SOIL AND SOIL FORMATION - LACOE Moodle AND SOIL FORMATION Soil is a mixture of parent rock, decayed organic matter, minerals, water and air. ... Soil pH Soil color Soil structure

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<ul><li><p>SOIL AND SOIL FORMATIONSoil is a mixture of parent rock,decayed organic matter, minerals,water and air.</p><p>It takes thousands of years to form.</p></li><li><p>Factors affecting soilformation</p><p> Climate (Temperature and Humidity) Slope of land (topography) Type of parent material (rock type) Type of vegetation growing on the soil Time</p></li><li><p>Soil formation</p><p>1. Weatheringa) Chemical weatheringb) Mechanical weathering</p><p>2. Decomposition of organic matter (plantand animal remains)</p></li><li><p>Mechanical Weathering</p><p> Weathering breaks the rock into to smallerpieces called sediment. (sand, silt andclay)</p></li><li><p>Mechanical Weathering</p><p> Mechanical weathering includes: growingplants between rock, ice wedging andburrowing animals.</p><p> Temperature changes can break rocksapart.</p><p>Where is mechanical weathering mostimportant? Why?</p></li><li><p>Which biome(s) have themost important mechanicalweathering and why?</p><p>In temperate climates, winter is coldenough for water to turn into ice. Icecan crack rocks into little pieces</p><p>In the desert, the temperature changesgreatly each day. This cracks the rocks.</p></li><li><p>Chemical Weathering</p><p> The chemical composition of the rockschanges in chemical weathering becausechemical reactions occur.</p><p> Natural acids, such as carbonic acid in rainand plant acids cause chemical weathering.</p><p> Oxygen in the air causes oxidation.</p><p>Why is chemical weathering is important inwarm, humid climates?</p></li><li><p>Why is chemical weathering isimportant in warm, humidclimates? Chemical reactions are faster when the</p><p>temperature is higher.</p><p> Chemical reactions are faster in solution</p><p> Chemical weathering is very important inTropical climates.</p></li><li><p> Oxidationreactions oftropical soilcause it tobe reddishin color.</p></li><li><p>Properties of soil that changequickly Temperature</p><p> Moisture content</p><p> Composition of air in the soil pores</p></li><li><p>Properties of soil that changeover months or years Soil pH Soil color Soil structure Organic content in the soil Fertility of the soil Microorganisms Density</p></li><li><p>Properties that change overhundreds or thousands of years</p><p> Mineral composition of the soil Particle size in the soil Horizon formation</p></li><li><p>Soil Horizons</p><p> O horizon surface litter (leaves and twigs) A horizon topsoil layer (contains humus) B horizon subsoil (inorganic) C horizon bedrock and parent material E horizon forms when the conditions are</p><p>wet or forested (eluvial horizon) lighter incolor</p><p> R horizon: A rock layer that is sometimesunder the soil profile</p></li><li><p>Identify O, A, B, C and E</p></li><li><p>Soil profile from a temperateforest in Jordan</p></li><li><p>Soil Profile from Buenos Aires,Argentina</p></li><li><p>More about soil profiles</p><p> Sometimes, not all of the horizons will bepresent in some soils.</p><p> For example, O and E are only in forestedareas</p><p> Agricultural, deserts and grassy areas willstart with an A horizon but do not have anE horizon.</p><p> If the area was eroded, the A horizon maybe gone!</p><p> Shallow soils might not have the B horizon.</p></li><li><p>Soils around the world</p><p> Grassland soils Forest soils Tropical soils Cold climate soils (tundra) Arid soils Wet soils</p></li><li><p>Grassland Soils Common in Midwest</p><p>of the USA, Argentinaand Ukraine</p><p> Deep and dark Good for crops High organic content Holds water and</p><p>nutrients</p></li><li><p>Soil Profile fromPennsylvania, USA</p></li><li><p>Soil Profile from Buenos Aires,Argentina</p></li><li><p>Coniferous forest soils</p><p> The organicmatter comesfrom leavesand roots oftrees.</p><p> The acidsfrom the rainand leavesform acidswhich leachmaterialsfrom the tophorizons.</p></li><li><p>Tropical Soils The soil is deepand bright red(iron oxides)</p><p> The horizons arehard to tell apart</p><p> Organic matterdecomposes veryquickly andtransforms intoinactive materialthat binds to clay</p><p> Nutrients areleached from thesoils</p></li><li><p>Tropical Soil 3 hours fromBangkok, Thailand</p></li><li><p>Tropical Soil from Ghana</p></li><li><p>Tundra soils The soil is not</p><p>very developedand only faintindications ofhorizons canbe seen.</p><p> Permafrost canbe seen at thebottom of theprofile</p></li><li><p>Arid soil</p><p> The A horizon is light brown because thereis a lack of organic matter or moisture.</p><p> The organic matter is not returned to thesoil because there are not very many plants</p><p> When it rains, materials are carrieddownward into the profile to the B horizon</p><p> Calcium carbonate accumulates over timeand becomes hard</p></li><li><p>Wet soil</p><p> The A horizon is dark from accumulationof organic matter.</p><p> The soil is saturated and not enoughoxygen is present to decompose theorganic matter.</p><p> The B horizon is grayish.</p></li><li><p>Poor soil use leads todesertification</p></li></ul>

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