lacustrine: Pertaining to or formed in a lake or lakes. GWAC.
lagoon: A shallow stretch of salt or brackish water, partly or completely separated from a sea or lake by an offshore reef, barrier island, sandbank or spit. NSSH.
lake: An inland body of permanently standing water fresh or saline, occupying a depression on the earth’s surface, generally of appreciable size and too deep to permit vegetation to take root completely across the expanse of water. NSSH.
lamina: The thinnest recognizable layer of original deposition in a sediment or sedimentary rock, differing from other layers in color, composition, or particle size. Several laminae constitute a bed. NSSH.
Langelier Index: L.I. A measure of balance in the water of the pH with presence of calcium carbonate. A negative index value (under saturation of calcium carbonate) will result in greater corrosivity; a positive index value (over saturation of calcium carbonate) will result in precipitation of the element, accumulating calcium on water fixtures, etc. CSU.
lateral: (1)A minor ditch used to direct water onto the land, headgating off the main ditch. A ditch may have many laterals depending on the amount of acreage irrigated, the slope of the land, and the rate of seepage losses. Douglas Co.
(2) A direction. More or less horizontal direction.
leaching: The process by which materials such as nutrients or pollutants are dissolved and penetrate deeper into the soil by percolation.
lens, lenticular: A porous, usually permeable sedimentary deposit completely surrounded and isolated by impervious sediment, beds or strata. A lens or lenticular stratum pinches out in all directions and is completely isolated, and is a singular pressure system within itself. Relative to aquifers, this would be a completely confined aquifer having no pressure communication with any other, where the quantity of water is finite and water renewal cannot take place. Also see aquifer (3) and abnormal pore pressure.
(2) A sedimentary rock consisting primarily of the mineral, calcium carbonate.
liquid: A fluid. The state of the fluid where it can take the shape of its container, but its volume is independent of the size of its container. Most liquids are nearly incompressible depending on gases dissolved in the liquid.
lithification: The conversion of unconsolidated sediment into a cohesive and solid rock, involving processes such as cementation, compaction, desiccation, crystallization, recrystallization, and compression. It may occur concurrently with, shortly after, or long after deposition. NSSH.
lithology: (1) Refers to the pattern, mineralogy and physical character of sequential beds and strata.
(2) The study of rocks.
lithostatic load: The net weight of the rock framework or structure from the depth of interest to the ground surface, exclusive of water or any other fluid contained in the pores. Expressed in psi. Compare hydrostatic load and geostatic load. See compaction (2).
loess: Material transported and deposited by wind and consisting predominantly of silt-size particles. Commonly a loess deposit thins and the meanparticle size decreases as distance from the source area increases. Loess sources are dominantly from either glacial meltwaters or from non-glacial, arid environments, such as deserts. NSSH.
log: (1) To log a well for the purpose of making a permanent record.
logging: Pertains to the running of scientific instruments downhole in a well bore for the purpose of obtaining records for analysis. Also see well log.
loss: The difference between the amount of water that actually is delivered and put to beneficial use and the amount of water that was physically diverted. On the ground surface, such losses usually are due to seepage and evaporation during transport or storage.
lost circulation: The undesirable condition where the drilling mud, conditioned to have a pressure greater than the pressure within an aquifer, and having a high water loss at the same time, penetrates freely into the formation and becomes lost. This failure is evidenced by the loss of mud returns to the surface. Not only does this halt the drilling process, but it might contaminate any aquifer where it occurs and might cause formation damage. See formation damage (1).
Compiled and Edited by Robert C. Ransom
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