Jet Stream Jet Stream is very strong westerly winds blowing at high altitudes (about 12 km), i.e., just below the tropopause. The speed of the winds varies from a mean of 110 km/h in summer to about 184 km/h in winter. There are two main types of jet stream: one that blows in the subtropical region and the other associated with polar front. Subtropical jet stream is fairly consistent in location, while polar front jet stream is very irregular in its location.
Kaolin (China Clay) Kaolin or Kaolinite is a white clay produced by the chemical breakdown of feldspars, especially those in granite, by the process of kaolinisation. This kaolinisation is caused either by weathering or by the action of ascending gases associated with igneous activity.
Karst Karst refers to a region of well-jointed limestone in which carbonation is the dominant weathering process. Sinkholes, limestone pavements with clints and grikes, caves containing stalactites and stalagmites, steep-sided gorges and underground drainage are the main features of Karst topography. Yugoslavia is famous for Karst topography.
Katabatic Wind Katabatic wind is a cold wind that blows down valleys at night and outwards from large ice-caps. It is caused by the gravitational movement of cold air near the earth's surface. The strongest Katabatic winds are those that blow off the Greenland and Antarctic icesheets.
Kettle Hole Kettle hole is an enclosed depression or hollow in glacial-drift deposits that are accumulated in a recently glaciated area. Kettle holes generally contain small lakes and are often found in groups forming a distinctive topography of hollows and ridges known as kettle moraine.
Khamsin An Arabic term, Khamsin refers to a very hot, dry, and often dust-laden southerly wind. Khainsin blqws periodically across Egypt from the Sahara desert. It is most common between April and June.
Kuroshio (Kurosiwo) Current A major boundary current in the ocean circulation system, Kuroshio (Kurosiwo) current develops as a deflected part of the North Equatorial current in the Pacific ocean Labrador. Current A major ocean current in the North
Atlantic Ocean, Labrador current flows southwards from the Arctic Ocean along the eastern coast of Greenland. It is one of the factors of high frequency of fogs in the Grand Banks area.
Laccolith Laccolith refers to a large dome-like mass of igneous rock that was intruded along a bedding plane in a sedimentary rock. If a number of laccoliths are stacked one above another from a single intrusion, they are called a cedar-tree laccolith.
Lacustrine The term lacustrine refers to landforms relatedto a lake, e.g., lacustrine delta, lacustrine plain, etc.
Lagoon A lagoon is a shallow stretch of water that is separated from the open sea by a barrier beach or a shingle ridge or a coral reef. Lagoons are frequently formed between coral reefs and the shore. It also refers to a circular body of water partly enclosed within an atoll.
Lake A lake may be defined as a body of water that lies in a hollow in the earth's surface and is entirely surrounded by land. Lakes are unconnected with the sea except by rivers. Some inland seas, such as Caspian Sea and Dead Sea, are large lakes.
Land Breeze and Sea Breeze Land breeze is a cool wind that blows from the land to the sea or a large lake during the night. It occurs when night time radiation chills the land and the air in contact with the ground surface. It is most common in tropical areas.
Sea breeze is a local wind that blows from sea or a large lake to the land during day time. It is caused by greater heating of the land relative to the sea during the day. It reaches its maximum strength in mid-afternoon when the temperature difference is greatest. Like land breeze, it is best developed in tropical areas.
Landslide (Landslip) Landslide or landslip is a form of mass movement in which rock and debris move rapidly downslope under the gravity.
Lapse Rate Lapse rate is defined as the rate of decrease of temperature with latitude. The lapse rate is applicable only up to tropopause. Sometimes also referred to as vertical temperature gradients, lapse rates are of three types: (i) environmental lapse rate (average 0.6 °C for. 100 m of ascent), (ii) dry adiabatic lapse rate (average 1.0°C for 100 m of ascent), and (iii) saturated adiabatic lapse rate (average between '0.2 °C and 0.9 °C for 100 m of ascent).
Latent Heat The amount of energy emitted or absorbed when a body changes its state (solid to liquid, etc.),
without any change of temperature with that body, is .known as latent heat. Latent heat is important in atmospheric process as it is emitted duridg condensation and freezing but absorbed during evaporation and melting. Latent heat of fusion is the energy required in conversion of solid into liquid, while latent heat of sublimation is the energy required in conversion of solid into gas.
Lateral Erosion When a river erodes its. bank in horizontal direction, it is known as lateral erosion. Such action is most marked in a meander zone where the river impinges more strongly on the outside of a meander. This outside cutting undercuts the banks and causes bank-caving.
Laterite Laterite refers to a red residual deposit. Such deposition is created from the weathering of rocks io humid tropical conditions.
Latitude The angular distance of a point on the earth's surface along a meridian north or south of the equator is called latitude. Every point on a particular parallel of latitude has the same latitude.
Lava Lava is molten or partially molten magma that is extruded from a volcano.or volcanic fissure on to the surface of the earth. Lavas are subdivided into basic, acidic and intermediate lavas.
Leaching Leaching refers to a process by which downward movement of water in soil removes humus in solution, soluble bases and sesquioxides from the upper horizon of the soil profile. As a result of leaching, the upper layer of soil becomes increasingly acid and mineral-deficient, forming eluvial horizon. If the material is deposited lower in the soil profile, an illuvial horizon is formed.
Leeward The term leeward refers to the downwind side or the side protected from the wind.
Leveche A Spanish term, leveche refer to a hot dry southerly wind blowing from North Africa over South Spain. Leveche occurs when a depression is passing through the West Mediterranean area. A sirocco type wind, leveche frequently carries dust.
Leeve Leeve is the bank of alluvium bordering a river in its lower course. It is built up by deposition and lies above the level of the flood plain. The formation of I
leeves tends to raise the level of the river channel, leading to widespread flooding once the leeves are breached. Thus artificial heightening and leeve building is done on flood-prone rivers.
Lithosphere The term lithosphere refers to the crustal component of the earth. Lithosphere includes sial, sima and upper mantle. Its base lies 2-3 km under midoceanic ridge, increasing up to 180 km beneath the old ocean crust.
Littoral zone The term littoral zone denotes the shore of a sea, lake or river. More specifically, the littoral zone is that part of the shore that lies between the highest high-water mark and the lowest watermark along a coast.
Loam Loam is a soil type that consists a mixture of sand and clay particles. Loam soils are the best agricultural soils as they combine the free movement of water and
air with the nutrient-retaining properties of the clay.
Loess Loess is a fine-grained deposit consisting of windborne dust Yellowish or grey in colour, it is usually stone-free and unstratified. The soils derived from loess are of the highest quality.
Longitude Longitude is defined as the angular distance of a point on the earth's surface east or west of prime meridian (or Greenwich meridian), which is longitude 0°. Every point on a particular meridian has the same longitude.
Lapolith Lapolith is an igneous rock that lies between rock strata and is concave upwards. Saucer-shaped, lapolith forms a large shallow basin at the surface. It is concordant as it lies between and not across the layers of rock.
Lunar Day Lunar day is defined as the time interval
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