Glossary of Terms: L

Lagoon - (1) A body of seawater that is almost completely cut off from the ocean by a barrier beach. (2) The body of seawater that is enclosed by an atoll.

Lahar - A very rapid type of downslope mass movement that involving mudflows from volcanic ash.

Lake - A body standing water found on the Earth's continental land masses. The water in a lake is normally fresh. Also see eutrophic lake, mesotrophic lake, and oligotrophic lake.

Land Breeze - Local thermal circulation pattern found at the interface between land and water. In this circulation system, surface winds blow from land to water during the night.

Landfall - The coastline location where a tropical storm or hurricane moves from ocean onto land.

Landsat - Series of satellites launched by NASA for the purpose of remotely monitoring resources on the Earth. The first Landsat satellite was launched by the United States in 1972. Landsat uses two types of sensors to monitor the Earth: Thematic Mapper and Multispectral Scanner. See the following website for more information - Landsat Program.

Landslide - Term used to describe the downslope movement of soil, rock, and other weathered materials because of gravity.

Landward - Positioned or located away from a water body but towards the land.

Langley - Unit of the intensity of radiation measured per minute and equal to one calorie.

La Niña - Condition opposite of an El NiƱo. In a La Niña, the tropical Pacific trade winds become very strong and an abnormal accumulation of cold water occurs in the central and eastern Pacific Ocean.

Laminar Flow - Movement of water within a stream that occurs as uninterrupted parallel flows. Laminar flow generally occurs in areas where friction is low.

Latent Heat - Is the energy required to change a substance to a higher state of matter (solid > liquid > gas). This same energy is released from the substance when the change of state is reversed (gas > liquid > solid).

Latent Heat Flux - Latent heat flux is the global movement of latent heat energy through circulations of air and water. Atmospheric circulation moves latent heat energy vertically and horizontally to cooler locations where it is condensed as rain or is deposited as snow releasing the heat energy stored within it.

Latent Heat of Condensation - The amount of heat energy release to the environment when a gas changes its state to a liquid. For one gram of water, the amount of heat energy released is 540 calories at a temperature of 100° Celsius.

Latent Heat of Vaporization - The amount of heat energy required from the environment to change the state of a liquid to a gas. For one gram of water, the amount of heat energy required is 540 calories at a temperature of 100° Celsius.

Lateral Moraine - Moraine that is found along the sides of a glacier. Commonly found on glaciers that occupy a valley.

Laterite - Hard subsurface deposit of oxides of aluminum and iron found in tropical soils where the water table fluctuates with seasonal changes in precipitation.

Laterization - Soil forming process that creates a laterite layer.

Latitude - Latitude is a north-south measurement of position on the Earth. It is defined by the angle measured from a horizontal plane located at the Earth's center that is perpendicular to the polar axis. A line connecting all places of the same latitude is termed a parallel. Latitude is measured in degrees, minutes, and seconds. Measurements of latitude range from equator (0°) to 90° North and South from this point.

Latosol - Soil order (type) of the United States Natural Resources Conservation Service Soil Classification System. This soil is characterized by a thin 0 horizon, the presence of a laterite layer, and a deeply weathered profile.

Laurasia - Northern section of Pangaea.

Lava - Molten magma released from a volcanic vent or fissure.

Lava Flow - Stream of lava flowing from a volcanic vent.

Law of Basin Areas - Morphometric relationship observed in the mean basin area size of stream segments of a particular classification order in stream channel branching. Proposed by R.E. Horton.

Law of Conservation of Energy - This law states that energy can be transferred from one system to another in many forms, however, it can not be created nor destroyed. Thus, the total amount of energy available in the universe is constant.

Law of Stream Lengths - Morphometric relationship observed in the cumulative size of stream segment lengths in stream channel branching. Proposed by R.E. Horton.

Law of Stream Number - Morphometric relationship observed in the number of stream segments of a particular classification order in stream channel branching. Proposed by R.E. Horton.

Law of the Minimum - This biological law suggests that organisms are normally limited by only one single physical factor that is in shortest supply relative to demand.

LDC - See less developed country.

Leachate - Solution containing material leached from a soil.

Leaching - Process in which water removes and transports soil humus and inorganic nutrients in solution.

Leaf Drip - The rain water that fall to the ground surface from plant leaves after it has been intercepted by these structures.

Lee - Side of a slope that is opposite to the direction of flow of ice, wind, or water. Opposite of stoss.

Leeward - Downwind side of an elevated area like a mountain. Opposite of windward.

Legume - Angiosperm plant species that is a member of the Fabaceae (Pea or Bean) family. These plants form symbiotic relationships with specific bacteria species for the purpose of acquiring nitrogen for growth.

Less Developed Country (LDC) - Country characterized by minimal industrialization, low technological development, low per capita income, and high population growth rates. Many of these countries are found in Asia, Africa, and Central and South America. Also see more developed country.

Levee - Ridge of coarse deposits found alongside the stream channels and elevated above the floodplain. Forms from the deposition of sediment during floods.

Liana - Species of plant that uses the support of wood plants to elevate its leaves above the forest canopy.

Lichen - Organism that consists of a symbiotic joining of a species of fungi and a species of algae.

Light - A humanly visible form of electromagnetic radiation. This radiation has a wavelength between 0.40 and 0.71 micrometers (µm).

Lightning - Visible discharge of electricity created by thunderstorms.

Light Year - Distance that light travels in the vacuum of space in one year. Approximately 9.7 trillion kilometers.

Lignite - Low grade coal. Also called brown coal.

Limestone - Sedimentary rock composed of carbonate minerals, especially calcium carbonate. Limestone can be created by clastic and non-clastic processes. Clastic limestones are formed from the break up and deposition of shells, coral and other marine organisms by wave-action and ocean currents. Non-clastic limestones can be formed either as a precipitate or by the lithification of coral reefs, marine organism shells, or marine organism skeletons.

Limiting Factor - Abiotic condition that most controls the growth of a species. For most terrestrial plants this condition is the supply of the nutrient nitrogen in the soil.

Lipid - Is an organic compound composed of carbon atoms that have two hydrogen atoms attached. Lipids are commonly known as fats and oils, and belong to the family of molecules known as hydrocarbons.

Liquefaction - Temporary transformation of a soil mass of soil or sediment into a fluid mass. Occurs when the cohesion of particles in the soil or sediment is lost. Often triggered by seismic waves from an earthquake. For this condition to take place the pore spaces between soil particles must be at or near saturation.

Liquid - A state of matter where molecules have the ability to flow and the surface of this mass displays the property of surface tension.

Lithification - Process by which sediments are consolidated into sedimentary rock.

Lithosphere - Is the solid inorganic portion of the Earth (composed of rocks, minerals, and elements). It can be regarded as the outer surface and interior of the solid Earth.

Litter - Accumulation of leaves, twigs and other forms of organic matter on the soil surface. In most soils, the surface layer of litter is at various stages of decomposition.

Litterfall - Movement of leaves, twigs and other forms of organic matter from the biosphere to the litter layer found in soil.

Little Climatic Optimum - Time period from 900 - 1200 AD. Warmest period since the Climatic Optimum.

Little Ice Age - Time period from 1550 to 1850 AD. During this period, global temperatures were at their coldest since the beginning of the Holocene.

Littoral Drift - The sediment that is transported by waves and currents through beach drift and longshore drift along coastal areas.

Littoral Transport - The process of sediment moving along a coastline. This process has two components: longshore transport and onshore-offshore transport.

Littoral Zone - The zone along a coastline that is between the high and low-water spring tide marks.

Loam - A soil that contains a roughly equal mixture of clay, sand, and silt. Good for growing most crops.

Lobe - A tongue-like extension of some material. For example, the ice lobe of an alpine glacier.

Location - A term used in geography that deals with the relative and absolution spatial position of natural and human-made phenomena.

Loess - Deposits of silt laid down by aeolian processes over extensive areas of the mid-latitudes during glacial and postglacial times.

Logarithmic Scale - Measurement scale based on logarithms. Values increase on this scale exponentially.

Longitude - Longitude is a west-east measurement of position on the Earth. It is defined by the angle measured from a vertical plane running through the polar axis and the Prime Meridian. A line connecting all places of the same longitude is termed a meridian. Longitude is measured in degrees, minutes, and seconds. Measurements of longitude range from Prime Meridian (0°) to 180° West and East from this point.

Longshore Current - A water current that moves parallel to the shoreline.

Longshore Drift - The movement and deposition of coastal sediments because of longshore currents.

Longshore Transport - The transport of sediment in water parallel to a shoreline.

Long Wave - A large wave in the polar jet stream and the westerlies that extends from the middle to the upper troposphere. Often associated with the formation of a mid-latitude cyclone at the ground surface. Contrasts with short waves. Also called Rossby waves.

Longwave Radiation - See infrared radiation.

Lovelock, James E. - British scientist and naturalist who is most famous for his development of the Gaia Hypothesis. This theory suggests that life on the Earth functions like super-organism regulating its environment through biological interactions that influence the atmosphere, lithosphere, and hydrosphere.

Low Pressure - An area of atmospheric pressure within the Earth's atmosphere that is below average. If this system is on the Earth's surface and contains circular wind flow and enclosed isobars it is called a cyclone.

Lower Mantle - Layer of the Earth's interior extending from 670 to 2,900 kilometers below the surface crust. Composed of ultramafic rock. This layer is hot and plastic and part of the mantle layer.

Luvisol Soil - Soil order (type) of the Canadian System of Soil Classification. This soil type is associated with forest vegetation. The most identifying traits of this soil is the presence of calcareous parent material which results in a high pH and strong eluviation of clay from the A horizon.

Lysimeter - Meteorological instrument used to measure potential and actual evapotranspiration.


Citation: Pidwirny, M. (2010). "Glossary of Terms: L". In: Glossary of Terms, www.our-planet-earth.net. Date Viewed. http://www.our-planet-earth.net/glossary/l.html




Created by Dr. Michael Pidwirny, University of British Columbia Okanagan

Email Corrections and Suggestions to: michael.pidwirny@ubc.ca

Copyright 2010 Michael Pidwirny

06/18/2010 11:02


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