4. Soil formation done.docx

Soil Formation Soil is the top surface of the earth’s surface. It consists of mineral and rock particles, organic matter, water and air. Irish soils are young because they were only formed after the last Ice Age. Soil provides a medium in which crops can be grown. Physical support for plant roots an...

Soil Formation Soil is the top surface of the earth’s surface. It consists of mineral and rock particles, organic matter, water and air. Irish soils are young because they were only formed after the last Ice Age. Soil provides a medium in which crops can be grown. Physical support for plant roots and a medium in which plant and animal remains can be decomposed, allowing for nutrient recycling. Soil holds water and air, which are necessary for crop growth. Types of rocks- there are three groups of rock igneous, sedimentary and metamorphic. Igneous Rock: molten melted rock underneath the earth’s crust appears on the earth’s surface as lava. When magma or lava solidifies it forms igneous rock. Sedimentary Rock when layers of sediments were deposited at the bottom of the seas and lakes they are compacted over millions of years to form sedimentary rocks. Limestone is formed from shells and other materials containing calcium. Metamorphic rock are formed when intense heat or pressure is put on igneous rocks or sedimentary rocks. Marble formed from Limestone Weathering of Rocks Physical Weathering due to frost forms cracks in a rock are filled by water & when this freezes it expands it causes the rock to shatter and break. Root Activity as roots grow, they put pressure on the rock and cause it to break. Animal Activity due to animals digging and burrowing contribute to rock breakdown. Chemical Weathering Known as Hydrolysis is a chemical reaction between water & rock minerals. It changes the chemical characteristics and size of the minerals in rock. Hydration is the addition of water to a rock mineral this typically occurs after oxidation where iron oxide is produced. Biological Decomposition of Rocks due to Bacteria, fungi and lichens gather around bare rocks. Most microorganism's break down nitrogen and carbon dioxide from the atmosphere and produce acids Five Factors that effect of Soil Formation Parent Material is the type of rock in which soils are formed from. Has an impact on acidity and texture of soil formed from it. Eg limestone is alkaline Topography or known as the ‘lie of the land’. Soil depth is affected by the slope on the land Soils on slopes are thin and hold a good depth of soil in the areas below. Aspect of the land refers to the direction in which the field is facing the sun south lying land always warms up faster than those lying north. Climate is affected by the way water contributes to weathering of rocks through frost action. Temperature plays a role in the heating & cooling of rocks. Living Organisms such as plants, animals and micro-organisms add humus to the soil when they die. Microorganisms decompose the organic matter and add nutrient to the soils. Soils that develop under tree are more acidic. Burrowing from some animals & roots of plants causes the weathering of rocks. Peat is rich in organic matter and is the main material that is produced from plant remains when oxygen is not present. There are three types of bog’s Basin peats, Raised bogs and Blanket bogs. Basin peats are flat bogs that have developed in lakes and water-logged areas where there is a mineral-rich water supply. Basin peats are slightly acidic Blanket bogs are developed in areas of high rainfall that have low evaporation. They are not as deep as basin peats. Very acidic with low fertility. Raised bogs are typically dome shaped with shallow depressions in the landscape. Water and nutrients are supplied from rainfall. They are more acidic than blanket bogs.