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Weathering  Weathering – is the process by which rock materials are broken down by the action of physical or chemical processes.  Mechanical Weathering.

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Presentation on theme: "Weathering  Weathering – is the process by which rock materials are broken down by the action of physical or chemical processes.  Mechanical Weathering."— Presentation transcript:

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2 Weathering  Weathering – is the process by which rock materials are broken down by the action of physical or chemical processes.  Mechanical Weathering – the breakdown of rock into smaller pieces by physical means  Chemical Weathering – the process by which rocks break down as a result of chemical reactions

3 Mechanical Weathering  Ice The alternate freezing and thawing of soil and rock – frost action Ice wedging – water seeps into cracks, water then freezes and expands causing the crack to widen  Abrasion – the grinding and wearing away of rock surfaces through the mechanical action of other rock or sand particles Wind Water Gravity

4  Plants Plant roots grow into existing cracks in rocks and expanding roots become so strong that the crack widens  Animals Any animal that burrows causes mechanical weathering (ants, worms, mice, coyotes, and rabbits) Mixing and digging by animals can also cause chemical weathering

5 Chemical Weathering  Water – dissolving of water into a rock can break the rock down over years  Acid Precipitation – rain, sleet, or snow, that contains a high concentration of acids Caused by burning fossil fuels High level of acidity can cause very rapid precipitation

6  Acid in Groundwater – chemical reactions occur between the acid in the groundwater and rock and breaks the rock down caverns  Acid in Living Things Lichens – grow on rocks and trees and slowly breaks down the rock  Air – oxygen in the air reacts with iron and forms rust oxidation

7 Rate of Weathering  Composition of rocks  Amount of time that rock is exposed to weathering  The amount of exposed surface  More joints or cracks easier broke down

8 From Bedrock to Soil  The source of soil Soil – a loose mixture of rock fragments, organic material, water, and air that can support the growth of vegetation ○ Soil is made from weathered rock fragments, the type of soil that forms depends on the type of rock that weathers Parent rock – a rock formation that is the source of soil Bedrock – the layer of rock beneath soil

9  Soil Properties Soil Texture and Soil Structure Soil Fertility ○ Humus – dark, organic material formed in soil from the decayed remains of plants and animals Soil Horizons – soil often ends up in a series of layers, with humus-rich soil on top, sediment below that, and bedrock on the bottom ○ Horizon tells you the layer the rock is in horizontal ○ Top layer of soil is often called topsoil and contains more humus than the layers below Soil pH

10 Soil Conservation  Soil conservation – is the method to maintain the fertility of the soil by protecting the soil from erosion and nutrient loss  The importance of soil – soil provides minerals and other nutrients for plants and all animals get their energy from plants Housing – soil provides a place for animals to live Water Storage – without soil to hold water, plants would not get the moisture of the nutrients they need. Soil also keeps water from running off

11  Soil Damage and Loss – can be caused by overuse, poor farming techniques or overgrazing Soil Erosion – the process by which wind, water, ice, or gravity transport soil and sediment from one location to another  Contour Plowing and Terracing Contour Plowing – plowing across the slope of hills Terracing – changing one steep field into a series of smaller flatter fields  Cover Crop and Crop Rotation Cover crops – crops that are planted between harvest to replace certain nutrients and prevent erosion Crop rotation – planting different crops

12 River Systems and Deposition  Streams join other small streams to form larger ones and eventually all of the water flows into one and forms a river  Network of streams and rivers that drains an area is its runoff.  Tributary – a stream that flows into a lake or into a larger streams.  Watershed (drainage basin) – is the area of land that is drained by a water system  Divide – the boundary between drainage areas that have streams that flow in opposite directions  Load – the material that is carried by a stream  Deposition – the process in which material is laid down or dropped. Rock and soil that is deposited by streams are called sediments

13 Reshaping Earth’s Surface  Sand dunes – a mound of wind- deposited sand that keeps its shape even though it moves  Glaciers – a large mass of moving ice  Mass movement – is the movement of any material, such as rock, soil, or snow, down a slope


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