Abandoned Mine

An abandoned mine refers to a mining site where operations have ceased, and the site is no longer being used for mining activities.  Abandoned mines are often considered hazardous due to potential environmental impacts such as water pollution or hazardous waste.  Remediation efforts, such as capping and reclamation, are often required to prevent these impacts and make the site safe for future use. In some cases, abandoned mines can also pose physical hazards due to unstable structures or open mine shafts, which can be dangerous for people and animals.

Ablation

Ablation refers to the process of removing material from the surface of a glacier or ice sheet through melting, sublimation, or erosion.  This term is commonly used in the study of glaciology and climate science.  Ablation can be a significant contributor to sea-level rise, as melting ice sheets and glaciers release water into the ocean.  Ablation can also impact local water resources, as glaciers and snowpacks provide a significant source of freshwater for many regions.

Abrasion

Abrasion refers to the process of wearing away or scraping of a material, usually due to friction or impact.  Abrasion can be caused by natural processes such as wind, water, or ice erosion, or by human activities such as manufacturing or construction.  The term is commonly used in the study of geology, engineering, and materials science.

Abyssal Plain

An abyssal plain is a flat, sediment-covered area of the ocean floor that lies at depths of over 3,000 meters (9,800 feet).  Abyssal plains are some of the largest and most flat features on Earth, covering approximately 50% of the ocean floor.  They are formed by the accumulation of sediment that slowly drifts down from the ocean surface, and are home to a diverse array of deep-sea organisms.

Aeolian

Aeolian is an adjective used to describe processes or features associated with wind erosion and deposition.  Aeolian processes are important in shaping landscapes, particularly in arid or semi-arid regions where wind erosion is prevalent.  Aeolian features include sand dunes, sand sheets, and loess deposits.

Aerial Photograph

An aerial photograph is a photograph of the Earth’s surface taken from above, typically from an airplane or satellite.  Aerial photographs can be used for a wide range of purposes, including mapping, urban planning, and environmental monitoring. They are also commonly used in the fields of archaeology and geology to identify and map features that may not be visible from ground level.

Aerial Photography

Aerial photography refers to the practice of taking photographs from an aircraft or other flying object, often for mapping or surveying purposes.  Aerial photography has been used for over a century and has played a critical role in the development of fields such as geography, archaeology, and urban planning.

Aeromagnetic Survey

An aeromagnetic survey is a type of geophysical survey that uses a magnetometer to measure variations in the Earth’s magnetic field.  These variations can provide information about the underlying geology and can be used to identify and map geological structures, such as faults and mineral deposits. Aeromagnetic surveys are commonly used in mineral exploration, oil and gas exploration, and geological mapping.

Aeronautical Chart

An aeronautical chart is a map designed for use by pilots and air navigation services. Aeronautical charts typically include information about airspaces, airports, radio navigation aids, and other features relevant to aviation. They are essential tools for safe and efficient air travel.

Aeronautical Navigation

Aeronautical navigation refers to the process of planning and executing a flight using various tools and techniques to ensure the safe and efficient movement of aircraft. Aeronautical navigation can involve the use of maps, charts, and GPS systems, as well as the interpretation of weather reports and other critical information. Pilots and air traffic controllers rely on accurate and timely navigation information to make critical decisions in real-time, ensuring the safety of passengers and crew.

Agate

Agate is a type of mineral commonly used in jewelry and decorative objects.  Agate is a form of chalcedony, a mineral made up of microscopic crystals of quartz, and is known for its distinctive banding patterns and wide range of colors.  Agate can be found all over the world and is often used in jewelry-making due to its beauty and durability. In addition to its ornamental uses, agate has also been used in a variety of industrial applications, including as a material for grinding and polishing.

Air Mass 

In meteorology, an air mass is a large body of air with similar temperature and humidity characteristics throughout. These air masses can cover large geographic areas and have a significant impact on local weather patterns when they collide or move across different regions. Air masses are classified according to their source region, with polar air masses originating from high latitudes and tropical air masses originating from lower latitudes. The characteristics of an air mass are determined by the temperature and humidity of the surface over which it forms, and can be identified using weather instruments and satellite imagery.

Air photo map

An air photo map is a type of map that uses aerial photography to show the features and topography of an area.  These maps are created by taking photographs of the Earth’s surface from an aircraft or satellite and then processing the images to create a detailed view of the landscape.  Air photo maps can be used for a variety of purposes, including urban planning, environmental monitoring, and natural resource management.  They provide a bird’s-eye view of an area, allowing for a more comprehensive understanding of the terrain and the features present.

Alidade

An alidade is a surveying instrument used to measure angles and distances in the horizontal and vertical planes. It consists of a telescope mounted on a swivel that can rotate 360 degrees, allowing the user to align the instrument with a specific target and determine its position.  Alidades are commonly used in mapping and cartography, as well as in the construction of large structures such as buildings and bridges.  They can also be used for military purposes, such as targeting and range-finding. 

Alkali metal

Alkali metals are a group of chemical elements that are highly reactive and easily form compounds with other elements.  These elements include lithium, sodium, potassium, rubidium, cesium, and francium. Alkali metals have a single valence electron, which makes them highly reactive and able to easily lose that electron to form positive ions.  They are found in many minerals, and have a wide range of uses, including in batteries, chemical synthesis, and nuclear reactors. 

Alkali soil

Alkali soils are soil types that have a high pH level, usually greater than 8.5, which can be detrimental to the growth of crops and plants.  These soils are characterized by the presence of high levels of soluble salts, particularly sodium carbonate, which can damage plant roots and reduce their ability to absorb water and nutrients.  Alkali soils are usually found in arid and semiarid regions with low rainfall, where the lack of water limits the leaching of salts from the soil.  Treatment of alkali soils involves the application of amendments such as gypsum or organic matter, which can help to reduce the soil pH and improve its fertility for crop growth.

Alluvial Fan

An alluvial fan is a geological feature formed by the deposition of sediment at the base of a mountain or hill.  As water flows down from the higher elevation, it carries with it rocks, sand, and other debris, which are deposited at the base of the slope.  Over time, these deposits build up and form a fan-shaped feature, which can be several kilometers wide.  Alluvial fans are common in arid and semi-arid regions, and can provide important information about the history of the landscape and the flow of water in the area. 

Alpine Glacier

An alpine glacier is a glacier that forms in mountainous regions, typically at high elevations.  These glaciers are formed from snow that accumulates over time and compresses into ice, which then begins to flow downhill under the force of gravity.  Alpine glaciers can be found in many parts of the world, and play an important role in shaping the landscape and providing water resources for nearby communities.  They are also sensitive indicators of climate change, and are monitored closely by scientists studying the effects of global warming. 

Altitude

Altitude refers to the height of an object or location above sea level or a reference point on the Earth’s surface.  It is commonly measured in feet or meters, and can be determined using a variety of tools, such as a barometer or GPS device.  Altitude is an important concept in aviation, as pilots must constantly monitor their altitude to ensure the safety of their aircraft and passengers.  Altitude can also impact weather patterns and environmental conditions, such as temperature and air pressure.  Altitude adjustment is the process of modifying an aircraft’s altitude in response to changing conditions, such as turbulence or the need to avoid other aircraft.

Altitude Adjustment

Altitude adjustment is the process of calibrating or correcting altitude measurements to account for variations in temperature, pressure, and other environmental factors that can affect the accuracy of altitude readings.  Altitude adjustment is necessary because air pressure and temperature can vary depending on the altitude, which can affect the accuracy of altimeters and other altitude measuring instruments.  Altitude adjustment is particularly important for aircraft and spacecraft, where precise altitude measurements are essential for navigation and control.

Ambiguity

Ambiguity refers to a situation in which something is open to more than one interpretation or meaning.  This can occur in language, where words or phrases can have multiple meanings depending on context, or in other forms of communication, such as images or symbols.  Ambiguity can lead to confusion and misunderstandings, and can make it difficult to communicate effectively.  In certain contexts, such as art or literature, ambiguity can be intentionally used to create a sense of mystery or to provoke thought and discussion.

Amphibole

Amphibole is a group of silicate minerals that are commonly found in igneous and metamorphic rocks.  These minerals are characterized by their long, thin crystal structure, and are typically dark in color.  Amphiboles are important minerals in the Earth’s crust, and can be used to determine the conditions under which rocks were formed.  They are also used in a variety of industrial applications, such as insulation, as well as in jewelry and other decorative items. 

Amplitude

Amplitude refers to the maximum displacement or distance moved by a wave from its resting position.  It is commonly used to describe the intensity or strength of a wave, and is typically measured in units such as meters or feet.  Amplitude can vary depending on the type of wave, with electromagnetic waves having a different amplitude than sound waves. In some cases, amplitude can also refer to the range of values in a data set, such as in statistics or signal processing. 

Amorphous

Amorphous refers to a substance or material that lacks a defined crystalline structure.  Amorphous materials do not have a repeating pattern of atoms or molecules, and their properties can vary significantly depending on their composition and preparation. Examples of amorphous materials include glass, rubber, and some plastics.  Amorphous materials are often used in engineering and manufacturing applications, as they can have unique properties such as high strength, flexibility, and transparency.

Analemma

An analemma is a figure-eight shaped curve that represents the position of the sun in the sky at a given location over the course of a year.  It is created by taking a photograph of the sun at the same time of day on different days throughout the year, and then superimposing the images on top of each other.  Analemmas are often used in astronomy and navigation to determine the position of the sun and the time of day, as well as to study the Earth’s orbit around the sun.

Anemometer

Anemometers are devices used to measure the speed and direction of the wind.  They typically consist of a set of cups or vanes that rotate in response to the wind, and sensors that measure the rotation speed. Anemometers are commonly used in weather forecasting, aviation, and environmental monitoring, as wind speed and direction can have a significant impact on weather patterns, air traffic, and pollution dispersion.

Angular Unconformity

An angular unconformity is a type of unconformity in which an older layer of sedimentary rock is overlain by a younger layer at an angle.  This occurs when there is a period of uplift and erosion that exposes the underlying rock layer, followed by a period of deposition of the younger layer on top.  The angle of the unconformity represents the amount of tilting or deformation that occurred during the uplift and erosion phase, and can provide important information about the geological history of an area.  Angular unconformities are often associated with tectonic activity and can be found in mountainous regions or areas of active seismic activity.

Anomaly

An anomaly is something that deviates from what is expected or standard.  In science, an anomaly can be an observation or result that does not fit with the established theories or models.  Anomalies can be useful for scientists as they may indicate new phenomena or suggest modifications to current theories. In other fields, anomalies can be seen as outliers or exceptions to the norm.

Anticline

An anticline is a geological formation characterized by a fold in the Earth’s crust, where the layers of rock are bent upwards into an arch-like shape. Anticlines are commonly found in areas of tectonic activity, such as mountain ranges, and can trap oil and natural gas within their folds.

Antimeridian

The antimeridian, also known as the 180th meridian, is an imaginary line of longitude that runs from the North Pole to the South Pole and divides the Earth into the Eastern Hemisphere and the Western Hemisphere.  It is the opposite of the Prime Meridian, which is located at 0 degrees longitude.

Apex

The apex is the highest point or tip of something, such as a mountain or a triangle.  In biology, the apex can refer to the tip of a plant shoot or the point of a leaf. In business, the apex can refer to the top of a hierarchical organization, such as the CEO or the board of directors.

Aquifer

An aquifer is an underground layer of permeable rock, soil, or sediment that contains and transmits water.  These underground formations can hold vast amounts of water and can provide a sustainable source of water for human use, such as drinking water or irrigation.  However, some aquifers may be contaminated, making the water unsuitable for human consumption.

Arc

In geography, an arc is a curved line that connects two points on a map or on the Earth’s surface.  Arcs can be used to represent geographical features such as rivers, coastlines, or mountain ranges. In mathematics, an arc is a portion of a circle, defined by two endpoints and the curve of the circle.

Arête

An arête is a narrow ridge of rock that separates two valleys or glacial cirques.  Arêtes are formed by erosion from multiple glaciers or by the erosion of a single glacier over time.  These geological formations can be found in mountainous regions and are popular locations for rock climbing and hiking.

Artificial Terrain Feature

An artificial terrain feature is a constructed feature on the Earth’s surface, designed to mimic or enhance natural terrain features.  Examples of artificial terrain features include ski slopes, artificial lakes, and golf courses.  These features can be designed for recreational, aesthetic, or practical purposes, and are often built using heavy machinery and landscaping techniques.

Aspect

In geography, aspect refers to the direction that a slope faces in relation to the sun.  The aspect of a slope can affect the amount of sunlight, wind, and precipitation it receives, which in turn can impact vegetation growth and other ecological processes.  In architecture, aspect can refer to the orientation of a building in relation to the sun and prevailing winds, which can impact heating, cooling, and energy efficiency.

Astrofix

An astrofix is a navigational point in space, used by spacecraft and satellites to maintain their position and orientation relative to the Earth or other celestial bodies.  Astrofixes are determined using a combination of sensors and algorithms, such as GPS, star trackers, and inertial measurement units.

Atlas

An atlas is a collection of maps, typically organized by geography or theme.  Atlases can include political maps, topographic maps, and thematic maps, and can be used for educational, research, or reference purposes.  In Greek mythology, Atlas was also the name of a Titan who was condemned to hold up the sky on his shoulders.

Atmos

Atmos is an abbreviation for “atmosphere,” the layer of gases that surrounds the Earth and protects it from the sun’s harmful radiation.  The atmosphere is composed primarily of nitrogen, oxygen, and trace amounts of other gases, and is divided into several layers based on temperature and pressure. The study of the atmosphere and its interactions with the Earth’s surface is known as atmospheric science.

Azimuth

In cartography, azimuth is the horizontal angle between a celestial body or a known point and the observer’s reference direction, usually measured clockwise from the north. It is a crucial measurement used for navigation and surveying to determine direction and location accurately.  Azimuths can be expressed in degrees, minutes, and seconds or in mils, which are units of angular measurement that divide a circle into 6400 parts.  Azimuth is a vital tool in a variety of fields, including aviation, astronomy, and military operations, as it allows for precise calculations of distances and angles, as well as targeting and tracking of moving objects.