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Shaping Earth Surface (Stability and change (Students understand that…

- - - - Chemical weathering - rocks break down, composition changes due to exposure to water and air. For year 4 the term being used is weathering caused by naturally produced chemicals.
        
        Acid weathering is when rainwater mixes with gases such as carbon dioxide in the air as it falls. In this case, the resulting carbonic acid dissolves rock such as limestone and sandstone.
        
        Oxidation occurs, in its most common form, when iron particles in rock combine with water and oxygen to form a coloured layer of oxidised mineral. Oxidation is similar to rusting and makes rocks softer. Rocks are then easier to wear away by mechanical means.
      - Physical weathering - rocks break down, exposed to physical forces such as wind and the expansion and contraction of rocks due to changes of temperature.
        
        Running water in streams and rivers wears rocks into smaller and smoother particles.
        
        Extremes and changes in temperature cause rocks to crack and split as they expand and contract. Excessive heating by the sun and rapid cooling overnight also create cracks. Small fragments of rock then fall off and are carried away by other forces such as rain or wind.
        
        Waves crashing on the shore forces air and water into rocks, creating spaces and cracks. As the waves move, small fragments of rock fall away and are washed away. Waves also undercut cliffs causing large chunks of rock to fall.
        
        Plants can force their roots into cracks of rocks and, as the roots grow they cause the rocks to break apart. Some lichens and moss grow on the surface of rocks, eventually eating into the rocks and causing them to split and break away. Plants also produce chemicals that can mix with rainwater to eat away rock
        surfaces. AKA Biological Weather
        
        Animals can also trample and crush rock. This, over a long time, wears them away. AKA Biological Weather
        
        Wind action removes rock grain by grain. High-speed wind scours rock smooth
        and swirls the grains around and around, creating cavities.
    - - Water erosion - This is where the material is moved away by water.
        
        Sheet erosion occurs when the top plain of the soil is moved. This occurs with the saturation of the soil and results in water and soil run-off.
        
        Splash erosion occurs when the force of rain droplet impact displaces soil particles.
        
        Rill erosion usually displays as many shallow channels. Water creates and flows down a slope. This is most often seen in cultivated fields.
        
        Gully erosion are carved by, and followed by water as it moves down a slope. Technically, gullies are as deep as they are wide
        
        Stream erosion.
        
        lateral erosion where part of the bank is being washed away
        
        vertical erosion (also called scour) where the bed of the stream is being washed away
        
        headward erosion is where a waterway extends its beginning location further up the slope
        
        mass movement (better known as a landslide or avalanche) occurs when the saturated surface of the slope weighs too much to stay attached to the ground underneath.
      - Wave erosion
        
        Coastal erosion is often due to wave erosion but can also be due to currents, tides or drainage. It occurs where the land meets the sea or ocean.
        
        Rock erosion occurs where waves crash into rock.
        
        Sand erosion occurs on the beach.
      - Ice erosion
        
        Plucking occurs when water solidifies around protrusions and cracks in rock and expands during freezing, widening cracks and breaking rock.
        
        Abrading occurs when ice and broken bits of rock slide as the ice scrapes away at the rock bed of the glacier
- - - - Sedimentary
      - Igneous
      - Metamorphic
    - - Ground Level
      - Top Soil
      - Subsoil
      - Weathered Parent Material
      - Bedrock