2Soil begins with rocks – so how is rock turned into soil? How does soil travel and move?
3Inside the EarthThe Earth's Crust is like the skin of an apple. It is very thin in comparison to the other three layers. The crust is only about 3-5 miles (8 kilometers) thick under the oceans(oceanic crust) and about 25 miles (32 kilometers) thick under the continents (continental crust). The temperatures of the crust vary from air temperature on top to about 1600 degrees Fahrenheit (870 degrees Celcius) in the deepest parts of the crust
4Weathering & ErosionWeathering – a natural process that breaks down and wears away rocks to create sedimentsErosion is the movement of small rock particles by wind, water and ice
5There are three kinds of weathering: 1. Mechanical2. Chemical3. Biological
6Mechanical Weathering– the physical break up of rocks.
7ExamplesGravity – pulls rocks down cliffs and mountains smashing them
8Moments before this rock fell, it was one large rock Moments before this rock fell, it was one large rock. How many pieces of rock do you think there are now?
12What do you think will happen to this rock when it falls?
13This rock froze and thawed so many times that it slowly burst from the strain.
14Erosion– wind, water, and ice wear away at the surfaces of rock and carry the pieces to another spot. E.g. dust storms, rivers, glaciers, ocean waves
15Mass MovementMass movement means the movement of any loose material (rocks, soil, mud) down slope under the influence of gravity.The loose material is known as regolith.The rate of mass movement is influenced by 4 factors.GradientWater ContentHuman ActivityVegetation
16Influences on Mass Movement Gradient – Mass movement occurs on sloping land. Mass movement is fastest on steep slopes.Water Content – After heavy rain the regolith (loose material) is heavier.Human Activity – People often cut into hillsides to make roads or railway lines. This creates steep slopes where mass movement can occur.Vegetation – The roots of trees and plants help keep the regolith together, slowing down mass movement.
17Speed – Slow Speed – Fast Types of Mass MovementThere are different types of mass movement. They are grouped according to the speed at which they occur.Types of Mass MovementSpeed – Slow Speed – Fast1. Soil Creep Landslides2. Bog bursts3. Mudflows
22Chemical Weathering– the breakdown of rocks by water, chemicals, and gasses Chemical reactions can speed up the process of erosion – e.g. acid rain.Acid rain dissolves minerals found in rock which weakens the entire rock making it easier to break.It occurs because rainwater mixes with carbon dioxide in the atmosphere, forming a weak carbonic acid.