materials, such as concrete blocks and lightweight fill.

Pyroclastic Flow

A pyroclastic flow is a fast-moving mixture of hot ash, rock fragments, and gas that is expelled during a volcanic eruption.  Pyroclastic flows can travel at speeds of up to 700 kilometers per hour and can be extremely destructive to surrounding areas, burying towns and villages in meters of ash and debris.  Pyroclastic flows are one of the most dangerous aspects of volcanic activity and can pose a significant hazard to human life and infrastructure. 

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