1. Soil & Erosion

2. Weathering Weathering breaks down rock – Two types: physical and chemical

3. Physical (Mechanical) Weathering The breakdown of rock by physical mean is physical (or mechanical) weathering. – Ice, wind, water, gravity, plants, and even animals can be agents of (cause) physical weathering.

4. Physical (Mechanical) Weathering – Abrasion: water or wind carrying debris rubs on rock surface – Freeze/thaw: water trapped in spaces of rock repeatedly freezes and thaws – Thermal expansion/contraction: solar radiation causes minerals to heat and cool at various speeds producing stresses in rock over time

5. Chemical Weathering Chemical processes (methods of changing chemical compounds) cause chemical weathering. – Water, weak acids, and air are agents of (cause) chemical weathering Water causes the composition of the mineral or rock to change – Primary minerals in rock are broken down to secondary minerals and this material can be carried away in solution. Acid precipitation can cause weathering Oxygen in the air can cause rusting

6. Chemical Weathering – Water causes the composition of the mineral or rock to change – Primary minerals in rock are broken down to secondary minerals and this material can be carried away in solution. – Acid precipitation can cause weathering when the acids come in contact with rocks – Oxygen in the air can cause rusting

7. Chemical Weathering

8. Erosion As soon as a rock particle is loosened by weathering and moves it is called erosion. Eroded rock is one of the main components of soil.

9. Erosion Rock can be eroded by wind, water (including waves), and glacial movement. Processes of erosion in part determine the shapes of landforms. Fragments (pieces) of rock that are produced by erosion and transported are called sediment. – Sediment that is transported by the energy of wind or water is deposited when that energy level decreases.

10. Soil Soil is made of multiple components – Minerals (45%) Comes from tiny pieces of eroded rock – Organic matter (5%) Comes from decaying plants and animals – Water (25%) – Air (25%)

11. Soil Particle Size The main particle sizes of soil from largest to smallest are: sand, silt, and clay.

12. Soil Particle Size