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BIOSPHERE

BIOSPHERE. Soils: What is a soil? What does soil contain? What factors affect soil formation? Soil Profiles. What is soil?. MINERALS FROM WEATHERED ROCKS. DEAD AND LIVING ORGANISMS. INORGANIC MATERIAL. ORGANIC MATERIAL. SOIL. AIR. WATER. WHAT ARE SOILS?.

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BIOSPHERE

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  1. BIOSPHERE Soils: What is a soil? What does soil contain? What factors affect soil formation? Soil Profiles

  2. What is soil? MINERALS FROM WEATHERED ROCKS DEAD AND LIVING ORGANISMS INORGANIC MATERIAL ORGANIC MATERIAL SOIL AIR WATER

  3. WHAT ARE SOILS? INORGANIC MATERIAL = 45% OF SOIL VOLUME WATER = 25% OF SOIL VOLUME AIR = 25% OF SOIL VOLUME ORGANIC MATERIAL = 5% OF SOIL VOLUME

  4. SOIL FORMATION AND SOIL PROFILES Soil Profile: A vertical section through the soil From surface to the bedrock Information comes from boring the soil with an auger Layers are called horizons

  5. SOIL FORMATION AND SOIL PROFILES Soil Profile: Horizons can be used to work out the type of soil There are usually four horizons in a model profile O horizon – the surface, organic layer of decaying vegetation (where present) LITTER – leaves, pine needles etc. FERMENTATION LAYER – organic material begins to decompose here HUMUS – decomposed remnants of plants and animals along with their waste products

  6. SOIL FORMATION AND SOIL PROFILES Soil Profile: 2. The A Horizon Main top layer Consists of organic and inorganic materials Usually nutrient rich Often referred to as topsoil 3. The B Horizon Known as the subsoil Coarser in texture: shows importance of weathering Nutrients may be leached into the B horizon from the A Leaching – removal of soluble minerals and humus downwards by rainwater

  7. SOIL FORMATION AND SOIL PROFILES Soil Profile: 4. The C Horizon Zone of regolith Large particles sit on top of underlying bedrock Soil profiles vary in depth Can be up to 50m Average in the UK is 1.5m

  8. SOIL FORMATION AND SOIL PROFILES Depending on the variations within these variations it is possible to group soils into a classification system These zones include soils with certain common characteristics. Closely linked with: CLIMATE VEGETATION

  9. SOIL FORMING FACTORS PARENT MATERIAL – the rock underneath, or other source material (e.g. from glacial, alluvial, volcanic deposition) VEGETATION – e.g. Coniferous, Deciduous LIVING ORGANISMS – worms and other creatures help to mix and improve the soil. Plants help stabilise soils and concentrate nutrients at surface of the soil CLIMATE – Temperature and Rainfall RELIEF – steepness of slopes, aspect of slope, height above sea level; TIME – 100,000 YEARS!!! NATURAL EVENTS – e.g. floods, glaciation, volcanic eruptions. HUMAN ACTIVITY – farming, deforestation

  10. WHAT ARE SOILS? ACTIVITIES: It is important to know the main factors which affect soil Formation. Use the Core Textbook to complete the following activities in the: Soil Formation and Soil Profiles section: Questions 1 – 6 on page 174

  11. SOIL FORMATION STAGES IN SOIL FORMATION: Weathering of parent rock over a considerable time period Water, gas, living organisms and decaying organic matter added Rate of weathering of parent rock depends greatly on climate (faster in hotter regions) Where rainfall is heavier minerals are transported downwards in a process called leaching Leached soils tend to be acidic Type of vegetation in an area is linked to precipitation – this provides the humus area – more found in forest areas

  12. TOPSOIL SUBSOIL REGOLITH (Weathered parent material)

  13. …and in more detail

  14. NEW TERMS Eluviation Downward movement of material where rainfall exceeds evaporation Illuviation Accumulation of material in one layer of soil which have been leached from a layer above Leaching Removal of soluble minerals and humus downwards by rainwater

  15. Homework-Biosphere Textbook Questions • Homework due next Thursday (20th January) • Page 174 • ‘Soil Types, Case Studies and Catenas’ • Questions 1 and 2 (all of) • Qu 2 a) use a whole jotter page for each soil profile.

  16. BROWN EARTHS FOREST SOILS

  17. BROWN EARTH SOILS DESCRIPTION: Horizons less distinct Mildly acidic due to a mull humus A-Horizon is dark brown B-Horizon is light brown A-Horizon has a loamy texture B-Horizon has a light texture Generally free draining soil EXPLANATION: Climate: Precipitation is greater than evaporation only in summer Leads to moderate leaching Warm summers

  18. BROWN EARTH SOILS EXPLANATION: Vegetation and Soil Organisms: Mixed broad leaf and much plant litter Broken down easily by active soil biota and warmer climate Greater abundance of earthworms, insects etc. Quicker breakdown of material than podsol soil Dark brown horizon as humus replaces material leached out Leaching is less pronounced because evaporation and precipitation are more equally balanced Colour lightens in the B horizon as humus becomes less abundant Deep roots can penetrate the C horizon and extract minerals to ensure greater recycling

  19. PODZOLS

  20. PODSOL (PODZOL) SOILS DESCRIPTION: Horizons well defined Mor humus Thin black layer with decaying litter needles A Horizon very dark, then ash grey B Horizon – red / dark brown Iron pan can develop A Horizon has a sandy texture B Horizon has a denser texture (clayey) Iron pan can impede drainage and cause waterlogging

  21. PODSOL (PODZOL) SOILS EXPLANATION: Climate: Colder climate – found at higher latitudes or altitudes Lowers the rate at which litter is decomposed Excess of precipitation over evaporation coupled with; Spring snowmelt and rainfall contribute to leaching Minerals are eluviated from the A horizon This leads to colouring and iron-pan formation in the B horizon Aluminium, iron and clay are re-deposited (illuviated) Vegetation: Coniferous vegetation – needles and cones These are acidic in nature with a waxy coating This leads to slow breakdown of organic matter And an acidic humus layer

  22. PODSOL (PODZOL) SOILS EXPLANATION: Biota: Clearly defined horizons show a lack of soil biota Lack of mixing of soil by earthworms Reflects low winter temperatures

  23. SOILS PAST PAPER QUESTION For Brown Earth Forest Soil or a Podsol Soil: Draw a soil profile and annotate it to show the main characteristics of the soil. Explain the processes which have created this soil profile. 12 marks Attempt b) 6 marks

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