Radar

Radar is a technology that is used to detect and locate objects. It works by sending out radio waves and then measuring the time it takes for the waves to bounce back after they hit an object.  The word “radar” stands for “radio detection and ranging.”

Radian

A radian is a unit of measurement for angles.  One radian is equal to the angle that is subtended by an arc of a circle with a length equal to the radius of the circle. This is approximately equal to 57.3 degrees.

Radiant Energy

Radiant energy is energy that is transmitted through electromagnetic waves, such as light or heat.  This energy is transferred from one object to another through radiation, which does not require a medium for transmission.

Radio Direction Finder

A radio direction finder is a device that is used to locate the source of a radio signal.  It works by measuring the direction from which the signal is coming, and can be used to locate anything from a distress signal to a radio transmitter.  This technology has been used in navigation and search and rescue operations.

Radioactivity

Radioactivity refers to the process by which the nucleus of an atom emits particles or radiation.  This radiation can take the form of alpha, beta, or gamma particles, and can be both harmful and beneficial to humans.  The term “radioactivity” was coined by Marie Curie in 1898, when she discovered the element radium.

Radiocarbon Dating

Radiocarbon dating is a method used to determine the age of an object by measuring the amount of carbon-14 it contains.  Carbon-14 is a radioactive isotope that is produced naturally in the atmosphere and is incorporated into all living organisms.  When an organism dies, the carbon-14 begins to decay, and the rate of decay can be measured to determine the age of the organism.

Radiolarian

A radiolarian is a type of marine protozoan that has a hard, intricate shell made of silica.  These shells are often used in geology to study the history of the Earth’s oceans and can provide valuable information about past climate and environmental conditions.

Rain Gauge

A rain gauge is a device used to measure the amount of precipitation that falls in a specific area.  The gauge consists of a funnel that collects the rain and channels it into a measuring cylinder or container.  The amount of rain that falls is then measured and recorded, and can be used to monitor weather patterns and predict droughts or floods.

Raised Beach

A raised beach is a type of shoreline feature that is created when sea levels change.  Over time, as the Earth’s climate and sea levels fluctuate, beaches can be left at higher elevations than they were originally formed.  These raised beaches can be found all over the world and can provide important information about past environmental conditions and sea level changes.

Raised Relief Map

A raised relief map, also known as a three-dimensional map, is a type of map that displays the physical features of an area in a three-dimensional format.  Unlike a flat map, a raised relief map has features that are elevated above the surface of the map, allowing the viewer to see the topography of the area in a more realistic way.  Raised relief maps are typically made from materials such as plaster, plastic, or wood, and are often used for educational and decorative purposes.  They can be found in museums, libraries, and schools, as well as in the homes of geographers, cartographers, and outdoor enthusiasts.  Raised relief maps are particularly useful for exploring mountainous regions, as they provide a better sense of the scale and depth of the terrain than a traditional flat map.  They are also helpful for understanding the relationship between landforms and bodies of water, such as rivers and lakes.

Random Error

Random error is a type of error that occurs in scientific measurements and experiments.  It refers to the variability in measurements that cannot be attributed to any specific cause or source.  Random errors can be caused by factors such as equipment inaccuracies or human error, and can be minimized by repeating measurements and using statistical methods to analyze the data.

Range

Range can refer to a number of different things in the context of topography.  It can refer to the geographical area over which a species or ecosystem is distributed, or to the difference between the highest and lowest values in a set of data.  In the context of firearms, range refers to the distance between the shooter and the target, and can be affected by factors such as wind, bullet trajectory, and elevation.

Rangeland

Rangeland is a type of land that is used for grazing livestock.  It can include grasslands, shrublands, and deserts, and is often found in arid or semi-arid regions where crops are difficult to grow.  Rangelands can provide important habitat for wildlife and can be managed sustainably to promote healthy ecosystems and livestock production.

Raster

Raster is a type of digital image format that is made up of a grid of pixels.  Each pixel is assigned a specific color or value, and when combined, these pixels create an overall image.  Raster images are commonly used in digital photography and graphic design, and can be edited using software such as Photoshop.

Ravine

A ravine is a steep-sided valley that is usually carved out by a river or stream.  These landforms are often found in mountainous or hilly areas and can provide important habitat for a variety of plant and animal species.  Ravines can be dangerous during heavy rain or flooding, as water can rush through them quickly and cause erosion and landslides.

Rayleigh Scattering

Rayleigh scattering is a physical phenomenon that occurs when light waves are scattered by particles that are much smaller than the wavelength of the light.  This can cause the sky to appear blue during the day, as the shorter blue wavelengths are scattered more than the longer red wavelengths. Rayleigh scattering is also responsible for the red and orange hues of sunrises and sunsets, as the longer wavelengths of light are scattered more during these times of day.

Recessional Moraine

A recessional moraine is a type of glacial feature that is created when a glacier temporarily stops its retreat and deposits a ridge of debris.  These moraines are often found at the margins of glaciers and can provide important information about the history of glacial retreat and climate change.

Reclamation

Reclamation is the process of restoring degraded land or water to a functional state.  This can include activities such as soil stabilization, water management, and habitat restoration.  Reclamation projects are often undertaken to reverse the damage caused by human activities such as mining, oil and gas development, or agricultural practices.

Rectification

Rectification is a process that is used to correct distortions in aerial or satellite imagery.  This can include correcting for changes in altitude, camera angle, or lens distortion.  Rectified imagery is important for a variety of applications, including cartography, land use planning, and environmental monitoring.

Red Tide

A red tide is a natural phenomenon that occurs when certain species of marine algae grow rapidly and produce toxins.  These toxins can cause harmful effects on fish, shellfish, and other marine organisms, and can sometimes be harmful to humans as well. Red tides can occur in coastal waters around the world and are often associated with nutrient-rich conditions, such as those created by agricultural runoff or sewage discharge.

Reef

A reef is a ridge of rock, sand, or coral that lies at or near the surface of the sea.  Reefs provide important habitat for a variety of marine life, including fish, sea turtles, and sharks.  Coral reefs, in particular, are known for their biodiversity and are often referred to as the “rainforests of the sea.”

Refraction

Refraction is a phenomenon that occurs when light waves pass through a material with a different density, causing them to change direction.  This can cause objects to appear distorted or even invisible, and is the reason why a straw appears to bend when placed in a glass of water.  Refraction is also important in the study of meteorology, as it can cause light to bend in the atmosphere and create optical illusions such as mirages.

Regolith

Regolith is a layer of loose, unconsolidated material that covers the surface of the Earth or other planets.  This material can include rocks, dust, and soil, and is important for geological processes such as erosion and weathering.  Regolith is also of interest to scientists studying the geology of other planets, such as Mars, as it can provide important clues about their geological history.

Rejuvenation

Rejuvenation is the process of renewing or restoring something to a more youthful state.  In the context of landforms, rejuvenation can refer to the process of a river cutting down into its bed and creating a new, deeper channel.  This can occur due to changes in sea level, tectonic uplift, or other geological processes.  Rejuvenation can have important implications for human activities such as agriculture and urban development, as it can lead to changes in water availability and flooding.

Relief 

Relief refers to the difference in elevation between the highest and lowest points on the surface of the Earth.  In other words, it is a measure of the vertical distance between mountains and valleys.  Relief is an important factor in determining the topography of a region and can have important implications for human activities such as agriculture, forestry, and urban development.

Relief Map

A relief map is a type of map that shows the topography of a region by using shading and color to represent changes in elevation.  Relief maps are often used for geological and environmental studies, as well as for planning and development purposes.

Relief Shading

Relief shading is a technique used to create a 3D-like effect on maps and other images of terrain.  This is done by using light and shadow to create the illusion of depth and texture, making it easier to visualize the shape and orientation of landforms.  Relief shading is commonly used on maps to highlight the topography of a region, and can also be used in other applications such as cartography, geology, and environmental studies.

Remote Sensing

Remote sensing refers to the use of sensors and other instruments to gather information about the Earth’s surface from a distance.  This can include using satellites, aircraft, or other platforms to collect data on land use, vegetation cover, water quality, and other environmental factors.  Remote sensing is an important tool for scientists studying the Earth’s climate, ecosystems, and natural resources, and can also be used in a variety of applications such as urban planning, disaster response, and national security.

Reservoir

A reservoir is a large artificial or natural body of water that is used to store water for various purposes such as irrigation, hydroelectric power generation, and public water supply.  Reservoirs can be formed by building dams across rivers or by excavating basins in the ground.  They can also be used for recreational activities such as boating, fishing, and swimming.

Residual Soil

Residual soil is soil that has been formed by the weathering of the underlying rock in place, rather than being transported from another location.  This type of soil is commonly found in areas with older rock formations and a stable climate.  Residual soils can have unique properties based on the characteristics of the parent rock, and can be used for agriculture, construction, and other purposes.

Resolution

Resolution refers to the level of detail that can be captured or displayed by a digital imaging system such as a camera or satellite sensor.  It is typically measured in terms of the number of pixels per unit area, with higher resolution meaning more detail can be captured or displayed. Resolution is an important factor in many applications such as remote sensing, digital mapping, and scientific imaging.

Resource Management

Resource management refers to the process of planning, organizing, and directing the use of natural and human resources to achieve specific goals. This can include managing resources such as water, land, forests, and minerals, as well as human resources such as labor and capital.  Resource management is an important aspect of sustainable development and is often guided by principles such as conservation, efficiency, and equity. Effective resource management can help to ensure the long-term availability and sustainability of resources for future generations.

Reticulation

Reticulation refers to the process of creating a network of interconnected channels or pipes for the distribution of water, electricity, or other resources. This term is often used in the context of irrigation systems, where reticulation is used to deliver water to crops in a controlled and efficient manner. Reticulation systems can also be used for the distribution of natural gas, telecommunications, and other utilities.

Retreat

Retreat refers to the process of the gradual withdrawal or movement back of a natural feature, such as a glacier or coastline, over time.  Glacial retreat is caused by the melting of ice due to rising temperatures, while coastal retreat can be caused by erosion from waves and tides.  Retreat can have significant impacts on ecosystems and human settlements that are located in these areas.

Reverse Fault

A reverse fault is a type of fault in which the rock on one side of the fault plane is pushed upward relative to the rock on the other side.  This type of fault is caused by compressional forces in the Earth’s crust and is characterized by steeply inclined fault planes.  Reverse faults can create mountains and other elevated landforms as the uplifted rock is exposed to erosion over time.

Rhumb Line

A rhumb line is a line on a map or chart that connects two points along a constant compass direction, typically expressed as an angle relative to true north.  Unlike a great circle route, which is the shortest distance between two points on the surface of a sphere, a rhumb line follows a constant compass direction and is therefore easier to navigate using a compass or other directional tool.  Rhumb lines are commonly used in marine navigation and aviation to plot courses between two points on the Earth’s surface.

Rhyolite

Rhyolite is a volcanic rock that is high in silica content and is usually light in color. It forms from the slow cooling of magma or lava, and is typically associated with explosive volcanic eruptions.  Rhyolite is known for its fine-grained texture and can be found in a variety of geological settings, including volcanic domes, lava flows, and ash layers.  It is commonly used in construction as a decorative stone due to its unique appearance.

Ridge

A ridge is a long, narrow elevation of land that rises higher than the surrounding terrain.  Ridges can be created by a variety of geological processes, such as the folding of rock layers, the erosion of softer rock layers surrounding a harder core, or the accumulation of sediment or volcanic material. Ridges can be found in many different environments, including mountain ranges, oceanic plateaus, and even on the seafloor.  They are important features for hikers and mountaineers, who often follow ridgelines as a means of navigation.

Riffle

A riffle is a shallow section of a river or stream with a rapid current and a rough bottom.  Riffles are formed by the erosion of the streambed and are characterized by the presence of rocks and gravel that create turbulence in the water.  Riffles are important habitats for many aquatic species, as they provide oxygen-rich water and shelter from predators.  They are also popular locations for recreational activities such as fishing and kayaking.

Riparian

Riparian refers to the zone of land that surrounds a body of water, such as a river or stream.  The riparian zone is characterized by the presence of vegetation that is adapted to the moist conditions, and serves as an important habitat for many aquatic and terrestrial species.  Riparian zones also play an important role in maintaining water quality, as the vegetation helps to filter pollutants and stabilize streambanks.  Riparian zones are under threat from development, agriculture, and other land use activities, and many efforts are underway to protect and restore these important ecosystems.

River

River is a term used to describe a natural watercourse that flows towards an ocean, a lake, a sea or another river.  The flow of a river can be affected by various factors, including the topography of the surrounding land, precipitation, and human intervention.  Rivers play a crucial role in the Earth’s ecosystem by transporting nutrients and sediment, providing habitats for fish and wildlife, and supporting human activities such as irrigation and transportation.

River Basin

A river basin refers to the land area drained by a river and its tributaries.  The river basin is usually defined by the topography of the surrounding land, with the highest points forming the basin’s boundaries.  River basins are important for managing water resources and protecting the environment.

River Delta

River delta is an area where a river flows into an ocean or lake and deposits sediment, creating a triangular or fan-shaped landform.  River deltas are formed by the accumulation of sediment carried by the river and are often fertile areas for agriculture.  River deltas are also important ecosystems and support a wide range of flora and fauna.

Riverine

Riverine refers to anything that is related to or found in or along a river.  Riverine ecosystems include not only the river itself but also the surrounding floodplains, wetlands, and riparian forests.  The term riverine can be used to describe the plants, animals, and human activities that are associated with rivers, such as fishing, boating, and water supply.

Robinson Projection

A Robinson projection is a type of map projection that was developed by Arthur H. Robinson in 1961.  It is a compromise projection that attempts to balance the distortion of size, shape, and distance of the Earth’s surface features.  The Robinson projection is commonly used for world maps and is known for its pleasing aesthetic qualities.

Rock

Rock is a naturally occurring solid substance composed of one or more minerals or mineraloids.  Rocks can be found on the surface of the Earth, buried beneath the surface, or formed in the Earth’s mantle.  Rocks are classified based on their mineral composition, texture, and formation process. They play a crucial role in the Earth’s geology and provide important clues about the Earth’s history and evolution.

Rock Cycle

The rock cycle is a continuous process of transformation and recycling of rocks on the Earth’s surface. It describes how rocks are formed, weathered, eroded, transported, and then re-formed into new rocks.  The rock cycle is driven by various geological processes, including plate tectonics, erosion, weathering, and sedimentation.

Rock Glacier

A rock glacier is a type of glacier that forms when a layer of rock debris covers the surface of a glacier.  The rock debris insulates the glacier from melting and can cause it to move downslope.  Rock glaciers are found in mountainous regions and are often associated with permafrost.  They are important indicators of past and present climate conditions and can provide information about the history of glaciation in a region.

Rockfall

Rockfall refers to the sudden and rapid movement of rock debris from a cliff or steep slope.  This can be triggered by a variety of factors such as earthquakes, weathering, or human activity.  The fallen rocks can cause significant damage to infrastructure and can even be fatal to people in the vicinity.

Rockslides

Rockslides, on the other hand, are a more massive and forceful type of rock movement that involves the sudden collapse of a large section of rock. This can be triggered by a variety of factors, including seismic activity, weathering, and gravity.  Rockslides can be particularly dangerous because of their size and force, often causing significant destruction to infrastructure and landscapes.

Rod

A rod is a unit of length commonly used in surveying and cartography. It is equivalent to 5.5 yards or 16.5 feet.  It is often used as a reference unit for measuring distances in land surveys and maps.

Roll

Roll refers to the movement of a ship or other vessel from side to side.  This can be caused by factors such as waves, wind, and changes in weight distribution on the vessel.  Roll can be a significant problem for ships and can cause damage to cargo, equipment, and the vessel itself.

Root Wedging

Root wedging is a type of physical weathering caused by the growth of plant roots. When roots grow into the cracks of rocks, they exert pressure on the surrounding rock, causing it to fracture and break apart.  The roots can also absorb water and expand, further widening the cracks. Root wedging is an important process in soil formation, as it helps break down solid rock into smaller particles that can be further broken down by chemical weathering. It can also play a role in slope stability, as it can weaken rocks and increase the likelihood of rockfalls or landslides.

Rotation

Rotation in topography refers to the movement of an object around an axis.  This can refer to the rotation of the Earth on its axis, which causes day and night, or the rotation of a planet around the sun, which causes seasons.  In terms of landforms, rotation can refer to the movement of soil or rock down a slope due to gravity.  This can cause rotational landslides, which occur when the ground rotates around a point, causing a curved surface to form.

Runoff

Runoff refers to the movement of water over the surface of the Earth, usually as a result of precipitation.  When rain falls on a surface, it can either infiltrate into the ground or flow over the surface as runoff.  Runoff can be affected by factors such as slope, vegetation cover, and soil type.  It plays an important role in the water cycle, as it can transport nutrients and pollutants from one location to another, and can contribute to the erosion and formation of landforms such as canyons and valleys.